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Applied Surface Science (v.246, #1-3)

Subject Index (pp. v-xv).

Author Index (pp. i-iii).

Understanding the effect of the spacer length on adsorption of gemini surfactants onto steel surface in acid medium by Ling-Guang Qiu; An-Jian Xie; Yu-Hua Shen (pp. 1-5).

Corrosion inhibition of carbon steel in 1M hydrochloride acid by gemini surfactants alkanediyl-α,ω-bis(dimethyl dodecylammonium bromide) with different spacer lengths (designated as 12- s-12, s=2, 3 or 6) was studied using the weight loss method. When monolayer forms on the metal surface below or near critical micelle concentrations (CMCs) of the gemini surfactants, it can be found that gemini surfactant with long spacer (12-6-12) tends to be adsorbed with two hydrophilic ionic groups onto the metal surface site, while gemini surfactants with short spacer (12-2-12 and 12-3-12) tend to be adsorbed with one hydrophilic group onto the meta surface site and the other hydrophilic group is free in solution phase, and further increase in surfactant concentration results in the formation of multilayer. Possible adsorption mechanisms of these gemini surfactants with different spacer lengths above and below their CMCs were discussed in detail, respectively.

Keywords: Gemini surfactant; Adsorption; Mechanism; Corrosion; Inhibition; Metal

Electronic process of Cu(Ag, V, Rh)(001) surface oxidation: atomic valence evolution and bonding kinetics by Chang Q. Sun / (pp. 6-13).

The electronic processes of Cu(Ag, V, Rh)(001) surface oxidation are comparatively analyzed based on the recent ‘chemical bond–valence band–potential barrier’ (BBB) correlation mechanism [C.Q. Sun, Prog. Mater. Sci. 48, 521–685 (2003)], which allows reaction formulae for all the observed phases with identification of individual atomic valence and the binding kinetics at the surfaces with the same geometry. It is consistently understood that the forming kinetics of the primary oxide tetrahedron and its derivative on the valence density-of-states (DOS) are intrinsically common for all these analyzed systems, though the patterns of observation in terms of morphology and crystallography vary from situation to situation. However, the lattice size and electronegativity of the host surfaces determine extrinsically the site selectivity of the oxygen, the order of bond formation and the orientation of the oxide tetrahedron.

Keywords: Chemical bond; Valence band; Surface potential; Cu; Ag; V; Rh; Oxygen; Oxidation; Reaction kinetics; Scanning tunneling microscopy; LEED; PES

Atomic-scale calculation of interface energy for Ag/Ni by Jian-Min Zhang; Hong Xin; Xiu-Mei Wei (pp. 14-22).

The energies of (001)Ag/(111)Ni, (011)Ag/(111)Ni and (111)Ag/(111)Ni twist boundaries have been calculated with modified analytical embedded atom method (MAEAM). The results show that the interface energies corresponding to (111)Ag/(111)Ni, (001)Ag/(111)Ni and (011)Ag/(111)Ni increase successively and three lowest energies corresponding to twist angles θ=2.10°, 15° and 28.93° for (111)Ag/(111)Ni, (001)Ag/(111)Ni and (011)Ag/(111)Ni are 272, 743.3 and 1094.3mJ/m², respectively. The epitaxial growth of Ag film on (111)Ni substrate driven solely by minimization of interface energy should result in the predominance of (111) grains, especially twist angle θ=2.10°.

Keywords: Ag/Ni; Interface energy; Calculation; MAEAM

Raman and infrared spectroscopy of Ge nanoparticles embedded in ZnO matrix by U. Pal; J. Garc�a Serrano (pp. 23-29).

Ge nanoparticles of 2.3–5.0nm size embedded in ZnO matrix were prepared by rf alternate sputtering and subsequent annealing technique. Raman and infrared (IR) absorption spectroscopy were used to characterize the Ge/ZnO nanocomposite films. Raman spectra of the composite films revealed 300cm⁻¹ Ge–Ge transverse optic (TO) vibrational band of Ge nanocrystals, which shifted towards lower frequencies on decreasing the size of Ge nanocrystals due to phonon confinement in smaller crystallites. IR spectra of the composite films revealed that the Ge nanocrystals remain with elemental core surrounded by oxidized cap-layer. The thickness of the oxide cap-layer decreased with the increase of annealing temperature.

Keywords: PACS; 78.30.Am; 78.55.Ap; 78.66.Sq; 78.67.BfNanocomposites; Semiconductors; Raman spectroscopy; Infrared spectroscopy

The energy distribution of the interface state density of SnO₂/p-Si (111) heterojunctions prepared at different substrate temperatures by spray deposition method by S. Karadeniz; N. Tuğluoğlu; T. Serin; N. Serin (pp. 30-35).

We have fabricated the Al/SnO₂/p-Si (111) Schottky diodes having the SnO₂/p-Si heterojunction prepared using the spray deposition process at various Si substrate temperatures and report the first investigation of the energy distribution of the interface state density of these diodes. The barrier height Φ_B estimated from the I– V and C– V measurements agrees with each other and increased with increasing substrate temperature. The energy distribution of interface state density N_ss was determined from the forward bias I– V characteristics by taking into account the bias dependence of the effective barrier height. The interface state density N_ss of the diodes has an exponential growth with bias from the midgap towards the top of the valance band for each diode; for example, from 1.46×10¹²eV⁻¹cm⁻² in (0.46− E_v) eV to 1.29×10¹²eV⁻¹cm⁻² in (0.53− E_v) eV for SD3 sample.

Keywords: PACS; 73.30.+y; 73.40.QvSnO; ₂; /p-Si heterojunction; MIS structure; Interface state energy distribution; Spray deposition method

Study on the combustion behavior of methane over Ce–Zr-modified Pd/Al₂O₃ catalysts by Baohua Yue; Renxian Zhou; Yuejuan Wang; Xiaoxiang Han; Xiaoming Zheng (pp. 36-43).

The effects of ceria and zirconium additions to alumina-supported palladium catalysts on methane combustion behavior have been investigated. A series of Ce–Zr-modified Al₂O₃ supports and their supported Pd catalysts are prepared using impregnation method and then characterized by BET, XRD, LR, TEM, XPS techniques. The results show that the addition of Ce–Zr improves the thermal stability of alumina. The thermal stability of alumina increases with increasing the loading of Zr. The methane oxidation activity and thermal stability is found to be dependent on the Ce:Zr ratio over the Pd/Ce_xZr1−_x/Al₂O₃ catalysts. The Pd/Ce_0.2Zr_0.8/Al₂O₃ exhibits the highest activity and thermal stability for methane oxidation. The temperatures for the 90% methane conversion are 448 and 455°C for the Pd/Ce_0.2Zr_0.8/Al₂O₃ catalysts calcined at 500 and 1100°C, respectively. TEM results show that the particle size of Pd is not the key factor influencing the activity of Pd/Ce_0.2Zr_0.8/Al₂O₃ catalyst. An induction period is present during methane combustion reaction for the Pd/Al₂O₃ and Pd/Ce_xZr1−_x/Al₂O₃ catalysts (calcined at 1100°C), but the lengths of induction period are obviously different and the Pd/Ce_0.2Zr_0.8/Al₂O₃ catalyst exhibits the shortest induction period. XPS results show that comparing to Pd/Al₂O₃ catalyst the addition of Ce–Zr stabilizes Pd in a high oxidation state and enhances the reoxidation of metallic Pd to the active PdO under reaction conditions. Therefore the Pd/Ce_xZr1−_x/Al₂O₃ catalysts compared to Pd/Al₂O₃ catalysts have higher thermal stability and shorter induction period.

Keywords: PACS; 82.65.+rPalladium; Ceria–zirconium–alumina; Thermal stabilization; Methane combustion

Laser-induced production of large carbon-based toroids by M. Elizabeth Lyn; Jibao He; Brent Koplitz (pp. 44-47).

We report on the production of large carbon-based toroids (CBTs) from fullerenes. The process involves two-step laser irradiation of a mixed fullerene target (76% C₆₀, 22% C₇₀). Transmission electron microscopy (TEM) clearly identifies toroidal-shaped structures as well as Q-shaped constructs. The typical diameters of the CBTs are ∼0.2–0.3μm with tubular diameters of ∼50–100nm, but toroids as wide as 0.5μm are observed making them nanostructures on the verge of being microstructures.

Keywords: PACS; 81.05.Tp; 81.15.FgLaser-induced production; Carbon-based toroids; TEM; Fullereness

Low-emissivity coating of amorphous diamond-like carbon/Ag-alloy multilayer on glass by Kiyoshi Chiba; Toshiyuki Takahashi; Takashi Kageyama; Hironori Oda (pp. 48-51).

Transparent low-emissivity (low-e) coatings comprising dielectrics of amorphous diamond-like carbon (DLC) and Ag-alloy films are investigated. All films have been prepared by dc magnetron sputtering. An index of refraction of the DLC film deposited in a gas mixture of Ar/H₂ (4%) shows n=1.80+0.047 i at 500nm wavelength. A multilayer stack of DLC (70nm thick)/Ag_87.5Cu_12.5-alloy (10nm)/DLC (140nm)/Ag_87.5Cu_12.5-alloy (10nm)/DLC (70nm) has revealed clear interference spectra with spectra selectivity. This coating performs low emittance less than 0.1 for black body radiation at 297K, exhibiting a transparent heat mirror property embedded in DLC films.

Keywords: PACS; 78.66.-wLow-emissivity coating; Diamond-like carbon; Heat mirror; Multilayer

Functionalization of atomically flat, dihydrogen terminated,1×1 (1 0 0) silicon via reaction with 1-alkyne by G.F. Cerofolini; C. Galati; S. Reina; L. Renna; G.G. Condorelli; I.L. Fragal�; G. Giorgi; A. Sgamellotti; N. Re (pp. 52-67).

An experimental study via X-ray photoelectron spectroscopy at different takeoff angles of the derivatization of atomically flat, hydrogen terminated,1×1 (1 0 0) Si surfaces with 1-octyne is reported. The major conclusion of the experimental analysis (that a large fraction of the grafted moieties contain unreactedπ bonds) is then compared with the results of high-level ab initio modelling with model molecules of the derivatization act.

Keywords: Alkyne; Silicon; Oxygen

Reactive gold thin films grown on iridium by Michio Okada; Shouhei Ogura; Wilson Agerico Di�o; Markus Wilde; Katsuyuki Fukutani; Toshio Kasai (pp. 68-71).

We report results of our studies on the dissociative adsorption of hydrogen on Au thin films grown epitaxially on Ir{111} surface, using nuclear reaction analysis. We found that H₂ dissociatively adsorbs on these Au{111} films. This feature can be contrasted to the well-known noble bulk Au surfaces, which do not dissociate hydrogen molecules. We attribute this to the local surface properties, e.g., electron localization (the narrowing of the s-band, the s-band center model), which can explain the unexpected high reactivity of a thin Au{111} film.

Keywords: PACS; PACS Code: 68.43.−hGold; Iridium; Hydrogen; Nuclear Reaction analysis; Dissociative adsorption

A chemical route to room-temperature synthesis of nanocrystalline TiO₂ thin films by Habib M. Pathan; Woo Young Kim; Kwang-Deog Jung; Oh-Shim Joo (pp. 72-76).

A lot of methods are developed for the deposition of TiO₂ thin films; however, in each of these methods as-deposited films are amorphous and need further heat treatment at high temperature. In the present article, a chemical bath deposition (CBD) method was used for the preparation of TiO₂ thin films. We investigated nanocrystalline TiO₂ thin films using CBD at room temperature onto glass and ITO coated glass substrate. The films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HRTEM) techniques. The chemically synthesized films were nanocrystalline and composed of crystal grains of 2–3nm.

Keywords: Nanocrystalline TiO; ₂; Chemical deposition; Synthesis and characterization

Effects of pore structure and surface state on the adsorption properties of nano-porous carbon materials in low and high relative pressures by W.H. Lee; J.S. Park; J.H. Sok; P.J. Reucroft (pp. 77-81).

The present investigation was undertaken to determine the adsorption characteristics of nano-scaled porous carbons using a gravimetric adsorption technique through CCl₄ and NH₃ adsorption studies in the two different relative pressure ranges. Nano-scaled pore volumes ( W₀) determined from CCl₄ adsorption isotherms were generally in good agreement with the BET surface area. However, the adsorption capacity of NH₃ in the very low relative pressure range was independent of the surface area of the carbon samples. This can be attributed to the presence of a greater number of active adsorption sites related to higher density of surface oxygen and surface oxygen functional groups on the lower surface area carbons. The degree of surface area development and nano-scaled pore volume control the adsorption process in the high relative pressure range, and the surface chemistry affects the adsorption process in the very low relative pressure range.

Keywords: PACS; 61.43.GNano-porous; Carbon; Adsorption; DR equation; XPS

Corrosion resistance properties of organic–inorganic hybrid coatings on 2024 aluminum alloy by Yan Liu; Dezhi Sun; Hong You; Jong Shik Chung (pp. 82-89).

Three kinds of organic–inorganic hybrid coatings modified by tetraethoxysilane (TEOS) were prepared using precursors of vinyltrimethoxysilane (VMS), [3-(methacryloxy)propyl] trimethoxysilane (MPMS) and (3-glycidoxyproyl) trimethoxysilane (GPMS). Properties of corrosion resistance were tested by potentiodynamic polarization curves. Salt spray test and SEM images were also employed to examine the ablitity of coatings to resist long-time corrosion. The results show that hybrid coatings are effective for inhibiting corrosion reaction. Corrosion currents of VMS coating and MPMS coating were 300 times smaller than that of bare sample. The corrosion current of hybrid coatings is smallest when TEOS content reaches 15–20%. It was found that VMS coatings have the strongest ability to resist salt spray corrosion.

Keywords: PACS; 81.65.KnOrganic–inorganic hybrid coatings; Anticorrosion properties; Potentiodynamic polarization curves; 2024 Aluminum alloy

Interface characterization between large area freestanding diamond films and molybdenum substrates by H.D. Zhang; H.Q. Li; J.H. Song; Y.M. Tong; F.X. Lu (pp. 90-95).

A study of an interfacial layers between freestanding diamond films and substrate diamond film growth was performed. Polycrystalline diamond films were grown on molybdenum substrates by dc arc jet plasma methods. A molybdenum carbide layer epitaxially was formed on the substrates used several times later, and its structure and composition were analyzed by different characterization techniques. The concentration of carbon decreased with an increase of distance from the substrate surface. Thicker and better-defined interfacial layers were found in diamond films grown on substrates used several times. This interface efficiently avoided carbon and hydrogen diffusion and also improved the chemical bond between diamond film and substrate during diamond growth. Characterization by X-ray diffraction, Raman spectroscopy and SEM analysis were also carried out.

Keywords: Freestanding diamond films; Interface; Layer

Periodic density functional investigation of Lewis acid sites in zeolites: relative strength order as revealed from NH₃ adsorption by Mohamed Elanany; Michihisa Koyama; Momoji Kubo; Ewa Broclawik; Akira Miyamoto (pp. 96-101).

Different types of cationic species acting as Lewis acid sites as well as Na-counter ion in dealuminated zeolites are investigated, for the first time, using periodic density functional method. The energy of ammonia adsorption is taken as a measure for the acidity. The results reveal that the relative strength of the investigated active sites increases in the order: Na⁺2⁺++. Moreover, the interaction of NH₃ with tri-coordinated aluminum dislodged in the framework is less favorable than that with the neighboring silicon ion.

Keywords: PACS; 31.15.Ew; 68.43.Bc; 68.43.Fg; 82.33.JxMordenite; Lewis acid site; Acidity; Ammonia adsorption; DFT; Dealumination

Irradiation effects of intense pulsed ion beam on the surface of Ni₃Al alloy by Zhi-Jian Liu; Xiao-Yun Le; Sha Yan; Wei-Jiang Zhao; Xing-Liu Jiang (pp. 102-107).

Ni₃Al base alloy was irradiated by intense pulsed ion beam (IPIB) with 250kV acceleration voltage, 100–200A/cm² current density and 60ns pulse duration. The surface morphology and the cross-section microstructures were observed with SEM, and the compositions were characterized by XEDS. The results showed that the appearance of craters induced by irradiation is one of the major factors affecting the irradiated surface roughness; irradiation leads to composition changes on the surface of IC6 alloy and may improve mechanical properties of IC6 alloy.

Keywords: PACS; 61.82.Bg; 81.40.Wx; 61.80.JhIntense pulsed ion beam; Ni; ₃; Al base alloy; Crater

Corrosion inhibition of pure iron in 0.5M H₂SO₄ solutions by ethanolamines by C. Jeyaprabha; S. Sathiyanarayanan; G. Venkatachari (pp. 108-116).

The inhibition of corrosion of pure iron in 0.5M H₂SO₄ by ethanolamines such as mono-, di- and triethanolamines has been investigated by dc polarization and ac impedance techniques. The results showed that a strong dependence of inhibitor performance with concentration in addition to the structural effects of amine molecules. From impedance data it is found that the corrosion of iron is controlled by charge transfer process at all concentrations of inhibitors. All the three inhibitors are found to hinder the formation of passive film on iron.

Keywords: Corrosion; Electrochemical impedance spectroscopy; Inhibitors; Iron; Passivation; Ethanolamines; Sulphuric acid

Monte Carlo simulation of interactions between energetic electron and cellulose film by Zhenyu Tan; Yueyuan Xia; Minwen Zhao; Xiangdong Liu (pp. 117-125).

Monte Carlo method of simulating the interactions between energetic electron and organic compound is presented. This method is based on the Mott cross-section and Rutherford cross-section for the elastic scattering of electrons in different energy regions and the cross-section derived by dielectric response theory with exchange effect included for the inelastic scattering of electrons. The comparisons have been done to show the reliability of the described method. Using this method, the systematic calculations of the mean energy loss of transmitted electrons through the cellulose films with different thickness for different primary energies have been performed. The dependence of the mean energy loss of transmitted electrons on cellulose film thickness is analyzed. A method to evaluate the mean energy loss of the transmitted electrons for the cellulose film with a fixed thickness at a given primary energy is proposed.

Keywords: PACS; 68.49.JK; 79.20.KzThin Film; Cellulose; Monte Carlo method; Energy loss; Plant breeding

AES investigation of anode deposits in magnetron-type sputter ion pump by Alenka Vesel; Miran Mozeti�?; Anton Zalar (pp. 126-131).

The composition of thin films deposited on the anode of a magnetron cell was studied by Auger electron spectroscopy (AES). The magnetron cell was constructed from a titanium cathode and a stainless steel anode. The cell was mounted on an UHV system with the ultimate pressure of 1×10⁻⁹mbar. A stable discharge was established in nitrogen atmosphere at 10⁻⁷mbar for 25 days. After the experiments, the electrodes were cut to small pieces and analyzed by AES. The results showed that a thin film of TiN slightly oxidized and contaminated by C was formed on the anode surface. The thickness of the film at the center of the anode was about 100nm and it monotonously decreased towards the edges, indicating a rather uniform erosion of the cathode rod.

Keywords: PACS; 81.65; 52.80.Sm; 52.80.VpAES depth profiles; Thin films; Titanium nitride; Sputter ion pump; Discharge cell; Magnetron cell; Anode

Nucleation, growth and structural properties of epitaxial Co–Ag alloy films by A. Azizi; J. Arabski; A. Dinia (pp. 132-138).

Granular Co–Ag alloy films elaborated by molecular-beam epitaxy at three temperatures: 20, 250 and 450°C, have been investigated. The influence of substrate temperatures on the growth and the structural properties is studied, using reflection high-energy electron diffraction (RHEED) and X-ray diffraction (XRD) techniques. For all growth temperatures, the in situ RHEED patterns of the Co–Ag alloys exhibit an in-plane six-fold symmetry, which indicates that the Co and Ag deposits are in epitaxy with the Ru buffer surface. At 20°C, the RHEED patterns show a unique lattice with diffuse lines, which is a feature of a rough surface. However, at 250°C, the RHEED patterns show double lines, which indicate the existence of two lattices, associated with Ag and Co metals. RHEED analysis indicates that the Co lattice constant relaxes to its bulk value after a critical thickness of 20Å, while the Ag has already relaxed at the growth beginning. XRD studies give evidence of a strongly textured alloy films, along the growth direction. It is found that, at 20°C, Co impurities are embedded in the Ag matrix. However, in the range 250–450°C, the system segregates and gives the formation of chemically pure entities of Co and Ag.

Keywords: PACS; 81.15; Hi; 82.80; Ej; 81.10; Aj; 61.14; HgCo–Ag alloy; MBE; Growth; RHEED; XRD

Chemical treatment effects of silicon surfaces in aqueous KF solution by Hiroshi Noguchi; Sadao Adachi (pp. 139-148).

The physical and chemical properties of Si(111), (110) and (100) surfaces treated in aqueous KF solution have been studied by means of spectroscopic ellipsometry (SE), ex situ atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and wettability measurements. The SE data indicate that the solution causes the removal of the silicon native oxide upon immersing the sample in the solution. The KF-treated Si(110) and (111) surfaces are nearly flat even after long-time etching. By contrast, the Si(100) surface is found to be considerably etched and roughened even if the etching time is shorter than the native oxide is completely etch-removed ( t<30min). The SE-estimated surface roughness is in reasonable agreement with the AFM rms value. The XPS data suggest that the KF-treated surface is cleaner than that etched in an HF solution. The as-degreased silicon surface is hydrophilic ( θ∼35°), while the KF-treated surface is hydrophobic ( θ∼80°). The properties of the KF-treated surface have also been discussed as compared to those obtained in aqueous NaF and HF solutions.

Keywords: PACS; 81.65.CfSi; Chemical treatment; Spectroscopic ellipsometry; Native oxide

Suitability of boron-nitride single-walled nanotubes as fluid-flow conduits in nano-valve applications by M. Grujicic; G. Cao; W.N. Roy (pp. 149-158).

Molecular-level simulations are used to examine the suitability of boron-nitride single-walled nanotubes (SWNTs) as fluid-flow conduits in the nano-valve applications based on a molecular-mono-layer functionalized silicon cantilever. The interaction between the constituent atoms in the nanotubes is modeled using the Universal Force Field inter-atomic potential. Key functional requirements (a large range of nanotube radii with a stable circular cross section, a low level of strain energy in the nanotube at the onset of bending-induced buckling, relatively high compliance with respect to the radial breathing mode and a low value of nanotube/fluid-molecule binding energy) have been identified for nanotube fluid-flow conduits. The results obtained suggest that boron-nitride SWNTs do not offer any significant functional advantage over their carbon-based counterparts when used in fluid-flow conduit applications. The results also suggests that several of the nanotube properties obtained through the use of the Universal Force Field are quite comparable to their counterparts based on the first-principles quantum-mechanical calculations.

Keywords: PACS; 81.05.TpSingle-walled carbon nanotubes; Boron-nitride nanotubes; Nano-devices; Nano-technology

Study of the Mo thin films and Mo/CIGS interface properties by L. Assmann; J.C. Bern�de; A. Drici; C. Amory; E. Halgand; M. Morsli (pp. 159-166).

Molybdenum thin film is the under electrode used in chalcopyrite solar cells family (CuInSe₂ and its alloys) because of the low resistivity of the Mo/CIS contact. During the solar cells process the Mo film is submitted to thermal and chemical constraints, therefore it should exhibits some specific properties to keep its mechanical and electrical properties. It is shown that the suitability of Mo films for such process depends strongly on the target–substrate distance and the argon pressure during deposition, i.e. to the internal constraints present in the films. Using an rf diode sputtering apparatus, adhesive films with small resistivity, �?=40μΩcm, can be achieved by modifying argon pressure during deposition.After co-evaporation of a Cu(In1−_xGa_x)Se₂ film the chemical and electrical properties of the Cu(In1−_xGa_x)Se₂/Mo interface have been studied. It is shown, by XPS depth profile, that MoSe₂ is present at the interface. The contact resistivity �?_c has been measured. Resistivities �?_c<0.08Ωcm² were found. From these XPS and electrical measurements it appears that the MoSe₂ interfacial layer mediates low resistivity Mo/CIGS contact.

Keywords: PACS; 65.35.−p; 68.55.jk; 73.4.CgMolybdenum; Thin film; Sputtering; Interface; Contact resistance

Selective silver seeding on laser modified polyimide for electroless copper plating by Dongsheng Chen; Yi Li; Qinghua Lu; Jie Yin; Zikang Zhu (pp. 167-173).

Copper was selectively deposited on PI surface catalyzed by laser-induced deposition of Ag particles. First, PI film was ablated by a focused Nd:YAG laser ( λ=266nm) for patterning, and then the ablated film was immersed in a silver diammine solution. Ag(NH₃)₂⁺ ions were reduced to Ag at the ablated region on the film, and the Ag particles were deposited in situ. After rinsing the film, copper was deposited on the seeded film by electroless plating successfully. Deposits and the ablated film were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and Stylus Profiler.

Keywords: PACS; 42.62.−bPolyimide; Laser; Electroless plating; Silver; Copper deposition

Formation of vacancy islands tailored by Pt nanocrystallites and Ar⁺ sputtering on TiO₂(110) surface by A. Berkó; A.M. Kiss; J. Szökő (pp. 174-182).

The effect of Ar⁺ bombardment was studied on TiO₂(110)-(1× n) surface decorated with Pt nanoparticles by scanning tunnelling microscopy (STM). Pt crystallites were fabricated in a large separation by the so-called seeding+growing method described earlier [A. Berkó, G. Klivényi, F. Solymosi, J. Catal. 182 (1999) 511]. It was shown that the presence of Pt crystallites results in an enhanced sputtering of the support in the vicinity of the particles at high temperatures. This process causes a dramatic increase in the average corrugation of the substrate and leads to formation of deep nanoditches in the orientation of [001]. The analysis of the geometry of the nanoparticles revealed that they are decorated with the material of the support. The noble metal nanocrystallites grown in large separation are suitable for the visualization of the accelerated surface diffusion and sputtering in the region around the crystallites. The phenomenon presented here prompts a nanotechnological tool capable of fabricating nanopits in tailored distribution (in the range of 5–200nm) that is determined by the original Pt nanoparticles formed on the TiO₂(110) surface.

Keywords: Pt nanoparticles; TiO; ₂; (1; 1; 0) support; Scanning tunnelling microscopy; Ar; ⁺; bombardment; Tailored distribution of nanopits

Initial reactivity of rf magnetron sputtered calcium phosphate thin films in simulated body fluids by E. van der Wal; J.G.C. Wolke; J.A. Jansen; A.M. Vredenberg (pp. 183-192).

Radio frequency (rf) magnetron sputtering of calcium phosphate (CaP) is a promising technique to apply thin bioactive films on bulk implant materials. In this paper the interaction is studied of thin (∼100nm) CaP films with Ca/P ratios ranging from 0.6 to 4.7, with simulated body fluids (SBFs) of different Ca and PO₄ concentrations. Analysis of the thickness and composition of the coatings was done with ion beam analysis.Amorphous coatings of all compositions were found to dissolve in all meta-stable SBFs. For coatings with a Ca/P ratio of 1.6, dissolution was linear and congruent.By heat-treating the coatings for 30min at 650°C, coatings were crystallized. Crystallized coatings with a Ca/P ratio of 1.6 remain inert when immersed in SBF for days. When immersed in doubly concentrated SBF, after an induction period of 40–60min where virtually no apposition of material is observed, a CaP precipitate is formed. After formation of these CaP crystals, continuous growth can proceed in SBFs with lower Ca and PO₄ concentrations.During the induction period, CaP sediments were found on the coating surface. Their role remains unclear, but their presence seems to be correlated with the ability to grow a precipitate layer from the solution. Completion of the induction period is essential for growth of the precipitate.

Keywords: Bioactivity; Calcium phosphate coating; Crystallisation; SBF (simulated body fluids); Surface analysis

STM-induced photon emission from sputter-deposited Ag nanoclusters by T. Arai; K. Nakayama (pp. 193-198).

We present results on a scanning tunneling microscope (STM)-induced photon emission from nanoclusters formed in sputter-deposited silver (Ag) films, whose surface consists of Ag clusters ranging from 20 to 60nm in diameter. The photon intensity images have been simultaneously obtained with the corresponding STM images. Those images show a good correlation between the topography and the intensity structure of photon emission. The intensity of photon emission exhibits an exponential-like increase with the increase of bias voltage. The photon emission spectra have separated peaks and exhibit a blue shift with the increase of bias voltage.

Keywords: PACS; 61.16.Ch; 73.20.Mf; 78.66.−wSTM; Photon emission; Ag; Nanocluster

Inhibition of the corrosion of steel in 1M HCl by eugenol derivatives by E. Chaieb; A. Bouyanzer; B. Hammouti; M. Benkaddour (pp. 199-206).

The effect of eugenol (Eug) and its derivative acetyleugenol (AcEug) extracted from the nail of giroflier on the corrosion of steel in molar hydrochloric acid has been studied using weight loss measurements, electrochemical polarisation and EIS methods. The naturally substances reduce the corrosion rate. The inhibition efficiency was found to increase with acetyleugenol content to attain 91% at 0.1737g/l. Eugenol compounds act as mixed type inhibitors. The effect of temperature on the corrosion behaviour of steel indicates that inhibition efficiency of the natural substance increases with the rise of temperature. The adsorption of natural product on the steel is found to follow the Langmuir adsorption isotherm.

Keywords: Corrosion; Inhibition; Steel; Eugenol; Adsorption

Pulsed laser deposition of metallic films on the surface of diamond particles for diamond saw blades by Jiang Chao; Luo Fei; Long Hua; Hu Shao-liu; Li Bo; Wang You-qing (pp. 207-213).

Ti or Ni films have been deposited on the diamond particle surfaces by pulsed laser deposition. Compressive resistance of the uncoated and coated diamond particles was measured, respectively, in the experiments. The compressive resistance of the Ti-coated diamonds particles was found much higher than that of the uncoated ones. It increased by 39%. The surface morphology is observed by the metallography microscope. The surface of the uncoated diamonds particles had many hollows and flaws, while the surface of Ni-coated diamond particles was flat and smooth, and the surface of Ti-coated diamond particles had some metal masses that stood out of the surface of the Ti-coated film. The components of the metallic films of diamond particles were examined by X-ray diffractometry (XRD). TiC was found formed on the Ti-coated diamond surface, which resulted in increased surface bonding strength between the diamond particles and the Ti films. Meanwhile, TiC also favored improving the bonding strength between the coated diamond particles and the binding materials. Moreover, the bending resistance of the diamond saw blade made of Ti-coated diamond was drastically higher than that of other diamond saw blades, which also played an important role in improving the blade's cutting ability and lifetime. Therefore, it was most appropriate that the diamond saw blade was made of Ti-coated diamond particles rather than other materials.

Keywords: Metallic films; Pulsed laser deposition; Compressive resistance; Bonding strength; Diamond saw blade

Microarc oxidation and spraying graphite duplex coating formed on titanium alloy for antifriction purpose by Y.M. Wang; B.L. Jiang; T.Q. Lei; L.X. Guo (pp. 214-221).

Microarc oxidation coatings were fabricated on Ti6Al4V alloy in NaAlO₂ containing solution. Microstructure and adhesion properties of the coatings were evaluated. For antifriction purpose, a novel duplex coating of microarc oxidation combined with spraying graphite process was developed. The results show that the microarc oxidation coating with 20μm thickness is compact and uniform in the inner layer, while porous in the surface layer. The coating has high adhesion strength of about 110MPa to the substrate. The novel duplex coating exhibits good antifriction property, registering friction coefficient of ≈0.12, which is 5 times lower than that of the microarc oxidation coating sliding in the similar condition. The good tribological property is attributed to the specially designed duplex structure, the coating adhering strongly to the substrate and serving as the underlying loading layer and the graphite layer on top of it working as solid lubricant.

Keywords: Ti6Al4V alloy; Microarc oxidation; Spraying graphite; Duplex coating; Microstructure; Antifriction property

Effect of CeO₂ addition on the structure and activity of RuO₂/γ-Al₂O₃ catalyst by Shaoxia Yang; Yujie Feng; Jiafeng Wan; Wanpeng Zhu; Zhanpeng Jiang (pp. 222-228).

RuO₂/γ-Al₂O₃ and RuO₂–CeO₂/γ-Al₂O₃ catalysts, prepared by impregnation of γ-Al₂O₃ with aqueous solution containing Ru and Ce were used to study the influence of CeO₂ on the structure and activity of RuO₂/γ-Al₂O₃ catalyst in catalytic wet air oxidation (CWAO) of phenol. The surface properties of two catalysts were measured by BET, SEM, XRD and XPS. Slight aggregates of Ru particles were observed on the surface of RuO₂/γ-Al₂O₃ catalyst, while a better dispersion of Ru particles was detected in the presence of CeO₂ on the surface of RuO₂/γ-Al₂O₃ catalyst. The chemical state of Ru and O was investigated. The results show that the addition of CeO₂ affects the chemical state of Ru and O elements and promotes the increase of the chemisorbed oxygen contents on the catalyst surface. Moreover, the removal of phenol with RuO₂–CeO₂/γ-Al₂O₃ catalyst is more complete than with RuO₂/γ-Al₂O₃ catalyst.

Keywords: Catalytic wet air oxidation; Rare earth; Metal catalyst; Phenol

Growth of ceramic coatings on AZ91D magnesium alloys by micro-arc oxidation in aluminate–fluoride solutions and evaluation of corrosion resistance by H.F. Guo; M.Z. An (pp. 229-238).

Micro-arc oxidization of AZ91D magnesium alloys was studied in solutions containing sodium aluminate and potassium fluoride at constant applied current densities. The influence of applied current densities, concentration and constituents of the electrolyte as well as treatment time on micro-arc oxidization process was investigated, respectively; surface morphology and phase structure were analyzed using scanning electron microscope (SEM) and X-ray powder diffraction (XRD). Potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) were used to evaluate the corrosion resistance of ceramic coatings formed on magnesium alloys. XRD analyses indicate that the ceramic coatings fabricated on the surface of magnesium alloys by micro-arc oxidization are composed of spinel phase MgAl₂O₄ and intermetallic phase Al₂Mg; variation of treatment time arises no obvious difference to phase structure of the ceramic coatings. A few circular pores and micro-cracks are also observed to remain on the ceramic coating surface; the number of the pores is decreasing, while the diameter of the pores is apparently increasing with prolonging of treatment time. The corrosion resistance of ceramic coatings is improved more than 100 times compared with magnesium alloy substrate.

Keywords: Micro-arc oxidization; Magnesium alloys; Ceramic coatings; Corrosion resistance

XPS and FTIR investigation of the surface properties of different prepared titania nano-powders by Henrik Jensen; Alexei Soloviev; Zheshen Li; Erik G. S�gaard (pp. 239-249).

Surface studies of nano-sized TiO₂ powders prepared by different methods showed that the preparation method had great impact on the surface properties. XPS measurements showed that the oxygen composition was related to the preparation method. The chloride method yielded the lowest amount of surface oxygen (29%) and sol–gel prepared powder showed the greatest amount of surface oxygen (66%) in the form of surface hydroxyl groups. The remaining oxygen was identified as lattice oxygen. The powder prepared by the sol–gel method contained carbon impurities originating from residual alkoxy groups. Supercritical sol–gel prepared powder and powder prepared by the sulphate method revealed same trends regarding oxygen composition with 44–47% being surface oxygen; neither contained carbon impurities. The results obtained from XPS were confirmed by FTIR measurements.

Keywords: PACS; 82.80.Pv; 82.50.-m; 82.65.-i; 82.80.chTiO; ₂; Surface hydroxyl groups; Preparation methods; XPS; FTIR

Surface reaction kinetics of metal β-diketonate precursors with O radicals in radical-enhanced atomic layer deposition of metal oxides by Trinh T. Van; Jane P. Chang (pp. 250-261).

The surface reaction kinetics of Er(TMHD)₃ and Y(TMHD)₃ with O radicals in radical-enhanced atomic layer deposition (ALD) of Er₂O₃ and Y₂O₃ was investigated in situ using a quartz crystal microbalance (QCM). The adsorption isotherms were fitted with the Langmuir–Hinshelwood adsorption model and the extracted adsorption rate coefficient was found to decrease with increasing temperature, exhibiting a negative apparent activation energy of −0.24±0.09eV for Er(TMHD)₃ and −0.14±0.05eV for Y(TMHD)₃. The corresponding activation energies for desorption were determined to be 0.29±0.03 and 0.16±0.03eV. Exposing the adsorbed Er(TMHD)₃ precursors to O radicals at 533K resulted in a rapid mass decrease followed by saturation, indicating that the reactions proceeded in a self-limiting manner. The critical O radical exposure needed to reach this saturation increased with increasing adsorbed mass and approached approximately 2 minutes as the adsorbed mass increased towards the saturation level. The net mass change ratio per cycle decreased with increasing temperature and reached 0.27 at 603K for deposition of pure Er₂O₃. In addition to effectively removing the β-diketonate ligands, the O radicals were found to create reactive sites for precursor adsorption. Specifically, when the O radical pulse time was shorter than the critical oxygen radical exposure, the removal of β-diketonate ligands by the O radicals was incomplete, and consequently, less reactive sites were created. This ultimately led to a decrease in adsorption during the subsequent precursor pulse. Finally, radical-enhanced ALD of Er₂O₃ thin films was achieved at temperatures ranging from 473 to 573K, using alternating pulses of metal β-diketonate precursors and O radicals.

Keywords: PACS; 81.15 (thin film-deposition methods); 82.65.J (surface reaction); 82.20 (chemical kinetics); 82.30 (chemical reactions)β-Diketonate; O radicals; Thin film; ALD; Atomic layer deposition

A XPS investigation of SO₂ adsorption on ceria–zirconia mixed-metal oxides by Esteban J. Romano; Kirk H. Schulz (pp. 262-270).

The interaction between ceria–zirconia mixed-metal oxide model catalysts and SO₂ was studied using X-ray photoelectron spectroscopy (XPS). An in situ reaction cell was employed to expose the polycrystalline ceria–zirconia mixed-metal oxide catalyst wafers to various partial pressures of SO₂ at elevated temperatures. Six compositions of CeO₂/ZrO₂ solid solutions were examined in this study, which include CeO₂/ZrO₂ molar ratios of 1:0, 9:1, 7:3, 5:5, 2:8, and 0:1. The samples were exposed to SO₂ at temperatures from 298 to 873K and pressures reaching 1000Torr. XPS results show an increased adsorption of SO₂ at either elevated temperatures or higher ceria mole fractions. Additionally, both a sulfate (SO₄) and sulfite (SO₃) surface species were identified. No significant change in sulfate-to-sulfite ratio as a function of temperature, exposure pressure, or composition was observed under the conditions of this study. However, surface hydroxyl functionalization was found to play an important role in the adsorption of sulfur dioxide on the materials studied.

Keywords: Cerium oxide; Zirconium oxide; XPS; Sulfur dioxide; Hydroxyl

Room temperature synthesis of compact TiO₂ thin films for 3-D solar cells by chemical arrested route by R.S. Mane; Yun Hee Hwang; C.D. Lokhande; S.D. Sartale; Sung-Hwan Han (pp. 271-278).

Essential requirement of compact TiO₂ thin films for 3-D solar cells prefers high temperature techniques (≥400°C) such as spray pyrolysis or sputtering. Under optimized preparative conditions, compact, uniform, adherent and pinhole free, TiO₂ thin films were synthesized at room temperature by using arrested precipitation technique on ITO substrates. As-deposited and heat-treated TiO₂ films were amorphous with small enlargement in grain size as evidenced from XRD and SEM studies. Small blue shift was detected due to annealing and attributed to change in grain size. As deposited and heat-treated TiO₂ films were used in this study showed water contact angles 66.14° and 66.44°, respectively. Efforts were also taken to use these films in dye-sensitized solar cells after introducing cis-dithiocyanato (4,4′-dicarboxylic acid-2,2′-bipyridide) ruthenium (II) (N₃) dye but no significant improvement due to low contact angle in photo-electrochemical cell performance was observed due to high compactness.

Keywords: TiO; ₂; thin films; XRD; SEM; UV; EDAX; Dye sensitization; Contact angle

Analysis of GaN cleaning procedures by M. Diale; F.D. Auret; N.G. van der Berg; R.Q. Odendaal; W.D. Roos (pp. 279-289).

In this study, various surface cleaning techniques for the removal of contaminants from GaN were investigated. Auger electron spectroscopy (AES) analysis was used to monitor the presence of surface contaminants and atomic force microscopy (AFM) was used to monitor surface roughness. AES analysis showed that KOH was effective in removing carbon (C). Comparing the topographies of GaN surfaces cleaned in HCl, KOH and (NH₄)₂S in aqueous solutions; it has been found that surfaces cleaned in (NH₄)₂S is the best cleaned, have the lowest values of both C and O, RMS roughness and Ga/N ratio. The nearly complete removal of C and O were achieved by heating the samples in AES in vacuum.

Keywords: PACS; 73.61Morphology; Wet chemical; Cleaning; GaN

The effect of thermal contact resistance on heat management in the electronic packaging by M. Grujicic; C.L. Zhao; E.C. Dusel (pp. 290-302).

A finite element analysis is carried out in order to investigate the role of thermal contact resistance on heat management within a simple central processing unit (CPU)/heat sink assembly. A special attention is paid in assessing the effect of surface roughness characteristics, mechanical and thermal properties of the contacting bodies, applied contact pressures and the use of thermal interface materials on the maximum temperature experienced by the CPU. Two classes of thermal interface materials: (a) phase-change materials and (b) acrylic- or silicone-based tapes are considered. The results clearly reveal that plastic deformation of micro-contacts (promoted by high contact pressures and lower micro-hardness levels) and the use of thermal interface materials which eliminate (high thermal resistance) micro-gaps can significantly lower the overall CPU/heat sink thermal contact resistance and facilitate heat management. It is also shown that the retention of asperity micro-contacts and good wetting of the mating surfaces by the thermal interface material are critical for achieving an effective removal of the heat generated by the CPU.

Keywords: PACS; 65.40.−bThermal contact resistance; Heat management

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Applied Surface Science (v.246, #1-3)