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Applied Surface Science (v.252, #5)

Electrostatic assembly of CTAB-capped silver nanoparticles along predefined λ-DNA template by Gang Wei; Li Wang; Hualan Zhou; Zhiguo Liu; Yonghai Song; Zhuang Li (pp. 1189-1196).

Cetyltrimethylammonium bromide (CTAB)-capped positively-charged silver nanoparticles synthesized in water–ethanol system was electrostatic assembled on predefined aligned λ-DNA template. Silver nanowire can be obtained by changing the reaction time and the particles concentration. In our work, the length of the silver nanowire obtained is about 10μm, and the dimension of the wires is about 20nm. AFM data reveal that the assembly of CTAB-capped silver nanoparticles on DNA is ordered, but there is space between two particles absorbed on the DNA template. X-ray photoelectron spectroscopy (XPS) was applied to characterize the linear silver clusters, which provides an additional proof that the silver particles were assembled onto DNA template with fine order.

Keywords: PACS; 61.46; 82.30.N; 41.20.C; 07.79.L; 79.60Nanoparticles; Clusters; Electrostatic; AFM; XPS

The surface modification of nanoporous SiO_x thin films with a monofunctional organosilane by D.-Q. Yang; M. Meunier; E. Sacher (pp. 1197-1201).

The surfaces of nanostructured, porous SiO_x/Si (air-oxidized Si) and SiO_x thin films, deposited by excimer laser ablation in He and He+O₂ gas ambients, respectively, have been modified by the deposition of a monofunctional organosilane. They were characterized using photoacoustic Fourier-transform infrared (FTIR) X-ray photoelectron (XPS) spectroscopies, and field-emission scanning electron microscopy (FESEM). Photoacoustic FTIR analysis indicates that the organosilane has hydrolyzed to form a silanol, which has chemically reacted with SiO_x through its surface silanol (SiOH) group, to form siloxane (SiOSi) structures. An enhanced IR spectral signal is found, due to the expansion and contraction of both the pores of the solid and the gas within them.

Keywords: PACS; 61.46.+w; 79.60.Jv; 81.65.−b; 82.33.−zNanoporous silicon; Surface chemical modification; Photoacoustic FTIR; XPS

Chemically abrupt interface between Ce oxide and Fe films by H.G. Lee; D. Lee; S. Kim; S.G. Kim; Chanyong Hwang (pp. 1202-1205).

A chemically abrupt Fe/Ce oxide interface can be formed by initial oxidation of an Fe film followed by deposition of Ce metal. Once a Ce oxide layer is formed on top of Fe, it acts a passivation barrier for oxygen diffusion. Further deposition of Ce metal followed by its oxidation preserve the abrupt interface between Ce oxide and Fe films. The Fe and Ce oxidation states have been monitored at each stage using X-ray photoelectron spectroscopy.

Keywords: PACS; 73.90.+f; 74.25.jb; 79.60; −; i; 79.60.DpMTJ; Ce oxide layer; XPS

Thermal desorption of dysprosium from tungsten microcrystal by R. Błaszczyszyn; T. Biernat (pp. 1206-1210).

Activation energy for thermal desorption of dysprosium from a tungsten microcrystal of about 300nm diameter was determined by means of the field-emission method. The desorption was detected from the whole W emitter surface in the temperature range 1490–1665K for dysprosium average coverage θ<0.06 monolayer. The average activation energy was determined to be 4.09±0.06eV/atom and the frequency factor to be about 10¹¹s⁻¹. The energy may mainly concern the desorption from the atomically rough regions of the microcrystal.

Keywords: PACS; 79.70.+qField emission; Thermal desorption; Dysprosium; Tungsten

Plasma-electrolytic formation, composition and catalytic activity of manganese oxide containing structures on titanium by V.S. Rudnev; M.S. Vasilyeva; N.B. Kondrikov; L.M. Tyrina (pp. 1211-1220).

In the present work, we report the data about formation of TiO₂-rutile or TiO₂ and Mn₂O₃, Mn₃O₄ containing oxide structures on titanium in aqueous electrolytes by means of plasma-electrolytic deposition. The layers formed are characterized by X-ray diffraction, electron probe microanalysis and scanning electron microscopy methods. The PEO coatings on titanium formed in sodium tetraborate solution contain the TiO₂ stabile rutile modification that is important when utilizing such a structure as a catalyst carrier. Manganese acetate adding into the electrolyte leads to formation of layers that contain Mn₂O₃, Mn₃O₄ and TiO₂-rutile in outer region. The manganese content in the surface layer depends on the formation conditions as well as on manganese acetate concentration in the electrolyte. Catalytic activity of the layers in CO→CO₂ reaction is studied in the static and flow conditions. The manganese-containing layers obtained possess the catalytic activity in CO→CO₂ oxidation reaction at the temperature range of 250–350°C. The catalytic activity depends on the concentration and surface distribution of manganese as well as on the layers morphology.

Keywords: PACS; 82.65.+r; 68.47.GhPlasma-electrolytic oxidation; Titanium; Thin films; Manganese oxides; CO oxidation

Local electronic edge states of graphene layer deposited on Ir(111) surface studied by STM/CITS by Z. Klusek; W. Kozlowski; Z. Waqar; S. Datta; J.S. Burnell-Gray; I.V. Makarenko; N.R. Gall; E.V. Rutkov; A.Ya. Tontegode; A.N. Titkov (pp. 1221-1227).

Scanning tunnelling microscopy and current imaging tunnelling spectroscopy were used to observe electronic structure of the edges of monolayer graphite film deposited on the Ir(111) surface. The electronic structure derived from the tunnelling spectra revealed peak in electron local density of states very close to the Fermi level. This electronic state was interpreted in terms of localised edge state caused by the topology of the π electrons networks typical for the zig-zag edges. The observed maximum of local density of states at about 0.2eV above the Fermi level was ascribed to the presence of resonant state caused by the appearance of disclinations centres in the vicinity of the graphite edges.

Keywords: PACS; 61.16.Ch; 61.72.Ff; 73.20.AtLocal electron states; Graphite; Scanning tunnelling spectroscopy

Electronic structure of gadolinium calcium oxoborate by A.J. Nelson; J.J. Adams; K.I. Schaffers (pp. 1228-1232).

Gadolinium calcium oxoborate (GdCOB) is a nonlinear optical material that belongs to the calcium–rare-earth (R) oxoborate family, with general composition Ca₄RO(BO₃)₃ (R³⁺=La, Sm, Gd, Lu, Y). X-ray photoemission was applied to study the valence band electronic structure and surface chemistry of this material. High resolution photoemission measurements on the valence band electronic structure and Gd 3d and 4d, Ca 2p, B 1s and O 1s core lines were used to evaluate the surface and near surface chemistry. These results provide measurements of the valence band electronic structure and surface chemistry of this rare-earth oxoborate.

Electrodeposition of polyaniline, poly(2-iodoaniline), and poly(aniline- co-2-iodoaniline) on steel surfaces and corrosion protection of steel by Gözen Bereket; Evrim Hür; Yücel Şahin (pp. 1233-1244).

Polyaniline (PANi), poly(2-iodoaniline) (PIANi), and poly(aniline- co-2-iodoaniline) ( co-PIANi) were synthesized using cyclic voltammetry in acetonitrile solution containing tetrabuthylammonium perchlorate (TBAP) and perchloric acid (HClO₄) on 304-stainless steel electrodes. Adherent and black polymer films were obtained on the electrodes. The structure and properties of these polymer films were characterized by FTIR and UV–vis spectroscopy and electrochemical method. The corrosion performance of PANi, PIANi, and co-PIANi coated electrodes were investigated in 0.5M hydrochloric acid (HCl) solutions by potentiodynamic polarization technique, open circuit potential–time curves and electrochemical impedance spectroscopy, EIS. It was found that the PANi film could provide much better protection than PIANi, and co-PIANi and PANi films have barrier property as well as acting as passivator. On the other hand PIANi and co-PIANi films are acting as barrier coatings which were related with the prevention of cathodic reaction taking place at metalelectrolyte interface. EIS measurement shows that every coating gives protection efficiency of greater than 75% after 48h of immersion time in corrosive test solution.

Keywords: Conducting polymer; Polyaniline; Corrosion; Stainless steel; Electropolymerization

Berberine as a natural source inhibitor for mild steel in 1M H₂SO₄ by Yan Li; Peng Zhao; Qiang Liang; Baorong Hou (pp. 1245-1253).

Berberine was abstracted from coptis chinensis and its inhibition efficiency on corrosion of mild steel in 1M H₂SO₄ was investigated through weight loss experiment, electrochemical techniques and scanning electronic microscope (SEM) with energy disperse spectrometer (EDS). The weight loss results showed that berberine is an excellent corrosion inhibitor for mild steel immersed in 1M H₂SO₄. Potentiodynamic curves suggested that berberine suppressed both cathodic and anodic processes for its concentrations higher than 1.0×10⁻⁴M and mainly cathodic reaction was suppressed for lower concentrations. The Nyquist diagrams of impedance for mild steel in 1M H₂SO₄ containing berberine with different concentrations showed one capacitive loop, and the polarization resistance increased with the inhibitor concentration rising. A good fit to Flory–Huggins isotherm was obtained between surface coverage degree and inhibitor concentration. The surface morphology and EDS analysis for mild steel specimens in sulfuric acid in the absence and presence of the inhibitor also proved the results obtained by the weight loss and electrochemical experiments. The correlation of inhibition effect and molecular structure of berberine was then discussed by quantum chemistry study.

Keywords: Berberine; Mild steel; Electrochemical measurement; SEM/EDS; Acid inhibitor

Tween-40 as corrosion inhibitor for cold rolled steel in sulphuric acid: Weight loss study, electrochemical characterization, and AFM by Xianghong Li; Guannan Mu (pp. 1254-1265).

The inhibition action of a non-ionic surfactant of tween-40 on the corrosion of cold rolled steel (CRS) in 0.5–7.0M sulphuric acid (H₂SO₄) was studied by weight loss and potentiodynamic polarization methods. Atomic force microscope (AFM) provided the surface conditions. The inhibition efficiency increases with the tween-40 concentration, while decreases with the sulphuric acid concentration. The adsorption of inhibitor on the cold rolled steel surface obeys the Langmuir adsorption isotherm equation. Effect of immersion time was studied and discussed. The effect of temperature on the corrosion behavior of cold rolled steel was also studied at four temperatures ranging from 30 to 60°C, the thermodynamic parameters such as adsorption heat, adsorption free energy and adsorption entropy were calculated. A kinetic study of cold rolled steel in uninhibited and inhibited acid was also discussed. The kinetic parameters such as apparent activation energy, pre-exponential factor, rate constant, and reaction constant were calculated for the reactions of corrosion. The inhibition effect is satisfactorily explained by both thermodynamic and kinetic parameters. Polarization curves show that tween-40 is a cathodic-type inhibitor in sulphuric acid. The results obtained from weight loss and potentiodynamic polarization are in good agreement, and the tween-40 inhibition action could also be evidenced by surface AFM images.

Keywords: Tween-40; Corrosion inhibitor; Cold rolled steel; AFM; Sulphuric acid; Adsorption

Spray pyrolysis deposition of YSZ and YSZ–Pt composite films by R. Todorovska; N. Petrova; D. Todorovsky (pp. 1266-1275).

In the present paper procedures are described for spray pyrolysis deposition of YSZ films (0.1–30μm in thickness) with 8 or 15mole% of YO_1.5 on different substrates. Aqueous or ethylene glycol solutions of Y–Zr-citrates were used as starting material and O₂ as carrier gas. The crystal structure and the morphology of the films were studied.The optimal deposition and post-deposition annealing conditions were defined, taking into account the desired film thickness and characteristics. Substrate temperatures of 250°C during the deposition followed by heating for 10min to 400°C after every spraying and to 590°C after every three sprayings with final annealing at 590°C for 2h in static air atmosphere were found to be suitable for the production of dense, uniform and cracks-free films.

Keywords: PACS; 81.15.-z; 81.15.Rs; 68.55.-a; 81.20.FwFilms; Citric complexes; Platinum; Spray pyrolysis; Yttria-stabilized zirconia

Craters formation in a graphite cathode produced by pulsed arc at low pressure by E. Restrepo; L.A. Garc�a; J.J. Castro; A. Devia (pp. 1276-1282).

DC pulsed arcs, between face to face opposite electrodes of graphite and stainless steel at pressures varying from 50 to 500Pa into nitrogen environment, with a current and voltage of 300A and 167V, respectively, and a pulsed arc time of 30ms were produced.Several consecutive craters, created by explosive way and by inclusions over the graphite cathode were found. These are located principally at the outskirts of the center and at the half of the graphite cathode radius; they are originated because of the cathode spots chaotic movement. The most representative craters have sizes over than 300μm and some melted sectors were observed by means of the SEM technique, corroborating that there are temperatures higher or equal than the melting point of the graphite. The film surface is composed by small spheres with structures similar to the ones in the cauliflower diamond. Craters in some melted sectors on the anode surface were observed.

Keywords: Cathode spot; Crater; Pulsed arcs; Graphite

Modulation of refractive index and thickness of poly(methyl methacrylate) thin films with UV irradiation and heat treatment by JianMing Yu; XiaoMing Tao; HwaYaw Tam; M. Suleyman Demokan (pp. 1283-1292).

This paper reports changes in refractive index and thickness of spin-coated poly(methyl methacrylate) (PMMA) thin films upon irradiation by a conventional high-pressure mercury UV lamp. Significant increase in refractive index and reduction in thickness are detected. Index modulations of greater than 0.01 are achieved in the thin films after 4min of irradiation. The thickness reduction of an irradiated PMMA film is consistent with its weight loss. This is caused by the escape of the volatile molecules generated during the irradiation process. A slight increase in the refractive index is also found in the film, heat-treated above its glass transition temperature (Tg). This thermal effect is detected in the UV irradiation process. We propose three possible aliphatic structures that are formed during the photochemical reaction and may exist in the main chain of irradiated PMMA after the irradiation. Their refractive indices in aggregate state are greater than that of PMMA based on an evaluation using the Lorentz–Lorenz equation. This is suggested to be an important reason for the refractive index increase in the UV-irradiated PMMA films. A UV-irradiated film, heat-treated above its Tg, has a rough surface with many tiny holes as illustrated by atomic force microscopy. These holes are attributed to the evaporation of the small molecules generated during the irradiation process.

Keywords: PACS; 78.66. Q; 78.20. CPMMA thin film; Refractive index; Thickness; UV lamp irradiation; Heat treatment

Pre-treatments applied to oxidized aluminum surfaces to modify the interfacial bonding with bis-1,2-(triethoxysilyl)ethane (BTSE) by M. Teo; J. Kim; P.C. Wong; K.C. Wong; K.A.R. Mitchell (pp. 1293-1304).

A remote microwave-generated H₂ plasma and heating to 250°C were separately used to modify high-purity oxidized aluminum surfaces and to assess whether these treatments can help enhance adhesion with bis-1,2-(triethoxysilyl)ethane (BTSE) coatings. Different initial oxide surfaces were considered, corresponding to the native oxide and to surfaces formed by the Forest Products Laboratory (FPL) treatment applied for either 15 or 60min. BTSE is applied from solution at pH 4, and competing processes of etching, protonation (to form OH groups) and coupling (to form AlOSi interfacial bonds) occur at the solid–liquid interface. Scanning electron microscopy (SEM) was used to determine how the topographies of the modified Al surfaces changed with the different pre-treatments and with exposure to a buffer solution of pH 4. Secondary-ion mass spectrometry (SIMS) was used to determine the direct amount of AlOSi interfacial bonds by measuring the ratio of peak intensities 71–70amu, while X-ray photoelectron spectroscopy (XPS) was used to determine the overall strength of the silane coating adhesion by measuring the Si 2p signals before and after application of an ultrasonic rinse to the coated sample. Measured Al 2p and O 1s spectra helped assess how the different pre-treatments modified the various Al oxidized surfaces prior to BTSE coating. Pre-treated samples that showed increased AlOSi bonding after BTSE coating corresponded to surfaces, which did not show evidence of significant etching after exposure to a pH 4 environment. This suggests that such surfaces are more receptive to the coupling reaction during exposure to the BTSE coating solution. These surfaces include all H₂ plasma-treated samples, the heated native oxide and the sample that only received the 15min FPL treatment. In contrast, other surfaces that show evidence of etching in pH 4 environments are samples that received lower amounts of AlOSi interfacial bonding. Overall, heating improved the BTSE adhesive bonding for the native Al oxide, while H₂ plasma treatment improved the BTSE bonding for surfaces that had initially been FPL-treated for 15 and 60min.

Keywords: PACS; 81.65.−bAluminum; Surface pre-treatment; Silane adsorption; SIMS; XPS

Pre-treatments applied to oxidized aluminum surfaces to modify the interfacial bonding with bis-1,2-(triethoxysilyl)ethane (BTSE) by J. Kim; M. Teo; P.C. Wong; K.C. Wong; K.A.R. Mitchell (pp. 1305-1312).

The methods of X-ray photoelectron spectroscopy (XPS), secondary-ion mass spectrometry (SIMS), and scanning electron microscopy (SEM) have been used to investigate aspects of the bonding of bis-1,2-(triethoxysilyl)ethane (BTSE) onto anodized samples of 7075-T6 aluminum alloy that have been subjected to the various pre-treatments considered in Part I. The oxide layer thins when this sample is subjected to a Forest Products Laboratory (FPL) treatment; topographical changes are detected by SEM after only 5min, and the “scallop structures�? increase in size for longer times of the FPL treatment. These 7075-Al surfaces adsorb more BTSE than the high-purity Al samples considered in Part I, although the interfacial bonding indicated by the [AlOSi]⁺/[Al₂O]⁺ SIMS ratios measured for the former samples are constant for different times of FPL treatment, unlike the situation for high-purity Al. Heating anodized 7075-Al samples, either before or after FPL treatment, has no significant effect on the subsequent BTSE adsorption, but a H₂ plasma treatment can enhance the interfacial Al–O–Si bonding with a decrease in the total BTSE polymerization.

Keywords: PACS; 81.65.−bAluminum; Surface pre-treatment; Silane adsorption; SIMS; XPS

Dry sliding wear behavior of TIG welding clad WC composite coatings by Soner Buytoz; Mustafa Ulutan; M. Mustafa Yildirim (pp. 1313-1323).

In this study, melted tungsten carbide powders on the surface of AISI 4340 steel was applied by using tungsten inert gas (TIG) method. It was observed that it has been solidified in different microstructures depending on the production parameters. As a result of microstructure examinations, in the surface modified layers an eutectic and dendrite solidification was observed together with WC, W₂C phases. In the layer produced, the hardness values varied between 950 and 1200HV. The minimum mass loss was observed in the sample, which was treated in 1.209mm/s production rate, 0.5g/s powder feed rate and 13.9kJ/cm heat input.

Keywords: TIG method; Surface modification; Abrasive wear; Dendrite; WC; M; ₇; C; ₃

Optimization of nickel adsorption from aqueous solution by using activated carbon prepared from waste apricot by chemical activation by S. Erdoğan; Y. Önal; C. Akmil-Başar; S. Bilmez-Erdemoğlu; Ç. Sarıcı-Özdemir; E. Köseoğlu; G. İçduygu (pp. 1324-1331).

Waste apricot supplied by Malatya apricot plant (Turkey) was activated by using chemical activation method and K₂CO₃ was chosen for this purpose. Activation temperature was varied over the temperature range of 400–900°C and N₂ atmosphere was used with 10°C/min heat rate. The maximum surface area (1214m²/g) and micropore volume (0.355cm³/g) were obtained at 900°C, but activated carbon was predominantly microporous at 700°C. The resulting activated carbons were used for removal of Ni(II) ions from aqueous solution and adsorption properties have been investigated under various conditions such as pH, activation temperature, adsorbent dosage and nickel concentration. Adsorption parameters were determined by using Langmuir model. Optimal condition was determined as; pH 5, 0.7g/10ml adsorbent dosage, 10mg/l Ni(II) concentration and 60min contact time. The results indicate that the effective uptake of Ni(II) ions was obtained by activating the carbon at 900°C.

Keywords: Activated carbon; Chemical activation; Waste apricot; Ni(II) adsorption; Langmuir

Enhancement of long-term stability of pentacene thin-film transistors encapsulated with transparent SnO₂ by Woo Jin Kim; Won Hoe Koo; Sung Jin Jo; Chang Su Kim; Hong Koo Baik; Jiyoul Lee; Seongil Im (pp. 1332-1338).

The long-term stability of pentacene thin-film transistors (TFTs) encapsulated with a transparent SnO₂ thin-film prepared by ion beam-assisted deposition (IBAD) was investigated. After encapsulation process, our organic thin-film transistors (OTFTs) showed somewhat degraded field-effect mobility of 0.5cm²/(Vs) that was initially 0.62cm²/(Vs), when a buffer layer of thermally evaporated 100nm SnO₂ film had been deposited prior to IBAD process. However, the mobility was surprisingly sustained up to 1 month and then gradually degraded down to 0.35cm²/(Vs) which was still three times higher than that of the OTFT without any encapsulation layer after 100 days in air ambient. The encapsulated OTFTs also exhibited superior on/off current ratio of over 10⁵ to that of the unprotected devices (∼10⁴) which was reduced from ∼10⁶ before aging. Therefore, the enhanced long-term stability of our encapsulated OTFTs should be attributed to well protection of permeation of H₂O and O₂ into the devices by the IBAD SnO₂ thin-film which could be used as an effective inorganic gas barrier for transparent organic electronic devices.

Keywords: OTFT; Ion beam-assisted deposition; Encapsulation; Lifetime; Pentacene

High-temperature oxidation of CrN/AlN multilayer coatings by U. Bardi; S.P. Chenakin; F. Ghezzi; C. Giolli; A. Goruppa; A. Lavacchi; E. Miorin; C. Pagura; A. Tolstogouzov (pp. 1339-1349).

Experiments are reported on sputter depth profiling of CrN/AlN multilayer abrasive coatings by secondary ion mass spectrometry (SIMS) coupled with sample current measurements (SCM). The coatings were deposited by a closed-field unbalanced magnetron sputtering. It is shown that after oxidation tests, performed in air at 900�C for 2h and at 1100�C for 4h, the layered structure begins to degrade but is not destroyed completely. Oxidation at 1100�C for 20h causes total destruction of the coatings that can be attributed to a fast diffusion of oxygen, nickel, manganese and other elements along defect paths (grain boundaries, dislocations, etc.) in the coating. There are practically no nitrides in the near-surface layer after such a treatment and all the metallic components are in the oxidized form as follows from the data obtained by X-ray photoelectron spectroscopy (XPS). According to XPS and mass-resolved ion scattering spectrometry (MARISS), the surface content of Al in the heat-treated coatings has decreased in comparison with the as-received sample and that of Cr increased. Both XPS and MARISS data exhibit real increase in superficial concentration of the substrate materials (Mn and Ni) that is controversial if using SIMS alone. SCM turned out to be an informative depth profiling method complementary to more expensive and complicated SIMS, being particularly useful for structures with different secondary electron emission properties of the layers. SCM with predetermined SIMS calibration allows a routine characterization of coatings and other multilayer structures, particularly, in situations where the expenses of analysis can be justified.

Keywords: PACS; 68.55.Nq; 82.80.MsDepth profiling; Mass-resolved ion scattering spectrometry (MARISS); Nitride multilayer coatings; Secondary ion mass spectrometry (SIMS); X-ray photoelectron spectroscopy (XPS); Unbalanced magnetron sputtering

The structure of n-alkane binary mixtures adsorbed on graphite by Philippe Espeau; John W. White; Robert J. Papoular (pp. 1350-1359).

The thermodynamics and structure of the surface adsorbed phase in binary C15–C16 and C15–C17 n-alkane mixtures confined in graphite pores have been studied by differential scanning calorimetry and small-angle X-ray scattering. The previously observed selective adsorption of the longer alkane for chain length differences greater than five carbon atoms is verified but reduced for chain length differences less than or equal to two. With a difference in chain length of one carbon atom, Vegard's law is followed for the melting points of the adsorbed mixture and the (02) d-spacing is a continuous function of the mole fraction x. With a two-carbon atom difference, samples aged for 1 week have a lamellar structure for which the entities A1−_xB_x try to be commensurate with the substrate. The same samples aged for 1 month show a continuous parabolic x-dependence for both the melting points and the d-spacings. An explanation in terms of selective probability of adsorption is proposed based on crystallographic considerations.

Keywords: PACS; 61.10. Eq; 61.43.Gt; 64.90.+b; 65.90.+i; 68.35.−pAlkanes; Graphite; Adsorbed phase; Binary mixtures; DSC; X-ray diffraction

Preparation of indium sulfide thin films by spray pyrolysis using a new precursor indium nitrate by Teny Theresa John; C. Sudha Kartha; K.P. Vijayakumar; T. Abe; Y. Kashiwaba (pp. 1360-1367).

Indium nitrate and thiourea were used as the precursor solutions for preparing indium sulfide thin films using Chemical Spray Pyrolysis (CSP) technique. Films having various In/S ratios were characterized using X-Ray Diffraction (XRD), Energy Dispersive X-ray Analysis (EDX), Scanning Electron Microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS), optical absorption, transmission and photosensitivity measurements. Sample having In/S ratio 2/3 showed better crystallinity with band gap 2.66eV. Depth profile of the sample also indicated the formation of indium sulfide. It was also observed that In/S ratio in the initial precursor solution determined the composition as well as electrical properties of the films. Maximum photosensitivity was observed for the sample prepared using solution having In/S ratio 2/4.

Keywords: PACS; 81.15.Rs; 82.45.MpIn; ₂; S; ₃; Indium nitrate; Chemical spray pyrolysis; In/S ratio

Measurement of particle velocity and characterization of deposition in aluminum alloy kinetic spraying process by Jingwei Wu; Hongyuan Fang; Sanghoon Yoon; HyungJun Kim; Changhee Lee (pp. 1368-1377).

Particle velocity is a very important parameter in kinetic spraying (or cold gas dynamic spraying). It is difficult to measure the velocity of a particle with supersonic speed at low temperature (lower than 500°C). Thus, in many investigations only estimated values are used for evaluating coating processes. In this paper, the modeling of particle acceleration was reviewed, and the measurement of in-flight particle velocity in a kinetic spraying process was performed. Particle velocity and flux distributions from different process gas temperatures and pressures were investigated. The influences of process gas temperature and pressure on particle velocity were discussed. Characteristic of Al–Si feedstock deposition onto a mild steel substrate was described by comparing coatings structures with the in-flight particle conditions. The deposition behavior showed two critical particle velocities for Al–Si powder deposition onto a substrate and for particle–particle bonding.

Keywords: PACS; 104570Kinetic spraying; Cold gas dynamic spraying; Particle velocity; Deposition; Critical velocity

The inhibitive effect of bipyrazolic derivatives on the corrosion of steel in hydrochloric acid solution by K. Tebbji; B. Hammouti; H. Oudda; A. Ramdani; M. Benkadour (pp. 1378-1385).

The effect of two pyrazole-type organic compounds, namely ethyl 5,5′-dimethyl-1′H-1,3′-bipyrazole-3 carboxylate (P1) and 3,5,5′-trimethyl-1′H-1,3′-bipyrazole (P2) on the corrosion behaviour of steel in 1M hydrochloric acid (HCl) solution is investigated at 308K by weight loss measurements, potentiodynamic polarisation and impedance spectroscopy (EIS) methods. The inhibition efficiencies obtained from cathodic Tafel plots, gravimetric and EIS methods are in good agreement. Results obtained show that the compound P2 is the best inhibitor and its efficiency reaches 84% at 10⁻³M. Potentiodynamic polarisation studies show that pyrazolic derivatives are cathodic-type inhibitors and these compounds act on the cathodic reaction without changing the mechanism of the hydrogen evolution reaction. The inhibition efficiency of P2 is temperature-dependent in the range from 308 to 353K and the associated activation energy has been determined. P2 adsorbs on the steel surface according to Langmuir adsorption model. The calculation of the total partial charge of inhibitor atoms is computed.

Keywords: Steel; Pyrazole; Inhibition; Corrosion; Hydrochloric acid

Three generations of inorganic phosphates in solvent and water-borne paints: A synergism case by G. Blustein; M.C. Dey�; R. Romagnoli; B. del Amo (pp. 1386-1397).

This research work is intended to compare the anti-corrosive properties of three generations of inorganic phosphate pigments in solvent-based paints and in water-borne ones, both of the epoxy type. The anti-corrosive properties of phosphate pigments were assessed by means of electrochemical techniques (corrosion potential measurements, polarisation tests, etc.), employing a steel electrode dipped into pigments suspensions. The behaviour of these pigments in anti-corrosive paints, formulated with different binders, have been studied by accelerated (salt spray cabinet and humidity chamber) and electrochemical tests (corrosion potential and ionic resistance measurements).Accelerated and electrochemical tests allowed to differentiate the anti-corrosive performance of the three phosphates studied in this research. These test are also able to detect and characterise possible synergism between the water-borne resin and the pigments.

Keywords: Corrosion protection; Steel passivation; Coatings; Phosphate pigments; Synergism; Protective layer

Comparison of CdS films deposited by different techniques: Effects on CdTe solar cell by Jaehyeong Lee (pp. 1398-1403).

Polycrystalline cadmium sulfide (CdS) thin-films were deposited on glass substrate by chemical bath deposition (CBD) and vacuum evaporation (VE) techniques. VE-CdS films consisted primarily of hexagonal phase, whereas CBD CdS films containing primarily the cubic form. VE-grown films were shown to have better crystallinity than CBD-grown films. The grain size of the CBD films is smaller than the ones of VE films. VE-CdS films exhibited relatively high transmittance in the above-gap region and band gap compared with CBD films. However, CdTe solar cells with these low quality CBD–CdS layers yield higher and more stable characteristics. Current–voltage–temperature measurements showed that the current transport for both cells was controlled by both tunneling and interface recombination but the cells with CBD–CdS displayed less tunneling.

Keywords: PACS; 84.60.J; 81.15; 81.15.ECadmium sulphide; Chemical bath deposition; Vacuum evaporation; Cadmium telluride; Solar cells

Enhanced mechanical properties and morphological characterizations of poly(vinyl alcohol)–carbon nanotube composite films by Wei Chen; Xiaoming Tao; Pu Xue; Xiaoyin Cheng (pp. 1404-1409).

Tensile tests were carried out on free-standing composite films of poly(vinyl alcohol) (PVA) and multiwall carbon nanotubes (MWNTs) for different loading levels. Results show that overall mechanical properties of the composite were greatly improved as compared to the neat PVA film. For PVA-based materials at significant high loading level such as 9.1wt.% MWNTs, considerable increases in Young's modulus, tensile strength and toughness by factors of 4.5, 2.7 and 4.1, respectively, were achieved. Raman, SEM, TEM, and DSC techniques were used to evaluate the PVA/MWNTs composite system. Strong acid-modification of the pristine MWNTs and the subsequent ultrasonication processing allowed good distribution of the nanotubes in the matrix. SEM together with DSC result shows apparent good wetting of the nanotubes by the PVA matrix, which are supportive of good interfacial bonding between the modified carbon nanotubes and the hosting polymer matrix.

Keywords: Poly(vinyl alcohol) (PVA); Multiwall carbon nanotube (MWNT); Composite films

Surface effect of natural zeolite (clinoptilolite) on the photocatalytic activity of TiO₂ by Fangfei Li; Yinshan Jiang; Lixin Yu; Zhengwen Yang; Tianyi Hou; Shenmei Sun (pp. 1410-1416).

The surface interaction between TiO₂ and natural zeolite, clinoptilolite, has been investigated by means of transmission electron microscope (TEM), atom force microscope (AFM), X-ray diffractometer (XRD), diffuse reflectance infrared Fourier transform (DRIFT) and far Fourier transform infrared ray (FTIR) spectroscopy. And the photocatalytic degradation (PCD) rate of methyl orange (MO), a model of recalcitrant azo dye, in aqueous system has been measured to compare the photocatalytic activities of different photocatalysts. A model has been carried out to explain the incorporation between TiO₂ particles and natural zeolite. The results show that the TiO₂ particles loaded on zeolite are 50nm or so, smaller than the pure one, and combine with zeolite via chemical force. Since the reserved adsorption ability and the existence of electron trapper, the TiO₂–zeolite performed more efficient at low initial concentration and in the later period of PCD process, as compared with pure TiO₂ nanopowders.

Keywords: TiO; ₂; Natural zeolite; Clinoptilolite; TiO; ₂; –zeolite; PCD

XPS analysis of down stream plasma treated wool: Influence of the nature of the gas on the surface modification of wool by R. Molina; J.P. Espin�s; F. Yubero; P. Erra; A.R. Gonz�lez-Elipe (pp. 1417-1429).

A microwave plasma treatment in a down stream configuration was used to modify the natural hydrophobocity of untreated wool fibers. This property is a consequence of the presence of a Fatty acid monolayer (F-layer) on the outermost part of the fiber surface. The wool fibers treated with plasma were analyzed by means of X-ray photoelectron spectroscopy (XPS) without previous exposure to the air. Experiments have been carried out with air, water vapor, oxygen and nitrogen as plasma gas. The “in situ�? analysis of the treated samples has permitted to differentiate between the plasma effects and those other linked to the exposure of the fibers to the air after their treatment. The results have evidenced the effects induced by the different active species generated by plasma from the different components of the air. In general, the intensity of CC peaks decreases and that of the CO, CO and OCO increases when using a gas containing oxygen species. Simultaneously, the intensity of the SS groups decreases and that of the sulphonate (SO₃⁻) increases. Other changes are also detected in the intensity of the N 1s level. The extent and characteristics of the oxidation and functionalisation of the hydrocarbon chains of the F-layer depend on the nature of gas. Thus, whereas treatments with plasmas of air and water vapor strongly affect the hydrocarbon chains of the F-layer, oxygen is less effective in the oxidation process. It has been also noted that the active species formed in the nitrogen plasma do not induce any significant change in the surface composition of the wool fibers.

Keywords: Plasma; Down stream plasma; Remote plasma; Wool; Fatty acid monolayer; XPS; Polymer; Surface functionalisation; Surface etching

Effect of substrate temperature on the growth of ITO thin films by M. Nisha; S. Anusha; Aldrin Antony; R. Manoj; M.K. Jayaraj (pp. 1430-1435).

Indium tin oxide (ITO) thin films were deposited onto glass substrates by rf magnetron sputtering of ITO target and the influence of substrate temperature on the properties of the films were investigated. The structural characteristics showed a dependence on the oxygen partial pressure during sputtering. Oxygen deficient films showed (400) plane texturing while oxygen-incorporated films were preferentially oriented in the [111] direction. ITO films with low resistivity of 2.05×10⁻³Ωcm were deposited at relatively low substrate temperature (150°C) which shows highest figure of merit of 2.84×10⁻³square/Ω⋅

Keywords: PACS; 81.40.−z; 78.66.−w; 81.40.EfTransparent conducting oxides; Indium tin oxide; Rf magnetron sputtering

Morphology development and oriented growth of single crystalline ZnO nanorod by Lili Wu; Youshi Wu; Wei L�; Huiying Wei; Yuanchang Shi (pp. 1436-1441).

Single crystalline ZnO nanorods were achieved by the assembly of nanocrystallines in tens of nanometer under hydrothermal conditions with the assistance of surfactant cetyltrimethylammonium bromide (CTAB). The obtained nanorod has rough surface as a result of oriented attachment growth. Transmission electron microscope (TEM) images showed the morphology evolution of the nanorod at different reaction time. Defects were observed and porous structure was left after the assembly of hundreds of nanocrystalline building blocks. Effect of pH condition on the morphology of the nanorod was also investigated.

Keywords: PACS; 68.65ZnO; Nanorod; Hydrothermal method; Oriented attachment

Effect of microstructure of MgO buffer layer on BaTiO₃ grown on silicon substrates by Xianhua Wei; Yanrong Li; Jun Zhu; Zhu Liang; Ying Zhang; Wen Huang; Shuwen Jiang (pp. 1442-1448).

MgO ultrathin films were grown on Si(100) substrates as buffer layers for the growth of ferroelectric BaTiO₃ thin films by laser molecular beam epitaxy (L-MBE). The deposition process of MgO buffer layers grown on silicon was in situ monitored by reflection high-energy electron diffraction (RHEED). The structure of BaTiO₃ films fabricated on MgO buffers was investigated by X-ray diffraction. Biaxially textured MgO was obtained at high laser energy density, but when the laser energy was lowered, MgO buffer was transformed to the form of texture with angular dispersion with the increase of the film thickness. BaTiO₃ films grown on the former buffer were completely (001) textured, while those on the latter were (001) preferred orientated. Furthermore, the fabricated MgO buffers and BaTiO₃ films had atomically smooth surface and interface. All these can reveal that the quality of textured MgO buffer is a key factor for the growth of BaTiO₃ films on silicon.

Keywords: PACS; 61.14.Hg; 68.55.Jk; 77.84.Bw; 81.15.FgBaTiO; ₃; thin film; Buffer layer; Texture; RHEED

Lime-pastes with different kneading water: Pore structure and capillary porosity by M. Arandigoyen; J.L. P�rez Bernal; M.A. Bello L�pez; J.I. Alvarez (pp. 1449-1459).

Lime-mortars to be used in restoration works of Cultural Heritage are being more and more studied. The knowledge on the lime-pastes allows understanding the behaviour of the binder fraction. The aim of this work is to study the influence of the kneading water on two critical aspects of the lime-pastes: pore structure and capillary porosity, because both of them are related to the service life of the material, particularly with the moisture transport. Mercury intrusion porosimetry has been performed to establish the pore size distribution: one pore range has been checked in the different pastes tested, setting linear relationships between the pore diameter and the water/lime ratio.Fractal geometry has been used from the MIP results in order to evaluate the pore surface complexity, as a function of the kneading water. From the results, it can be concluded that kneading water is only responsible for a swelling of the structure, but it does not change the pore surface (keeping constant the surface fractal dimension). DIA analysis has been carried out, confirming the previous results. Finally, the correlation obtained between the capillary coefficient and the water/lime ratio confirms the postulated pore structure for the different amount of kneading water in lime-pastes.

Keywords: PACS; 81.05.Rm; 68.35.FxLime-pastes; Porosimetry; Fractal geometry; Capillary; Kneading water; Microstructure

Crystallization kinetics of amorphous SiC films: Influence of substrate by H. Schmidt; E.R. Fotsing; G. Borchardt; R. Chassagnon; S. Chevalier; M. Bruns (pp. 1460-1470).

The crystallization kinetics of amorphous silicon carbide films was studied by means of X-ray diffractometry (XRD) and transmission electron microscopy (TEM). The films were deposited by radio frequency (r.f.) magnetron sputtering on glassy carbon and single crystalline silicon substrates, respectively. TEM micrographs and XRD patterns show the formation of nano-crystalline β-SiC with crystallite sizes in the order of 50nm during annealing at temperatures between 1200 and 1600°C. A modified Johnson–Mehl–Avrami–Kolmogorov (JMAK) formalism was used to describe the isothermal transformation of amorphous SiC into β-SiC as an interface controlled, three-dimensional growth processes from pre-existing small crystallites in the order of 10nm. These pre-existing crystallites are formed in a transient process in the early stages of crystallization. For films deposited on the silicon substrate, the obtained rate constants of crystallite growth obey an Arrhenius behavior with an activation enthalpy of 4.1±0.5eV in accordance with literature data. Films deposited on glassy carbon show an increased stability of amorphous SiC films, which is reflected in smaller rate constants of crystallite growth of several orders of magnitude at low temperatures and a higher activation enthalpy of 8.9±0.9eV. A model is proposed, where the faster crystallization of films on silicon substrates can be explained with the presence of superabundant point defects, which diffuse from the substrate into the film and accelerate the incorporation of atoms from the amorphous into the crystalline phase.

Keywords: PACS; 61.43.−jCrystallization kinetics; Silicon carbide; Amorphous films; Sputter deposition

Carbon nanotube synthesis on oxidized porous silicon by K. Kord�s; A.E. Pap; J. V�h�kangas; A. Uusim�ki; S. Lepp�vuori (pp. 1471-1475).

Carbon nanotubes were grown on thermally oxidized porous silicon by catalytic chemical vapor deposition from the mixture of ferrocene and xylene precursor. The growth rate of carbon nanotubes showed dependence on the oxidation extent of porous silicon. On pristine porous silicon surfaces, only poor nanotube growth was observed, whilst samples oxidized in air at 200, 400, 600 and 800°C prior to the deposition process proved to be suitable substrates for carbon nanotube synthesis. Networks of carbon tubes with diameter of ∼40 and ∼10nm observed on the surfaces of samples were investigated by electron microscopy and by energy dispersive X-ray analysis.

Keywords: PACS; 61.46.+w (structure of nanoscale materials: clusters, nanoparticles, nanotubes, and nanocrystals); 66.30.−h (diffusion in solids); 68.55.−a (thin film structure and morphology); 81.05.Rm (porous materials; granular materials: fabrication; treatment; testing and analysis); 81.07.De (nanotubes: fabrication and characterization); 82.33.Hk (chemical reactions on clusters)Catalytic chemical vapor deposition; Carbon nanotubes; Porous silicon

Formation of Ge self-assembled quantum dots on a Si_xGe1−_x buffer layer by Hyungjun Kim; Chansun Shin; Joonyeon Chang (pp. 1476-1480).

Ge self-assembled quantum dots (SAQDs) grown on a relaxed Si_0.75Ge_0.25 buffer layer were observed using an atomic force microscopy (AFM) and a transmission electron microscopy (TEM). The effect of buried misfit dislocations on the formation and the distribution of Ge SAQDs was extensively investigated. The Burgers vector determination of each buried dislocation using theg�b=0 invisibility criterion with plane-view TEM micrographs shows that Ge SAQDs grow at specific positions related to the Burgers vectors of buried dislocations. The measurement of the lateral distance between a SAQD and the corresponding misfit dislocation with plane-view and cross-sectional TEM images reveals that SAQDs form at the intersections of the top surface with the slip planes of misfit dislocations. The stress field on the top surface due to misfit dislocations is computed, and it is found that the strain energy of the misfit dislocations provides the preferential formation sites for Ge SAQDs nucleation.

Keywords: PACS; 85.30.V; 81.15.H; 61.16.BGe self-assembled quantum dots; Molecular beam epitaxy (MBE); Transmission electron microscopy (TEM)

Characterization of LaMnAl₁₁O₁₉ by FT-IR spectroscopy of adsorbed NO and NO/O₂ by M. Kantcheva; A. Agiral; O. Samarskaya; M. Stranzenbach; B. Saruhan (pp. 1481-1491).

The nature of the NO_x species produced during the adsorption of NO at room temperature and during its coadsorption with oxygen on LaMnAl₁₁O₁₉ sample with magnetoplumbite structure obtained by a sol–gel process has been investigated by means of in situ FT-IR spectroscopy. The adsorption of NO leads to formation of anionic nitrosyls and/or cis-hyponitrite ions and reveals the presence of coordinatively unsaturated Mn³⁺ ions. Upon NO/O₂ adsorption at room temperature various nitro–nitrato structures are observed. The nitro–nitrato species produced with the participation of electrophilic oxygen species decompose at 350°C directly to N₂ and O₂. No NO decomposition is observed in absence of molecular oxygen. The adsorbed nitro–nitrato species are inert towards the interaction with methane and block the active sites (Mn³⁺ ions) for its oxidation. Noticeable oxidation of the methane on theNOx−-precovered sample is observed at temperatures higher than 350°C due to the liberation of the active sites as a result of decomposition of the surface nitro–nitrato species. Mechanism explaining the promoting effect of the molecular oxygen in the NO decomposition is proposed.

Keywords: PACS; 81.05.Je; 81.20.Fw; 82.45.In; 82.65.+rLaMnAl; ₁₁; O; ₁₉; Sol–gel synthesis; In situ FT-IR spectroscopy; Adsorption of NO and NO/O; ₂; Reactivity of stable NO; _x; species; NO decomposition

Femtosecond pulsed laser-induced periodic surface structures on GaN/sapphire by X.C. Wang; G.C. Lim; F.L. Ng; W. Liu; S.J. Chua (pp. 1492-1497).

Femtosecond pulsed laser-induced periodic surface structure on GaN/sapphire is reported in this paper. It was found that the period of the laser-induced ripples was much dependent on the incident laser fluence. Through finely adjusting laser fluence and pulse number, uniform ripples could be formed on the sapphire surface. We attributed the formation of such periodic two-dimensional structures to optical interference of the incident laser light with scattered waves from a surface disturbance. Also, it was found that the GaN capping layer played a very important role in forming the periodic structures on the sapphire surface.

Keywords: PACS; 79.20.DsFemtosecond pulsed laser; Ripple formation; GaN/sapphire; Laser fluence; Period

Nano-porous manganese oxide formed by self-assembled agglomeration of nanocrystallites by Nobuyasu Suzuki; Hidehiro Sasaki; Yasunori Morinaga; Yuka Yamada (pp. 1498-1501).

We synthesized specific nano-porous dendritic structures similar to cedar leaves of manganese oxides using pulsed laser ablation (PLA) process, with the potential for use as highly active nano-catalysts. The nano-porous structures were formed by self-assembled agglomeration of nanocrystallites without templates. Furthermore, the dendritic nano-porous manganese oxide as an electrocatalyst showed a significant decrease in overpotential on oxygen reduction in alkaline electrolyte.

Keywords: Pulsed laser ablation; Nano-porous structure; Manganese oxide; Electrocatalyst

Studies on sprayed lanthanum sulphide (La₂S₃) thin films from non-aqueous medium by G.D. Bagde; H.M. Pathan; C.D. Lokhande; S.A. Patil; M. Muller (pp. 1502-1509).

Thin films of lanthanum sulphide (La₂S₃) have been deposited onto glass substrates by spray pyrolysis technique from non-aqueous (methanol) medium. The structural, morphological, optical, dielectric, electric and thermoemf properties were studied. The films were polycrystalline with an irregular shaped particles present over the porous structure within a fibrous network structure. The optical band gap was estimated to be 2.50eV. The dielectric properties were measured in the range 100Hz–1MHz. The electrical resistivity was of the order of 10⁴ to 10⁵Ωcm. Thermoemf study revealed that the La₂S₃ films exhibit p-type electrical conductivity.

Keywords: Spray pyrolysis; X-ray diffraction; Dielectric properties; Scanning electron microscopy; Rutherford back scattering

Characterisation of passive films formed on low carbon steel in borate buffer solution (pH 9.2) by electrochemical impedance spectroscopy by L. Hamadou; A. Kadri; N. Benbrahim (pp. 1510-1519).

The comprehension of passivity and its protective character against corrosion is closely connected with the electronic properties of passive films. Passive films formed anodically on carbon steel in borate/boric acid solution, pH 9.2, have been characterised by electrochemical impedance spectroscopy (EIS). Mott–Schottky plots and impedance measurements were made on films formed at different potentials and times. The investigation allowed the determination of the semiconductive properties of the films. The results of the capacitance response indicate that the passive films behave like highly doped n-type semiconductors, showing that the passive film properties are dominated by iron. The value of donors density ( N_D) for the passive film is of the order of 10²¹cm⁻³ and decreases with increasing formation time and potential, indicating that defects decrease with increasing film thickness. Based on the information about the physical phenomena, an equivalent circuit is proposed to fit the experimental data, leading to determination of anodic film capacitance and film resistance.

Keywords: Electrochemical impedance spectroscopy; Mott–Schottky plot; Carbon steel; Anodic passive film; Semiconductor; Capacitance

Optical multilayer post growth instabilities: Analyses of Gd₂O₃/SiO₂ system in combination with scanning probe force spectroscopy by N.K. Sahoo; S. Thakur; M. Senthilkumar (pp. 1520-1537).

Post growth multilayer instabilities of a certain periodic Gd₂O₃/SiO₂ multilayer systems have been investigated using scanning probe force–distance spectroscopy and optical spectrophotometric techniques. In the present work, we have noticed a strong correlation between the force spectroscopic results and the spectral properties of multilayer thin films, although measurement techniques and operating principles are quite different. From the experimental analysis, it was quite evident that the instability process, which starts during the nucleation and growth stage in thin films, continues to persist at a much longer time scale under post growth conditions. During this study it has been noticed that the elastic properties of the constituent thin films, the layer geometry and the bilayer thickness have strong correlation in trickling the multilayer instabilities. Such aspects also have strong interconnections with the morphological and viscoelastic changes. It is also noticed that most of the instabilities results cannot only be explained through elastic nature of the material alone. Instead, total number of layers, the layer structures, morphological changes, corresponding stiffness and the adhesion properties of the multilayer contribute substantially to these phenomena.

Keywords: PACS; 42.79.Wc; 78.66.-w; 78.20.Ci; 61.16.Ch; 51.70.+f; 52.70.KzDeep UV optical coatings; Multilayer instability; Force–distance spectroscopy; Spectrophotometry

Pulsed laser deposition and its current research status in preparing hydroxyapatite thin films by Quanhe Bao; Chuanzhong Chen; Diangang Wang; Qianmao Ji; Tingquan Lei (pp. 1538-1544).

Pulsed laser deposition (PLD) is a conceptually and experimentally simple yet highly versatile tool for thin films and multi-layer film research. The mechanisms, advantages and disadvantages of pulsed laser deposition were reviewed. The process and some methods to resolve the drawbacks of PLD were discussed. Pulsed laser deposition of hydroxyapatite thin films was reviewed. Simple adjustment of PLD parameters can deposit hydroxyapatite in situ in crystalline form, amorphous films or HA with other calcium phosphate phases. Compared with plasma sprayed HA coatings the pulsed laser deposition HA thin films have higher coating/substrate adhesion and have minor undesirable phases under optimal conditions. Finally, we suggested some new researches should be done.

Keywords: Pulsed laser deposition; Mechanism; Hydroxyapatite; Thin films

Ultra-hard ceramic coatings fabricated through microarc oxidation on aluminium alloy by Hanhua Wu; Jianbo Wang; Beiyu Long; Beihong Long; Zengsun Jin; Wang Naidan; Fengrong Yu; Dongmei Bi (pp. 1545-1552).

Ultra-hard ceramic coatings with microhardness of 2535Hv have been synthesized on the Al alloy substrate by microarc oxidation (MAO) technique. The effects of anodic current density ( j_a) and the ratio of cathodic to anodic current density ( j_c/ j_a) on the mechanical and corrosion resistance properties of MAO coatings have been studied by microhardness and pitting corrosion tests, respectively. In addition, the phase composition and microstructure of the coatings were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The results show that the coatings prepared at high anodic current density consist mainly of α-Al₂O₃, while those fabricated at low anodic current density are almost composed of γ-Al₂O₃. Microhardness test shows that the coatings have high microhardness, and the highest one is found in the coating formed at j_a=15A/dm² and j_c/ j_a=0.7. Pitting corrosion test shows that the structure of coatings is strongly influenced by the varying j_c/ j_a.

Keywords: Microhardness; Current density; Chemical synthesis; Pitting corrosion

Properties of physisorbed water layers on gold revealed in a FEM study by J. Plšek; P. Hrubý; K. Nikiforov; Z. Knor (pp. 1553-1560).

Field emission study of thin water layers was performed to examine their properties and their changes after application of a high electric field. Comparison of field emission characteristics of water layers adsorbed on clean tungsten and gold-covered tungsten suggested that, whereas water molecules adsorbed on tungsten are oriented by oxygen atoms towards the metal surface, water layer on gold-covered tungsten has amorphous character with no preferential orientation. Both heated and non-heated layers are heavily influenced by applied high electric field strengths ( F ≈30MV/cm). Decrease of the work function and of the voltage needed for a constant emission current during successive increase of the electric field was tentatively interpreted in terms of chemical and morfological changes of the water layer due to the field dissociation and solvation.

Keywords: PACS; 79.70; 73.30; 79.60.DpWater adsorption; Work function; Field emission microscopy

Influence of substrate temperature and post-treatment on the properties of ZnO:Al thin films prepared by pulsed laser deposition by Xin Chen; Wenjie Guan; Guojia Fang; X.Z. Zhao (pp. 1561-1567).

Highly transparent conductive Al₂O₃ doped zinc oxide (AZO) thin films have been deposited on the glass substrate by pulsed laser deposition technique. The effects of substrate temperature and post-deposition annealing treatment on structural, electrical and optical properties of AZO thin films were investigated. The experimental results show that the electrical resistivity of films deposited at 240°C is 6.1×10⁻⁴Ωcm, which can be further reduced to as low as 4.7×10⁻⁴Ωcm by post-deposition annealing at 400°C for 2h in argon. The average transmission of AZO films in the visible range is 90%. The optical direct band gap of films was dependent on the substrate temperature and the annealing treatment in argon. The optical direct band gap value of AZO films increased with increasing annealing temperature.

Keywords: AZO films; Substrate temperature; Post-deposition annealing; Pulsed laser deposition

Annealing induced microstructural evolution of electrodeposited electrochromic tungsten oxide films by M. Deepa; A.K. Srivastava; T.K. Saxena; S.A. Agnihotry (pp. 1568-1580).

A significant influence of microstructure on the electrochromic and electrochemical performance characteristics of tungsten oxide (WO₃) films potentiostatically electrodeposited from a peroxopolytungstic acid (PPTA) sol has been evaluated as a function of annealing temperature. Powerful probes like X-ray diffractometry (XRD), transmission electron microscopy (TEM), UV–vis spectrophotometry, multiple step chronoamperometry and cyclic voltammetry have been employed for the thin film characterization. The as-deposited and the film annealed at 60°C are composed of nanosized grains with a dominant amorphous phase, as well as open structure which ensues from a nanoporous matrix. This ensures a greater number of electroactive sites and a higher reaction area thereby manifesting in electrochromic responses superior to that of the films annealed at higher temperatures. The films annealed at temperatures ≥250°C are characterized by a prominent triclinic crystalline structure and a hexagonal phase co-exists at temperatures ≥400°C. The deleterious effect on the electrochromic properties of the film with annealing is ascribed to the loss of porosity, densification and the increasing crystallinity and grain size. Amongst all films under investigation, the film annealed at 60°C exhibits a high transmission modulation (Δ T ∼ 68%) and coloration efficiency ( η ∼ 77.6cm²C⁻¹) at λ=632.8nm, charge storage capacity ( Q_ins ∼ 21mCcm⁻²), diffusion coefficient (6.08×10⁻¹⁰cm²s⁻¹), fast color-bleach kinetics ( t_c ∼ 275s and t_b ∼ 12.5s) and good electrochemical activity, as well as reversibility for the lithium insertion–extraction process upon cycling. The remarkable potential, which the film annealed at 60°C has, for practical “smart window�? applications has been demonstrated.

Keywords: PACS; 81.15.Pq; 81.70.Fy; 82.45.Mp; 68.37.-dElectrochromic; Electrochemical; Transmission electron microscopy (TEM); Peroxopolytungstic acid (PPTA); Nanoporous

Short-time plasma surface modification of HDPE powder in a Plasma Downer Reactor – process, wettability improvement and ageing effects by C. Arpagaus; A. Rossi; Ph. Rudolf von Rohr (pp. 1581-1595).

The effectiveness of improving the wettability of HDPE powders within less than 0.1s by plasma surface modification in a Plasma Downer Reactor is investigated. A correlation is revealed between the XPS results (O/C-ratio) and the wettability (contact angle, polar surface tension by capillary rise method). The O₂-content in the plasma feed gas has been adjusted for best wettability properties. XPS results indicate the formation of CO and COOH functional groups on the powder surface. The O/C-ratio increased from 0.0 (no oxygen on the non-treated powder) up to 0.15 for the plasma treated HDPE powder surface. With pure O₂-plasma treatment, a water contact angle reduction from >90� (no water penetration into the untreated PE powder) down to 65� was achieved. The total surface free energy increased from 31.2 to 45mN/m. Ageing of treated powders occurs and proceeds mostly within the first 7 days of storage. Contact angle measurements and O1s/O2s intensity ratio data support that ageing is mainly a diffusion-controlled process. Nevertheless, XPS results show the presence of oxygen functional groups even after 40 days, which explains why the powder is still dispersible in water without any addition of surfactants.

Keywords: PACS; 52.77.−j; 81.05.Lg; 81.65.−b; 79.60.Fr; 68.08.BcRadio frequency (RF) plasma; Surface modification; Polyethylene powder; Wettability; Contact angle measurement; X-ray photoelectron spectroscopy

Electrochemical, SEM/EDS and quantum chemical study of phthalocyanines as corrosion inhibitors for mild steel in 1mol/l HCl by Peng Zhao; Qiang Liang; Yan Li (pp. 1596-1607).

The inhibition effect of metal-free phthalocyanine (H₂Pc), copper phthalocyanine (CuPc) and copper phthalocyanine tetrasulfuric tetrasodium salt (CuPc·S₄·Na₄) on mild steel in 1mol/l HCl in the concentration range of 1.0×10⁻⁵ to 1.0×10⁻³mol/l was investigated by electrochemical test, scanning electron microscope with energy dispersive spectrometer (SEM/EDS) and quantum chemical method. The potentiodynamic polarization curves of mild steel in hydrochloric acid containing these compounds showed both cathodic and anodic processes of steel corrosion were suppressed, and the Nyquist plots of impedance expressed mainly as a capacitive loop with different compounds and concentrations. For all these phthalocyanines, the inhibition efficiency increased with the increase in inhibitor concentration, while the inhibition efficiencies for these three phthalocyanines with the same concentration decreased in the order of CuPc·S₄·Na₄>CuPc>H₂Pc according to the electrochemical measurement results. The SEM/EDS analysis indicated that there are more lightly corroded and oxidative steel surface for the specimens after immersion in acid solution containing 1.0×10⁻³mol/l phthalocyanines than that in blank. The quantum chemical calculation results showed that the inhibition efficiency of these phthalocyanines increased with decrease in molecule's LUMO energy, which was different from the micro-cyclic compounds.

Keywords: Phthalocyanine compounds; Acid inhibitor; Electrochemical measurement; SEM/EDS; Quantum chemistry

Characterization of microroughness parameters in gadolinium oxide thin films: A study based on extended power spectral density analyses by M. Senthilkumar; N.K. Sahoo; S. Thakur; R.B. Tokas (pp. 1608-1619).

Spectral microroughness is a performance-limiting factor for optical thin films like Gd₂O₃, which have dedicative applications in ultraviolet or deep ultraviolet region of the electromagnetic spectrum. Such a morphological parameter of a thin film surface can be very well characterized by power spectral density (PSD) functions. The PSD provides a more reliable description to the topography than the RMS roughness and imparts several useful information of the surface including fractal and superstructure contributions. Through the present study it has been noticed that deposition parameters like evaporation rate and oxygen pressure can play very definite, dominant and predictable roles in the evolution of fractal and superstructures in thin film topographies recorded through atomic force microscopy (AFM). In this work, the PSD functions derived from morphologies of various gadolinia thin films have been fitted with a novel multi peak-shifting Gaussian model along with fractal and k-correlation functions, to extract characteristic parameters of the precision surfaces. Using such information, roughness contributions of the fractal components (substrate dominated), pure film and the aggregates have been successfully extracted. Higher spectral fractal strengths have depicted lower refractive index values. The microroughness and grain sizes of the pure film have been influenced very differently with deposition rate and oxygen pressure. The oxygen pressure strongly influenced the grain sizes where as the deposition rate influenced the microroughness of the gadolinia films.

Keywords: PACS; 42.79W; 68.35.C; 61.16C; 81.15EReactive electron beam evaporation; Surface microroughness; Power spectral density

Development and evaluation of electroless Ag-PTFE composite coatings with anti-microbial and anti-corrosion properties by Q. Zhao; Y. Liu; C. Wang (pp. 1620-1627).

Electroless Ag-polytetrafluoroethylene (PTFE) composite coatings were prepared on stainless steel sheets. The existence and distribution of PTFE in the coatings were analysed with an energy dispersive X-ray microanalysis (EDX). The contact angle values and surface energies of the Ag-PTFE coatings, silver coating, stainless steel, titanium and E. coli Rosetta were measured. The experimental results showed that stainless steel surfaces coated with Ag-PTFE reduced E. coli attachment by 94–98%, compared with silver coating, stainless steel or titanium surfaces. The anti-bacterial mechanism of the Ag-PTFE composite coatings was explained with the extended Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. The anticorrosion properties of the Ag-PTFE composite coatings in 0.9% NaCl solution were studied. The results showed that the corrosion resistance of the Ag-PTFE composite coatings was superior to that of stainless steel 316L.

Keywords: Electroless deposition; Composite coating; Ag-PTFE; Adhesion; Corrosion

Magnetic and spectroscopic characteristics of ZnMnO system by A.K. Pradhan; D. Hunter; Kai Zhang; J.B. Dadson; S. Mohanty; T.M. Williams; K. Lord; R.R. Rakhimov; U.N. Roy; Y. Cui; A. Burger; Jun Zhang; D.J. Sellmyer (pp. 1628-1633).

We report on the observation of room-temperature ferromagnetism in epitaxial (Zn,Mn)O films grown by a pulsed-laser deposition technique using high-density targets. The X-ray, microscopic, spectroscopic and magnetic properties of target material containing 6at.% of Mn and films were compared. The target shows the presence of large clusters exhibiting paramagnetic behavior. However, ferromagnetic properties were observed in (Zn,Mn)O films grown at a substrate temperature of 500�C and with an oxygen partial pressure of 1mTorr. Although, crystalline quality of the film improves with increasing substrate temperature, the ferromagnetism becomes weaker.

Keywords: PACS; 81.05.Ea; 75.60.−d; 76.30.−v; 76.50.+g

Corrosion inhibition of iron in acidic solutions by alkyl quaternary ammonium halides: Correlation between inhibition efficiency and molecular structure by Lin Niu; Hu Zhang; Fenghua Wei; Suxiang Wu; Xiaoli Cao; Pengpeng Liu (pp. 1634-1642).

The corrosion inhibition of iron in 0.5M H₂SO₄ solutions by alkyl quaternary ammonium halides (AQAH) inhibitors has been studied by potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) measurements. The correlation between inhibition efficiency and molecular structure of the AQAH compounds is investigated. The results show that besides the concentration, the structure of alkyl groups and the type of halide ions of these AQAH inhibitors greatly influence the inhibition efficiency. Data obtained from EIS measurements are analyzed to model the corrosion inhibition process through appropriate equivalent circuit models.

Keywords: PACS; 81.65.K; 75.50.BCorrosion inhibition; Polarization curves; Electrochemical impedance spectroscopy; Alkyl quaternary ammonium halides

Structural, electrical and optical properties of TiO₂ doped WO₃ thin films by P.S. Patil; S.H. Mujawar; A.I. Inamdar; P.S. Shinde; H.P. Deshmukh; S.B. Sadale (pp. 1643-1650).

TiO₂ doped WO₃ thin films were deposited onto glass substrates and fluorine doped tin oxide (FTO) coated conducting glass substrates, maintained at 500°C by pyrolytic decomposition of adequate precursor solution. Equimolar ammonium tungstate ((NH₄)₂WO₄) and titanyl acetyl acetonate (TiAcAc) solutions were mixed together at pH 9 in volume proportions and used as a precursor solution for the deposition of TiO₂ doped WO₃ thin films. Doping concentrations were varied between 4 and 38%. The effect of TiO₂ doping concentration on structural, electrical and optical properties of TiO₂ doped WO₃ thin films were studied. Values of room temperature electrical resistivity, thermoelectric power and band gap energy ( E_g) were estimated. The films with 38% TiO₂ doping in WO₃ exhibited lowest resistivity, n-type electrical conductivity and improved electrochromic performance among all the samples. The values of thermoelectric power (TEP) were in the range of 23–56μV/K and the direct band gap energy varied between 2.72 and 2.86eV.

Keywords: Spray pyrolysis technique; TiO; ₂; doped WO; ₃; thin films; Optical; Electrical and structural properties; Electrochromism

XPS study of the phase transition in pure zirconium oxide nanocrystallites by S. Tsunekawa; K. Asami; S. Ito; M. Yashima; T. Sugimoto (pp. 1651-1656).

Pure zirconium oxide nanocrystallites with diameters 6–140nm are fabricated from ultrafine metallo-organic complexes by thermal hydrolysis at 120°C and/or heat treatment at 125–1025°C. X-ray photoelectron spectroscopy shows that effective ionic valence of Zr decreases with decreasing particle diameter. The size dependence of the ionic valences suggests that the phase transition from cubic to tetragonal occurs at an effective Zr valence of 2.0 near 3nm in diameter and that the phase transition from tetragonal to monoclinic takes place at a critical size of 25nm diameter with an effective Zr valence of about 2.6.

Keywords: PACS; 61.66.Fn; 64.70.Nd; 79.60.−i; 81.07.BcZirconium oxide; Nanocrystallite; Gel–sol method; Ionic valence; Phase transition; Critical size; Oxygen deficiency

Corrosion behaviour of steel in concentrated phosphoric acid solutions by M. Benabdellah; B. Hammouti (pp. 1657-1661).

The corrosion rates of steel in concentrated phosphoric acid (1.0–11.0M) were determined by the weight loss method, at three temperatures 298, 308 and 323K. Results obtained show that corrosion rate increases with both acid concentration and temperature. The logarithm of corrosion rate was fitted against the acid concentration, values of Hammett H_o and Strehlow R_o( H) functions. The activation energies, enthalpies and entropies of the dissolution process were determined.

Keywords: Steel; Phosphoric acid; Corrosion; Hammett function; Strehlow function; Activation thermodynamic characterisation

Analysis and self-lubricating treatment of porous anodic alumina film formed in a compound solution by Hui Wang; Hongzhan Yi; Haowei Wang (pp. 1662-1667).

A porous anodic film on aluminum was prepared in a mixed electrolyte of phosphoric acid and organic acid and cerium salt, and ultrasonic impregnation technology was applied on it to form self-lubricating surface composite. The structure and chemical composition of the film and its lubricity after self-lubricating treatment were investigated in detail. EPMA indicates the cross-section of anodized film has two distinct oxide layers. Al, O and P are found in the film with different distribution in the two layers. XPS analysis on the electron binding energy of the component elements show the chemical composition of film surface are Al₂O₃, Ce(OH) and some phosphates. The structure of anodized film is amorphous with XRD analysis.The tribological tests shows the frictional coefficient of the self-lubricating surface composite coating is 0.25, much lower than anodized aluminum and aluminum substrate, which is about 0.55 and 0.85, respectively, and it is also durable for a long period of time in comparison with the lubricating coating fabricated by hot-dipping method. SEM images show some PTFE particles are added into the nanoholes of anodic oxide film.

Keywords: Anodization; Self-lubricating; Ultrasonic impregnation; PTFE

Fabrication of self-ordered nanohole arrays on Si by localized anodization and subsequent chemical etching by Hidetaka Asoh; Akihiko Oide; Sachiko Ono (pp. 1668-1673).

Nanohole arrays with a 60nm hole periodicity were fabricated on a Si substrate by the anodization of an aluminum film sputtered on a Si substrate in sulfuric acid and subsequent chemical etching. The transfer of the nanoporous pattern of anodic alumina into the Si substrate was achieved by the selective removal of silicon oxide, which was produced by the anodic oxidation of the underlying Si substrate through the anodic porous alumina used as a mask.

Keywords: Anodization; Anodic porous alumina; Nanopatterning; Chemical etching

Segregation of Sn and Sb in a ternary Cu(100)SnSb alloy by J.K.O. Asante; J.J. Terblans; W.D. Roos (pp. 1674-1678).

Surface segregation studies of Sn and Sb in Cu(100)–0.14at.% Sn–0.12at.% Sb ternary alloy, have been done by making use of Auger Electron Spectroscopy. The method of Linear Temperature Ramp (LTR) was employed, whereby the sample was heated and cooled linearly at a constant rate. The positive heating rate showed both a kinetic segregation profile, as well as a narrow equilibrium segregation region, at higher temperatures. The equilibrium segregation profile was extended by cooling the sample. Sn was first to segregate to the surface due to its higher diffusion coefficient, mainly from a smaller activation energy E_Sn. Sb, due to its higher segregation energy, eventually replaced Sn from the surface. The modified Darken model was used to simulate the profile yielding the following segregation parameters: D_o(Sn)=6.3×10⁻⁶m²/s, D_o(Sb)=2.8×10⁻⁵m²/s; E_Sn=175.4kJ/mol, E_Sb=186.3kJ/mol;ΔGSn°=64.2kJ/mol,ΔGSb°=84.3kJ/mol; Ω_Cu–Sn=3.4kJ/mol, Ω_Cu–Sb=15.9kJ/mol and Ω_Sn–Sb=−5.4kJ/mol.

Keywords: Segregation energy; Cu, Sn, Sb; Ternary alloy; Interaction energy; Modified Darken

Effect of Ni interlayer on stress level of CoSi₂ films in Co/Ni/Si(100) bi-layered system by K. Ma; J.Y. Feng (pp. 1679-1684).

The effect of Ni interlayer on stress level of cobalt silicides was investigated. The X-ray diffraction patterns (XRD) show that low temperature formation of Co1−_xNi_xSi₂ solid solution was obtained while Ni interlayer was present in Co/Si system, which was confirmed by Auger electron spectrum (AES) and sheet resistance measurement. XRD was also used to measure the internal stress in CoSi₂ films by a 2 θ_ψ−sin² ψ method. The result shows that the tensile stress in CoSi₂ films evidently decreased in Co/Ni/Si(100) system. The reduction of lattice mismatch, due to the presence of Ni in Co_xNi1−_xSi₂ solid solution, is proposed to explain this phenomenon.

Keywords: PACS; 68.35.−p; 68.60.−pCoSi; ₂; Stress; The solid solution; Lattice mismatch

Fracture mechanisms of Hg_0.8Cd_0.2Te induced by pulsed TEA-CO₂ laser by H. Cai; Z.H. Cheng; H.H. Zhu; D.L. Zuo (pp. 1685-1692).

The fracture mechanisms of Hg_0.8Cd_0.2Te induced by pulsed TEA-CO₂ laser have been investigated theoretically and experimentally in this paper. The Hg_0.8Cd_0.2Te target was irradiated by a TEA-CO₂ laser with wavelength of 10.6μm and spike width of 240ns in an ambient atmosphere. The evident cracks can be found on the surface of the target from the scanning electron microscopy (SEM) photos, indicating that the severe breaks happened during the experiment. Theoretical analysis has also been carried out and the results show that the fracture of Hg_0.8Cd_0.2Te is mainly induced by thermal stresses, although there are three forces (thermal stress, evaporation wave and laser-supported detonation (LSD) wave) exerted on the target surface during the process.

Keywords: PACS; 61.80.Ba; 42.55.L; 85.60.GzFracture mechanism; Laser irradiate; TEA-CO; ₂; HgCdTe

Preparation and characterization of boron-incorporated amorphous carbon films from a natural source of camphoric carbon as a precursor material by M. Rusop; X.M. Tian; T. Kinugawa; T. Soga; T. Jimbo; M. Umeno (pp. 1693-1703).

The boron-incorporated amorphous carbon (a-C:B) film has been prepared by pulsed laser deposition (PLD) in high vacuum at room temperature using natural source of camphoric carbon (CC) as a precursor material. The effects of various B weight percentages in the target (Bwt.%) on the properties of a-C:B films have been investigated using standard measurement techniques and discussed. The optical band gap ( E_g) is almost unchanged up to 10Bwt.%, decreased a little, and with decrease of electrical resistivity ( �?) with higher Bwt.%, we considered that the variation of E_g and electrical properties can be related to interstitial doping of B in carbon films through modifications of C–B bonding configurations by rearranging B atoms and the B incorporation induced by doping, which are responsible for the decrease in �?. The decrease of �? is considered not due to the graphitization caused by the increase of sp²-bonded carbon. This is further confirmed by the variation of surface morphology (AFM), Raman and FT-IR as the structural and bonding properties of these films was unchanged with B incorporation up to 16Bwt.%.

Keywords: Camphoric carbon; Graphite; Boron doping; AFM; Raman; FT-IR; PLD

Mild corrosion behavior on sulphurized steel surface during friction by Wang Hai-Dou; Xu Bin-Shi; Liu Jia-Jun; Zhuang Da-Ming; Zhang Xian-Cheng; Wei Shi-Cheng (pp. 1704-1709).

After treatment by low temperature ion sulphuration, the solid lubrication sulphuration layers (FeS films) were produced on the AISI 1045 and stainless steel. A mass of corrosion peeling pits occurred on the worn scars of 1045 steel sulphuration layer after wear test, whereas none of them on the stainless steel one. AFM was used to observe the morphology of sulphuration layer, SEM equipped EDS was utilized to analyze the morphologies and compositions of worn scars. XPS and XRD were employed to detect the valence states of sulphuration layer and its worn scars, as well as the phase structures. The results showed that during friction, under the frictional heat, the sulfate radical with mild corrosion was produced, so that the 1045 steel without any anti-corrosion was corroded in some certain, meanwhile the stainless steel was not corroded depending on its excellent corrosion resistance.

Keywords: Sulphuration layer; FeS; Friction; Sulfate radical; Corrosion

Use of plasma polymerisation process for fabrication of bio-MEMS for micro-fluidic devices by Marshal Dhayal; Hyung Gon Jeong; Jeong Sik Choi (pp. 1710-1715).

Using a plasma polymerisation process with optical lithography, wet and dry etching techniques we have fabricated an organic micro-fluidic device (OMDF) on silicon/glass substrate. An asymmetric electrode array used in micro-fluidic device (MFD) with small electrode (4μm wide) separated from the large electrode (20μm wide) by 20μm and 6μm gaps in both sides respectively. In this study we have found that plasma polymerisation process is not only important for changing the surface chemical and physical properties but also has advantage in bonding of these micro devices at low temperature (∼100°C) due to low T_g of polymeric material. The fluidic velocity measurement shows a maximum of about 450μm/s in a 150μm channel width of organic micro-fluidic devices after plasma surface modification.

Keywords: Plasma polymerisation; Bio-MEMS; Micro-fluidics; Acrylic acid; Bonding

Dependence of the interband transitions on the in mole fraction and the applied electric field in In_xGa1−_xAs/In_0.52Al_0.48As multiple quantum wells by J.H. Kim; J.T. Woo; I. Lee; T.W. Kim; K.H. Yoo; M.D. Kim; L.R. Ram-Mohan (pp. 1716-1722).

Transmission electron microscopy (TEM) and photocurrent (PC) measurements were carried out to investigate the microstructural properties and excitonic transitions in In_xGa1−_xAs/In_0.52Al_0.48As multiple quantum wells (MQWs) for x=0.54, 0.57 and 0.60. TEM images showed that high-quality 11-period In_xGa1−_xAs/In_0.52Al_0.48As MQWs had high-quality heterointerfaces. The results for the PC spectra at 300K showed that the peaks corresponding to the excitonic transitions from the ground state electronic sub-band to the ground state heavy-hole band (E₁-HH₁) and the ground state electronic sub-band to the ground state light-hole band (E₁-LH₁) became closer to each other with decreasing In mole fraction and that E₁-HH₁ and E₁-LH₁ excitonic peaks shifted to longer wavelength with increasing applied electric field. The calculated values of the E₁-HH₁ interband transition energies were in qualitative agreement with those obtained form the PC measurements with and without applied electric field. These results can be helpful in understanding potential applications of In_xGa1−_xAs/In_yAl1−_yAs MQWs dependent on In mole fraction and applied electric field in long-wavelength optoelectronic devices.

Keywords: PACS; 68. 37. Lp; 73. 21. Fg; 78. 66. FdIn; _x; Ga; 1−; _x; As/In; _y; Al; 1−; _y; As; Multiple quantum wells; Excitonic transitions

Microstructure analysis of magnesium alloy melted by laser irradiation by S.Y. Liu; J.D. Hu; Y. Yang; Z.X. Guo; H.Y. Wang (pp. 1723-1731).

The effects of laser surface melting (LSM) on microstructure of magnesium alloy containing Al8.57%, Zn 0.68%, Mn0.15%, Ce0.52% were investigated. In the present work, a pulsed Nd:YAG laser was used to melt and rapidly solidify the surface of the magnesium alloy with the objective of changing microstructure and improving the corrosion resistance. The results indicate that laser-melted layer contains the finer dendrites and behaviors good resistance corrosion compared with the untreated layer. Furthermore, the absorption coefficient of the magnesium alloy has been estimated according to the numeral simulation of the thermal conditions. The formation process of fine microstructure in melted layers was investigated based on the experimental observation and the theoretical analysis. Some simulation results such as the re-solidification velocities are obtained. The phase constitutions of the melted layers determined by X-ray diffraction were β-Mg₁₇Al₁₂ and α-Mg as well as some phases unidentified.

Keywords: PACS; 61.82.B; 42.60.R; 42.70.H; 02.60Magnesium alloy; Nd:YAG pulsed laser; Laser surface melting; Numerical simulation

The effect of interface states, excess capacitance and series resistance in the Al/SiO₂/p-Si Schottky diodes by H. Kanbur; Ş. Altındal; A. Tataroğlu (pp. 1732-1738).

The current–voltage ( I– V) characteristics of Al/SiO₂/p-Si metal–insulator–semiconductor (MIS) Schottky diodes were measured at room temperature. In addition the capacitance–voltage ( C– V) and conductance–voltage ( G– V) measurements are studied at frequency range of 10kHz–1MHz. The higher value of ideality factor of 3.25 was attributed to the presence of an interfacial insulator layer between metal and semiconductor and the high density of interface states localized at Si/SiO₂ interface. The density of interface states ( N_ss) distribution profile as a function of ( E_ss− E_v) was extracted from the forward bias I– V measurements by taking into account the bias dependence of the effective barrier height ( Φ_e) at room temperature for the Schottky diode on the order of ≅4×10¹³eV⁻¹cm⁻²_. These high values of N_ss were responsible for the non-ideal behaviour of I– V and C– V characteristics. Frequency dispersion in C– V and G– V can be interpreted only in terms of interface states. The N_ss can follow the ac signal especially at low frequencies and yield an excess capacitance. Experimental results show that the I– V, C– V and G– V characteristics of SD are affected not only in N_ss but also in series resistance ( R_s), and the location of N_ss and R_s has a significant on electrical characteristics of Schottky diodes.

Keywords: PACS; 73.30.+y; 73.40.Qv; 73.40.NsExcess capacitance; Interface states; Series resistance; Insulator layer; Frequency dependent

Characterisation of the anodic layers formed on 2024 aluminium alloy, in tetraborate electrolyte containing molybdate ions by V. Moutarlier; S. Pelletier; F. Lallemand; M.P. Gigandet; Z. Mekhalif (pp. 1739-1746).

Anodic layer growth on 2024 aluminium alloy at 70°C, under 40V, during 60min, in 50gL⁻¹ di-sodium tetraborate solution containing di-sodium molybdate from 0.1 to 0.5M (pH 10) is examined. Anodising behaviours strongly depend on additive concentration. Development of anodic films is favoured with weak molybdate additions (<0.3–0.4M). The film thicknesses increase and the porosity of anodic layers decreases. Molybdenum (+VI), detected by X-ray photoelectron spectroscopy (XPS) analysis, is present in the anodic films and the Mo incorporation, studied by energy dispersive spectroscopy (EDS) analysis, increases with molybdate concentration. However, for high molybdate concentrations (>0.4M), anodising behaviour becomes complex with the formation of a blue molybdenum oxide at the cathode. The growth of aluminium oxide is hindered. As the anodic layers are thinner, the Mo(+VI) incorporation significantly decreases. These two configurations implicate different corrosion performances in 5% sodium chloride solution at 35°C. As the alkaline anodic layer formed with 0.3M molybdate species is the thickest and the Mo incorporation is the more pronounced, its corrosion resistance is the highest. The effect of morphology and composition of anodic films on pitting corrosion is also discussed.

Keywords: Anodic layers; 2024 aluminium alloy; Alkaline electrolyte; Molybdate

Electron-spin polarization in anti-parallel doubleδ-magnetic-barrier nanostructures by Mao-Wang Lu (pp. 1747-1753).

We present a theoretical study on spin-dependent transport of electrons in any anti-parallel doubleδ-magnetic-barrier nanostructure, which can be experimentally realized by depositing a ferromagnetic stripe on the surface of a semiconductor heterostructure. A general fomula of tranmission probability for electrons tunneling through this kind of nanostructures, is obtained. It is shown that large spin-polarized current can be achieved in such a device. It also is shown that the degree of electron-spin polarization is strongly dependent upon magnetic-strength difference of twoδ-barriers. These interesting properties may provide an alternative scheme to spin-polarize electrons into semiconductors, and this device may be used as a tunable spin-filter.

Keywords: PACS; 73.40.Gk; 73.23.; −; b; 72.25.; −; b; 75.75.+aSpintronics; Spin polarization; Spin filtering; Magnetic nanostructure

Epitaxial growth and characterization of layered magnetic nanostructures by R. Bertacco; M. Cantoni; M. Riva; A. Tagliaferri; F. Ciccacci (pp. 1754-1764).

We describe the construction and operation of an ultrahigh-vacuum system devoted to the study of layered magnetic nanostructures. The apparatus includes two growth chambers, where specimens nanostructured along the direction of growth (heterostructures, nanometric and subnanometric thin films and multilayers) are deposited either by molecular beam epitaxy or pulsed laser deposition, and a measurement chamber, where they are analyzed in situ by a variety of electron spectroscopies. Magnetic characterization is obtained by spin resolved inverse photoemission spectroscopy and magneto optical Kerr effect technique. Vacuum transfer towards other experimental facilities is also available. As examples of application, results from half metallic magnetic oxides, such as magnetite (Fe₃O₄) and manganite (La_2/3Sr_1/3MnO₃) thin films, and ferromagnet/semiconductor interfaces (Fe/Ge(001)) are also reported.

Keywords: PACS; 75.70.−i (magnetic films and multilayers); 79.60.Jv (interfaces; heterostructures, nanostructures (photoemission)); 85.75.−d (magnetoelectronics; spintronics: devices exploiting spin polarized transport)Thin magnetic films; Epitaxial growth; Spin resolved electron spectroscopy; Spintronics

Characterization of DNA chips on the molecular scale before and after hybridization with an atomic force microscope by Marie H�l�ne Rouillat; Vincent Dugas; Jean Ren� Martin; Magali Phaner-Goutorbe (pp. 1765-1771).

Using two different 25-mer oligonucleotide probes covalently grafted on a silicon substrate, we demonstrate how efficient atomic force microscopy (AFM) can be for monitoring each step of DNA chip preparation: from probe immobilization to hybridization on the molecular scale. We observed the probe-molecule organization on the chip after immobilization, and the target molecules, which hybridized with probes could be individually identified. This article presents a method of straightforwardly identifying not only single and double DNA strands, but also, and more significantly, the hybridized part on them.

Keywords: PACS; 68.37.−Ps; 68.47.−Pe; 87.14.−Gg; 87. 15.−vAFM; DNA chip; DNA hybridization; Biological molecules on surfaces

Determination of the hydrophilic character of membranes by pulsed force mode atomic force microscopy by M. Meincken; S.P. Roux; E.P. Jacobs (pp. 1772-1779).

Hydrophilic polysulphone (PSU) membranes were modified with hydrophilic polyethylene oxide (PEO) to obtain membranes less susceptible to fouling. Pulsed force atomic force microscopy was employed to determine the hydrophilic character of the different membranes and to acquire quantitative values that can be compared easily. This technique proved to be extremely valuable in the characterisation and quantification of membrane hydrophilicity.

Keywords: PACS; 07.79.Lh; 81.05.Rm; 82.35.GhPulsed force mode; Atomic force microscopy; Adhesive force mapping; Membrane fouling

Forming abilities of monatomic chains of several fcc and bcc metals in different crystallographic orientations by D. Liu; W.T. Zheng; Q. Jiang (pp. 1780-1784).

The forming abilities of monatomic chains (MC) of several fcc and bcc metals stretched in three principal crystallographic orientations of [111], [100] and [110] are analyzed in terms of a ratio between Peierls stress of a bulk crystal with dislocations ( τ_p) and theoretical shear stress of a monatomic chain ( τ_m). It is found that the structure and orientation dependent τ_m/ τ_p values are proportional to the forming abilities of MC while τ_m/ τ_p is a function of Possion's ratio ν. The above considerations are in agreement with known experimental and simulation results of Au. In addition, Nb as a candidate for MC formation is suggested.

Keywords: PACS; 33.15.Fm; 62.20.−x; 62.20.FeMonatomic chains; Possion's ratio; Structure dependent; Orientation dependent

Determination of the thickness and density of the ion bombardment induced altered layer in SiC by means of reflection electron energy loss study by L. Kotis; A. Sulyok; M. Menyhard; J.B. Malherbe; R.Q. Odendaal (pp. 1785-1792).

The steady state surfaces of ion bombarded 3C-, 4H- and 6H-SiC samples were studied by means of reflected electron energy loss spectroscopy (REELS). The REELS exhibit a well-defined loss peak in the region of about 20eV. The position of the maximum of the loss peak depends on the bombarding ion energy (decreasing with increasing ion energy), and on the primary electron beam energy (increasing with increasing primary energy). This behavior can be explained if we suppose that the plasmon energy in the altered layer (produced by ion bombardment) is different from that of the unaltered bulk. In this case the measured loss peak is the sum of two overlapping plasmon peaks. With modeling the system as a homogeneous altered layer and a homogeneous unaltered substrate the plasmon energy in the altered layer was derived to be 19.8eV. The large change of the plasmon energy with respect to the bulk value of 23eV is explained by a thin low density overlayer on the surface of the sample produced by the ion bombardment.

Keywords: SiC; Ion sputtering induced surface alteration; Density of surface layer; Plasmon energy of SiC

Effect of copper ions implantation on corrosion behavior of zircaloy-4 in 1M H₂SO₄ by D.Q. Peng; X.D. Bai; F. Pan; H. Sun; B.S. Chen (pp. 1793-1800).

In order to study the effect of copper ion implantation on the aqueous corrosion behavior, samples of zircaloy-4 were implanted with copper ions with fluences ranging from 1�10¹⁶ to 1�10¹⁷ ions/cm², using a metal vapor vacuum arc source (MEVVA) operated at an extraction voltage of 40kV. The valence states and depth distributions of elements in the surface layer of the samples were analyzed by X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES), respectively. Glancing angle X-ray diffraction (GAXRD) was employed to examine the phase transformation due to the copper ion implantation. The potentiodynamic polarization technique was employed to evaluate the aqueous corrosion resistance of implanted zircaloy-4 in a 1M H₂SO₄ solution. It was found that a significant improvement was achieved in the aqueous corrosion resistance of zircaloy-4 implanted with copper ions when the fluence is smaller than 5�10¹⁶ ions/cm². The corrosion resistance of implanted samples declined with increasing the fluence. Finally, the mechanism of the corrosion behavior of copper-implanted zircaloy-4 was discussed.

Keywords: Zircaloy-4; Corrosion resistance; Copper ion implantation; X-ray photoemission spectroscopy (XPS); Auger electron spectroscopy (AES)

XPS and UPS study of Na deposition on thin film V₂O₅ by Qi-Hui Wu; A. Thi�en; W. Jaegermann (pp. 1801-1805).

The deposition of Na on thin film V₂O₅ has been study by using photoelectron spectroscopy. Vanadium ions are strongly reduced due to the deposition of Na. Three kinds of Na species were observed on the surface: the first is assigned to intercalated Na; the second is contributed to Na₂O₂; the third is appointed to metallic Na. The formation of Na₂O₂ leads to arise an emission line at about 10.3eV in the valence band spectra. The metallic Na will further react with the oxides substrate and form Na₂O₂ on the surface in UHV chamber.

Keywords: Na deposition; V; ₂; O; ₅; UPS; XPS

High-temperature Auger electron spectroscopy of Zircaloy-4 by N. Stojilovic; E.T. Bender; R.D. Ramsier (pp. 1806-1811).

The near-surface region of Zircaloy-4 (Zry-4) has been probed using Auger electron spectroscopy (AES). In particular, the behavior of impurity (sulfur) and alloying (tin) elements has been monitored as a function of annealing temperature and time. High-temperature AES experiments above 900K are reported, with a primary focus on changes in the S(LMM) Auger feature that overlaps with the primary Zr(MNV) transition. We find that the sulfur content of the near-surface region increases linearly with annealing time at higher temperatures. Tin is the only alloying element whose Auger signal intensity significantly exceeds the noise level at these temperatures.

Keywords: Zircaloy-4; Sulfur; Tin; Auger electron spectroscopy; Annealing

Characteristics of Cu films prepared using a magnetron sputter type negative ion source (MSNIS) by Namwoong Paik (pp. 1812-1817).

Cu films have been deposited at room temperature using a magnetron sputter type negative ion source (MSNIS) at various conditions. By the principle of operation, the negative ion production probability is the function of the Cs flow rate in MSNIS. A set of films were deposited at different Cs flow rates and compared with normal-magnetron-sputtered films. The long-throw method was combined to MSNIS to increase the directionality and the negative ion arrival ratio. The film properties, such as resistivity, surface roughness, film structure, and step coverage on high aspect-ratio trench samples were obtained and analyzed using SEM, SIMS and AFM methods. The results showed that the resistivity of the film improved toward the theoretical values from 2.3 to 1.8μΩcm for the 100nm thickness films. AFM scan of the film showed surface roughness was improved using MSNIS by ion bombarding effect. Depth profiling SIMS result showed Cs level resided in the film was less than 1×10¹⁹at./cm³. As an application, Cu seed layer deposition on trench structure was investigated. Cross-sectional SEM was employed to see the step coverage of the film. The biasing effect was investigated. The different biasing conditions resulted as the clearly different coverage mode.

Keywords: Cu metallization; Trench; Negative ion

The properties of copper films deposited on polyimide by nitrogen and oxygen plasma pre-treatment by Chih-hao Yang; Shih-chin Lee; Jun-ming Wu; Tien-chai Lin (pp. 1818-1825).

Extensive studies on the relationship between a copper thin film and its polyimide substrate show that the adhesion strength is very weak. In this work, we show how to reduce Cu film resistivity and improve the adhesion strength between Cu and polyimide. After nitrogen and oxygen plasma treatment, polyimide substrates can substantially improve the resistivity and adhesion strength deposited Cu. It is found that the lowest resistivity is 4.22μΩcm and the maximum adhesion strength is 72.23MPa for a polymide substrate treated in oxygen plasma for 5min.

Keywords: Cu film; Plasma treatment; Adhesion; XPS; Sputtering; Polyimide; Resistivity

W₂B-based ohmic contacts to n-GaN by Rohit Khanna; S.J. Pearton; F. Ren; I. Kravchenko; C.J. Kao; G.C. Chi (pp. 1826-1832).

Ohmic contact formation on n-GaN using a novel Ti/Al/W₂B/Ti/Au metallization scheme was studied using contact resistance, scanning electron microscopy and Auger electron spectroscopy measurements. A minimum specific contact resistivity of 7×10⁻⁶Ωcm² was achieved at an annealing temperature of 800°C. The contact resistance was essentially independent of measurement temperature, indicating that field emission plays a dominant role in the current transport .The Ti began to outdiffuse to the surface at temperatures of ∼500°C, while at 800°C the Al also began to intermix within the contact. By 1000°C, the contact showed a reacted appearance and AES showed almost complete intermixing of the metallization. The contact resistance showed excellent stability for extended periods at 200°C, which simulates the type of device operating temperature that might be expected for operation of GaN-based power electronic devices.

Keywords: Ohmic contact formation; Ti/Al/W; ₂; B/Ti/Au metallization scheme; GaN-based power electronic devices

Insulating method using cataphoretic paint for tungsten tips for electrochemical scanning tunnelling microscopy (ECSTM) by L. Zhu; B. Claude-Montigny; M. Gattrell (pp. 1833-1845).

A new tip insulating process for active metal tips allowing atomic resolution ECSTM imaging has been developed. This new method using cathodic cataphoretic paint deposition has been tested successfully. The insulating deposited film appears homogeneous under optical microscopy and it has been characterised by infra red and SEM analysis. The depositing layer of the paint is sufficiently dense to effectively resist electrolyte ion penetration and resists corrosion in various acidic, basic aqueous or non-aqueous media. The coating film does not reduce the imaging capability of the ECSTM even to atomic resolution. This new insulating method adds to the approaches available to those preparing tips for ECSTM. This approach would also be of great utility for the preparation of microelectrodes using active metals.

Keywords: ECSTM; Tip; Cataphoretic paint; Insulating; Tungsten; Active metals

Thermal stability of W₂B and W₂B₅ contacts on ZnO by K. Ip; Rohit Khanna; D.P. Norton; S.J. Pearton; F. Ren; I. Kravchenko; C.J. Kao; G.C. Chi (pp. 1846-1853).

Rectifying contact formation on n-type bulk single crystal ZnO using novel W₂B or W₂B₅ metallization schemes was studied using current–voltage, scanning electron microscopy and Auger electron spectroscopy (AES) measurements. When a single Au overlayer was used to reduce the metal sheet resistance, the contacts were ohmic for all annealing conditions due to outdiffusion of Zn through the metal. By sharp contrast, when a bilayer of Pt/Au was used on top of the boride layers, rectifying contacts with barrier heights of ∼0.4eV for W₂B were obtained. The highest barrier height of 0.66eV was achieved for W₂B₅ annealed at 600°C, although at this condition the contact showed a reacted appearance and AES showed almost complete intermixing of the metallization.

Keywords: Scanning electron microscopy; Auger electron spectroscopy; Schottky barrier height

XPS identification of surface-initiated polymerisation during monomer transfer moulding of poly(ɛ-caprolactone)/Bioglass^® fibre composite by G. Jiang; G.S. Walker; I.A. Jones; C.D. Rudd (pp. 1854-1862).

In this work, X-ray photoelectron spectroscopy (XPS) was demonstrated to be a useful method to characterise surface-initiated polymerisation. Both E-glass fibre and Bioglass^® fibre were treated using 3-aminopropyltrimethoxysilane (and propyltrimethoxysilane as a control) and then they were used as a reinforcement, respectively, in monomer transfer moulding to prepare poly(ɛ-caprolactone)/glass fibre composites with stannous octoate as the catalyst for ɛ-caprolactone polymerisation. The fibre was extracted and then analysed using XPS to probe the presence of PCL chemically bonded to the glass fibre surface. Both tin and PCL were detected on the surface of the fibres sized with 3-aminopropyltrimethoxysilane, confirming surface-initiated polymerisation of ɛ-caprolactone.

Keywords: PACS; 79.60Poly(ɛ-caprolactone); Surface-initiated polymerisation; XPS

Nanomechanical characteristics of SnO₂:F thin films deposited by chemical vapor deposition by Te-Hua Fang; Win-Jin Chang (pp. 1863-1869).

The nanoindentation characterizations and mechanical properties of fluorine-doped tin oxide (SnO₂:F) films deposited on glass substrates, using chemical vapor deposition (CVD) method, were studied, which included the effects of the indentation loads, the loading time and the hold time on the thin film. The surface roughness, fractal dimension and frictional coefficient were also studied by varying the freon flow rates. X-ray diffraction (XRD), atomic force microscopy (AFM) and frictional force microscopy (FFM) were used to analyze the morphology of the microstructure. The results showed that crystalline structure of the film had a high intensity (110) peak orientation, especially at a low freon flow rate. According to the nanoindentation records, the Young's modulus ranged from 62.4 to 75.1GPa and the hardness ranged from 5.1 to 9.9GPa at a freon flow rate of 8000sccm. The changes in measured properties were due to changing loading rate.

Keywords: Chemical vapor deposition; Thin films; Tin oxide; Nanoindentation

FT-IR, XPS and PEC characterization of spray deposited hematite thin films by J.D. Desai; H.M. Pathan; Sun-Ki Min; Kwang-Deog Jung; Oh Shim Joo (pp. 1870-1875).

Hematite thin films were prepared by spraying ethanolic solution of ferric trichloride and have been characterized by using Fourier transform infra-red (FT-IR) and X-ray photoelectron spectroscopic (XPS) techniques. The film prepared by spray consists of a single phase of α-Fe₂O₃. The XPS studies confirm that chemical states of Fe³⁺ and O²⁻ in the film; thereby confirming the formation of the hematite thin films. The photoelectrochemical (PEC) studies have been carried out by forming a three-electrode system using 1M NaOH electrolyte. The junction is illuminated with white light to obtain I– V characteristics in chopped light. The studies indicate the films exhibit n-type conductivity.

Keywords: Hematite; Thin film; FT-IR; XPS and PEC characterization

Characteristics of sandwich-structured Al₂O₃/HfO₂/Al₂O₃ gate dielectric films on ultra-thin silicon-on-insulator substrates by Xinhong Cheng; Zhaorui Song; Jun Jiang; Yuehui Yu (pp. 1876-1882).

Sandwich-structure Al₂O₃/HfO₂/Al₂O₃ gate dielectric films were grown on ultra-thin silicon-on-insulator (SOI) substrates by vacuum electron beam evaporation (EB-PVD) method. AFM and TEM observations showed that the films remained amorphous even after post-annealing treatment at 950°C with smooth surface and clean silicon interface. EDX- and XPS-analysis results revealed no silicate or silicide at the silicon interface. The equivalent oxide thickness was 3nm and the dielectric constant was around 7.2, as determined by electrical measurements. A fixed charge density of 3×10¹⁰cm⁻² and a leakage current of 5×10⁻⁷A/cm² at 2V gate bias were achieved for Au/gate stack /Si/SiO₂/Si/Au MIS capacitors. Post-annealing treatment was found to effectively reduce trap density, but increase in annealing temperature did not made any significant difference in the electrical performance.

Keywords: PACS; 77.55. +f; 73.40QvHigh; -k; gate dielectric films; SOI

Preparation and characterisation of Au(1 1 0) and Cu(1 1 0) surfaces for applications in ambient environments by G.E. Isted; D.S. Martin (pp. 1883-1890).

The preparation of metal surfaces that in ambient conditions are flat and smooth over micron length scales is desirable for a wide range of applications. Scanning probe microscopy (SPM) studies of biomolecular adsorption and cell attachment require such well-prepared substrates. Standard polishing finishes are often found to exhibit considerable roughness and damage including scratches when investigated by SPM. We have prepared by means of UHV technology Au(1 1 0) and Cu(1 1 0) surfaces that when in ambient air exhibit a more homogeneous morphology and are considerably smoother than conventional polished surfaces. SPM techniques and the optical technique of reflection anisotropy spectroscopy (RAS) are used to characterise the morphological and electronic properties of these surfaces, respectively. The RA response of both Au(1 1 0) and Cu(1 1 0) surfaces in ambient conditions can be interpreted in terms of optical transitions between surface-modified bulk bands.

Keywords: PACS; 68.35.Bs; 78.40.Kc; 78.68.+mCopper; Gold; Low index single crystal surfaces; Reflection spectroscopy

Correlation between Al₂O₃ particles and interface of Al–Al₂O₃ coatings by cold spray by Ha Yong Lee; Se Hun Jung; Soo Yong Lee; Young Ho You; Kyung Hyun Ko (pp. 1891-1898).

Al–Al₂O₃ composite coatings with different Al₂O₃ particle shapes were prepared on Si and Al substrate by cold spray. The powder compositions of metal (Al) and ceramic (Al₂O₃) having different sizes and agglomerations were varied into ratios of 10:1wt% and 1:1wt%. Al₂O₃ particles were successfully incorporated into the soft metal matrix of Al. It was found that crater formation between the coatings and substrate, which is typical characteristic signature of cold spray could be affected by initial starting Al₂O₃ particles. In addition, when the large hard particles of fused Al₂O₃ were employed, the deep and big craters were generated at the interface between coatings and hard substrates. In the case of pure soft metal coating such as Al on hard substrate, it is very hard to get proper adhesion due to lack of crater formation. Therefore, the composite coating would have certain advantages.

Keywords: Cold spray; Al–Al; ₂; O; ₃; Composites; Interface; Crater

Magnetic force microscopy studies of domain walls in nickel and cobalt films by C.T. Hsieh; J.Q. Liu; J.T. Lue (pp. 1899-1909).

A magnetic force microscopy is used to examine the domain walls in nickel and cobalt films deposited by argon ion sputtering. Thin nickel films deposited at high substrate temperatures exhibit coexistent Bloch and Neel walls. Films grown at room temperature display alternative Bloch lines with cap switches. These films agglomerate to form grains after annealed at high temperatures. The film composed of larger grains behaves better nucleation implying magnetic domains of closure, while the film composed of smaller grains exhibits more defects implying alternative Bloch lines. We have also observed domain displacements and cap switches, which occur due to precipitation of particles in small grain size films. Stripe domains are observed for film thicknesses larger than 100nm. They become zigzag cells when an external field of 1.5T is applied perpendicular to the surface of the films. This experiment indicates that the domain sizes in thin films and the strip widths for thick films both depend on the square-root of the film thickness, which varies from 5 to 45nm and from 100 to 450nm, respectively.

Keywords: PACS; 75.50.Rr; 61.16.Ch; 75.60.-d; 73.20.-rMagnetic domain walls; Nickel and cobalt films; Magnetic force microscopy

Elimination of cracking during UV laser ablation of SrTiO₃ single crystals by employing a femtosecond laser by S. Zoppel; D. Gray; M. Farsari; R. Merz; G.A. Reider; C. Fotakis (pp. 1910-1914).

We have performed a comparative study of UV laser ablation of SrTiO₃ with nanosecond- and sub-picosecond sources, respectively. The experiments were performed with lasers at a wavelength of 248nm and pulse durations of 34ns and 500fs. Femtosecond ablation turns out to be more efficient by one order of magnitude and eliminated the known problem of cracking of SrTiO₃ during laser machining with longer pulses. In addition, the cavities ablated with femtosecond pulses display a smoother surface with no indication of melting and well-defined, sharp edges. These effects can be explained by the reduced thermal shock effect on the material by using ultrashort pulses.

Keywords: PACS; 42.65.Re; 81.05.Je; 42.55.LtAblation; SrTiO; ₃; Perosvskite

Quantification issues in the identification of nanoscale regions of homopolymers using modulus measurement via AFM nanoindentation by Charles A. Clifford; Martin P. Seah (pp. 1915-1933).

Since 1989, AFMs have been used to map the nanomechanical properties of surfaces using measurements such as force–distance curves. Quantification of the force and elastic parameters are critical to the nanomechanical analysis and positive identification of materials at the nanoscale, as well as for assessing behaviour at surfaces. In recent years, there have been AFM papers publishing “quantitative�? values for the indentation modulus, however, many involved large uncertainties arising from the lack of calibration of key components, the use of manufacturers’ nominal values for these components or the use of incorrect models. This paper addresses the quantification issues in modulus measurement at surfaces for homogeneous materials using force–distance curves and how to do this with sufficient accuracy to identify materials at the nanoscale. We review the available theory and describe two routes to quantitative modulus measurement using both the AFM on its own and the AFM combined with a nanoindenter. The first involves the direct measurement of modulus using a fully calibrated instrument and allows depth analysis. The second uses indirect measurement through calibration by reference materials of known reduced modulus. For depth analysis by this second route, these reference moduli need to be known as a function of depth. We show that, using the second route, an unknown polymer may be analysed using the nanoindenter, its modulus determined and, providing the moduli of the polymers to be identified or distinguished differ by more than 20%, identified with 95% confidence. We recommend that users evaluate a set of reference samples using a traceable nanoindenter via the first route, and then use these to calibrate the AFM by the second route for identification of nano-regions using the AFM.

Keywords: PACS; 07.79.Lh; 68.37.Ps; 68.35.Gy; 82.35.LrAtomic force microscopy; Scanning probe microscopy; Nanoindentation; Nanomechanics

Intrinsic coercivities of molecular beam epitaxy grown single-crystal Ni films on Ag buffer layer by S.U. Jen; T.C. Wu; C.C. Yu (pp. 1934-1940).

Single-crystal Ni films were made by the molecular beam epitaxy (MBE) method on Si(100) and Si(110) substrates, respectively, with an 100Å thick Ag buffer layer. The growth temperature T_S was 270°C, and the film thickness t was 500Å. From reflection high-energy electron diffraction (RHEED) patterns, the crystalline symmetries of the two films are clear and as expected. Intrinsic coercivities, H_C(100) and H_C(110), are plotted as a function of the angle of rotation ϕ around the crystal axes [100] and [110], respectively. The results show that both H_C(100) and H_C(110) exhibit mixed features of the crystalline ( K_C) and the induced uniaxial magnetic ( K_u) anisotropies. K_u is the magneto-elastic energy, due to lattice mismatch at the Ni/Ag interface. Moreover, the crystalline anisotropy fields, H_K(100) and H_K(110), and the induced anisotropy filed, H_u, can be calculated as a function of ϕ, respectively. Then, each H_C curve is fitted by the equation: H_C= H_o+ H_K+ H_u, where H_o is the isotropic pinning field. Meanwhile, domain structures were examined by the Bitter method, using Ferrofluid 707. On the Ni(100) film, we observed the charged cross-tie walls, and on the Ni(110) film, the un-charged Bloch walls.

Keywords: PACS; 75.60.−d; 75.30.Gw; 75.30.Pd; 75.70.ChEpitaxy Ni films; Interface; Magnetic anisotropies; Domain walls

Characterisation and stability of hydrophobic surfaces in water by M. Maccarini; M. Himmelhaus; S. Stoycheva; M. Grunze (pp. 1941-1946).

The stability of four different hydrophobic surfaces in contact with water is assessed and discussed: H-terminated silicon, hexamethyldisilazane (HMDS) coated silicon, silicon surfaces covered with self-assembled monolayers (SAMs) of octadecyltrichlorosilane (OTS) and gold surfaces modified with SAMs of alkanethiols. Changes in hydrophobicity and surface oxidation were determined by contact angle measurements, X-ray photoelectron spectroscopy and AFM.

Keywords: Hydrophobic surfaces; Stability; Surface modification; Self-assembling monolayers

Fabrication of structures with tunable morphologies and sizes by soft molding by Xinhong Yu; Zhe Wang; Rubo Xing; Shifang Luan; Yanchun Han (pp. 1947-1953).

This paper presents a simple and versatile patterning method to fabricate polymer patterns with different morphologies and sizes by utilizing soft molding. When a patterned elastomeric stamp was placed on the polymer solution dropped on the substrate, the polymer solution will fill into the grooves of the stamp under capillary force. Through the modulation of the polymer concentration, it is possible to produce highly regular and reproducible polymer patterns with tunable morphologies and sizes using the same microscopic patterned mold. The gained polymer patterns can be further transferred to produce second-generation stamps.

Keywords: Pattern; Soft molding; Capillarity

Self-organized amorphous material in silicon (001) by focused ion beam (FIB) system by Y. Huang; D.J.H. Cockayne; C. Marsh; J.M. Titchmarsh; A.K. Petford-Long (pp. 1954-1958).

A method using a focused ion beam (FIB) to prepare a silicon amorphous material is presented. The method involves the redeposition of sputtered material generated during the interaction of the Ga⁺ ion beam with a silicon substrate material. The shape and dimensions of this amorphous material are self-organized and reproducible. The stability of this amorphous material under electron irradiation was investigated in the transmission electron microscopy (TEM). Electron irradiation can induce recrystallization of the amorphous material, resulting in the lateral and vertical growth, starting at an amorphous–crystalline interface, of polysilicon containing defects.

Keywords: Focused ion beam (FIB); Amorphous silicon; TEM

Preparation and characterization of carbonate terminated polycrystalline Al₂O₃/Al films by C. Tornow; P.-L.M. Noeske; S. Dieckhoff; R. Wilken; K. G�rtner (pp. 1959-1965).

X-ray photoelectron spectroscopy (XPS) was applied to investigate the surface reactivity of polycrystalline Al films in contact with a gas mixture of carbon dioxide and oxygen at room temperature. Based on the characterization of interactions between these substrates and the individual gases at selected exposures, various surface functionalities were identified. Simultaneously dosing both carbon dioxide and oxygen is shown to create surface-terminating carbonate species, which contribute to inhibiting the formation of an Al₂O₃ layer. Finally, a reaction scheme is suggested to account for the observed dependence of surface group formation on the dosing conditions.

Keywords: PACS; 79.60.−i; 81.65.Mq; 82.65.MyAluminium surface; Oxygen; Carbon dioxide; Gas mixture; Carbonate

Electronic and interface state density distribution properties of Ag/p-Si Schottky diode by Mustafa Okutan; Engin Basaran; Fahrettin Yakuphanoglu (pp. 1966-1973).

Electronic and interface state distribution properties of Ag/p-Si Schottky diode have been investigated. The diode indicates non-ideal current–voltage behavior with an ideality factor greater than unity. The capacitance–voltage ( C– V) characteristic is linear in reverse bias indicating rectification behavior and charge density within depletion layer is uniform. From I– V and C– V characteristics, junction parameters such as diode ideality factor and barrier height were found as 1.66 and ϕB( I– V₎=0.84eV ( ϕB( C– V₎=0.90eV), respectively. The interface state density N_ss and relaxation time τ of the Schottky diode were determined by means of Schottky capacitance spectroscopy method. The results show the presence of thin interfacial layer between the metal and semiconductor.

Keywords: Schottky diode; Interface state density; Conductance–capacitance technique

Impact of yttrium ion implantation on corrosion behavior of laser beam welded zircaloy-4 in sulfuric acid solution by Qian Wan; Xinde Bai; Xiaoyang Liu (pp. 1974-1980).

In order to study the effect of yttrium ion implantation on the aqueous corrosion behavior of laser beam welded zircaloy-4 (LBWZr4), The butt weld joint of zircaloy-4 was made by means of a carbon dioxide laser, subsequently the LBWZr4 samples were implanted with yttrium ion using a MEVVA source at an energy of 40keV, with a fluence range from 1�10¹⁶ to 4�10¹⁶ions/cm² at about 150�C. Three-sweep potentiodynamic polarization measurement was employed to evaluate the aqueous corrosion behavior of yttrium-implanted LBWZr4 in a 0.5M H₂SO₄ solution. Scanning electron microscopy (SEM) was used to examine the surface topographic character of the yttrium-implanted LBWZr4 before and after the potentiodynamic polarization measurement. The valences of the carbon, yttrium, and zirconium in the surface layer were analyzed by X-ray photoemission spectroscopy (XPS). It was found that a significant improvement was achieved in the aqueous corrosion resistance of yttrium-implanted LBWZr4 compared with that of the un-implanted LBWZr4. The mechanism of the corrosion resistance improvement of the yttrium-implanted LBWZr4 is probably due to the addition of the yttrium oxide dispersoid into the zirconium matrix.

Keywords: Zircaloy-4; Laser beam weld; Yttrium ion implantation; Corrosion resistance

Rapid growth of nanocrystalline CuInS₂ thin films in alkaline medium at room temperature by Seung Jae Roh; Rajaram S. Mane; Habib M. Pathan; Oh-Shim Joo; Sung-Hwan Han (pp. 1981-1987).

Layer-by-layer (LbL) deposition of CuInS₂ (CIS) thin films at room temperature (25°C) from alkaline CuSO₄+In₂(SO₄)₃ and Na₂S precursor solutions was reported. The method allowed self-limited growth of CIS films with nanocrystalline structure and composed of densely packed nanometer-sized grains. The as-deposited CIS film was 250nm thick and composed of closely packed particles of 20–30nm in diameter. The alkaline cationic precursor solution was obtained by dissolving CuSO₄ and InSO₄ in deionized water with a appropriate amount of hydrazine monohydrate (H–H) and 2,2′,2″-nitrilotriethanol (TEA). CIS films were annealed at 200°C for 2h and effect of annealing on structural, optical, and surface morphological properties was thoroughly investigated by means of X-ray diffraction, scanning electron microscopy, transmission electron microscopy, UV–vis spectrometer, C-V, and water contact angle techniques, respectively.

Keywords: CuInS; ₂; XRD; SEM; TEM; UV–vis; C-V; Water contact angle

An XPS study and electrical properties of Pb_1.1Zr_0.53Ti_0.47O₃/PbO/Si (MFIS) structures according to the substrate temperature of the PbO buffer layer by Chul-Ho Park; Mi-Sook Won; Young-Hun Oh; Young-Gook Son (pp. 1988-1997).

PbO and PZT thin films were deposited on the p-type (100) Si substrate by the rf magnetron sputtering method with PbO and Pb_1.1Zr_0.53Ti_0.47O₃ targets for the application of the metal–ferroelectric–insulator–semiconductor (MFIS) structure. The MFIS structures with the PbO buffer layer show the good electric properties including a high memory window and a low leakage current density. The maximum value of the memory window is 2.0V under the applied voltage of 9V for the Pt/PZT (200nm, 400°C)/PbO (80nm)/Si structures with the PbO buffer layer deposited at the substrate temperature of 300°C. From the X-ray photoelectron spectroscopy (XPS) results, we could confirm that the substrate temperature of PbO affects the chemical states of the interface between the PbO buffer layer and Si substrate, which results in the inter-diffusion of Pb and the formation of the intermediate phases (PbSiO₃). And the existence of the undesired SiO₂ layer, which is the low dielectric layer, was confirmed at the surface region of the Si substrate by the XPS depth profile analysis.

Keywords: Pb; _1.1; Zr; _0.53; Ti; _0.47; O; ₃; thin film; PbO buffer layer; MFIS structure; Ferroelectric properties; Ferroelectric random access memory

X-ray photoelectron spectroscopy characterization of the layered intercalated compound K2_xMn1−_xPS₃ by L. Silipigni; G. Di Marco; G. Salvato; V. Grasso (pp. 1998-2005).

Polycrystalline powders of the layered MnPS₃ compound have been intercalated with K⁺ ions by ion-exchange to yield the K2_xMn1−_xPS₃ intercalate. X-ray photoelectron spectroscopy has been applied to learn about the electronic structure of this compound. In particular, we have studied the XPS spectra of the Mn 2p and 3p, P and S 2p, K 2p and 3p core levels and of the valence band region. The binding energies for various core levels of the elements present in this compound and their observed chemical shifts are analyzed. The data give evidence for the lack of non-equivalent atoms of K, Mn, P and S. Shake-up satellites are present at the Mn 2p and 3p core levels. The occurrence of such lines allows us to hypothesize that K2_xMn1−_xPS₃ is a large-gap insulating Mn compound. Confirmation that only an ion transfer accompanies the intercalation process is given from both the strong observed similarity with the corresponding XPS spectra in MnPS₃ and the observed binding energy positions of the K 2p and 3p levels. As regards the valence band XPS spectrum, the observed analogies with the corresponding XPS spectra of the pure compound and of other K compounds have allowed us to single out two regions and their probable contributors.

Keywords: PACS; 33.60.FyLayered intercalation materials; Potassium intercalated compounds; XPS spectra

Transparent conducting zirconium-doped zinc oxide films prepared by rf magnetron sputtering by Maoshui Lv; Xianwu Xiu; Zhiyong Pang; Ying Dai; Shenghao Han (pp. 2006-2011).

Transparent and conducting zirconium-doped zinc oxide films with high transparency and relatively low resistivity have been successfully prepared by rf magnetron sputtering at room temperature. The lowest resistivity achieved was 2.93×10⁻³Ωcm for a thickness of 475nm with a Hall mobility of 13cm²V⁻¹s⁻¹ and a carrier concentration of 1.71×10²⁰cm⁻³. The films are polycrystalline with a hexagonal structure and a preferred orientation along the c-axis. All the films present a high transmittance of approximately 90% in the visible range. The optical band gap decreases from 3.42 to 3.27eV as the thickness increases from 100 to 600nm.

Keywords: PACS; 68.55.Jk; 73.61.Ga; 78.30.FsZirconium; Zinc oxide; Sputtering; Transparent conducting films

Investigation of carbon plasma species emission at relatively high KrF laser fluences in nitrogen ambient by S. Abdelli-Messaci; T. Kerdja; A. Bendib; S.M. Aberkane; S. Lafane; S. Malek (pp. 2012-2020).

Optical emission spectroscopy diagnostic of carbon plasma created by an excimer KrF laser pulse at three different laser fluences (12, 25 and 32J/cm²) is performed under nitrogen ambience at a pressure of 1mbar. A spatio-temporal evolution study of different species such as CII, CI, NII, C₂ and CN is presented and comparisons between them are made. We found that C₂ and CN emission intensity did not depend on laser fluence while CII and NII emission intensity increases continuously with the raise of the fluence. The spatio-temporal evolution of CN follows the C₂ one at the vicinity of the target surface, whereas for greater distances, it follows the CII one. A scenario of CN formation is thus proposed, by stating that at the neighbourhood of the target surface CN molecules comes directly from this surface or from the bimolecular reaction between C₂ and N₂ in the gas phase. However, at greater distances, CN molecules are mainly produced by a three-body reaction between the atomic species C and N.

Keywords: PACS; 52.50.Jm; 52.38.Mf; 81.15.FgLaser ablation; Laser induced plasma; Optical emission spectroscopy

The metallurgical behavior of B₄C in the iron-based surfacing alloy during PTA powder surfacing by Wang Xibao (pp. 2021-2028).

The metallurgical behavior of B₄C in the iron-based surfacing alloy during plasma transferred-arc (PTA) Fe–B₄C composite powder surfacing was investigated and discussed in this paper. Based on the experiment results it is found that Fe–B₄C composite coatings can only be prepared by PTA powder surfacing in the case that the employed surfacing current is little enough. The metallurgical reactions between Fe and B₄C are limited in a very narrow region at their contacting interface in this case. With the increasing of employed surfacing current more and more B₄C particles will be fully melted and reacted with the liquid iron-based alloys. However, the products of the metallurgical reactions between them are various for the different powder compositions and surfacing conditions. Most of the B₄C particles will be fully melted during the PTA powder surfacing while 200A or greater surfacing current is used. Furthermore, most of the C element in B₄C particles is tending to be graphite rather than reacting with Fe to be carbides during the processing under the Fe–B₄C composite powder PTA surfacing conditions.

Keywords: B; ₄; C; Metallurgical behavior; Iron-based alloy; Powder surfacing

Structures and electrochromic properties of tungsten oxide films prepared by magnetron sputtering by Tien-Syh Yang; Zhong-Ron Lin; Ming-Show Wong (pp. 2029-2037).

Tungsten oxide (WO₃) films were deposited by DC magnetron sputtering of tungsten target in O₂/Ar atmosphere. The structures of the films following the various O₂ flow rate in a fixed Ar gas supply were investigated by X-ray diffraction patterns, Raman spectra and transmission electron microscopy. The electrochromic properties were characterized by a cyclic voltammetry and UV–vis absorption spectra. The results show that nanocrystalline WO₃ film with crystallite size about 10–20nm, deposited at 16sccm O₂, has larger charge capacity and coloration efficiency than the other amorphous films. Post-annealing the film at 200°C would create 30–50nm nanocrystalline film, whose electrochromic properties are promoted further due to even larger internal volume, essential to conduct ions and electrons for electrochromic intercalation. However, the electrochromic property deteriorates apparently in the film with 60–100nm nanocrystallites annealed at 300°C, which may be caused by another electrochromism occurring always in the well-crystallized WO₃ films.

Keywords: Tungsten oxide; Magnetron sputtering; Electrochromic; Nanocrystalline

Characterization of bioactive surface oxidation layer on NiTi alloy by Y.W. Gu; B.Y. Tay; C.S. Lim; M.S. Yong (pp. 2038-2049).

To enhance the bioactivity of NiTi alloy, the surface oxidation layers were synthesized by heat treatment in air in the temperature range of 300–800°C. The surface oxidation layer on NiTi alloy was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The heat treated sample was soaked in simulated body fluid (SBF) to study the bioactivity of the thermally grown oxide layer. Results showed that a protective layer of TiO₂ was formed on the surface of NiTi alloy at heat treatment temperatures of 600°C or higher with varying degree of anatase and rutile. Small amount of nickel oxide was found on the surface of 300 and 400°C treated samples by X-ray photoelectron spectroscopy. With further increase in the heat treatment temperature, the nickel concentration on the surface decreased and there was almost no nickel species on the surface after heat treatment at 600°C or 800°C. Depth profiling revealed that the amount of TiO₂ (Ti⁴⁺) decreased with depth with a concomitant increase of metallic Ti. In addition, both TiO (Ti²⁺) and Ti₂O₃ (Ti³⁺) increased initially and then decreased gradually with depth. Ni existed mainly in the oxidized state on the surface of heat treated samples and it changed to metallic state with increasing depth. In vitro test revealed that the titanium oxide layer formed on the 600 and 800°C heat treated samples was bioactive, and a layer of apatite was formed on the surface of the titanium oxide layer after soaking in simulated body fluid.

Keywords: NiTi; Heat treatment; Titanium oxide; Coating; Surface chemistry; Bioactivity

Photocatalytic activity and interfacial carrier transfer of Ag–TiO₂ nanoparticle films by Baifu Xin; Zhiyu Ren; Haiyuan Hu; Xiangyu Zhang; Chunlei Dong; Keying Shi; Liqiang Jing; Honggang Fu (pp. 2050-2055).

The electrodes of Ag–TiO₂ with different Ag content are prepared by a modified sol–gel method. The photochemical properties of Ag–TiO₂ with different Ag content are characterized by surface photovoltage spectroscopy (SPS). The results show that the SPS intensity decreased with increasing Ag contents. This demonstrates that the doping Ag plays the roles trapping photoinduced electrons, which inhibiting the recombination of photoinduced electrons and holes. The photoelectrochemical properties of Ag–TiO₂ electrodes with different Ag content are performed by electrochemical impedance spectroscopy (EIS) under high-pressure mercury lamp (160W) illuminating, and photocatalytic degradation of RhB are studied at the same time. The experimental results indicate that the process of charge transfer is a controlled-step of photocatalytic reaction. The SPS intensity and the electrical impedance values of EIS equivalent circuits are contrary to photocatalytic degradation ratio of RhB.

Keywords: PACS; 73.50.Pz; 73.90.+f; 84.37.+qAg modified TiO; ₂; Photocatalysis; Charge carrier transfer

AES depth profiling and interface analysis of C/Ta bilayers by A. Zalar; J. Kova�?; B. Pra�?ek; S. Hofmann; P. Panjan (pp. 2056-2062).

To study the AES sputter depth profiling of a layered structure with different layer densities and sputtering yields, a bilayer structure of C-graphite (60nm)/Ta (50nm) was sputter deposited onto smooth silicon substrates. The sputtering rates of C and Ta and the depth resolution, Δ z, at the C/Ta interfaces were investigated using 1 and 3keV Ar⁺ ions, respectively, varying the angle of incidence in the range between 22° and 82°. It was found that the sputtering rates of Ta and C as well as their ratio are strongly angle dependent. The sputtering induced surface topography deteriorated the depth resolution and was studied by atomic force microscopy (AFM). The ripple structures formed on the surfaces of carbon layers during sputter depth profiling of stationary samples could be avoided by sample rotation. The measured carbon concentration profile revealed a strong electron incidence angle dependent backscattering effect on the C (272eV) Auger signal. The measured AES depth profile obtained with 1keV Ar⁺ ions at an angle of incidence of 49° was compared to the theoretical depth profile calculated by the mixing, roughness, information depth (MRI) model taking into account backscattering effect of primary electrons. The measured AES concentration profile agrees well with the simulated one obtained with the MRI model.

Keywords: AES depth profiling; C/Ta bilayer; Interfaces; Depth resolution; Sputtering rate; Backscattering

Micro-patterning of chemical functionality of anthracene-bis-resorcinol film using focused ion beam by Hiroyuki Yoshikawa; Shuhei Namba; Yoshihiro Yokote; Yasuhiro Aoyama; Hiroshi Masuhara (pp. 2063-2070).

Anthracene-bis-resorcinol is an interesting molecule as it forms a hydrogen-bonded network when guest molecules with weak polarity are included. Focused ion beam (FIB) was irradiated on a part of its amorphous film with low dose, and the film was exposed to the vapor of guest molecules. From fluorescence and AFM analyses of this film, it was found that no inclusion compound was formed in FIB irradiated area, i.e. FIB irradiation suppresses the ability to form the inclusion compounds. By utilizing this phenomenon, we succeeded in a microfabrication of relief structures consisting of inclusion compounds which has different fluorescence from its surrounding. Morphology, fluorescence, and IR absorption analyses indicated that hydroxyl or resorcin groups are damaged by ion beams, and consequently a formation of hydrogen-bonded networks, which play a role of a lattice caging guest molecules, becomes impossible.

Keywords: PACS; 8540Ux; 7920Rf; 3350Dq; 8764Ni; 3170KsAnthracene-bis-resorcinol; Focused ion beam; Atomic force microscope; Inclusion compound; Fluorescence spectrum

Effects of 248nm excimer laser irradiation on the properties of Mg-doped GaN by X.C. Wang; G.C. Lim; W. Liu; C.B. Soh; S.J. Chua (pp. 2071-2077).

The effects of 248nm KrF excimer laser irradiation on the properties of Mg-doped GaN film were investigated. The laser irradiation-induced property changes were studied by photoluminescence, I– V, C– V, DLTS, AFM measurements. It was found that under appropriate laser conditions, 248nm KrF excimer laser irradiation could significantly increase the PL intensity of Mg-doped GaN film. The electrical properties (hole concentration and conductivity) were also improved by laser irradiation. From DLTS results, the hole-trap level appeared to have been effectively eliminated by laser treatment. The process has potential applications in the fabrication of GaN-based electronic and opto-electronic devices.

Keywords: PACS; 61.80.Ba; 79.20.Ds; 81.40.-z248; nm KrF excimer laser; Mg-doped GaN; Laser-induced activation; Optical property; Electrical property

Study on the adsorptive stripping voltammetric determination of trace cerium at a carbon paste electrode modified in situ with cetyltrimethylammonium bromide by Shumei Liu; Junan Li; Shijie Zhang; Jianqing Zhao (pp. 2078-2084).

A procedure was developed for the determination of trace cerium based on the oxidation of the absorbed cerium (III)–alizarin complexon (ALC) complex at a carbon paste electrode (CPE) modified in situ with cetyltrimethylammonium bromide (CTAB). Optimum experiment conditions included 2.0×10⁻⁶moll⁻¹ ALC, 6.0×10⁻⁵moll⁻¹ CTAB, 0.1moll⁻¹ acetic acid and sodium acetate (HAc–NaAc) and 0.2moll⁻¹ potassium biphthalate (KHP), pH 5.0, an accumulation potential of −0.1V, and a scan rate of 100mVs⁻¹. Linearity between peak currents and concentrations existed for 8.0×10⁻¹⁰ to 8.0×10⁻⁹moll⁻¹ for 120s accumulation and 8.0×10⁻⁹ to 1.0×10⁻⁷moll⁻¹ for 60s accumulation. The detection limit after a 120s preconcentration was 6.0×10⁻¹⁰moll⁻¹ (S/N=3). The relative standard deviation was 4.9% for eight successive determinations on the same electrode surface at 2.0×10⁻⁸moll⁻¹ level. The procedure was expected to determine trace cerium with elevated selectivity. The results were quite consistent with the certified values for the determination of cerium in rare earth nodular cast iron samples.

Keywords: Cerium; Alizarin complexon; Cetyltrimethylammonium bromide; Carbon paste electrodes; Adsorptive stripping voltammetry

Coating tips used in electrical scanning probe microscopy with W and AuPd by H.S. Huang; H.M. Cheng; L.J. Lin (pp. 2085-2091).

A conductive tip is essential for probing the electrical characterization in scanning probe microscopy (SPM). This study investigates the efficiency of W and AuPd as coating materials in a silicon cantilever for application to conductive SPM. The results show that the two self-coated probes could both be used in SCM and SPO modes. However, they were not appropriate for use in CAFM mode because the conductive films do not strongly resist wear. The presented AuPd probe outperforms the W probe because it more strongly resists the oxide formation at the end of tip.

Keywords: PACS; 81.15.Cd; 09.79.−vConductive film; Scanning probe microscopy; Wear resistance

The influence of polyaniline (PANI) top coat on corrosion behaviour of nickel plated copper by A.T. Özyılmaz; M. Erbil; B. Yazıcı (pp. 2092-2100).

The polyaniline (PANI) was carried out on Ni plated (1μm) copper (Cu/Ni). The synthesis was achieved under cyclic voltammetric conditions from 0.1M aniline containing oxalic acid solutions. AC impedance spectroscopy (EIS) and anodic polarization curves were used to evaluate the corrosion performance of PANI coated and uncoated electrodes in 3.5% NaCl. It was found that nickel coating exhibited significant barrier property against the attack of corrosive agents. However, the porosity rate of nickel coating increased in time. PANI modified nickel plating provided much better barrier property to copper for longer periods. It was important that PANI coating by its catalyzing effect constituted lower permeability with the formation of stable nickel oxides on top of nickel plating and the catalytic behaviour of polymer film prevented increase of the porosity in longer periods, in such an aggressive medium.

Keywords: Nickel plating; Polyaniline; Corrosion; AC impedance spectroscopy; Copper

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Applied Surface Science (v.252, #5)