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Applied Surface Science (v.253, #2)

Thickness dependence of electrical properties of ITO film deposited on a plastic substrate by RF magnetron sputtering by Dong-Ho Kim; Mi-Rang Park; Hak-Jun Lee; Gun-Hwan Lee (pp. 409-411).

Indium tin oxide (ITO) films with various thicknesses in range of 40–280nm were prepared onto a plastic substrate (PMMA). Deposition was carried out with RF magnetron sputtering method and the substrate temperature was held at ∼70°C, in lack of the thermal damage to the polymer substrate. Changes in microstructure and electrical properties of ITO films according to their thicknesses were investigated. It was found that amorphous layer with thickness of 80nm was formed at the interface on the polymer substrate and polycrystalline ITO could be obtained above the thickness. Conductivity of ITO films was found to be strongly dependent on the crystallinity. Consequently, it is suggested that crystallinity of the deposited films should be enhanced at the initial stage of deposition and the thickness of amorphous region be reduced in order to prepare high quality ITO thin films on polymer substrates.

Keywords: PACS; 77.84.Bw; 77.84.Jd; 81.15.Cd; 73.50.−h; 68.55.jkITO; Plastic substrate; Sputtering; Electrical transport properties; Microstructure

Characterization of ion species of silicon oxide films using positive and negative secondary ion mass spectra by Kiyoshi Chiba; Shun Nakamura (pp. 412-416).

Secondary ion species of silicon oxide films have been investigated using time-of-flight secondary ion mass spectrometry (TOF-SIMS). Characterization of thermally grown SiO₂ films on silicon has been performed. A diagram showing secondary ion spectra of SiO₂ films in both positive and negative polarities indicates the pattern of change in polarities and intensities of ion species from SiO⁺ to Si₅O₁₁⁻. The ions mostly change from positive to negative polarity between Si_nO2 n₋₁ and Si_nO2_n. Ion peaks with the strongest intensities in the respective cluster ions correspond to the Si_nO2 n₊₁ negative ion. Intensities of ion species of Si_nO2 n₊₂ appear negligibly small. Ion species of Si₃O⁺, Si₃O₂⁺ and Si₃O₃⁺ have been found at the interface between silicon and SiO₂ films. The intensity patterns of these ion species compared to those of SiO₂ films indicate that most of these species are not emitted from the SiO₂ films, but likely from the SiO structures.

Keywords: PACS; 61.43.Fs; 68.49.Sf; 68.55.JkSilicon oxides; Secondary ion species; Time-of-flight secondary ion mass spectrometry

Dependence of excess bismuth content in precursor sols on ferroelectric and dielectric properties of Bi_3.25La_0.75Ti₃O₁₂ thin films fabricated by chemical solution deposition by X.L. Zhong; J.B. Wang; S.X. Yang; Y.C. Zhou (pp. 417-420).

Bi_3.25La_0.75Ti₃O₁₂ (BLT) thin films were fabricated on Pt/Ti/SiO₂/Si(100) substrates by chemical solution deposition (CSD), and the dependence of ferroelectric and dielectric properties of the as-deposited BLT thin films on excess Bi content in precursor sols was studied. It is found that the prepared BLT thin film shows the best polarization–electric field, capacitance–voltage and dielectric constant ( ɛ_r)–frequency characteristics, when the value of excess Bi content in precursor sols is 10%. In detail, its remnant polarization (2 P_r) value is 40μC/cm², the capacitance tunability is 21% measured at room temperature under conditions of an applied voltage of 8V and measurement frequency of 10kHz, and the ɛ_r is 696 at 100kHz frequency.

Keywords: PACS; 77.84.Dy; 77.55.+f; 77.80.−eBLT thin films; Excess bismuth content; Ferroelectric properties; Dielectric properties

Use of successive ionic layer adsorption and reaction (SILAR) method for amorphous titanium dioxide thin films growth by S.S. Kale; R.S. Mane; Hoeil Chung; Moon-Young Yoon; C.D. Lokhande; Sung-Hwan Han (pp. 421-424).

Use of successive ionic layer adsorption and reaction (SILAR) method was preferred for the growth of amorphous titanium dioxide (TiO₂) thin films at ambient temperature. Further, these films were annealed at 673K for 2h in air for structural improvement and characterized for structural, surface morphological, optical and electrical properties. An amorphous structure of TiO₂ was retained even after annealing as confirmed from XRD studies. The spherical grains of relatively large size were compressed after annealing. A red shift in band gap energy and decrease in electrical resistivity were observed due to annealing treatment.

Keywords: Titanium dioxide; SILAR; XRD; SEM; UV–vis; Electrical resistivity

Fabrication and characterization of facing-target reactive sputtered polycrystalline TiO₂ films by G.K. Li; J.J. Shen; W.B. Mi; Z.Q. Li; P. Wu; E.Y. Jiang; H.L. Bai (pp. 425-431).

Polycrystalline TiO₂ films were fabricated using dc facing-target reactive sputtering at different sputtering pressures. The films deposited consist of pure anatase phase or a mixture of anatase and rutile and increasing rutile content to some extent deteriorates the crystallinity of the anatase. It was found that the plasma heating effect, which plays the role of substrate heating, is an important factor for the crystallinity of the films in the case of without substrate heating. The roughness of the films increases monotonically with the increase of the sputtering pressure, which can be ascribed to the decrease in the mobility of the impinging particles. UV–vis transmission measurements reveal that the pure anatase films have higher transmittance than those having mixed phases of anatase and rutile. The band gap value decreases from ∼3.35 to 3.29eV owing to the increase in the fraction of rutile phase.

Keywords: PACS; 68.55.−a; 61.10.Nz; 81.15.Cd; 07.60.Rd; 71.20.NrTiO; ₂; films; Anatase; Rutile; Optical band gap

Effect of cerium ions on corrosion inhibition of PANI for iron in 0.5M H₂SO₄ by C. Jeyaprabha; S. Sathiyanarayanan; G. Venkatachari (pp. 432-438).

In recent years conducting polymers such as polyaniline are used as corrosion inhibitors for metals in acids. The performance of the inhibitor can be enhanced either by the addition of halide ions or metal cations. A study has been made on the effect of addition of ceric ions on the corrosion inhibition performance of polyaniline for iron in 0.5M H₂SO₄. Techniques such as electrochemical impedance spectroscopy, potentiodynamic polarization and linear polarization resistance methods have been employed to study the corrosion inhibition. The polyaniline has been used in the concentration range of 10–100ppm and the ceric ions concentration has been maintained at 1×10⁻³M. The inhibition efficiency of polyaniline at 10ppm has been increased from 53 to 88% and for 50ppm from 71 to 90% in the presence of ceric ions. The enhanced inhibition of polyaniline in presence of ceric ions is due to the higher coverage of polyaniline–cerium complex.

Keywords: Corrosion inhibition; Iron; Sulphuric acid; Cerium ions; Polyaniline; EIS

Effects of experimental parameters on composition of boron carbon nitride thin films deposited by magnetron sputtering by Lihua Liu; Yongnian Zhao; Yanchun Tao; Dapeng Yang; Hongmei Ma; Yingai Li (pp. 439-443).

We have synthesized boron carbon nitride thin films by radio frequency magnetron sputtering. The films structure and composition were characterized by X-ray diffraction, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The results indicate that the three elements of B, C, N are chemically bonded with each other and atomic-level hybrids have been formed in the films. The boron carbon nitride films prepared in the present experiment possess a disordered structure. The influence ofPN2/PN2+Ar, total pressure and substrate bias voltage on the composition of boron carbon nitride films is investigated. The atomic fraction of C atoms increases and the fractions of B, N decrease with the decrease ofPN2/PN2+Ar from 75% to 0%. There is an optimum total pressure. That is to say, the atomic fractions of B, N reach a maximum and the fraction of C atoms reaches a minimum at the total pressure of 1.3Pa. The boron carbon nitride films exhibit lower C content and higher B, N contents at lower bias voltages. And the boron carbon nitride films show higher C content and lower B, N contents at higher bias voltages.

Keywords: PACS; 81.15.Cd; 68.55.NqRadio frequency magnetron sputtering; Boron carbon nitride films

Growth process of β-FeSi₂ epitaxial film on Si(111) by molecular beam epitaxy by S.Y. Ji; J.F. Wang; J.-W. Lim; M. Isshiki (pp. 444-448).

We have reported a one step growth of a high quality β-FeSi₂ epitaxial film on hydrogen terminated Si(111) by using molecular beam epitaxy (MBE) without template layer or post-growth annealing. In the present work, the growth process was studied by analyzing X-ray diffraction (XRD) spectra, reflective high energy electron diffraction (RHEED) and atomic force microscopy (AFM) observations on the samples grown with different growth times from 10s to 1h. A phase transformation from γ-FeSi₂ to β-FeSi₂ was confirmed existing in the crystal film growth, as well as the growth mode changing from three-dimensional (3D) to two-dimensional (2D) mode.

Keywords: PACS; 68.55.−a; 81.15.H; 73.61.Jβ-FeSi; ₂; MBE; Growth process; RHEED

Microstructure effect on microtopography of chemically etched α+β Ti alloys by P.Y. Lim; P.L. She; H.C. Shih (pp. 449-458).

Microstructure effect on chemical etching behavior of the annealed Ti–6Al–4V and Ti–3Al–2.5V titanium (Ti) alloys was compared with that of unalloyed commercially pure titanium. The microstructural evolution of structure phases after annealing the titanium and its alloys at temperature near and above β transus and followed by furnace cooling to room temperature was studied using optical microscope, scanning electron microscope and X-ray diffraction techniques. The microstructure study illustrates that the heat treatment enhanced partitioning effect allows extensive formation of hemispherical and near spherical pits roughened surface to be readily acquired by chemically etching the annealed α+β titanium alloys. The kinetics of the chemical etching reaction process show a linear dependence on time. The annealed α+β titanium alloys that exhibit relatively lower weight loss and thickness reduction rate illustrate less chemical activity than the annealed unalloyed titanium.

Keywords: Titanium; Immersion test; Chemical etching; Roughness; Profilometry; SEM

Optical properties of cadmium sulfide nanocrystal film prepared by electrochemical synthesis at liquid–liquid interface by Yemei Luan; Maozhong An; Guoqi Lu (pp. 459-463).

Dendritic nanocrystalline CdS film was deposited at liquid–liquid interface of surfactants and an electrolyte containing 4mmolL⁻¹ cadmium chloride (CdCl₂) and 16mmolL⁻¹ thioacetamide (CH₃CSNH₂) with an initial pH value of 5 at 15°C by electrochemical synthesis. The nanofilm was characterized by transmission electron microscopy (TEM), field emission scanning electron microscope (FE-SEM), atomic force microscopy (AFM), ultraviolet visible (UV–vis) absorption spectroscopy and fluorescence spectroscopy. The surface morphology and particle size of the nanofilm were investigated by AFM, SEM and TEM, and the crystalline size was 30–50nm. The thickness of the nanofilm calculated by optical absorption spectrum was 80nm. The microstructure and composition of the nanofilm was investigated by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), showing its polycrystalline structure consisting of CdS and Cd. Optical properties of the nanofilm were investigated systematically by UV–vis absorption and fluorescence spectroscopy. A λ_onset blue shift compared with bulk CdS was observed in the absorption spectra. Fluorescence spectra of the nanofilm indicated that the CdS nanofilm emitted blue and green light. The nanocomposites film electrode will bring about anodic photocurrent during illumination, showing that the transfer of cavities produces photocurrent.

Keywords: Cadmium sulfide; Liquid–liquid interface; Electrochemical synthesis; Nanocomposites; Optical properties

A nanoindentation study of the mechanical properties of ZnO thin films on (0001) sapphire by R. Navamathavan; Kyoung-Kook Kim; Dae-Kue Hwang; Seong-Ju Park; Jun-Hee Hahn; Tae Geol Lee; Gwang-Seok Kim (pp. 464-467).

The mechanical properties of epitaxial ZnO thin films grown on (0001) sapphire substrate were investigated by nanoindentation with a Berkovich tip and compared with that of bulk ZnO single crystal. In all indents on ZnO film a single discontinuity (‘pop-in’) in the load versus indentation depth data was observed at a specific depth of between 13 and 16nm. In bulk ZnO, however only 65% of indents showed pop-in event at a specific depth of between 12 and 20nm. The mechanism responsible for the ‘pop-in’ event in the epitaxial ZnO thin films as well as in bulk ZnO was attributed to the sudden propagation of dislocations, which had been pinned down by pre-existing defects, along the pyramidal101¯1 and basal {0001} planes (cross slip). The elastic modulus and hardness of the epitaxial ZnO thin films were determined to be 154±5 and 8.7±0.2GPa, respectively, at an indentation depth of 30nm.

Keywords: Epitaxial ZnO; Berkovich tip; Mechanical properties

Study on the deterioration process of a chromium-free conversion coating on AZ91D magnesium alloy in NaCl solution by Ming Zhao; Shusen Wu; Ping An; Jirong Luo (pp. 468-475).

The morphology of a chromium-free conversion coating for AZ91D magnesium alloy was observed with an Atomic Force Microscopy. The results showed the uniform conversion coating has a relatively smooth appearance with shallow valleys. The EDX results indicated that the compositions of the coating were mainly compounds of Mg, Al, Mn, P, Ca and O. The XRD result showed that the coating contained amorphous materials and a small quantity of crystalline compound. The pitting product of the coating in NaCl water solution mainly composed of Mg, Cl, Mn, P, Ca and O. The corrosion behavior of the samples in NaCl solution was also studied by electrochemical impedance spectroscopy (EIS), which was characterized by one capacitive loop and one inductive loop. Based upon study on both a mathematical model for Faradic admittance of coating in NaCl solution and EIS, it could be considered that the inductive loop was caused by the adsorption of Cl anion and the appearance of pitting corrosion. A degradation mechanism of the coating in NaCl solution is set forth: dissolution velocity of the Cl⁻ adsorption regions of the coating is higher than those non-adsorption regions, for Cl⁻ anions are selective adsorption at some regions of coating surface. When the adsorption regions of coating layer are penetrated by dissolution, the pitting comes into being. The degradation mechanism of conversion coating and the mathematical model are consistent with the EIS results, polarization measurement results and coating's corrosion test results.

Keywords: Magnesium alloys; Impedance spectroscopy; Pitting corrosion; Mathematical model; Degradation mechanism

Ultraviolet photoconductive detector based on Al doped ZnO films prepared by sol–gel method by Zi-Qiang Xu; Hong Deng; Juan Xie; Yan Li; Xiao-Tao Zu (pp. 476-479).

We report a study on the fabrication and characterization of ultraviolet photodetectors based on ZnO:Al films. Using sol–gel technique, highly c-axis oriented ZnO films with 5mol% Al doping were deposited on Si(111) substrates. The photoconductive UV detectors based on ZnO:Al thin films, having a metal–semiconductor–metal (MSM) structure with interdigital (IDT) configuration, were fabricated by using Au as a contact metal. The characteristics of dark and photocurrent of the UV detector and the UV photoresponse of the detector were investigated. The linear current–voltage ( I– V) characteristics under both forward and reverse bias exhibit ohmic metal–semiconductor contacts. Under illumination using monochromatic light with a wavelength of 350nm, photo-generated current was measured at 58.05μA at a bias of 6V. The detector exhibits an evident wide-range spectral responsivity and shows a trend similar to that in transmittance and photoluminescence spectrum.

Keywords: PACS; 61.72.Vv; 73.50.Pz; 73.61.Ga; 85.60.GzSol–gel; ZnO:Al; Photoconductive UV detector; Ohmic contact; Photoresponsivity

Process of direct copper plating on ABS plastics by Wang Gui-xiang; Li Ning; Hu Hui-li; Yu Yuan-chun (pp. 480-484).

The processes of direct copper plating on ABS plastics were investigated by atomic force microscopy (AFM), ultraviolet–visible absorption spectrometry (UV–vis) and X-ray fluorescence spectroscopy (XRF) techniques. The substrates were etched by CrO₃/H₂SO₄ solution containing Pd²⁺ ions, catalyzed by Pd/Sn colloids solution and accelerated in an alkaline solution containing copper ions. The Pd²⁺ ions in etching solution can reduce the surface roughness and enhance the colloids adsorption. The good dispersivity colloids have excellent catalysis and its UV–vis peaks broaden. After acceleration, when the stability of Cu²⁺-complex is relatively low, Sn²⁺ was oxidized by Cu²⁺ in the alkaline solution meanwhile Cu₂O can be formed. The disproportionation reaction of Cu₂O will proceed and metallic copper forms between the Pd particles, so the conductivity of ABS surface increased. The copper particles play an important role in determining the uniformity of the propagation of copper plating. The particles of copper plating layer were uniformity and fine. The atomic concentration and the thickness of copper layer were analyzed by XRF.

Keywords: Direct plating; ABS plastics; Palladium colloid solution; Etching; Activation

Synthesis and photoluminescence of single-crystal GaN nanorods prepared by sol–gel method by Yuxin Wu; Chengshan Xue; Huizhao Zhuang; Deheng Tian; Yi’an Liu (pp. 485-487).

A new method was applied to prepare GaN nanorods. In this method, gallium oxide (Ga₂O₃) gel was firstly formed by a sol–gel processing using gallium ethanol, Ga(OC₂H₅)₃, as a new precursor. GaN nanorods were successfully synthesized after annealing of the Ga₂O₃ gel at 1000°C for 20min in flowing ammonia. The as-prepared nanorods were confirmed as single crystalline GaN with wurtzite structure by X-ray diffraction (XRD), selected-area electron diffraction (SAED) and high-resolution transmission electron microscopy (HRTEM). Transmission electron microscopy (TEM) displayed that the GaN nanorods were straight and smooth, with diameters ranging from 200nm to 1.8μm and lengths typically up to several tens of microns. When excited by 280nm light at room temperature, the GaN nanorods had a strong ultraviolet luminescence peak located at 369nm and a blue luminescence peak located at 462nm, attributed to GaN band-edge emission and the existence of the defects or surface states, respectively.

Keywords: PACS; 68.65.-k; 71.55.-Eq; 78.67.-n; 81.20.FwGaN; Nanorods; Sol–gel; Luminescence

Distribution and formation of molecularly thin lubricants by thermostatic high vacuum AFM by Chongjun Pang; Mingwu Bai (pp. 488-492).

Distribution and formation of molecularly thin lubricants (95% Zdol and 5% X-1P) on CHx carbon surfaces has been studied by thermostatic high vacuum atomic force microscopy (THV-AFM). Results show that Zdol or/and X-1P distribute in island-shaped aggregation independent of topography of CHx surfaces at different temperatures. At 20°C, 10⁻⁷Torr, distribution of X-1P additive can be mapped distinctly without interfering features from Zdol lubes. As temperature decreases, features from Zdol gradually present both in topographic images and in phase images. Measured heights of Zdol islands increase with temperature varying from −20 to −60°C, however, the island diameters do not change significantly. At −60°C and 10⁻⁷Torr, lubricant islands have a typical height of ∼3.5nm and a typical diameter of ∼100nm. The area coverage ratio of lubricant islands to CHx surfaces is ∼0.59. To interpret these results, we present a lubricant distribution model involving an initial site-specific adsorption process in the solutions and a long time reorganization process after solvent evaporation.

Keywords: Distribution; Formation; Thin film; Lubricant; Thermostatic AFM; Perfluoropolyether

The effect of pH and role of Ni²⁺ in zinc phosphating of 2024-Al alloy by A.S. Akhtar; K.C. Wong; K.A.R. Mitchell (pp. 493-501).

Coatings formed on 2024-T3 aluminum alloy were studied by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) after dipping in zinc phosphating (ZPO) baths at different acidities, for different lengths of time, and with or without Ni²⁺ additive. The overall objective was to learn more about the role of Ni²⁺ on the ZPO coating mechanism, particularly since this additive is believed to improve corrosion protection for the Al alloy. Secondary phosphates dominate the coatings when the Ni-containing solution is adjusted to starting pH values of either 3 or 5, while tertiary phosphate is predominant at pH 4. AlF₃ precipitates during the early stages of the coating process. Ni²⁺ has two main roles in the mechanism. First, the rate of increase in local solution pH is retarded by the slower kinetics of reactions involving Ni²⁺ compared to Zn²⁺, leading to thinner ZPO coatings when Ni²⁺ is present in the coating solution. Second, most Ni²⁺ deposition occurs during the later stages of the coating process, by nickel phosphate deposition and/or by formation of a Ni-rich oxide.

Keywords: PACS; 81.65 Kn, 82.80 PvAluminum alloy; Conversion coatings; Zinc phosphate; Ni; ²⁺; additive; Photoelectron spectroscopy; Scanning electron microscopy

The effect of pH and role of Ni²⁺ in zinc phosphating of 2024-Al alloy by A.S. Akhtar; D. Susac; P.C. Wong; K.A.R. Mitchell (pp. 502-509).

Coatings formed on 2024-T3 aluminum alloy were studied by scanning electron microscopy (SEM) and scanning Auger microscopy (SAM) after dipping in zinc phosphating (ZPO) baths at different acidities, with or without the Ni²⁺ additive. The objective was to learn more about the ZPO coating mechanism on the different microstructural regions of 2024-T3. When the initial coating solution pH is 4 (optimal acidity), a slower etching rate at the Al–Cu–Fe–Mn intermetallic particle causes significant precipitation of ZnO, which differs from the coating on other regions of the surface where phosphate predominates. The larger crystals (∼μm dimension) on the matrix and the Al–Cu–Mg particle contain more phosphate compared to other areas on the surface. When Ni²⁺ is added to the coating solution, the Al–Cu–Mg particle is more thickly coated compared to when the Ni²⁺ is not present. The slower rate of precipitation when Ni²⁺ is present in the coating solution increases the exposure of the alloy substrate to the acidic environment, so allowing more dissolution of Mg and Al from the Al–Cu–Mg particle. This results in the particle becoming more cathodic in nature, and therefore more coating deposits at this location. Evidence from SAM supports the presence of NiAl₂O₄, hypothesized in Part I, forming at coating pores later in the process.

Keywords: PACS; 81.65.Kn; 81.05.Bx; 68.37.XyAluminum alloy; Conversion coatings; Zinc phosphate; Ni; ²⁺; additive; Auger electron spectroscopy; Scanning electron microscopy

Study of ZnO-coated SnO₂ nanostructures synthesized by a two-step process by Hyoun Woo Kim; Seung Hyun Shim (pp. 510-514).

We investigated the influence of the ZnO coating on the properties of one-dimensional (1D) nanostructures of SnO₂. We have employed X-ray diffraction, scanning electron microscope, transmission electron microscope and photoluminescence (PL) spectroscopy to characterize both as-synthesized and ZnO-coated products. We observed that deposition process of ZnO by using an atomic layer deposition technique resulted in the SnO₂ core/ZnO shell structure. The photoluminescence of the ZnO-coated products exhibited broad bands in the UV and green region, suggesting a possible contribution of the emission from the ZnO outlayers.

Keywords: SnO; ₂; One-dimensional nanostructures; ZnO; Atomic layer deposition

Optical characteristics of MBE grown GaMnAs embedded with MnAs clusters by P.B. Parchinskiy; Fu Cheng Yu; Se Young Jeong; Cunxu Gao; Dojin Kim; Hyojin Kim; Young Eon Ihm (pp. 515-518).

Photoluminescence (PL) measurements of the GaMnAs layers embedded with MnAs clusters have been performed. It was shown that the presence of MnAs clusters in the semiconducting matrix leads to appearance in the PL spectra a broad peak with local maximums at 1.36 and 1.33eV, which are related with the defects generated in the phase separation process. The effect of the MnAs clusters on the temperature dependent band gap of GaMnAs was also observed.

Keywords: PACS; 75.50.Pp.; 72.80.Ey.; 78.55.CrGaMnAs; MnAs cluster; Photoluminescence

XPS study of the surfactant film adsorbed onto growing titania nanoparticles by Giuseppe Cappelletti; Claudia L. Bianchi; Silvia Ardizzone (pp. 519-524).

TiO₂ particles, prepared by following a sol–gel preparative route, were submitted to hydrothermal growing stages in the presence of an anionic surfactant, sodium dodecyl-sulfate (SDS), at solution pH values corresponding, respectively, to positive surface charges and to the isoelectric point of the oxide. The concentration of the surfactant in the aqueous solution was varied in order to produce different conditions of self-aggregation between the amphiphilic molecules. XPS analyses were performed on the aged and dried precursors to characterize the surfactant films adsorbed onto the oxide. The regions of Ti 2p, O 1s, and C 1s were specifically investigated. The samples, calcined at 600°C, were characterized for phase composition-crystallinity, by X-ray diffraction, and for surface area. The role played by the oxide–surfactant interactions and by the surfactant self-aggregation phenomena in affecting the physico-chemical properties of the powders is discussed.

Keywords: PACS; 68.43.−h; 61.10.−i; 61.46.+w; 79.60.−i; 81.10.−hNanocrystalline titanium oxide; XPS; Hydrothermal growth; Surfactant–oxide interactions

Synthesis and characterization of silica microspheres functionalized with porphyrin monolayer by Xiangqing Li; Line Zhang; Jin Mu (pp. 525-529).

A new type of inorganic and organic composite (SiO₂-MPS-TAPPI), oppositely charged meso-tetra-(4-trimethylaminophenyl)porphyrin iodide (TAPPI) bonded on the surface of silica microspheres coated with mercaptopropyltrimethoxysilane (MPS), was prepared by self-assembly method. The composite was tested by TEM, XRD and TG. The TEM images show that SiO₂-MPS microspheres in the composite are uniform. There are linkages among some different SiO₂-MPS microspheres. The XRD measurement bears out that the composite structure is the same with SiO₂-MPS. TG curves show that thermal stability of TAPPI assembled onto SiO₂-MPS microspheres is higher than that of TAPPI. Solid UV diffusion reflection spectra and fluorescence spectra are used to investigate the photophysical properties of the SiO₂-MPS-TAPPI composite. It is showed that the spectra of the composite exhibit significant enhancement of the spectra range. The strong interaction between TAPPI and SiO₂-MPS in the composite is responsible for the different spectra.

Keywords: Silica microspheres; Porphyrin; Composite; Assembly; Photophysical properties

Copper diffusion in Ti–Si–N layers formed by inductively coupled plasma implantation by Y.C. Ee; Z. Chen; S.B. Law; S. Xu; N.L. Yakovlev; M.Y. Lai (pp. 530-534).

Ternary Ti–Si–N refractory barrier films of 15nm thick was prepared by low frequency, high density, inductively coupled plasma implantation of N into Ti_xSi_y substrate. This leads to the formation of Ti–N and Si–N compounds in the ternary film. Diffusion of copper in the barrier layer after annealing treatment at various temperatures was investigated using time-of-flight secondary ion mass spectrometer (ToF-SIMS) depth profiling, X-ray diffractometer (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX) and sheet resistance measurement. The current study found that barrier failure did not occur until 650°C annealing for 30min. The failure occurs by the diffusion of copper into the Ti–Si–N film to form Cu–Ti and Cu–N compounds. FESEM surface morphology and EDX show that copper compounds were formed on the ridge areas of the Ti–Si–N film. The sheet resistance verifies the diffusion of Cu into the Ti–Si–N film; there is a sudden drop in the resistance with Cu compound formation. This finding provides a simple and effective method of monitoring Cu diffusion in TiN-based diffusion barriers.

Keywords: TiSiN; Copper diffusion

Highly concentrated toluene decomposition on the dielectric barrier discharge (DBD) plasma–photocatalytic hybrid system with Mn-Ti-incorporated mesoporous silicate photocatalyst (Mn-Ti-MPS) by Ji-Young Ban; Yeon-Hee Son; Misook Kang; Suk-Jin Choung (pp. 535-542).

This study investigates the Mn-Ti-incorporated mesoporous silicate (Mn-Ti-MPS) as a photocatalyst for highly concentrated toluene removal in a plasma–photocatalytic hybrid system. Various Mn-Ti-MPS [Ti/Si molar ratio=1/4, Mn/Ti molar ratio=0.01/1 (1mol%), 0.05/1 (5mol%) and 0.1/1 (10mol%)] photocatalysts were successfully synthesized using a common hydrothermal method without causing any structural damage. In the X-ray diffraction (XRD) pattern, the main peaks of the TiO₂ anatase structure and MnO did not show. All samples displayed hexagonal specific peaks at 2.5° ( d10₀ plane), 4.1° ( d11₀ plane) and 4.7° ( d20₀ plane). This indicates that the Ti ions and Mn ions were well substituted into the Si ion sites in the framework of MCM-41. Their surface areas decreased compared with that of pure MCM-41, while the hexagonal straight pore size was distributed in a range of 2.5–3.5nm. In the Mn-Ti-MPS, much more water and toluene molecules were absorbed compared to the Ti-MPS. From the X-ray photoelectron spectroscopy (XPS) result, it was determined that the hydrophilicity of the Mn-Ti-MPS was stronger than that of the Ti-MPS. Photocatalytic decomposition for highly concentrated toluene of 1000ppm increased in the Mn-Ti-MPS when compared with the Ti-MPS, while toluene decomposition on 5mol% Mn-Ti-MPS was remarkably enhanced to 80% in the plasma system. The conversion to CO₂, however, did not improve in the case of the plasma-only system. Nonetheless, in the plasma–photocatalytic hybrid system, the conversion to CO₂ for 5mol% Mn-Ti-MPS reached 43% (in an 800ppm toluene conversion).

Keywords: Mn-Ti-MPS; Toluene decomposition; Plasma–photocatalytic hybrid system

Langmuir–Blodgett and Langmuir–Schaefer films of poly(5-amino-1-naphthol) conjugated polymer by C.P.L. Rubinger; R.L. Moreira; L.A. Cury; G.N. Fontes; B.R.A. Neves; A. Meneguzzi; C.A. Ferreira (pp. 543-548).

Langmuir-type films of poly(5-amino-1-naphthol) conductive polymer were formed at the air/water interface. The surface pressure versus molecular area isotherms of the polymeric layers showed a high tendency to aggregate and non-monomolecular behavior on the water surface. Langmuir–Blodgett (LB) and Langmuir–Schaefer (LS) procedures have been successfully used to transfer the Langmuir films of this polymer onto hydrophilic silicon substrates. Atomic force microscopy images showed that the films obtained by the LS method have much better quality than those obtained by the LB one. In particular, we have obtained uniform and smooth LS films covering practically all the substrate, while the LB films showed rather aggregated material, only partially covering the substrate.

Keywords: PACS; 61.41.+e; 68.18.−g; 68.37.Ps; 68.47.PeLangmuir–Blodgett; Langmuir–Schaefer; Poly(5-amino-1-naphthol); Conducting polymers; Atomic force microscopy

Growth of Ag thin films on ZnO(000−1) investigated by AES and STM by E. Duriau; S. Agouram; C. Morhain; T. Seldrum; R. Sporken; J. Dumont (pp. 549-554).

The growth of Ag films on ZnO(000−1) has been investigated by Auger electron spectroscopy (AES) and scanning tunneling microscopy (STM). A high density of islands is nucleated at the earliest stages of the growth. An upstepping mechanism causes these islands to coalesce while the uncovered fraction of the ZnO surface remains constant (30%).

Keywords: PACS; 68.37.Ef; 68.49.Uv; 68.47.Fg; 68.47.Gh; 68.55.JkSTM; AES; ZnO; Silver; Ag; Zinc oxide; In situ growth

Effect of the addition of oxo-anions on the corrosion and passivation of tin in synthetic industrial water by E.H. Ait Addi; L. Bazzi; M. Elhilali; R. Salghi; B. Hammouti; M. Mihit (pp. 555-560).

Effect of the addition of oxo-anions MoO₄²⁻, SiO₄²⁻, HPO₄²⁻ and HCO₃⁻ on the corrosion and passivation of tin in a synthetic medium similar to industrial water has been studied by using electrochemical techniques. The results show that tin manifests a passivation phenomenon with breakdown of passivity. Addition of oxo-anions leads to retard a breakdown of passivation and the inhibition of pitting process of tin. The more marked inhibiting effect is obtained in the presence of MoO₄²⁻ and SiO₄²⁻. The detailed study of the influence of the MoO₄²⁻ shows that the pitting sensitivity of tin decreases when the molybdate concentration increases in solution. Then, these ions offer a good efficiency even at high temperature and for a chloride concentration up to 0.5M.

Keywords: Corrosion; Passivation; Inhibition; Oxo-anions; Tin; Industrial water

Surfactant effect of Sb on the growth of MnSi_1.7 layers on Si(001) by A. Mogilatenko; M. Falke; H. Hortenbach; S. Teichert; G. Beddies; H.-J. Hinneberg (pp. 561-565).

Deposition of one monolayer of Sb prior to the deposition of Mn at 600°C is observed to increase the MnSi_1.7 island density by about two orders of magnitude as well as to change the crystalline orientation of the silicide grains. The preferential epitaxial orientation of MnSi_1.7 grains grown by this process is determined to be MnSi_1.7(100)[010]||Si(001)[100]. This growth procedure results in the silicide growth into the Si matrix. For comparison, the same deposition process carried out without Sb leads to silicide formation on top of the substrate surface. The observed morphological changes of the MnSi_1.7 layers can be explained by a reduced surface diffusion of the Mn atoms on Si(001) in presence of the Sb monolayer. Additionally, lateral Si diffusion is considered to be nearly suppressed, which is responsible for the observed silicide growth into the substrate.

Keywords: PACS; 68.37.Lp; 68.55.Jk; 81.15.HiSilicides; Surfactant; MnSi; _1.7; Reactive deposition

Caffeine as non-toxic corrosion inhibitor for copper in aqueous solutions of potassium nitrate by Thuanny Fallavena; Muriel Antonow; Reinaldo Simões Gonçalves (pp. 566-571).

Different electrochemical methods were employed in order to confirm the ability of caffeine (1,3,7-trimethylxanthine) to inhibit the corrosion processes of copper in aqueous potassium nitrate solutions in the absence and in the presence of chloride. Some experiments were repeated in potassium perchlorate in order to compare the influence of the medium. The interaction between the organic compound and the electrode surface occurs independently of the electrode potential. However, maximum interaction was observed at 0.0V (Ag/AgCl) in aerated solutions, and at −0.25V (Ag/AgCl) in deaerated solutions.The presence of the organic compound adsorbed on the electrode surface was confirmed by comparing the voltammograms of copper electrode in the absence and presence of 1.5mmolL⁻¹ of dissolved caffeine. The same results were observed by comparing polarization curves in the absence and in the presence of caffeine.Anodic currents decrease noticeably in the presence of the organic compound. Chronoamperometric experiments were conclusive to prove the inhibitor capability of caffeine to decrease the corrosion dissolution processes of copper under anodic polarization.

Keywords: Caffeine; Copper; Corrosion inhibitor; Aqueous solutions

Ammonia adsorption and decomposition on silica supported Rh nanoparticles observed by in situ attenuated total reflection infrared spectroscopy by C.M. Leewis; W.M.M. Kessels; M.C.M. van de Sanden; J.W. Niemantsverdriet (pp. 572-580).

Attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) is applied to study NH₃, adsorbed from the gas phase, and its decomposition products, i.e. NH_x species, on Rh nanoparticles, produced by spincoating from a RhCl₃ solution in water followed by reduction. A silicon ATR crystal with a hydroxilated SiO₂ layer acts as the support for the nanoparticles. Upon exposure to NH₃ in the vacuum chamber, NH₃ adsorbed to both silica and Rh is detected (sensitivity ∼5×10⁻⁵ absorbance units). Interaction of the NH₃ with the silica OH groups is observed around ∼2840cm⁻¹ in combination with peaks showing the disappearance of unperturbed OH vibrations between 3500 and 3700cm⁻¹. In addition, NH bend vibrations at 1634cm⁻¹ and NH stretch vibrations at 3065 and 3197cm⁻¹ are observed for substrate temperatures between 20 and 100°C. The latter two correspond to NH on Rh, as verified with a sample without Rh, and probably correspond to undecomposed NH₃. Moreover, they remain after evacuation, suggesting strongly bound species. For a substrate temperature of 75 and 100°C, additional NH stretch peaks at 3354 and 3283cm⁻¹ are observed, possibly due to NH₂ intermediates, indicating NH₃ decomposition. It is shown that ATR-FTIR can contribute to the sensitive detection of adsorption and decomposition of gaseous species on realistic planar model catalysts.

Keywords: PACS; 82.80.Gk; 82.30.Lp; 68.43.−h; 68.35.Ja; 82.65.−sIn situ attenuated Fourier transform infrared spectroscopy; NH; ₃; adsorption; NH; ₃; decomposition; Rhodium; Vibrational analysis

A simple and low temperature process for super-hydrophilic rutile TiO₂ thin films growth by R.S. Mane; Oh-Shim Joo; Sun-Ki Min; C.D. Lokhande; Sung-Hwan Han (pp. 581-585).

We investigate an environmentally friendly aqueous solution system for rutile TiO₂ violet color nanocrystalline thin films growth on ITO substrate at room temperature. Film shows considerable absorption in visible region with excitonic maxima at 434nm. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), UV–vis, water surface contact angle and energy dispersive X-ray analysis (EDX) techniques in addition to actual photo-image that shows purely rutile phase of TiO₂ with violet color, super-hydrophilic and densely packed nanometer-sized spherical grains of approximate diameter 3.15±0.4nm, characterize the films. Band gap energy of 4.61eV for direct transition was obtained for the rutile TiO₂ films. Film surface shows super-hydrophilic behavior, as exhibited water contact angle was 7°. Strong visible absorption (not due to chlorine) leaves future challenge to use these films in extremely thin absorber (ETA) solar cells.

Keywords: TiO; ₂; thin films; Rutile; Super-hydrophilic; UV–vis

Simulation of dynamics of phase transitions in CdTe by pulsed laser irradiation by S.P. Zhvavyi; G.L. Zykov (pp. 586-591).

Numerical simulation of melting and solidification processes induced in CdTe by nanosecond radiation of ruby laser ( λ=694nm, τ=20 and 80ns) and KrF excimer laser ( λ=248nm, τ=20ns) taking into account components diffusion in melt and their evaporation from the surface has been carried out. Cd atoms evaporation has shown to essentially affect the dynamics of phase transitions in the near-surface region. Thus, in the case of the influence of ruby laser irradiation intensive surface cooling results in the formation of nonmonotone temperature profile with maximum temperature in semiconductor volume at the distance of ∼20nm from the surface. The melt formed under the surface extends both to the surface and to the semiconductor volume as well. As a result of cadmium telluride components evaporation and diffusion in the melt the near-surface region is enriched with tellurium. The obtained melting threshold value of irradiation energy density is in a reasonable agreement with experimental data.

Keywords: PACS; 61.50.Nw; 61.80.B; 78.55.EtLaser irradiation; CdTe; Melting; Solidification; Evaporation; Stoichiometric composition

Electrochemical behavior and microstructural characterization of 1026 Ni–B coated steel by A. Contreras; C. León; O. Jimenez; E. Sosa; R. Pérez (pp. 592-599).

Ni–B coatings have been deposited on the surfaces of commercial steels (SAE-1026). The depositions were carried out using the electroless plating technique employing a nickel chloride solution with borane–dimethylamine as the reducing agent. These specimens were subsequently heat treated at different temperatures (300–500°C) and different periods of time. The obtained coating thickness was in the order of approximately 1.5μm. X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques were used to characterize the structure and superficial morphology of the coatings. Phases like Ni, Ni₃B and Ni₄B₃ were observed through X-ray diffraction and confirmed by differential scanning calorimeter (DSC) studies. Some of the precipitated phases have been structurally characterized. The corrosion behavior of the coated surfaces was carried out by electrochemical impedance spectroscopy (EIS) using electrolytic sodium chlorine solutions with pH 2 and 7. The EIS results showed an active corrosion mechanism in acid solution while diffusion-reaction phenomena are predominant in neutral solution.

Keywords: PACS; 82.45.Bb; 81.65.kn; 81.15.−z1026 Steel; Corrosion; Coatings; Electroless plating; Electrochemical impedance spectroscopy (EIS)

A non-thermal lattice gas model for a dimer–trimer reaction on a catalytic surface: A computer simulation study by Waqar Ahmad; M. Parvez; Musa Kaleem Baloach; A.U. Qaisrani; M. Khalid (pp. 600-605).

The kinetics of an irreversible dimer–trimer reaction of the type 3A₂+2B₃→6AB have been studied using a non-thermal (precursor mechanism) model on a square as well as on a hexagonal lattice surface by Monte Carlo simulation. When the range of the precursors (A atoms) is increased, the model gives production rates (reactive window widths) that are quite large as compared with those for thermal (Langmuir–Hanshelwood mechanism) model. The phase diagrams qualitatively resemble with the standard ZGB model except that the continuous transition point is eliminated when the range of the precursors is extended up to the third nearest neighbourhood. The diffusion of A atoms on the surface as well as their desorption from the surface with a certain probability is also considered to see their effects on the reaction mechanism.

Keywords: Adsorption; Desorption; Catalytic surface reactions; Phase transitions; Monte Carlo simulation

Transmission electron microscopy studies of HfO₂ thin films grown by chloride-based atomic layer deposition by D.R.G. Mitchell; A. Aidla; J. Aarik (pp. 606-617).

Detailed transmission electron microscopy characterization of HfO₂ films deposited on Si(100) using atomic layer deposition has been carried out. The influence of deposition temperature has been investigated. At 226°C, a predominantly quasi-amorphous film containing large grains of cubic HfO₂ ( a₀=5.08Å) was formed. Grain morphology enabled the nucleation sites to be determined. Hot stage microscopy showed that both the cubic phase and the quasi-amorphous phase were very resistant to thermal modification up to 500°C. These observations suggest that nucleation sites for the growth of the crystalline cubic phase form at the growing surface of the film, rather homogeneously within the film. The films grown at higher temperatures (300–750°C) are crystalline and monoclinic. The principal effects of deposition temperature were on: grain size, which coarsens at the highest temperature; roughness with increases at the higher temperatures due to the prismatic faceting, and texture, with texturing being strongest at intermediate temperatures. Detailed interfacial characterization shows that interfacial layers of SiO₂ form at low and high temperatures. However, at intermediate temperatures, interfaces devoid of SiO₂ were formed.

Keywords: PACS; 68.37.-d; 68.55.-aAtomic layer deposition; ALD; HfO; ₂; TEM; Thin film deposition

Superior refractive index tailoring properties in composite ZrO₂/SiO₂ thin film systems achieved through reactive electron beam codeposition process by N.K. Sahoo; S. Thakur; R.B. Tokas (pp. 618-626).

Composite optical thin-film materials have received a significant amount of interest in order to relieve the material constraints on refractive indices as well as reducing the number of layers required in optical coating design. Amongst others binary zirconia–silica composite thin films have attracted considerable attentions due to their several favorable opto-mechanical properties. In the present studies such a composite system under certain compositional mixings displayed both refractive index and band gap supremacy over pure zirconia films violating the most popular Moss rule. This unexpected evolution has several practical applications one of which can be directly employed in extending the range of tunability of the refractive index. Besides, the probing of such a novel evolution through the analysis of ellipsometric refractive index modeling and morphological correlation functions has revealed several novel as well as superior microstructural properties in the composite thin film systems. All these characterization and analysis techniques distinctly indicate a strong interrelation between the microstructural ordering and superior optical properties of the present zirconia–silica codeposited composites.

Keywords: PACS; 42.79.Wc; 78.66.−w; 78.20.Ci; 61.16.Ch; 51.70.+f; 52.70.KzOptical coatings; Optical thin films; Codeposition; Electron beam evaporation; Ellipsometry; Atomic force microscopy; Composite films; Correlation functions

Quantitative analysis of multi-element oxide thin films by angle-resolved XPS: Application to ultra-thin oxide films on MgAl substrates by L.P.H. Jeurgens; M.S. Vinodh; E.J. Mittemeijer (pp. 627-638).

An original procedure has been developed for the quantitative analysis and microstructural interpretation of angle-resolved X-ray photoelectron spectra (AR-XPS) of very thin (<6nm), multi-element oxide films as grown on metallic binary alloy substrates by, e.g., thermal or plasma oxidation. To this end, first an approach has been given to retrieve the different metallic, oxidic and oxygen primary zero-loss (PZL) intensities from the measured AR-XPS spectra of the bare and oxidized alloy. The principal equations for the determination of the oxide-film thickness, composition and constitution from the resolved PZL intensities have been presented. On this basis, various corresponding calculation routes have been distinguished. The procedure has been applied to the case of very thin (<6nm), mixed (Mg, Al)-oxide films on bare Mg-based MgAl substrates as grown by dry, thermal oxidation at room temperature. The results obtained on the thickness, composition, defect structure and constitution of the oxide-film have been discussed as function of the bulk Al alloying content and the applied partial pressure of oxygen.

Keywords: PACS; 79.60.−i; 68.55.−a; 07.05.Kf; 81.65.Mq; 81.70.JbAngle-resolved XPS; Quantitative analysis; Oxidation; Binary alloys; Multi-element oxide films

Surface morphology of Dy_xO_y films grown on Si by K. Lawniczak-Jablonska; N.V. Babushkina; E. Dynowska; S.A. Malyshev; L.I. Romanova; D.V. Zhygulin; T. Laiho (pp. 639-645).

The crystalline structure and surface morphology of Dy_xO_y dielectric films grown on Si substrates were studied by grazing incidence diffraction and absorption with use of synchrotron radiation and by atomic force microscopy. The crystalline structure and the roughness of Dy_xO_y films were found to be strongly dependent on the deposition rate. The dielectric-silicon interface depends on the type of gas used in the annealing process. Moreover, results from the near edge X-ray absorption studies, have revealed that none of the examined films has a stoichiometry close to the Dy₂O₃. The level of stoichiometry is determined by the technological conditions. Nevertheless, MOS structures with Dy_xO_y films (EOT∼23Å) have shown a rather good Dy_xO_y-Si interface properties, which can be further improve by thermal annealing, and introducing of several additives, therefore Dy_xO_y films can be considered as suitable candidates for gate dielectric in MOS devices.

Keywords: PACS; 85.50; 61.10.H; 78.70.DDielectrics; Dysprosium oxide; X-ray diffraction; X-ray absorption; Atomic force microscopy

Nanoimprint lithography using IR laser irradiation by V. Grigaliūnas; S. Tamulevi�?ius; M. Muehlberger; D. Jucius; A. Guobienė; V. Kopustinskas; A. Gudonytė (pp. 646-650).

A new technique called “infrared laser-assisted nanoimprint lithography�? was utilised to soften the thermoplastic polymer material mR-I 8020 during nanoimprint lithography. A laser setup and a sample holder with pressure and temperature control were designed for the imprint experiments. The polymer was spin coated onto crystalline Si <111> substrates. A prepatterned Si <111> substrate, which is transparent for the CO₂ laser irradiation, was used as an imprint stamp as well. It was shown, that the thermoplastic resist mR-I 8020 could be successfully imprinted using the infrared CW CO₂ laser irradiation ( λ=10.6μm). The etching rate of the CO₂ laser beam irradiated mR-I 8020 resist film under O₂ RF (13.56MHz) plasma treatment and during O₂ reactive ion beam etching was investigated as well.

Keywords: Nanoimprint lithography; CO; ₂; laser; Plasma treatment; RIBE

Barrier height imaging of Si(111)3×1–Ag reconstructed surfaces by Takahisa Furuhashi; Yoshifumi Oshima; Hiroyuki Hirayama (pp. 651-654).

We investigated the bias voltage polarity dependence of atomically resolved barrier height (BH) images on Si(111)3×1–Ag surfaces. The BH images were very similar to scanning tunneling microscopy (STM) images in both the empty and filled states. This similarity strongly supports the interpretation that the BH image reflects the vertical decay rate of the surface local density of states (LDOS). Differences in contrast and protrusion shapes between BH and STM images were observed. We attributed these differences to the geometric contribution to the STM image and to the improved spatial resolution of the BH image due to the lock-in technique.

Keywords: PACS; 68.37.Ef; 68.47.Fg; 73.30+y; 73.20.At; 63.35.Bs; 68.43.FgScanning tunneling microscopy (STM); Barrier height (BH); Decay rate; Surface local density of state (LDOS); Ag; Si(1; 1; 1)

Metal contacts to n-GaN by L. Dobos; B. Pécz; L. Tóth; Zs.J. Horváth; Z.E. Horváth; A. Tóth; E. Horváth; B. Beaumont; Z. Bougrioua (pp. 655-661).

Al, Au, Ti/Al and Ti/Au contacts were prepared on n-GaN and annealed up to 900°C. The structure, phase and morphology were studied by cross-sectional transmission and scanning electron microscopy as well as by X-ray diffraction (XRD), the electrical behaviour by current–voltage measurements. It was obtained that annealing resulted in interdiffusion, lateral diffusion along the surface, alloying and bowling up of the metal layers. The current–voltage characteristics of as-deposited Al and Ti/Al contacts were linear, while the Au and Ti/Au contacts exhibited rectifying behaviour. Except the Ti/Au contact which became linear, the contacts degraded during heat treatment at 900°C. The surface of Au and Ti/Au contacts annealed at 900°C have shown fractal-like structures revealed by scanning electron microscopy. Transmission electron microscopy and XRD investigations of the Ti/Au contact revealed that Au diffused into the n-GaN layer at 900°C. X-ray diffraction examinations showed, that new Ti₂N, Au₂Ga and Ga₃Ti₂ interface phases formed in Ti/Au contact at 900°C, new Ti₂N phase formed in Ti/Al contact at 700 and 900°C, as well as new AlN interface phase developed in Ti/Al contact at 900°C.

Keywords: PACS; 68.37.−d/68.37.Lp; 68.55.−a/68.55.JkGaN; Thin films; Transmission electron microscopy; Solid phase reaction; Electrical properties

Study of the interplay of vaporisation, melt displacement and melt ejection mechanisms under multiple pulse irradiation of metals by J.M. Fishburn; M.J. Withford; D.W. Coutts; J.A. Piper (pp. 662-667).

A threefold study combining profilometry, high speed imaging and recoil momentum measurements is used to deconvolve the relative contributions to material removal attributable to vaporisation, melt displacement and explosive melt ejection. The interplay of these three mechanisms is studied as a function of the number of laser pulses incident on an aluminium target and pulse repetition frequency. This study shows cumulative heating affects matter removed as both vapour and liquid melt, and highlights the influence of the vapour plume and ablation crater morphology on the proportions of material removed as melt displacement and melt ejection.

Keywords: Nanosecond laser; Laser ablation; Plume; Melt ejection; Cumulative heating; Micromachining

Studies on surface modification of UHMWPE fibers via UV initiated grafting by Jieliang Wang; Guozheng Liang; Wen Zhao; Shenghua Lü; Zengping Zhang (pp. 668-673).

In this research, the surface of ultra high molecular weight polyethylene (UHMWPE) fiber was modified by high energy ultraviolet (UV) initiated grafting reactions and acrylamide groups were grafted onto UHMWPE chains. The initiating and grafting mechanism of the reactions was studied. Some important factors influencing the grafting effect, e.g. crystallinity of UHMWPE fiber, concentration of the initiating reagent, grafting time and the concentration of grafting monomer (acrylamide) were discussed. Fourier transform infrared (FTIR) was used to manifest the mechanism of the grafting reaction. Scanning electron microscopy (SEM) was used to show the morphology changing of the fiber surface. Single fiber pull-out strength and ILSS tests of the composite showed that acrylamide grafted onto the surface of the fiber could improve the interfacial adhesion between treated fibers and matrices.

Keywords: PACS; 81.65.−bUHMWPE fiber; Surface modification; UV initiated grafting

Growth process and wear resistance for ceramic coatings formed on Al–Cu–Mg alloy by micro-arc oxidation by Changzheng Wang; Dong Zhang; Yongfeng Jiang (pp. 674-678).

The growth process, distribution of chemical elements, phase constitutions and relative wear resistance of the ceramic coatings formed on Al–Cu–Mg alloy by ac micro-arc oxidation are investigated by scanning electron microscopy (SEM), energy dispersive X-ray spectroscope (EDX), X-ray diffraction (XRD) and reciprocating friction and wear tests. The results indicate that there are three stages with the formation of the ceramic coatings: (1) the formation of ceramic particles, (2) sintering growth in sawtooth structure, (3) the increase of thickness by remolting and sintering. The ceramic coatings are made up of a mixture of α-alumina, γ-alumina and amorphous alumina, whose relative contents varied with the position in the ceramic coatings, respectively. The chemical elements altered in ceramic coatings produced in different electrolytes and varied along the depth in ceramic coatings obtained in phosphate electrolyte. Meanwhile, the results of friction and wear tests against Gr15 after 16h indicate that the weight loss of ceramic coatings became almost unchanged.

Keywords: PACS; 68.37.Hk; 81.05.Je; 82.45.JnMicro-arc oxidation; Al–Cu–Mg alloy; Ceramic coatings; Wear resistance; Weight loss

Thermal analysis of electron gun for travelling wave tubes by K.S. Bhat; K. Sreedevi; M. Ravi (pp. 679-682).

Thermal analysis of a pierce type electron gun using the FEM software ANSYS and its experimental validation are presented in this paper. Thermal analysis of the electron gun structure has been carried out to find out the effect of heater power on steady state temperature and warm-up time. The thermal drain of the supporting structure has also been analyzed for different materials. These results were experimentally verified in an electron gun. The experimental results closely match the ANSYS results.

Keywords: Thermal analysis; Pierce electron gun; Dispenser cathodes; FEM

The adsorption behavior and corrosion inhibition mechanism of anionic inhibitor on galvanic electrode in 1% NaCl solution by J.Z. Ai; X.P. Guo; Z.Y. Chen (pp. 683-688).

The adsorption behavior of dodecanoic acid and its sodium salt (DDAS) as an anionic inhibitor on the galvanic electrode has been investigated by using electrochemical methods, Fourier transform infrared spectroscopy (FT-IR), and atomic force microscopy (AFM). The galvanic electrode was prepared by coupling N80 carbon steel (CS) and S31803 stainless steel (SS), and all experiments were performed in NaCl solution at pH 4 in the presence or absence of DDAS. Electrochemical experiments reveal SS and CS carry positive and negative excess charges in NaCl solution at pH 4, and DDAS is mainly anodic type inhibitor for the galvanic corrosion. FT-IR and AFM were used to analyze the protective layer formed on the electrodes, a stronger adsorbability of the inhibitor on the anode (CS) of GE was measured. Results indicate the protective layer formed on the single CS electrode is less compact than which on the coupled CS. The adsorption regulation of anionic inhibitor on the galvanic electrode is summarized based on the results obtained from electrochemical methods, FT-IR and AFM.

Keywords: PACS; 81.65 kAtomic force microscopy; Electrochemical method; Galvanic corrosion; Inhibitor; Adsorption behavior

Potential dependence of cuprous/cupric duplex film growth on copper electrode in alkaline media by Jian-Bo He; Dao-Yong Lu; Guan-Ping Jin (pp. 689-697).

The duplex oxide film potentiostatically formed on copper in concentrated alkaline media has been investigated by XRD, XPS, negative-going voltammetry and cathodic chronopotentiometry. The interfacial capacity was also measured using fast triangular voltage method under quasi-stationary condition. The obvious differences in the thickness, composition, passivation degree and capacitance behavior were observed between the duplex film formed in lower potential region (−0.13 to 0.18V versus Hg|HgO electrode with the same solution as the electrolyte) and that formed in higher potential region (0.18–0.60V). Cuprous oxides could be formed and exist stably in the inner layer in the both potential regions, and three cupric species, soluble ions and Cu(OH)₂ and CuO, could be independently produced from the direct oxidation of metal copper, as indicated by three pairs of redox voltammetric peaks. One of the oxidation peaks appeared only after the scan was reversed from high potential and could be attributed to CuO formation upon the pre-accumulation of O²⁻ ions within the film under high anodic potentials. A new mechanism for the film growth on the investigated time scale from 1 to 30min is proposed, that is, the growth of the duplex film in the lower potential region takes place at the film|solution interface to form a thick Cu(OH)₂ outer layer by field-assisted transfer of Cu²⁺ ions through the film to solution, whereas the film in the higher potential region grows depressingly and slowly at the metal|film interface to form Cu₂O and less CuO by the transfer of O²⁻ ions through the film to electrode.

Keywords: Copper; Solid oxide film; Ion transfer; Interface reaction; Oxygen ion; Capacitance behavior

Energy and volume expansion in Ag[1¯10] STGB by Yu-Hong Huang; Jian-Min Zhang; Ke-Wei Xu (pp. 698-702).

The energies of[1¯10] STGB have been calculated with MAEAM for a series of 44GBs in FCC metal Ag. They are unrealistically high for the two crystals rigid joined together, this is caused by the atoms near GB plane are very close so that they will repel each other and result in a GB expansion and energy decreasing. The minimum energy after expansion E_min depends on rotation angle θ, four lowest energies are corresponding to (111) ( θ=70.53°), (113) ( θ=129.52°), (331) ( θ=26.53°) and (112) ( θ=109.47°) GB successively. Considering minimization of the energy, these four boundaries should be preferable in ( h h k) GB. It is found that the lowest-energy GB corresponds to the smallest volume expansion δV and miscoordination coefficient C( m) successively. The former is consistent with the results of rotating sphere-on-a-plate experiments. In addition, the minimum GB energy E_min increases linearly with increasing excess volume δV.

Keywords: STGB; Energy; Volume expansion; Miscoordination coefficient; MAEAM

Removal of chemisorbed lubricant on the surface of silver flakes by chemicals by Fatang Tan; Xueliang Qiao; Jianguo Chen (pp. 703-707).

Lubricants generally are used in the milling process of silver powders to flakes to nullify the forces of welding and thereby inhibit agglomeration. The study was carried out to fully understand the interaction of silver flakes with a commonly used lubricant, oleic acid. Silver flakes were prepared by ball milling of precipitated fine silver powders with oleic acid in amounts about 1.0wt.%. Thermal properties of lubricated silver flakes and silver flakes treated by several chemicals were studied; the efficiency of the lubricant removal was estimated by the DSC exothermic peak in air. It was found that a mixture of solvent and diluted sulfuric acid can fully remove the lubricant on the surface of silver flakes. The morphology of silver flakes before and after treatment by a mixture of alcohol and diluted sulfuric was observed by scanning electron microscopy; the lubricant removal was also confirmed.

Keywords: PACS; 81.20.Ev; 81.20.WkSilver flakes; Mechanical comminution process; Surfaces; Differential scanning calorimetry (DSC); Chemisorption

Optimal design of a convergent-barrel cold spray nozzle by numerical method by Wen-Ya Li; Hanlin Liao; Hong-Tao Wang; Chang-Jiu Li; Ga Zhang; C. Coddet (pp. 708-713).

A convergent-barrel (CB) cold spray nozzle was designed through numerical simulation. It was found that the main factors influencing significantly particle velocity and temperature include the length and diameter of the barrel section, the nature of the accelerating gas and its pressure and temperature, and the particle size. Particles can achieve a relatively low velocity but a high temperature under the same gas pressure using a CB nozzle compared to a convergent–divergent (CD) nozzle. The experiment results with Cu powder using the designed CB nozzle confirmed that particle deposition can be realized under a lower gas pressure with a CB nozzle.

Keywords: Cold spraying; Numerical simulation; Optimal design; Convergent-barrel nozzle; Copper coating

A transmission electron microscopy study on the atomic arrangement and grain growth of hexagonal structured Ge₂Sb₂Te₅ by Yu Jin Park; Jeong Yong Lee; Yong Tae Kim (pp. 714-719).

The atomic arrangement and grain growth of the hexagonal structured Ge₂Sb₂Te₅ were investigated by a transmission electron microscopy study. Unlike the isotropic crystallization of face-centered-cubic (fcc) structured Ge₂Sb₂Te₅, the hexagonal structured Ge₂Sb₂Te₅ grain was preferably grown to a large degree with a specific direction. As a result, we have revealed that the grain growth occurred parallel to the (0001) plane, and identified the atomic arrangement of the hexagonal structured Ge₂Sb₂Te₅ having nine cyclic layers by analyzing the high-resolution transmission electron microscopy images and simulated images obtained in the direction of〈112¯0〉 zone axis.

Keywords: PACS; 68.37.Lp; 68.55.Jk; 61.50.KsGe; ₂; Sb; ₂; Te; ₅; Transmission electron microscopy; Atomic arrangement; Grain growth

Preparation of TiO₂ thin films from autoclaved sol containing needle-like anatase crystals by Lei Ge; Mingxia Xu; Haibo Fang; Ming Sun (pp. 720-725).

A new inorganic sol–gel method was introduced in this paper to prepare TiO₂ thin films. The autoclaved sol with needle-like anatase crystals was synthesized using titanyl sulfate (TiOSO₄) and peroxide (H₂O₂) as starting materials. The transparent anatase TiO₂ thin films were prepared on glass slides from the autoclaved sol by sol–gel dip-coating method. A wide range of techniques such as Fourier transform infrared transmission spectra (FT-IR), X-ray diffraction (XRD), thermogravimetry-differential thermal analysis (TG-DTA), scanning electron microscopes, X-ray photoelectron spectroscopy (XPS) and ultraviolet–visible spectrum were applied to characterize the autoclaved sol and TiO₂ thin films. The results indicate that the autoclaved sol is flavescent, semitransparent and stable at room temperature. The anatase crystals of TiO₂ films connect together to form net-like structure after calcined and the films become uniform with increasing heating temperature. The surface of the TiO₂ films contain not only Ti and O elements, but also a small amount of N and Na elements diffused from substrates during heat treatment. The TiO₂ films are transparent and their maximal light transmittances exceed 80% under visible light region.

Keywords: Needle-like anatase crystals; Autoclaved sol; TiO; ₂; thin films; Sol–gel method

Enhanced hardness in B-doped ZnO thin films on fused quartz substrates by pulsed-laser deposition by Songqing Zhao; Yueliang Zhou; Yuzi Liu; Kun Zhao; Shufang Wang; Wenfeng Xiang; Zhen Liu; Peng Han; Ze Zhang; Zhenghao Chen; Huibin Lu; Kuijuan Jin; Bolin Cheng; Guozhen Yang (pp. 726-729).

B-doped ZnO thin films have been fabricated on fused quartz substrates using boron–ZnO mosaic target by pulsed-laser deposition technique, and the mechanical properties have been studied by nanoindentation continuous stiffness measurement technique and transmission electron microscope (TEM). Nanoindentation measurement revealed that the hardness of B-doped ZnO films, 9.32±0.90 to 12.10±1.00GPa, is much greater than that of undoped ZnO films and very close to that of traditional semiconductor Si. The mean transmittance (%) is larger than 81% in the visible range (380–780nm) for all the films, and the Hall effect measurement showed that the carrier density is around 2×10²⁰cm⁻³ and the resistivity lower than 3×10⁻³Ωcm. TEM characteristics show undoped thin films have more amorphous area between grains while the B-doped ZnO films have thin grain boundaries. We suggest that the grain boundaries act as the strain compensation sites and the decrease in thickness of grain boundaries enhances the hardness of the B-doped ZnO films.

Keywords: PACS; 68.60.Bs; 81.70.Bt; 78.66.Hf; 81.15.FgNanoindentation; Hardness; ZnO thin film; B-doped; TEM

A computational analysis of the ballistic performance of light-weight hybrid composite armors by M. Grujicic; B. Pandurangan; K.L. Koudela; B.A. Cheeseman (pp. 730-745).

The ability of hybrid light-weight fiber-reinforced polymer–matrix composite laminate armor to withstand the impact of a fragment simulating projectile (FSP) is investigated using a non-linear dynamics transient computational analysis. The hybrid armor is constructed using various combinations and stacking sequences of a high-strength/high-stiffness carbon fiber-reinforced epoxy (CFRE) and a high-ductility/high-toughness Kevlar fiber-reinforced epoxy (KFRE) composite laminates of different thicknesses. The results obtained indicate that at a fixed thickness of the armor both the stacking sequence and the number of CFRE/KFRE laminates substantially affect the ballistic performance of the armor. Specifically, it is found that the armor consisting of one layer of KFRE and one layer of CFRE, with KFRE laminate constituting the outer surface of the armor, possesses the maximum resistance towards the projectile-induced damage and failure. The results obtained are rationalized using an analysis of the elastic wave reflection and transmission behavior at the inter-laminate and laminate/air interfaces.

Keywords: Impact; Fragment simulating projectile; Hybrid composite laminate; AUTODYN

Thermal stability of Ti/Al/Pt/Au and Ti/Au Ohmic contacts on n-type ZnCdO by Jau-Jiun Chen; Soohwan Jang; F. Ren; S. Rawal; Yuanjie Li; Hyun-Sik Kim; D.P. Norton; S.J. Pearton; A. Osinsky (pp. 746-752).

The specific contact resistivity and chemical intermixing of Ti/Au and Ti/Al/Pt/Au Ohmic contacts on n-type Zn_0.05Cd_0.95O layers grown on ZnO buffer layers on GaN/sapphire templates is reported as a function of annealing temperature in the range 200–600°C. A minimum contact resistivity of 2.3×10⁻⁴Ωcm² was obtained at 500°C for Ti/Al/Pt/Au and 1.6×10⁻⁴Ωcm² was obtained at 450°C for Ti/Al. These values also correspond to the minima in transfer resistance for the contacts. The Ti/Al/Pt/Au contacts show far smoother morphologies after annealing even at 600°C, whereas the Ti/Au contacts show a reacted appearance after 350°C anneals. In the former case, Pt and Al outdiffusion is significant at 450°C, whereas in the latter case the onset of Ti and Zn outdiffusion is evident at the same temperature. The improvement in contact resistance with annealing is suggested to occur through formation of TiO_x phases that induce oxygen vacancies in the ZnCdO.

Keywords: ZnCdO; Ohmic contacts

XPS characterization of supported Ziegler–Natta catalysts by V.K. Kaushik; V.K. Gupta; D.G. Naik (pp. 753-756).

Surface analytical technique ESCA (electron spectrometer for chemical analysis) has been used for analysis of catalysts used in propylene polymerization. As a result of this analysis it has been shown that productivity of a catalyst can be correlated to Ti/Mg atomic ratio that indicates dispersion of titanium atoms on magnesium support. A quantitative indicator of productivity, i.e. “titanium index�? has also been evaluated for studied catalysts.

Keywords: Ziegler–Natta catalyst; Propylene polymerization; ESCA; Dispersion; Titanium index

Computer simulation of monolayer growth kinetics of Fe₂B phase during the paste-boriding process: Influence of the paste thickness by M. Keddam (pp. 757-761).

This paper deals with the effect of boron paste thickness on the study of the monolayer growth kinetics of Fe₂B phase forming on AISI 1045 steel by the paste-boriding process. A mathematical diffusion model based on the Fick's phenomenological equations was applied in order to estimate the growth rate constant at (Fe₂B/γ-Fe) interface, the layer thickness of iron boride as well as the associated mass gain depending on the boriding parameters such as time, temperature and surface boron concentration related to the boron paste thickness. The simulation results are found to be in a fairly good agreement with the experimental data derived from the literature.

Keywords: Computer simulation; Fe–B system; Paste-boriding; Fick's laws; Growth kinetics

Influence of AlN interfacial layer on electrical properties of high-Al-content Al_0.45Ga_0.55N/GaN HEMT structure by Cuimei Wang; Xiaoliang Wang; Guoxin Hu; Junxi Wang; Jianping Li; Zhanguo Wang (pp. 762-765).

Unintentionally doped high-Al-content Al_0.45Ga_0.55N/GaN high electron mobility transistor (HEMT) structures with and without AlN interfacial layer were grown by metal–organic chemical vapor deposition (MOCVD) on two-inch sapphire substrates. The effects of AlN interfacial layer on the electrical properties were investigated. At 300K, high two-dimensional electron gas (2DEG) density of 1.66×10¹³cm⁻² and high electron mobility of 1346cm²V⁻¹s⁻¹ were obtained for the high Al content HEMT structure with a 1nm AlN interfacial layer, consistent with the low average sheet resistance of 287Ω/sq. The comparison of HEMT wafers with and without AlN interfacial layer shows that high Al content AlGaN/AlN/GaN heterostructures are potential in improving the electrical properties of HEMT structures and the device performances.

Keywords: PACS; 68.55.Jk; 81.15.Gh; 81.05.Ea; 72.80.Ey; 85.30.TvAlGaN/AlN/GaN; Two-dimensional electron gas; MOCVD

Effect of hydrothermal treatment on the acidity distribution of γ-Al₂O₃ support by Li Jun-Cheng; Xiang Lan; Xu Feng; Wang Zhan-Wen; Wei Fei (pp. 766-770).

The influence of hydrothermal treatment on the total acidity and the acidity distribution of γ-Al₂O₃ were studied in this paper. The experimental results indicated that the hydrothermal treatment of γ-Al₂O₃ at moderate condition (140°C, 1.0–24.0h) led to the formation of the plate-like γ-AlOOH crystallites with different morphologies, which resulted in the change of the surface acidity of the corresponding γ-Al₂O₃ supports. The increase of the reaction time in the period of 1.0–2.0h led to the increase of the specific surface area, the surface OH, the total acidity and the ratio of the weak acidity in the acidity distribution of γ-Al₂O₃. The further prolongation of reaction time caused the overgrowth of γ-AlOOH crystallites, leading to the decrease of the specific surface area, the surface OH and the total acidity of the corresponding γ-Al₂O₃.

Keywords: γ-Al; ₂; O; ₃; Hydrothermal treatment; Morphology; Surface OH; Acidity distribution

Hydrogen uptake kinetics of Pd coated FeTi films by E.M.B. Heller; A.M. Vredenberg; D.O. Boerma (pp. 771-777).

The kinetics of hydrogen uptake of thin films of FeTi deposited on Si substrates and covered with 20nm Pd were studied. The films serve as a model system for powdered FeTi, with grains that are (partly) covered with Pd, which serves as a protection for severe oxidation. Two FeTi compositions near the 50/50 composition were studied. The hydrogen uptake kinetics as a function of temperature and pressure were measured by probing the differential pressure between a small hydriding reaction chamber and a reference chamber. Both compositions showed first order kinetics for the largest portion of the uptake. Using results of additional measurements in which the thickness of the layers was varied, a model is proposed in which the uptake proceeds via fast channels through the film, followed by slower diffusion into the bulk. Finally, the influence of oxidation was studied. An FeTi-oxide underneath the Pd layer is a barrier for H diffusion. It was found that by annealing the H uptake rate could be increased. This is probably due to the decomposition of the oxide. Samples partly covered with Pd and partly by FeTi-oxides, obtained by decomposing the fully covered structure by air annealing at 250°C, showed uptake throughout the entire FeTi film with an even faster rate than in a fully covered film. Some explanation with simple models of the observed phenomena is given.

Keywords: PACS; 68.35 Fx; 81.05 Bx; 81.65 Mq; 89.30 xfFeTi; Pd; Hydrides; Hydrogen uptake kinetics; Thin films; Hydrogen storage

Emissivity measurements on carbon–carbon composites at high temperature under high vacuum by M. Balat-Pichelin; J.F. Robert; J.L. Sans (pp. 778-783).

Carbon–carbon composites are candidate materials for the conception of the thermal shield of the “Solar Probe�? space mission. To understand their behavior under solar aggressions and know the possible interactions with the shipped-in instruments, these materials were tested in a facility that allows to partially simulate the solar environment and to carry out in situ measurements. In this paper, we present the experimental results obtained for the α/ ɛ ratio, i.e. the ratio of the solar absorptivity α to the total hemisherical emissivity ɛ that controls the thermal equilibrium of the thermal shield. The objective is to find the lower ratio α/ ɛ in order to have the lowest temperature on the shield at 4solar radii.

Keywords: Carbon; Ceramic–matrix composites (CMCs); High temperature; Thermophysical properties; Emissivity

Direct chemical assembly of quaternary ammonium groups on a surface of highly dispersed silica by Lyudmila A. Belyakova; Anatoly M. Varvarin; Nadiya V. Roik (pp. 784-791).

Direct assembly of quaternary ammonium groups onto a silica surface has been realized by use of many-stage chemical reactions. Adsorption of cholic acid in dependence on duration, equilibrium concentration, and pH solution onto a surface of silicas modified with quaternary ammonium groups has been studied. The main parameters of cholic acid adsorption have been calculated.

Keywords: Silica; Reaction of nucleophilic addition; Chemical assembly on a surface; Quaternary ammonium groups; Cholic acid; Adsorption; Ion exchange; Hydrophobicity; IR and UV–vis spectroscopy

Field emission from patterned SnO₂ nanostructures by Yongsheng Zhang; Ke Yu; Guodong Li; Deyan Peng; Qiuxiang Zhang; Hongmei Hu; Feng Xu; Wei Bai; Shixi Ouyang; Ziqiang Zhu (pp. 792-796).

A simple and reliable method has been developed for synthesizing finely patterned tin dioxide (SnO₂) nanostructure arrays on silicon substrates. A patterned Au catalyst film was prepared on the silicon wafer by radio frequency (RF) magnetron sputtering and photolithographic patterning processes. The patterned SnO₂ nanostructures arrays, a unit area is of ∼500μm×200μm, were synthesized via vapor phase transport method. The surface morphology and composition of the as-synthesized SnO₂ nanostructures were characterized by means of scanning electron microscopy (SEM) and X-ray diffraction (XRD). The mechanism of formation of SnO₂ nanostructures was also discussed. The measurement of field emission (FE) revealed that the as-synthesized SnO₂ nanorods, nanowires and nanoparticles arrays have a lower turn-on field of 2.6, 3.2 and 3.9V/μm, respectively, at the current density of 0.1μA/cm². This approach must have a wide variety of applications such as fabrications of micro-optical components and micropatterned oxide thin films used in FE-based flat panel displays, sensor arrays and so on.

Keywords: PACS; 82.45.Yz; 81.16.Rf; 85.45.DbTin oxide nanostructure; Patterned growth; Field emission

Model of workpiece erosion for electrical discharge machining process by Leonid I. Sharakhovsky; Aruy Marotta; Alexei M. Essiptchouk (pp. 797-804).

The previously published step-wise model (SWM) of cold electrodes erosion of electric arc heaters (EAHs) was modified for the calculation of workpiece removal rate (WRR) in electrical discharge machining (EDM) process. Modified model applies both relations the step-wise erosion model and the point heat source erosion model and takes into account the discharge current, the discharge pulse/pause time and thermophysical properties of machined material. The results of calculations show a reasonable agreement with data obtained experimentally by different authors about different materials and conditions.

Keywords: PACS; 52.50.Nr; 81.65.Cf; 52.77.BnElectric discharge; Electrical discharge machining process; Heat source; Ablation; Effective enthalpy of erosion

Influence of the viscosity and the substrate on the surface hydrophobicity of polyurethane coatings by M. Meincken; A. Klash; S. Seboa; R.D. Sanderson (pp. 805-809).

Tailor-made polyurethane (PU) dispersions were synthesized as coatings for paperboard for dry food packaging. For this purpose a low moisture-vapor transmission rate and a high surface hydrophobicity are desirable characteristics, which are both met by PU. However, it was found that the surface hydrophobicity of water-borne PU dispersions depends strongly on the viscosity of the dispersion. This dependency was studied by static contact angle measurements (SCA) as well as a novel technique using digital pulsed-force mode atomic force microscopy (DPFM-AFM). Comparison of the results validated that DPFM-AFM is a valuable tool to characterize the surface hydrophilicity. Both techniques confirmed that the surface hydrophobicity varies with the viscosity and that an optimum viscosity for the PU coating with a maximum surface hydrophobicity can consequently be determined. It was found that both lower as well as higher viscosities led to a less hydrophobic surface.

Keywords: PACS; 68.37.Ps; 81.16.Dn; 82.35.LrPolyurethanes; Coatings; Surface hydrophobicity; Atomic force microscopy (AFM); Static contact angle (SCA)

Ion beam induced crystal-edge nanoclusters at the origin of poly(ethylene glycol) film stabilization by M. Manso; A. Valsesia; G. Ceccone; F. Rossi (pp. 810-813).

PEG films stabilized by noble gas ion beam irradiation showed characteristic clustering at the crystal edges. These structures appear in determined ion beam conditions after exposure to Ar and Kr ions. Atomic force microscopy exploration indicates that, rather than presenting drastic topographic features, the nanostructures show radically different elastic properties. Within the concerned set of ion beam conditions, the surface properties are observed to vary according to the absorbed energy as suggested by X-ray photoelectron spectroscopy and contact angle measurements. These analyses predict that Ar irradiation in the 500–600V extraction potential range is an appropriate condition for PEG stabilization.

Keywords: PACS; 61.41; 34.50.D; 52.75.R; 79.60; 61.72.S; 07.79PEG; Ion beam modification; Polymers; Nanocluster; XPS

Protection of iron corrosion by stearic acid and stearic imidazoline self-assembled monolayers by Xiuyu Liu; Shenhao Chen; Houyi Ma; Guangzeng Liu; Lixia Shen (pp. 814-820).

A type of stearic imidazoline (IM) inhibitor was prepared using stearic acid (SA) and diethylenetriamine (DETA) as raw materials. The monolayers of IM and SA were assembled on the iron surface. The electrochemical characterization of stearic acid (SA) and stearic imidazoline (IM) on an oxide free iron surface had been studied. The monolayers of IM inhibitor were characterized by electrochemical impedance spectroscopy (EIS), electrochemical polarization curves, double layer capacitance, X-ray photoelectron spectroscopy (XPS) and molecular simulation. The results of electrochemical studies had illustrated that the inhibition efficiency of IM was higher than SA. XPS showed that the IM molecules adsorbed on the iron surface. The molecular simulation calculations showed that the IM molecules were tilted at an angle on the iron surface.

Keywords: Electrochemical impedance spectroscopy (EIS); Iron; Imidazoline; Inhibitor; Self-assembled monolayers (SAMs)

Synthesis and characterization of activated carbon from asphalt by Munther Issa Kandah; Reyad Shawabkeh; Mahmoud Ar’ef Al-Zboon (pp. 821-826).

Asphalt (cheap and available in huge amount in Jordan) was converted into activated carbon powder by chemical treatment with sulphuric and nitric acids at 450°C. The final product was characterized and found effective as adsorbent material. Its cation exchange capacity reaches 191.2meq/100-g carbons when treated with 30wt% acid/asphalt ratio without airflow rate injection and 208meq/100-g carbons when 6.5ml air/min was injected into the surface of the asphalt during activation at the same acid/asphalt weight ratio of 30 and temperature 450°C. The zero point of charge for this product was found to be stable at pH value around 3 in the range of initial pH between 3 and 10.

Keywords: PACS; 68.43.MnAsphalt; Activated carbon; Chemical activation; Ion exchange

Characteristics of ZnO–Cu–ZnO multilayer films on copper layer properties by D.R. Sahu; Jow-Lay Huang (pp. 827-832).

ZnO/Cu/ZnO multilayers on glass with different copper layer thickness were prepared by simultaneous RF magnetron sputtering of ZnO and dc magnetron sputtering of Cu. Different optimization procedure were used for good transparent conductive film. Several analytical tools such as spectrophotometer, scanning electron microscope (SEM), four point probes were used to explore the causes of the changes in electrical and optical properties. The sheet resistance of the structure was severely influenced by the deposition condition of both top ZnO and intermediate Cu layer. Effect of substrate temperature and annealing treatment on ZnO and Cu layer was analyzed. A sheet resistance of 10Ω/sq and transmittance over 85% at 580nm wavelength was achieved and could be reproduced by controlling the preparation process parameter. The results of an optimization condition of both oxide layers and metallic Cu layers are illustrated.

Keywords: ZnO; Cu; Multilayers; Optical properties and electrical properties

Atomistic modeling of dislocation activity in nanoindented GaAs by Sheng-Rui Jian; Te-Hua Fang; Der-San Chuu; Liang-Wen Ji (pp. 833-840).

The mechanical behavior of GaAs was investigated by nanoindentation with the aid of molecular dynamics (MD) analysis based on the Tersoff potential. Particular attention was devoted to the evolution characterization of dislocation activity during deformation. The transition from elastic-to-plastic deformation behavior was clearly observed as a sudden displacement excursion occurring during the load–displacement curves of larger loads (single pop-in), faster impact velocity and higher temperature (multiple pop-ins). Even for an ultra-small penetration depth (<3nm), the MD simulation shows that GaAs deforms plastically and a good description is given in the results. The plastic deformation occurs due to the anticipated change in the twinning and/or dislocation motion. Dislocation nucleations occurred inside the material near the top of the surface and generated loops in the {111} slip planes. The MD analysis of the deformation behavior shows an agreement with that of previous atomic force microscopy (AFM) and transmission electron microscopy (TEM) experiments.

Keywords: PACS; 02.70.Ns; 62.20.-x; 62.25.+gMolecular dynamics simulations; Tersoff potential; GaAs; Nanoindentation

ZnO thin films on Si(111) grown by pulsed laser deposition from metallic Zn target by Jie Zhao; Lizhong Hu; Zhaoyang Wang; Jie Sun; Zhijun Wang (pp. 841-845).

ZnO thin films with highly c-axis orientation have been fabricated on p-type Si(111) substrates at 400°C by pulsed laser deposition (PLD) from a metallic Zn target with oxygen pressures between 0.1 and 0.7mbar. Experimental results indicate that the films deposited at 0.3 and 0.5mbar have better crystalline and optical quality and flatter surfaces than the films prepared at other pressures. The full width at half maximum (FWHM) of (0002) diffraction peak decreases remarkably from 0.46 to 0.19° with increasing annealing temperature for the film prepared at 0.3mbar. In photoluminescence (PL) spectra at room temperature, the annealed film at 700°C exhibits a smaller ultraviolet (UV) peak FWHM of 108meV than the as-grown film (119meV). However, an enhanced deep-level emission is observed. Possible origins to above results are discussed.

Keywords: PACS; 81.15.Fg; 68.55.Jk; 78.55.EtZnO; Pulsed laser deposition; Oxygen pressure; Annealing; X-ray diffraction; Photoluminescence

The inhibition of corrosion of mild steel in 0.5M sulfuric acid solution in the presence of benzyl triphenyl phosphonium bromide by Kalpana Bhrara; Gurmeet Singh (pp. 846-853).

Benzyl triphenyl phosphonium bromide (BTPPB) has been evaluated as a corrosion inhibitor for mild steel in aerated 0.5M sulfuric acid solution by galvanostatic polarization and potentiostatic polarization methods. The effect of BTPPB on the corrosion current is measured at various temperatures and concentrations. The inhibitor efficiencies, effective activation energies and heat of adsorption have been calculated. The inhibition efficiency increases with increase in inhibitor concentration to reach 99.3% for 10⁻²M. The nature of adsorption of BTPPB on the metal surface has also been examined. Probable mode of adsorption on the metal surface has been proposed using infrared spectroscopic studies. The electrochemical results have also been supplemented by surface morphological studies and quantum chemical analysis.

Keywords: Benzyl triphenyl phosphonium bromide (BTPPB); Galvanostatic polarization studies; Potentiostatic polarization studies; Infrared spectroscopy; Scanning electron microscopy and quantum chemical parameters

The energy and structure of (001) twist grain boundary in noble metals by Xiu-Mei Wei; Jian-Min Zhang; Ke-Wei Xu (pp. 854-858).

The relaxed energy and structure of (001) twist grain boundary (GB) in noble metals Au, Ag and Cu are simulated by the MAEAM. In-boundary translation between two adjacent grains results in a periodic energy variation and the period is a square with the side length L_Σ/ Σ. The lowest energy appears when the two grains are translated relatively to either corner or center of the periodic square. The relaxed GB energy increases smoothly for low-angle boundaries and levels off for larger-angle boundaries except a cusp appeared at θ=36.87° ( Σ=5). After relaxation, the symmetry of the GB structure is not changed but the displacement of the atoms parallel to the GB plane decreases with increasing the distance of the atoms from the GB plane.

Keywords: PACS; 61.43.Bn; 61.72.Mm; 98.38.BnGrain boundary energy; MAEAM; Translation

The influence of H₂ plasma treatment on the field emission of amorphous GaN film by F. Ye; E.Q. Xie; H.G. Duan; H. Li; X.J. Pan (pp. 859-862).

The influence of H₂ plasma treatment on the field emission properties of amorphous GaN (a-GaN) films is studied. It is found that the treatment makes little change to the surface morphology. The current density of the treated film decreases from 400 to 30μA/cm² at the applied field of about 30V/μm. The treatment can reduce the defects in a-GaN films, and therefore the treatment results in the weakening of the tunneling emission of the a-GaN film at the high field region. The treatment also seems to change the conduction mechanism of the a-GaN film.

Keywords: PACS; 79.70.+q; 73.20.HbField emission; H; ₂; plasma treatment; Defect levels; Conduction mechanism

Improvement of surface porosity and properties of alumina films by incorporation of Fe micrograins in micro-arc oxidation by Fanya Jin; Paul K. Chu; Honghui Tong; Jun Zhao (pp. 863-868).

Micro-arc oxidation (MAO) is an effective approach to improve the properties of aluminum and its alloy by forming ceramic films on the surface. However, the oxide layers often have a porous surface structure, which exhibits relatively high friction coefficients. In this work, in order to enhance the surface and mechanical properties of the films produced by micro-arc oxidation, Al₂O₃ coatings embedded with Fe micrograins of different thicknesses were produced on aluminum alloys by adding Fe micrograins into the electrolyte during MAO. Compared to the Al₂O₃ coatings without Fe micrograins, the MAO Al₂O₃ coatings with Fe micrograins are much denser and harder, and the wear resistance is also improved significantly. The enhancement can be attributed to the enhancement of the surface structure and morphology of the MAO Al₂O₃ coatings with embedded Fe micrograins.

Keywords: PACS; 68.35.Ct; 68.35.Gy; 68.55.Jk; 68.60.Bs; 81.15.PqMicro-arc oxidation; Al; ₂; O; ₃; coatings; Fe micrograins; Surface properties

Structure of dioctadecyll-glutamide-derived lipid self-assembled monolayers on Au(111) surface by Toshihiko Sakurai; Maki Horikawa; Md. Saleh Chowdhury; Makoto Takafuji; Hiroshi Hachisako; Atsushi Kubo; Isao Taniguchi; Hirotaka Ihara (pp. 869-873).

Anl-glutamic acid-derived lipid with a terminal thiol has been synthesized and its corresponding self-assembled structure on Au(111) surfaces described. The surface morphology of the lipid self-assembled monolayer (SAM) exhibits nano-order patterning, where the height of the monolayer (approximately 1.5nm) could be interpreted as due to the monolayer structure estimated from molecular models. The molecular orientation in the monolayer is almost perpendicular to the Au(111) surface depending on the three-point hydrogen-bonding sites in the molecule.

Keywords: PACS; 81.07.-b; 81.16.DnSelf-assembled monolayer; AFM; Nanofiber; FT-IR/RAS; Molecular orientation

Simulation of island aggregation influenced by substrate temperature, incidence kinetic energy and intensity in pulsed laser deposition by Duanming Zhang; Li Guan; Zhihua Li; Guijun Pan; Xinyu Tan; Li Li (pp. 874-880).

Using kinetic Monte Carlo method, we have simulated a pulsed energetic growth process in pulsed laser deposition. During the growth of film, substrate temperature mainly influences upon film morphology by directly enhancing the adatom mobility through the temperature-dependent thermal vibration. By contrast, the effect of incidence kinetic energy on film growth is complex resulting from the collisions between the incident particles and the adatoms. The results show that improving incident kinetic energy cannot significantly accelerate the migration rate of adatom but change surface microstructure and promote single adatom formation resulting in more island aggregation density. Moreover, since pulse–influx characterizes pulsed laser deposition, the intensity per pulse contributes to the evolvement of nucleation density and the results illustrate that a general scaling law different from ordinary power law still exists in energetic growth of pulsed laser deposition.

Keywords: PACS; 81.15.Fg; 02.70.Uu; 68.55.AcPulsed laser deposition; Kinetic Monte Carlo methods; Nucleation

Effect of surface roughness on the development of protective Al₂O₃ on Fe–10Al (at.%) alloys containing 0–10at.% Cr by Z.G. Zhang; P.Y. Hou; F. Gesmundo; Y. Niu (pp. 881-888).

The effect of alloy surface roughness, achieved by different degrees of surface polishing, on the development of protective alumina layer on Fe–10at.% Al alloys containing 0, 5, and 10at.% Cr was investigated during oxidation at 1000°C in 0.1MPa oxygen. For alloys that are not strong Al₂O₃ formers (Fe–10Al and Fe–5Cr–10Al), the rougher surfaces increased Fe incorporation into the overall surface layer. On the Fe–10Al, more iron oxides were formed in a uniform layer of mixed aluminum- and iron-oxides since the layer was thicker. On the Fe–5Cr–10Al, more iron-rich nodules developed on an otherwise thin Al₂O₃ surface layer. These nodules nucleated preferentially along surface scratch marks but not on alloy grain boundaries. For the strong Al₂O₃-forming Fe–10Cr–10Al alloy, protective alumina surface layers were observed regardless of the surface roughness. These results indicate that the formation of a protective Al₂O₃ layer on Fe–Cr–Al surfaces is not dictated by Al diffusion to the surface. More cold-worked surfaces caused an enhanced Fe diffusion, hence produced more Fe-rich oxides during the early stage of oxidation.

Keywords: PACS; 68.55.Nq; 81.65.Mq; 81.65.PsHigh temperature oxidation; Alumina; Surface roughness; Nodules; Third element effect

Dry etching of bulk single-crystal ZnO in CH₄/H₂-based plasma chemistries by Wantae Lim; Lars Voss; Rohit Khanna; B.P. Gila; D.P. Norton; S.J. Pearton; F. Ren (pp. 889-894).

The effect of inert gas additive (He, Ar, Xe) to CH₄/H₂ discharges for dry etching of single crystal ZnO was examined. The etch rates were higher with Ar or Xe addition, compared to He but in all cases the CH₄/H₂-based mixtures showed little or no enhancement over pure physical sputtering under the same conditions. The etched surface morphologies were smooth, independent of the inert gas additive species and the Zn/O ratio in the near-surface region decreases as the mass number of the additive species increases, suggesting preferential sputtering of O. The plasma etching improved the band-edge photoluminescence intensity from the ZnO for the range of ion energies used here (290–355eV), due possibly to removal of surface contamination layer.

Keywords: ZnO; Dry etching

Fabrication of p-type Li-doped ZnO films by pulsed laser deposition by Bin Xiao; Zhizhen Ye; Yinzhu Zhang; Yujia Zeng; Liping Zhu; Binghui Zhao (pp. 895-897).

p-Type ZnO thin films have been realized via doping Li as acceptor by using pulsed laser deposition. In our experiment, Li₂CO₃ was used as Li precursor, and the growth temperature was varied from 400 to 600°C in pure O₂ ambient. The Li-doped ZnO film prepared at 450°C possessed the lowest resistivity of 34Ωcm with a Hall mobility of 0.134cm²V⁻¹s⁻¹ and hole concentration of 1.37×10¹⁸cm⁻³. X-ray diffraction (XRD) measurements showed that the Li-doped ZnO films grown at different substrate temperatures were of completely (002)-preferred orientation.

Keywords: ZnO; p-Type conduction; Pulsed laser deposition

Design and fabrication of a TiO₂/nano-silicon composite visible light photocatalyst by Chun Yu Lin; Yean Kuen Fang; Che Hao Kuo; Shih Fang Chen; Chun-Sheng Lin; Tse Heng Chou; Yu-Hua Lee; Jui-Che Lin; Sheng-Beng Hwang (pp. 898-903).

Nano-silicon (nc-Si) was utilized as the charges generator to promote the photocatalytic and super-hydrophilic reactivity of TiO₂ film under visible light irradiation. The photocatalytic ability of TiO₂/nc-Si composite photocatalyst was evaluated by a set of experiments to photodecompose 100ppm methylene blue (MB) in aqueous solution. And the super-hydrophilic property was characterized by measuring the water droplet contacts angle, under visible light irradiation in atmospheric air and at room temperature. Under 100mW/cm² visible light irradiation, the droplet contact angles were reduced to 0° within 4h with nc-Si charge generator. Additionally, the rate constant of MB photo-degradation was promoted 6.6 times.

Keywords: Nano-silicon; TiO; ₂; Photocatalyst; Methylene blue; Super-hydrophilic

Study on effects of substrate temperature on growth and structure of alignment carbon nanotubes in plasma-enhanced hot filament chemical vapor deposition system by Chun Dang; Tingzhi Wang (pp. 904-908).

Alignment carbon nanotubes (ACNTs) were synthesized on silicon substrate coated with Ni catalyst film and Ta buffer layer by plasma-enhanced hot filament chemical vapor deposition using CH₄, NH₃, and H₂ as the reaction gas, and they were investigated by scanning electron microscopy and transmission electron microscopy. It is found that the diameter of the bamboo-structured ACNTs is increased from 62 to 177nm when the substrate temperature was changed from 626 to 756°C. Their growth rate is enhanced by the substrate temperature in a range of 626–683°C and it is reversely reduced with the substrate temperature after the substrate temperature is over 683°C. Beginning with wetting phenomenon, the effects of the substrate temperature on the structure and growth rate of the ACNTs are analyzed.

Keywords: PACS; 52.77.Bn; 81.07.Bc; 81.15.GhChemical vapor deposition; Alignment carbon nanotubes; Substrate temperature

Rapid synthesis of novel flowerlike ZnO structures by thermolysis of zinc acetate by Xianhui Xia; Zhizhen Ye; Guodong Yuan; Liping Zhu; Binghui Zhao (pp. 909-914).

Novel flowerlike ZnO structures have been rapidly synthesized on (100)-Si substrates via thermolysis of zinc acetate in air ambient without any catalyst. The obtained ZnO products exhibit well-defined flowerlike morphologies consisting of multilayer petal crystals with tapering feature. High-resolution transmission electron microscope (HRTEM) and corresponding selected area electron diffraction pattern (SAED) reveal that these petal crystals are single crystal in nature and preferentially oriented in the c-axis direction. Room-temperature photoluminescence (PL) spectra show that all the samples exhibit prominent UV emissions around 376.8nm and very weak visible emission peaks, which demonstrates that there are few deep-level defects in the single crystal petals of the flowerlike ZnO structures. The growth mechanism of the as-synthesized flowerlike ZnO structures was also discussed.

Keywords: PACS; 81.05.Dz; 81.05.Rm; 81.10.AjFlowerlike ZnO structures; Crystal morphology; Crystal growth; ZnO; Semiconducting materials

Dependence of film thickness on the electrical and optical properties of ZnO–Cu–ZnO multilayers by D.R. Sahu; Jow-Lay Huang (pp. 915-918).

ZnO–Cu–ZnO multilayers were prepared by simultaneous RF magnetron sputtering of ZnO and DC magnetron sputtering of Cu. Cu films with different thickness were used as the intermediate metal layer. The optical and electrical properties of the multilayers studied by UV–vis spectrophotometer and four point probe method, respectively, shows that transmittance increases with decrease of copper thickness up to an optimum thickness of 5nm and sheet resistance decreases with increase of thickness. Low resistivity and high transmission were obtained when the film structure has a thickness of ZnO/Cu/ZnO: 50/5/50nm. The performance of the multilayers as transparent conducting material was better than the single layer ZnO of equal thickness.

Keywords: ZnO; Multilayers; Optical properties and Electrical properties

Electrochemical and theoretical investigation on the corrosion of aluminium in acidic solution containing some Schiff bases by A. Yurt; S. Ulutas; H. Dal (pp. 919-925).

The effect of newly synthesised three Schiff bases—2-[2-aza-2-(5-methyl(2-pyridly))vinyl]phenol, 2-[2-aza-2-(5-methyl(2-pyridly))vinyl]-4-bromophenol, 2-[2-aza-2-(5-methyl(2-pyridly))vinyl]-4-chlorophenol—on the corrosion behaviour of aluminium in 0.1M HCl were investigated using potentiodynamic polarisation, electrochemical impedance spectroscopy and linear polarisation methods. Polarisation curves indicate that all studied Schiff bases were acting as mixed type inhibitors. All measurements show that inhibition efficiencies increase with increase in inhibitor concentration. This reveals that inhibitive actions of inhibitors were mainly due to adsorption on aluminium surface. Adsorption of these inhibitors follows Langmuir adsorption isotherm. Thermodynamic parameters of adsorption ( K_ads, Δ G_ads) of studied Schiff bases were calculated using Langmuir adsorption isotherm. The variation in inhibition efficiency values depends on the type of functional groups substituted on benzene ring. It was found that the presence of bromine and chlorine atoms in the molecular structure of studied Schiff bases facilitate the adsorption of molecule on aluminium surface.The correlation between the inhibition efficiencies of studied Schiff bases and their molecular structure has been investigated using quantum chemical parameters obtained by MNDO semi-empirical SCF-MO methods. These results indicate that adsorption of studied Schiff bases depends on the charge density of adsorption centres and dipole moments.

Keywords: Corrosion; Aluminium; Schiff base; Hydrochloric acid; Quantum chemical calculations

Effect of atmospheric pressure dielectric barrier discharge air plasma on electrode surface by Changquan Wang; Xiangning He (pp. 926-929).

In order to study the influence of plasma on electrode, atmospheric pressure dielectric barrier discharge (DBD) air plasma is employed here to treat copper electrode surface. Plasma is generated between the parallel plate electrodes by means of high voltage produced by a high-frequency power supply with transformer. Electrode surface alterations induced by air plasma are investigated by using field emission scanning electron microscope (FE-SEM), X-ray energy dispersion spectroscopy (EDS) and contact angle measurement. The results show that DBD air plasma removes the organic contaminant on surface and causes electrode surface roughness, oxidization and nitridation. In addition, surface wettability is also improved, as concluded from contact angle measurements.

Keywords: PACS; 52.40.Hf; 68.37.Hk; 81.05.BxDielectric barrier discharge; Electrode; Plasma treatment; Scanning electron microscope; X-ray energy dispersion spectroscopy

Room temperature chemical synthesis of lead selenide thin films with preferred orientation by R.B. Kale; S.D. Sartale; V. Ganesan; C.D. Lokhande; Yi-Feng Lin; Shih-Yuan Lu (pp. 930-936).

Room temperature chemical synthesis of PbSe thin films was carried out from aqueous ammoniacal solution using Pb(CH₃COO)₂ as Pb²⁺ and Na₂SeSO₃ as Se²⁻ ion sources. The films were characterized by a various techniques including, X-ray diffraction (XRD), energy dispersive X-ray analysis (EDAX), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HR-TEM), selected area electron diffraction (SAED), Fast Fourier transform (FFT) and UV–vis-NIR techniques. The study revealed that the PbSe thin film consists of preferentially oriented nanocubes with energy band gap of 0.5eV.

Keywords: PACS; 61.10.Nz; 61.46.+w; 68.37.Hk; 68.37.Nq; 68.37.Ps; 68.55.NqChemical synthesis; PbSe thin films; Nanomaterials; Structural and optical properties

Range of Er ions in amorphous Si by J. Liu; W.N. Lennard; J.-K. Lee (pp. 937-943).

We have measured the range and range straggling for energetic 100–900keV Er ions in amorphous Si by means of Rutherford backscattering followed by spectrum analysis. The results are compared with other experimental data and Monte Carlo (SRIM-2003) calculations. Our experimental results show that, although the measured values for both range and range straggling exceed the SRIM predictions, they are nevertheless consistent with trends that have been previously observed. We see no anomalous trends in range and range straggling parameters for the rare earth ions for implant energies E≥100keV. We present a detailed consideration of⁴He stopping powers in Si due to its crucial impact on RBS range measurements.

Keywords: PACS; 81.70.Jb; 79.20.Rf; 68.55.Ln; 34.50.−sIon implantation; Range distribution; Rare earth elements; Silicon

Structural distortion in thiourea-mixed ADP crystals by A. Jayarama; S.M. Dharmaprakash (pp. 944-949).

Single crystals of ammonium dihydrogen phosphate (ADP) mixed with different mole concentrations of thiourea were grown using slow evaporation solution technique at 30°C. In order to study the effect of mixing thiourea on the structural characteristics of ADP, X-ray diffraction studies were carried out on the crystals using Shimadzu X-ray diffractometer with Cu Kα radiation. X-ray study revealed that the structures of the thiourea-mixed ADP are slightly distorted compared to the pure ADP crystal structure. Inclusion of thiourea enhances the growth of (1¯00) plane of the ADP crystal. Thiourea-mixed ADP crystals were found to have maximum inclusion, as the thiourea concentration was 10mol%.

Keywords: Non-linear; X-ray diffraction

Fundamental processes of aluminium corrosion studied under ultra high vacuum conditions by M. Frerichs; F. Voigts; W. Maus-Friedrichs (pp. 950-958).

Surface sensitive electron spectroscopy was applied to study the fundamental processes of aluminium corrosion. We used metastable induced electron spectroscopy (MIES) and ultraviolet photoelectron spectroscopy (UPS) for the investigation of the densities of states of surface and bulk, respectively. Furthermore we applied X-ray photoelectron spectroscopy (XPS) to investigate the chemical composition of the top surface layers. All measurements were performed under ultra high vacuum conditions.Al films with thicknesses of 7nm were investigated. Both the interaction of oxygen and water with these films leads to the formation of an aluminium–oxygen layer, which is partly composed of stoichiometric Al₂O₃. Weak heat treatment at 770K transforms the surface layer into Al₂O₃ with a thickness of about 2nm. Further gas offer does not lead to an increase of this thickness, neither for oxygen nor for water. Additional to the oxygen offer, water exposure leads to the formation of OH species in the top aluminium–oxygen layer to a small amount. Weak heat treatment to 770K removes this species completely. Water exposure leads to a much faster oxide formation than oxygen exposure. We try to give a model for the fundamental corrosion processes on a molecular scale.

Keywords: PACS; 68.43.−h; 73.20.At; 69.60.−i; 81.65.MqCorrosion; Aluminium; Photoelectron spectroscopy (UPS, XPS); Metastable induced electron spectroscopy (MIES)

Characterization of Ag nanoparticles on Si wafer prepared using Tollen's reagent and acid-etching by Dong Chan Lim; Ignacio Lopez-Salido; Young Dok Kim (pp. 959-965).

Ag nanoparticles on SiO₂/Si surfaces synthesized using the Tollen's reagent and a subsequent acid-etching were characterized using X-ray photoelectron spectroscopy (XPS). Combining the reduction of the Tollen's reagent and the chemical etching, one can create naked Ag nanoparticles with various sizes in the size range below ∼10 nanometers (nm). The reduced particle size by the chemical etching was identified using positive core level shifts with increasing etching time. Ag nanoparticles smaller than ∼3nm undergo a reversible oxidation and reduction cycle by reacting with H₂O₂/H₂O and a subsequent heating under vacuum to 150°C, which was not found for the bulk counterparts and larger particles, demonstrating unique chemical properties of nanoparticles compared to the bulk counterparts.

Keywords: Ag; Nanoparticle; Oxidation; XPS

AFM lateral force imagining of modified polychloroprene: A study based on roughness analysis by Kristina Žukienė; Virginija Jankauskaitė; Stasė Petraitienė (pp. 966-973).

Films of a binary polymer blends comprising polychloroprene (PCP) and piperylene–styrene copolymer (PSC) have been prepared by solution casting. The dependence of the surface morphology of the free blend films on PSC content was studied with both roughness and correlation analysis of lateral force microscopy (LFM) images. Significant changes in roughness and lateral parameter values of different blend film sides have been observed depending on the blend composition. It was shown that up to 15wt.% PSC is distributed continuously in PCP bulk. The increase of roughness and lateral parameter values at the air/film surface shows the enrichment of PCP in the blends containing 25wt.% or more PSC. The enrichment of PCP on the air/film surface favours the increase of PSC concentration at the backing/film surface. The films underside morphology becomes similar to that of PSC, when its content reaches 40wt.%.

Keywords: PACS; 68.35.Ct; 68.37.PsPolychloroprene; Surface morphology; Lateral force microscopy; Roughness; Correlation analysis

Implication of the role of oxygen anions and oxygen vacancies for methanol decomposition over zirconia supported copper catalysts by Gui-Sheng Wu; Lu-Cun Wang; Yong-Mei Liu; Yong Cao; Wei-Lin Dai; He-Yong He; Kang-Nian Fan (pp. 974-982).

The interaction of methanol with Cu, monoclinic ZrO₂, and Cu/m-ZrO₂ catalysts has been investigated by temperature programmed desorption (TPD) and reaction (TPRS) with the aim of understanding the nature of the surface sites and the mechanism involved in methanol decomposition. A synergetic effect has been detected since the combination of copper and ZrO₂ significantly facilitates the methanol decomposition with the facile evolution of H₂ and CO species at much lower desorption temperature. In conjunction with DRIFTS and H₂-TPD measurements of the Cu/ZrO₂ sample reduced at elevated temperatures, methanol decomposition over Cu/ZrO₂ is suggested to occur primarily on ZrO₂ with the aid of the presence of oxygen anions and oxygen vacancies generated by species-spillover between copper and zirconia. The interface between copper and zirconia is also evidenced to be crucial to the decomposition of methanol, with the main role of metallic Cu being to provide sites for H₂ removal by efficiently recombining the hydrogen atoms formed during the dehydrogenation of species located on zirconia.

Keywords: Temperature programmed desorption (TPD); Methanol decomposition; Cu/ZrO; ₂; The reduction temperature; Anionic vacancies

Preparing polymer brushes on polytetrafluoroethylene films by free radical polymerization by Wei Sun; Yiwang Chen; Qilan Deng; Lie Chen; Lang Zhou (pp. 983-988).

Films of polytetrafluoroethylene (PTFE) were exposed to sodium naphthalenide (Na/naphtha) etchant so as to defluorinate the surface for obtaining hydroxyl functionality. Surface-initiators were immobilized on the PTFE films by esterification of 4,4′-azobis(4-cyanopentanoic acid) (ACP) and the hydroxyl groups covalently linked to the surface. Grafting of polymer brushes on the PTFE films was carried out by the surface-initiated free radical polymerization. Homopolymers brushes of methyl methacrylate (MMA) were prepared by free radical polymerization from the azo-functionalized PTFE surface. The chemical composition and topography of the graft-functionalized PTFE surfaces were characterized by X-ray photoelectron spectroscopy (XPS), attenuated total reflectance (ATR) FT-IR spectroscopy and atomic force microscopy (AFM). Water contact angles on PTFE films were reduced by surface grafting of MMA.

Keywords: PACS; 68.47.MnPolyterafluoroethylene; Free radical polymerization; Surface science; Topogaphy

Surface modification by oil jet peening in Al alloys, AA6063-T6 and AA6061-T4: Residual stress and hardness by A. Sahaya Grinspan; R. Gnanamoorthy (pp. 989-996).

The life of structural members that experience cyclic loading is improved by the introduction of surface compressive residual stresses. A high-pressure oil jet is used for the introduction of surface compressive residual stresses in aluminum alloys, AA6063-T6 and AA6061-T4. The peening machine designed and developed in the laboratory is capable of generating high pressures using hydraulic oil. The magnitude of residual stress developed depends upon the stand-off distance and yield strength of the material. A hardened layer up to a depth of about 350μm was developed in the materials investigated. The residual stresses and surface hardening induced are comparable to that produced by other peening processes. An analytical model is proposed to predict the impact pressure.

Keywords: PACS; 62.50.+p; 81.40.−z; 81.65.−bPeening; Oil jet; Impact pressure; Residual stress; Hardening

Surface modification by oil jet peening in Al alloys, AA6063-T6 and AA6061-T4 by A. Sahaya Grinspan; R. Gnanamoorthy (pp. 997-1005).

Oil jet peening is a new surface treatment technique that can be potentially applied to impart compressive residual stresses in metal parts. The effect of oil jet pressure on the surface integrity and texture of metals are discussed. The surface morphology, mass loss rate, indentation, and erosion are reported. With increasing stand-off distance, the size of indents significantly decreases and reduces the average roughness in the both specimens. Results are also compared with other mechanical surface treatment process such as shot peening, laser shock peening, and water jet peening.

Keywords: PACS; 62.50.+p; 68.37.-d; 81.40.–zOil jet peening; Surface topography; Indent; Coverage; Erosion

Characterisation of passive films on 300 series stainless steels by T.L. Sudesh L. Wijesinghe; D.J. Blackwood (pp. 1006-1009).

The formation and breakdown of the passive films on stainless steels are mainly controlled by ionic and electronic transport processes. Both these processes are in part controlled by the electronic properties of the oxide film. Consequently, it is vital to gain a detailed perception of the electronic properties of the passive films together with structural and compositional information for a comprehensive understanding of mechanisms behind passivity and localised corrosion. As a step towards this goal the passive films formed on two main austenitic stainless steels AISI 316L and AISI 304L in borate solution were characterised by in situ Raman spectroscopy and photocurrent spectroscopy coupled with electrochemical measurements. This revealed the formation of an Fe-Cr spinel as the dominant constituent in the passive films with more Cr enrichment in the oxide film on 316L than that of 304L. Bandgap readings and semiconductivities of the two stainless steels suggested that three different applied potential regions existed; 800mV(SCE) to 300mV(SCE), 200mV(SCE) to −300mV(SCE) and below −500mV(SCE).

Keywords: Passive films; Stainless steels; Photocurrent spectroscopy; Raman spectroscopy; Fe-Cr spinel

Quantitative depth profiling of photoacid generators in photoresist materials by near-edge X-ray absorption fine structure spectroscopy by Vivek M. Prabhu; Sharadha Sambasivan; Daniel Fischer; Linda K. Sundberg; Robert D. Allen (pp. 1010-1014).

Near-edge X-ray absorption fine structure (NEXAFS) spectroscopy was used to quantify the surface composition and depth profiling of photoacid generators in thin film photoresist materials by varying the entrance-grid bias of a partial electron yield detector. By considering model compositional profiles, NEXAFS distinguishes the surface molar excess within the top 6nm from the bulk. A surface enriched system, triphenylsulfonium perfluorooctanesulfonate, is contrasted with a perfluorobutanesulfonate photoacid generator, which displays an appreciable surface profile within a 6nm segregation length scale. These results, while applied to 193-nm photoresist materials, highlight a general approach to quantify NEXAFS partial electron yield data.

Keywords: Immerison lithography; Lithography; Photoresist; Segregation; Near edge X-ray absorption fine spectroscopy; NEXAFS; Thin film

Using time-of-flight secondary ion mass spectrometry and multivariate statistical analysis to detect and image octabenzyl-polyhedral oligomeric silsesquioxane in polycarbonate by V.S. Smentkowski; H.M. Duong; R. Tamaki; M.R. Keenan; J.A. Tony Ohlhausen; P.G. Kotula (pp. 1015-1022).

Silsesquioxane, with an empirical formula of RSiO_3/2, has the potential to combine the mechanical properties of plastics with the oxidative stability of ceramics in one material [D.W. Scott, J. Am. Chem. Soc. 68 (1946) 356; K.J. Shea, D.A. Loy, Acc. Chem. Res. 34 (2001) 707; K.-M. Kim, D.-K. Keum, Y. Chujo, Macromolecules 36 (2003) 867; M.J. Abad, L. Barral, D.P. Fasce, R.J.J. William, Macromolecules 36 (2003) 3128]. The high sensitivity, surface specificity, and ability to detect and image high mass additives make time-of-flight secondary ion mass spectrometry (ToF-SIMS) a powerful surface analytical instrument for the characterization of polymer composite surfaces in an analytical laboratory [J.C. Vickerman, D. Briggs (Eds.), ToF-SIMS Surface Analysis by Mass Spectrometry, Surface Spectra/IMPublications, UK, 2001; X. Vanden Eynde, P. Bertand, Surf. Interface Anal. 27 (1999) 157; P.M. Thompson, Anal. Chem. 63 (1991) 2447; S.J. Simko, S.R. Bryan, D.P. Griffis, R.W. Murray, R.W. Linton, Anal. Chem. 57 (1985) 1198; S. Affrossman, S.A. O’Neill, M. Stamm, Macromolecules 31 (1998) 6280]. In this paper, we compare ToF-SIMS spectra of control samples with spectra generated from polymer nano-composites based on octabenzyl-polyhedral oligomeric silsesquioxane (BnPOSS) as well as spectra (and images) generated from multivariate statistical analysis (MVSA) of the entire spectral image. We will demonstrate that ToF-SIMS is able to detect and image low concentrations of BnPOSS in polycarbonate. We emphasize the use of MVSA tools for converting the massive amount of data contained in a ToF-SIMS spectral image into a smaller number of useful chemical components (spectra and images) that fully describe the ToF-SIMS measurement.

Keywords: PACS; 68.49.Sf; 82.80.Ms; 02.50.Sk; 68.37.–dTime-of-flight secondary ion mass spectrometry; Multivariate statistical analysis; Surface analysis; Polymer additive; Octabenzyl-polyhedral oligomeric silsesquioxane; Microscopy

Rare earth oxide doping in oxide cathodes by Daniel den Engelsen; Georg Gaertner (pp. 1023-1028).

The effect on life performance and poisoning with O₂ by doping oxide cathodes with rare earth oxides and pseudo rare earth oxides, notably yttria, is qualitatively explained in terms of electrolysis of BaO during emission of electrons. Doped cathodes show less electrolysis and consume therefore less Ba during life: consequently, doped cathodes have a better life performance. However, the lower Ba-production makes doped cathodes more sensitive to oxygen poisoning. The experimentally found relation between conductivity and yttria concentration was the motive to propose a new model for the crystal imperfections in BaO. In this new imperfection model most Y³⁺-ions will combine with barium vacancies, therefore, the increase of the conductivity is modest and also the effect on the position of the Fermi level is modest. By assuming a combination of bulk and surface conductivity, the agreement between experiment and theory can be improved further.

Keywords: BaO; Yttria; Electrolysis; Electron emission; Crystal imperfection; Schottky defect

Hybrid LCVD of micro-metallic lines for TFT-LCD circuit repair by J.B. Park; C.J. Kim; P.E. Shin; S.H. Park; H.S. Kang; S.H. Jeong (pp. 1029-1035).

The deposition of micrometer-scale metallic lines by laser chemical vapor deposition (LCVD) on glass is investigated for the repair of open-circuit type defects of thin film transistor-liquid crystal display (TFT-LCD) panels. In this work, a third harmonic Nd:YLF laser (351nm) of high repetition rates was used as the illumination source and W(CO)₆ was selected as the reaction material for the deposition of tungsten interconnects on glass substrate. General characteristics of the tungsten deposit such as height, width, morphology as well as electrical resistivity were examined for various process conditions. Height of the deposited tungsten lines ranged from 35 to 500nm depending on laser power and scan speed while the width was controlled in the range of 3–50μm by adjusting the size of a slit placed in the beam path. The resistivity of deposited tungsten lines was measured to be below 1Ωμm. The tungsten deposit is considered to form through a hybrid process, namely through the combination of photolytic and pyrolytic mechanisms. The deposited tungsten lines developed in this study are successfully applied for the repair of TFT-LCD circuit defects without damaging the glass substrate.

Keywords: PACS; 42.62.Cf; 73.61.−r; 81.15.Fg; 81.16.MkLCVD; Circuit repair; LCD; Micropatterning; Laser application

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Applied Surface Science (v.253, #2)

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Applied Surface Science (v.253, #2)