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Applied Surface Science (v.253, #11)

Preparation and characterization of p-type transparent conducting tin-gallium oxide films by Yixian Huang; Zhenguo Ji; Chen Chen (pp. 4819-4822).

p-Type transparent conducting tin-gallium oxide (TGO) films were successfully fabricated on quartz substrates by DC magnetron sputtering of GaSn alloy films followed by thermal oxidation. XRD characterization indicated that the TGO films maintain rutile structure of the tin oxide (SnO₂). UV–vis transmittance spectra indicated that the films have a transmittance higher than 85% in the visible region, with an optical band-gap around 3.8eV. Hall effect measurement showed that electrical properties of the TGO films were dependent on oxidation temperature. Oxidation at too high or low temperature was unfavorable for p-type conduction. It is found that the optimum oxidation temperature for highest hole concentration (8.84×10¹⁸cm⁻³) was in the range of 600–650°C.

Keywords: PACS; 42.55PxDC magnetron sputtering; Tin-gallium oxide; p-Type conducting; Transparent conducting films

A novel approach for the preparation of PMMA–PDMS core–shell particles with PDMS in the shell by Xiaobo Deng; Bailing Liu; Shunsheng Cao; Rong Luo; Hualin Chen (pp. 4823-4829).

The core/shell particles consisting of polymethyl methacrylate (PMMA) core and polydimethylsiloxane (PDMS) shell via 3-(methacryloxypropyl)-trimethoxysilane (MPS) as the medium to link the core and shell were prepared in our present study by successive seeding polymerization under kinetically controlled conditions and were characterized by FT-IR, particle size analyzer, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS).The picture of optical microscope showed the clear form of PDMS-0 and PDMS-40 (the content of PDMS in the particles), which approached to monodispersed distribution. Compared with the PMMA microspheres, PDMS-40 presented an evident core/shell structure through the observation of TEM. Additionally, the study of XPS revealed that PDMS could be grafted onto the surface of PMMA particles and the atomic ratio of C/Si on the surface of PDMS-40 was very close to the ratio of C/Si in the molecule of PDMS. The surface properties of the films produced from the core/shell microspheres also were investigated by contact angle method, contrast with the homopolymer of PMMA, the core/shell particles were more effective to form hydrophobic surface and the water repellency on the surface would be better than that of PMMA.

Keywords: Core/shell particles; PMMA; MPS; PDMS

Comparative adsorption of phenyl selenolate and selenocyanate on Au nanoparticle surfaces by Jong Kuk Lim; Sang-Woo Joo (pp. 4830-4835).

UV–vis absorbance spectra taken at different elapsed time for the surface plasmon band shift indicated that the self-assembly of PhSeCN on gold should be slower than that of phenyl selenolate (PhSeH). A surface-enhanced Raman scattering (SERS) study showed that a trace amount of CN species could remain on Au surfaces when aromatic selenocyanates are reduced to give CN and their selenium atoms bound to the surface. Our concentration dependent SERS spectra suggested that the CN adsorption should be more favorable at higher concentrations of PhSeCN as indicated from more prominent intensites of the CN stretching vibration at 2110–2150cm⁻¹.

Keywords: Au nanoparticles; Adsorption; Phenyl selenocyanate; SERS; Surface plasmon resonance

Crystalline quality of 3C-SiC formed by high-fluence C⁺-implanted Si by S. Intarasiri; A. Hallén; J. Lu; J. Jensen; L.D. Yu; K. Bertilsson; M. Wolborski; S. Singkarat; G. Possnert (pp. 4836-4842).

Carbon ions at 40keV were implanted into (100) high-purity p-type silicon wafers at 400°C to a fluence of 6.5×10¹⁷ions/cm². Subsequent thermal annealing of the implanted samples was performed in a diffusion furnace at atmospheric pressure with inert nitrogen ambient at 1100°C. Time-of-flight energy elastic recoil detection analysis (ToF-E ERDA) was used to investigate depth distributions of the implanted ions. Infrared transmittance (IR) and Raman scattering measurements were used to characterize the formation of SiC in the implanted Si substrate. X-ray diffraction analysis (XRD) was used to characterize the crystalline quality in the surface layer of the sample. The formation of 3C-SiC and its crystalline structure obtained from the above mentioned techniques was finally confirmed by transmission electron microscopy (TEM). The results show that 3C-SiC is directly formed during implantation, and that the subsequent high-temperature annealing enhances the quality of the poly-crystalline SiC.

Keywords: PACS; 61.72.Ss; 61.72.Tt; 78.30.−j; 61.10.Nz; 68.37.LpIon beam synthesis (IBS); Silicon; Silicon carbide (SiC); Infrared spectroscopy (IR); Raman spectroscopy; Time-of-flight energy elastic recoil detection analysis (ToF-E ERDA); X-ray diffraction (XRD) analysis; Transmission electron microscopy (TEM)

Preparation of activated carbon from a renewable bio-plant of Euphorbia rigida by H₂SO₄ activation and its adsorption behavior in aqueous solutions by Özgül Gerçel; Adnan Özcan; A. Safa Özcan; H. Ferdi Gerçel (pp. 4843-4852).

The use of activated carbon obtained from Euphorbia rigida for the removal of a basic textile dye, which is methylene blue, from aqueous solutions at various contact times, pHs and temperatures was investigated. The plant material was chemically modified with H₂SO₄. The surface area of chemically modified activated carbon was 741.2m²g⁻¹. The surface characterization of both plant- and activated carbon was undertaken using FTIR spectroscopic technique. The adsorption process attains equilibrium within 60min. The experimental data indicated that the adsorption isotherms are well described by the Langmuir equilibrium isotherm equation and the calculated adsorption capacity of activated carbon was 114.45mgg⁻¹ at 40°C. The adsorption kinetics of methylene blue obeys the pseudo-second-order kinetic model and also followed by the intraparticle diffusion model up to 60min. The thermodynamic parameters such as Δ G°, Δ H° and Δ S° were calculated to estimate the nature of adsorption. The activation energy of the system was calculated as 55.51kJmol⁻¹. According to these results, prepared activated carbon could be used as a low-cost adsorbent to compare with the commercial activated carbon for the removal textile dyes from textile wastewater processes.

Keywords: PACS; 61.43.Gt; 67.70.+n; 68.08.−p; 68.43.−Mn; 81.05.RmActivated carbon; Adsorption; Basic dye; Euphorbia rigida; Biomass; Kinetics

Development of porous metal oxide thin films by co-evaporation by T. Tesfamichael; Nunzio Motta; Thor Bostrom; J.M. Bell (pp. 4853-4859).

This paper focuses on the development of mixed metal oxide thin films and physical characterization of the films. The films were produced by co-evaporation of titanium oxide and tungsten oxide powders. This allowed the development of titanium oxide–tungsten oxide films as analyzed using XPS. Examination in the SEM and AFM showed that the films were nanoporous with the pore size and pore orientation varying as a function of the deposition angle. UV–vis spectra of the films show an increase of transmittance with increasing deposition angle which is attributed to the structure and porosity of the films. Raman analysis indicated that the as-deposited films have broad and weak Raman characteristics, attributed to the nanocrystal nature of the films and the presence of defects, and the peak broadening deceases after annealing the film, as expected.

Keywords: PACS; 81.05.Rm; 61.43.Gt; 78.66.Qn; 68.55.Jk; 07.07.Df; 61.72.−yMetal oxide gas sensors; Oblique deposition; Co-evaporated TiO; ₂; –WO; ₃; thin film; Surface characterization; Porosity

Reactivity screening of silica by S. Funk; T. Nurkic; U. Burghaus (pp. 4860-4865).

As a screening of the chemical activity of silica [SiO₂/Si(100)], which is one of the most often used supports for nanostructures, thermal desorption spectroscopy data have been gathered for a variety of gases such as n-nonane, n-hexane, n-butane, iso-butane, ethane, CO₂, CO, O₂, and H/H₂. Whereas, the alkanes with chain lengths larger than three adsorb with large binding energies ( E_d=50–70kJ/mol), the activity towards the other probe molecules is negligible (<24kJ/mol) down to adsorption temperatures of 95K. The adsorption of n- and iso-butane has additionally been studied by molecular beam scattering and follows standard precursor mediated adsorption dynamics.

Keywords: Surface chemistry; Short chain alkanes; Silica; SiO; ₂; /Si(1; 0; 0); Thermal desorption spectroscopy; Molecular beam scattering

Adhesive interfaces of enamel and dentin prepared by air-abrasion at different distances by Michelle Alexandra Chinelatti; Thais Helena Andreolli do Amaral; Maria Cristina Borsatto; Regina Guenka Palma-Dibb; Silmara Aparecida Milori Corona (pp. 4866-4871).

The purpose of this study was to analyse, by scanning electron microscopy (SEM), the morphology of enamel and dentin/adhesive interfaces in cavities prepared by air-abrasion at different working distances. Thirty sound third human molars were selected and, on both their buccal and lingual surfaces, class V cavities were prepared by air-abrasion, at 2-, 4-, 6-, 8- and 10-mm working distances, or high-speed bur (control group). After preparation, all cavities were etched with 35% phosphoric acid gel and restored with Single Bond/Filtek Z-250. Buccal and lingual surfaces were separated and restorations sectioned in a buccolingual direction, providing two sections of each cavity, which were analysed by scanning electron microscopy. It was observed that the distances of 6 and 8mm promoted more homogeneous dentin/adhesive interfaces, with tags formation, and more uniform for enamel, which were similar to the control group. It may be concluded that the air-abrasion working distance can influence the morphology of enamel and dentin/adhesive interfaces, and the intermediate distances provided better adhesive interfaces.

Keywords: PACS; 80. Interdisciplinary physics and related areas of science and technology; 81. Materials scienceDentistry; Cavity preparation; Air-abrasion; Enamel; Dentin; Adhesive interface; Scanning electron microscopy

X-ray photoelectron spectroscopic analysis of oxidized Fe–16Cr–16Ni–2Mn–1Mo–2Si austenitic stainless steel by James A. Poston Jr.; Ranjani V. Siriwardane; J.S. Dunning; D.E. Alman; J.C. Rawers (pp. 4872-4885).

Depth profile analysis (argon ion etching/X-ray photoelectron spectroscopy) was conducted on a series of Fe–16Cr–16Ni–2Mn–1Mo–2Si austenitic stainless steel samples oxidized at 973 and 1073K with exposure times of 25, 100, 193, 436 and 700h. Surface and near surface rearrangement following oxidation resulted in a region of high Cr concentration on all oxidized samples. Temperature and time dependence to O₂ penetration depth was observed. In general, O₂ penetration depth was found to increase with increasing exposure up to 436h. No increase in depth was observed between 436 and 700h exposure time.

Keywords: Austenitic stainless steel alloys; High temperature stainless steels; Oxidation; Oxidation resistance; Depth profile

Study on the electrical and optical properties of Ag/Al-doped ZnO coatings deposited by electron beam evaporation by D.R. Sahu; Shin-Yuan Lin; Jow-Lay Huang (pp. 4886-4890).

A layer of silver was deposited onto the surface of glass substrates, coated with AZO (Al-doped ZnO), to form Ag/AZO film structures, using e-beam evaporation techniques. The electrical and optical properties of AZO, Ag and Ag/AZO film structures were studied. The deposition of Ag layer on the surface of AZO films resulted in lowering the effective electrical resistivity with a slight reduction of their optical transmittance. Ag (11nm)/AZO (25nm) film structure, with an accuracy of ±0.5nm for the thickness shows a sheet resistance as low as 5.6±0.5Ω/sq and a transmittance of about 66±2%. A coating consisting of AZO (25nm)/Ag (11nm)/AZO (25nm) trilayer structure, exhibits a resistance of 7.7±0.5Ω/sq and a high transmittance of 85±2%. The coatings have satisfactory properties of low resistance, high transmittance and highest figure of merit for application in optoelectronics devices including flat displays, thin films transistors and solar cells as transparent conductive electrodes.

Keywords: Al-doped ZnO; Ag; TCO; Optical and electrical properties

Novel self-assembled nanostructured alumina array with nanoscale grooves by Haixin Chang; Nanlin Shi; Jun Gong; Yifu Guan (pp. 4891-4894).

A unique novel self-assembled nanostructured alumina array with nanoscale grooves can be induced and controlled in nanometer dimension by a general electrochemical oxidation of aluminum in sulfuric acid. Almost inter-perpendicular self-assembled alumina nanostructure arrays separated by a few tens nanometer thick interface sheet were also observed in many domains. And the formation of this nanostructured array is considered as the result of the special competition balance between electrochemical oxidation and etching. Because of similarities of aluminum anodization with semiconductor anodization, our results may be proved useful for Si or GaAs nanostructure synthesis.

Keywords: PACS; 61.46.−w; 61.43.GtSelf-assembled; Nanostructured alumina array; Nanoscale grooves; Electrochemical oxidation; Anodization

Influence of the lithium salt nature over the surface film formation on a graphite electrode in Li-ion batteries: An XPS study by S. Leroy; H. Martinez; R. Dedryvère; D. Lemordant; D. Gonbeau (pp. 4895-4905).

The formation of a passivation film (solid electrolyte interphase, SEI) at the surface of the negative electrode of full LiCoO₂/graphite lithium-ion cells using different salts (LiBF₄, LiPF₆, LiTFSI, LiBETI) in carbonate solvents as electrolyte was investigated by X-ray photoelectron spectroscopy (XPS). The analyzes were carried out at different potential stages of the first cycle, showing the potential-dependent character of the surface film species formation and the specificity of each salt. At 3.8V, for all salts, we have mainly identified carbonated species. Beyond this potential, the specific behavior of LiPF₆ was identified with a high LiF deposit, whereas for other salts, the formation process of the SEI appears controlled by the solvent decomposition of the electrolyte.

Keywords: XPS; Core peaks; Valence bands; Lithium-ion batteries; Solid electrolyte interphase

Fabrication of multilayer thin film filters by hydrofluoric acid bonding by L. Chen; H. Nishimura; K. Fukumi; J. Nishii; K. Hirao (pp. 4906-4910).

A hydrofluoric acid (HF) bonding technique for multilayer thin films was studied to fabricate dielectric multilayer interference filters. The effects of pressure, HF concentration and annealing treatment on bonding strength were studied. Bonding strength of multilayer thin films of more than 5MPa were obtained. In addition, a new type edge filter of 47 layers (47L) and a band-pass filter of 63 layers (63L), with their films sandwiched between glass substrates, were fabricated using this method. The measured transmittance spectra agreed well with the designed ones.

Keywords: PACS; 42.79.Wc; 42.79.CiMultilayer; Interface; Bonding

Electrical and optical properties of Al-doped ZnO thin films by sol–gel process by Young-Sung Kim; Weon-Pil Tai (pp. 4911-4916).

Al-doped ZnO (AZO) thin films oriented along the (002) plane have been prepared by the sol–gel process and their electrical and optical properties with post-deposition heating temperature were investigated. The preferred c-axis orientation along the (002) plane was enhanced with increasing post-deposition heating temperature and the surface of the films showed a uniform and nano-sized microstructure. The electrical resistivity of the films decreased from 73 to 22Ωcm as the post-deposition heating temperature increased from 500 to 650°C; however, the film postheated at 700°C increased greatly to 580Ωcm. The optical transmittance of the films postheated below 650°C was over 86%, but it decreased at 700°C. The electrical and optical properties of the AZO films with post-deposition heating temperature are discussed.

Keywords: Sol–gel; Al-doped ZnO; Surface process; Surface structure

Broad-beam laser cladding of Al–Cu alloy coating on AZ91HP magnesium alloy by Yali Gao; Cunshan Wang; Hongjie Pang; Hongbin Liu; Man Yao (pp. 4917-4922).

The resistance to wear and corrosion of AZ91HP Mg alloy was improved by laser cladding Al–Cu alloy. It was found that the clad layer was characterized by AlCu₄ and Mg₁₇Al₁₂ grains embedded in a AlMg matrix. The bonding zone exhibited a white-light planar crystal band with thickness of 10–13μm. The heat-affected zone formed a eutectic structure due to the Mg diffusion. The microhardness and wear resistance of the coating were improved due to the formation of the hard phases AlCu₄ and Mg₁₇Al₁₂. Owing to the formation of dense Al₂O₃ oxide film, the coating exhibited better corrosion resistance in 3.5wt.% NaCl solution.

Keywords: Magnesium alloy; Al–Cu alloy; Laser cladding; Microstructure; Property

Titanium carbonitride films on cemented carbide cutting tool prepared by pulsed high energy density plasma by Wenran Feng; Chizi Liu; Guangliang Chen; Guling Zhang; Weichao Gu; Erwu Niu; Si-Ze Yang (pp. 4923-4927).

Hard films prepared by pulsed high energy density plasma (PHEDP) are characterized by high film/substrate adhesive strength, and high wear resistance. Titanium carbonitride (TiCN) films were deposited onto YG11C (ISO G20) cemented carbide cutting tool substrates by PHEDP at room temperature. XRD, XPS, SEM, AES, etc. were adopted to analyze the phases (elements) composition, microstructure and the interface of the films, respectively. The results show that, the uniform dense films are composed of grains ranging from 70 to 90nm. According to the AES result, there is a broad transition layer between the film and the substrate, due to the ion implantation effect of the PHEDP. The transition layer is favorable for the film/substrate adhesion.

Keywords: Thin films; PHEDP; Nanostructure; Carbides

Improving Fe₃Al alloy resistance against high temperature oxidation by pack cementation process by Piotr Juzoń; Marta Ziemnicka; Sébastien Chevalier; Kazimierz Przybylski; Jean Pierre Larpin (pp. 4928-4934).

The paper presents the results of oxidation tests of Fe₃Al-based alloys containing additions of Cr, Zr, B, and C, with and without an aluminide coating. The coating was formed by a pack cementation process in which the surface of material got enriched in aluminum. The Al-rich layer was intended to enhance the tendency of Al₂O₃ formation. The slow-growing Al₂O₃ scale provides the best corrosion protection for structural materials at high temperatures. The cyclic oxidation tests were performed in laboratory air at 1373K. The structure and composition of oxide scales as well as their adherence were evaluated and compared for the materials with and without aluminide coatings. Surface enrichment in aluminum and effect minor addition of Zr on oxidation behavior was discussed.

Keywords: Oxidation resistance; Iron aluminide alloys; Protective coatings; Zr doping effect

Diamond-like carbon films deposited by a hybrid ECRCVD system by C.T. Guo; K.-H. Dittrich (pp. 4935-4941).

A novel hybrid technique for diamond-like carbon (DLC) film deposition has been developed. This technique combines the electron cyclotron resonance chemical vapor deposition (ECRCVD) of C₂H₂ and metallic magnetron sputtering. Here we described how DLC film is used for a variety of applications such as stamper, PCB micro-tools, and threading form-tools by taking advantage of hybrid ECRCVD system. The structure of the DLC films is delineated by a function of bias voltages by Raman spectroscopy. This function includes parameters such as dependence of G peak positions and the intensity ratio ( I_D/ I_G). Atomic force microscope (AFM) examines the root-mean-square (R.M.S.) roughness and the surface morphology. Excellent adhesion and lower friction coefficients of a DLC film were also assessed.

Keywords: Diamond-like carbon (DLC); Raman; ECRCVD

Piezoelectric evaluation of ion beam etched Pb(Zr,Ti)O₃ thin films by piezoresponse force microscopy by C. Legrand; A. Da Costa; R. Desfeux; C. Soyer; D. Rèmiens (pp. 4942-4946).

The evolution of piezoelectric properties of Pb(Zr,Ti)O₃ (PZT) thin films after ion beam etching have been investigated at the nanoscale level by piezoelectric force microscopy. A comparison of the piezoelectric properties on etched and unetched films is realized. Piezoelectric contrasts imaging evidences a modification of the domain architecture at the film surface. Local piezoelectric hysteresis loops measurements on grains indicate that the coercive voltage for switching is much higher for the etched films (2.3V) compared to the unetched ones (1.0V) while the average piezoelectric activity is slightly lower. The results are explained in terms of grain-damaging during etching and domain-wall pinning.

Keywords: PACS; 68.37.-d; 68.37.Ps; 68.55.-a; 77.65.-j; 77.80.Dj; 77.80.Fm; 81.65.-b; 85.85.+jPb(Zr,Ti)O; ₃; thin films; Ion beam etching; Atomic force microscopy; Surface morphology; Piezoresponse force microscopy; Local piezoelectric hysteresis loops

Laser surface alloying of Ni-plated steel with CO₂ laser by A. Hussain; I. Ahmad; A.H. Hamdani; A. Nussair; S. Shahdin (pp. 4947-4950).

Laser surface alloying of low carbon steel electroplated with thin (10μm) Ni using an 850W CW CO₂ laser is reported for the first time. Fe–Ni binary alloys of different concentrations are formed by varying laser traverse speed from 0.5 to 5m/min. The phase transformation from α to α+γ is discussed as a function of Ni contents. Development of microstructure in the modified zone is analysed in terms of solidification rate and Ni concentration. A three-fold increase in the microhardness of the binary alloy is observed. Formation of homogenous, adherent and crack free surface alloys is reported.

Keywords: PACS; 42.62.Cf; 81.65.−b; 68.35.RhLaser; Surface melting; Microstructure; Martensite transformation; Binary alloy Fe–Ni; Solidification rate

Ceria concentration effect on chemical mechanical polishing of optical glass by Liangyong Wang; Kailiang Zhang; Zhitang Song; Songlin Feng (pp. 4951-4954).

It was found material removal rate (MRR) sharply increased from 250 to 675nm/min as the concentration decreased from 1 to 0.25wt% in optical glass chemical mechanical polishing (CMP) using ceria slurries. Scanning electron microscopy was employed to characterize the ceria abrasive used in the slurry. Atomic force microscopy results showed good surface had been got after CMP. Schematic diagrams of the CMP process were shown. Furthermore, the absorption spectra indicated a sudden change from Ce⁴⁺ to Ce³⁺ of the ceria surface when the concentration decreased, which revealed a quantum origin of the phenomenon.

Keywords: PACS; 81.65.PsCMP; Ceria; Concentration; Physical model; Quantum origin

Pulsed Nd:YAG laser depositions of ITO and DLC films for OLED applications by T.K. Yong; S.S. Yap; György Sáfrán; T.Y. Tou (pp. 4955-4959).

Indium-tin oxide (ITO) films deposited on heated and non-heated glass substrates by a pulsed Nd:YAG laser at 355nm and ∼2.5J/cm² were used in the fabrication of simple organic light-emitting diodes (OLEDs), ITO/(PVK+Alq₃+TPD)/Al. The ITO was deposited on heated glass substrates which possessed resistivity as low as ∼3×10⁻⁴Ωcm, optical transmission as high as ∼92% and carrier concentration of about ∼5×10²⁰cm⁻³, were comparable to the commercial ITO. Substrate heating transformed the ITO microstructure from amorphous to polycrystalline, as revealed by the XRD spectrum. While the polycrystalline ITO produced higher OLED brightness, it was still lower than that on the commercial ITO due to surface roughness. A DLC layer of ∼1.5nm deposited on this ITO at laser fluence of >12.5J/cm² improved its device brightness by suppressing the surface roughness effect.

Keywords: PACS; 81.15.Fg; *1.05.Uw; 78.60.FiPulsed laser deposition; Indium-tin oxide; Diamond-like carbon; OLED; Surface roughness

Adhesive and cohesive properties by indentation method of plasma-sprayed hydroxyapatite coatings by Z. Mohammadi; A.A. Ziaei-Moayyed; A. Sheikh-Mehdi Mesgar (pp. 4960-4965).

Adhesive and cohesive properties of the plasma-sprayed hydroxyapatite (HA) coatings, deposited on Ti–6Al–4V substrates by varying the plasma power level and spray distance (SD), were evaluated by an indentation method. The crystallinity and the porosity decreased with increasing both of these two parameters. The microhardness value, Young's modulus ( E) and coating fracture toughness ( K_C) were found to increase with a combinational increase in spray power and SD. The Knoop and Vickers indentation methods were used to estimate E and K_C, respectively. The critical point at which no crack appears at the interface was determined by the interface indentation test. This was used to define the apparent interfacial toughness ( K_Ca) which is representative of the crack initiation resistance of the interface. It was found that K_Ca reaches to a maximum at a medium increase in both spray power and SD, while other mechanical properties of the coatings reaches to the highest value with further increase in these two plasma parameters. The tensile adhesion strength of the coatings, measure by the standard adhesion test, ISO 13779-4, was shown to alter in the same manner with K_Ca results. It was deduced that a combinational increase in spray power and SD which leads to a higher mechanical properties in the coatings, does not necessarily tends to a better mechanical properties at the interface.

Keywords: Adhesion; Indentation; Hydroxyapatite; Plasma spraying; Interface

The water/graphitic-carbon interaction energy by Ahmed K. Helmy; Eladio A. Ferreiro; Silvia G. de Bussetti (pp. 4966-4969).

The water/graphitic-carbon interaction energy was obtained for a sample having a water surface site adsorption density of 13.3μmolm⁻². The interaction energy was determined from the spreading pressure of water, its surface tension and the water contact angle and using a formula obtained by the combination of the Young equation with a general equation of pair interaction. The values obtained for contact angles 42° and 86° are 7.63 and 7.18kJmol⁻¹ of water are similar to the water binding energies obtained from molecular dynamic simulations of water droplets on a graphite surface: 6.7–8.33kJmol⁻¹.

Keywords: Adsorption; Graphite; Graphitic carbon; Surface properties

Sub-wavelength surface structures on silicon irradiated by femtosecond laser pulses at 1300 and 2100 nm wavelengths by T.H.R. Crawford; H.K. Haugen (pp. 4970-4977).

We present periodic ripples and arrays of protrusions formed on the surface of silicon after irradiation by low-fluence linearly polarized femtosecond laser pulses. Laser-induced periodic surface structures (LIPSS) are observed for irradiation at center wavelengths of 800,∼ 1300, and∼ 2100 nm, with the structure periods somewhat less than the incident wavelengths in air. Additionally, we observe structures with spatial periods substantially less than the incident laser wavelengths. These sub-wavelength periodic structures form only when the photon energy is less than the silicon bandgap energy. We discuss a number of factors which may contribute to the generation of this surface morphology.

Keywords: PACS; 61.80.Ba; 78.30.Am; 79.20.DsFemtosecond pulsed laser; Silicon; Surface morphology; Sub-wavelength period

Carbon nanotubes supported Pt–Ni catalysts and their properties for the liquid phase hydrogenation of cinnamaldehyde to hydrocinnamaldehyde by Yan Li; Guo-Hua Lai; Ren-Xian Zhou (pp. 4978-4984).

The Pt–Ni catalysts supported on CNTs have been prepared by wet impregnation and the selective hydrogenation of cinnamaldehyde (CMA) to the corresponding hydrocinnamaldehyde (HCMA) over the catalysts has been studied in ethanol at different reaction conditions. The results show that Pt–0.34wt% Ni/CNTs catalyst exhibits the highest activity and selectivity at a reaction temperature of 70°C under a pressure of around 2.0MPa, and 98.6% for the conversion of CMA and 88.2% for the selectivity of CMA to HCMA, respectively. The selective hydrogenation for the CC bond in CMA would be improved as increasing the reaction temperature, and the hydrogenation for the CO bond in CMA is enhanced as increasing the H₂ pressure. In addition, these catalysts have also been characterized using TEM-EDS, XPS, H₂-TPR and H₂-TPD techniques. The results show that Pt particles are dispersed more homogeneously on the outer surface of the nanotubes, while the strong interaction between Pt and Ni would improve the increasing of activated hydrogen number because of the hydrogen spillover from reduced Pt⁰ onto CNTs and increase the catalytic activity and selectivity of CMA to HCMA.

Keywords: Cinnamaldehyde (CMA); Hydrocinnamaldehyde (HCMA); Pt–Ni/CNTs catalyst; Selective hydrogenation

UV light impact on ellagitannins and wood surface colour of European oak ( Quercus petraea and Quercus robur) by S. Zahri; C. Belloncle; F. Charrier; P. Pardon; S. Quideau; B. Charrier (pp. 4985-4989).

Two European oak species ( Q. petraea and Q. robur) have a high content of phenols which may participate in the alteration of colour upon UV irradiation. To study the photodegradation process of oak surfaces, the two oak species extractives, vescalagin, castalagin, ellagic acid and gallic acid were analysed quantitatively by HPLC before and after UV irradiation. Irradiation time was altered between 3, 24, 72, 96, 120, 144, 192 and 216h. In parallel, any colour changes of Oak wood surface was followed after 120h of UV-irradiation by measuring CIELAB parameters (DL*, Da*, Db* and DE*). We observed that 60% of total phenol content of extractives decreased after the maximal exposure time. Our findings also showed that castalagin and gallic acid were destroyed after 216h and vescalagin and ellagic acid after 72h. This study proves the photosenibility of oakwood extractives which, supplementary to lignin degradation, would strongly result in the discolouration of oak heartwood.

Keywords: Castalagin; Ellagic acid; Ellagitannins; Gallic acid; European oak; Photodegradation; Vescalagin; Wood colour

Post-annealing influence on properties of N–In codoped ZnO thin films prepared by ion beam enhanced deposition method by Ningyi Yuan; Lining Fan; Jinhua Li; Xiuqin Wang (pp. 4990-4993).

N–In codoped ZnO thin films were prepared by ion beam enhanced deposition method (IBED) and were annealed in nitrogen and oxygen ambient after deposition. The influence of post-annealing on structure, electrical and optical properties of thin films were investigated. As-deposited and all post-annealed samples showed preferential orientation along (002) plane. Electrical property studies indicated that the as-deposited ZnO film showed p-type with a sheet resistance of 67.5kΩ. For ZnO films annealed in nitrogen with the annealing temperature increasing from 400 to 800°C, the conduction type of the ZnO film changed from p-type to n-type. However, for samples annealed in oxygen the resistance increased sharply even at a low annealing temperature of 400°C and the conduction type did not change. Room temperature PL spectra of samples annealed in N₂ and in O₂ showed UV peak located at 381 and 356nm, respectively.

Keywords: PACS; 61.72; 68.55; 73.50ZnO thin films; Ion beam enhanced deposition; Post-annealing; Electrical properties; Photoluminescence

Spray pyrolytic synthesis of samarium doped ceria (Ce_0.8Sm_0.2O_1.9) films for solid oxide fuel cell applications by B.B. Patil; S.H. Pawar (pp. 4994-5002).

Uniform, adherent, single phase samarium doped ceria films have been successfully deposited by spray pyrolysis technique for their application in solid oxide fuel cell. These films have been deposited at different substrate temperatures on glass substrate and subsequently heat treated in tube furnace. Effect of substrate temperature and annealing temperature on phase formation was studied with thermo-gravimetric analysis and differential temperature analysis, X-ray diffraction, scanning electron microscope, and energy dispersive X-ray analysis techniques. These studies showed the formation of single phase Ce_0.8Sm_0.2O_1.9 films, at substrate temperature 400°C and annealing temperature 550°C. Electrical resistivity of the films, at room temperature was of the order of 10⁷Ωcm while at 400°C it is found to be of the order of 10¹Ωcm. This reveals the use of these films for making low temperature solid oxide fuel cells.

Keywords: PACS; 82.47.EdSolid oxide fuel cell; CeO; ₂; based ceramics; Spray deposition technique; Samarium doped ceria films

Effect of plasticizer and surface topography on the cleanability of plasticized PVC materials by J. Määttä; H.-K. Koponen; R. Kuisma; H.-R. Kymäläinen; E. Pesonen-Leinonen; A. Uusi-Rauva; K.-R. Hurme; A.-M. Sjöberg; M. Suvanto; T.A. Pakkanen (pp. 5003-5010).

A quantitative radiochemical measuring procedure was used to investigate soil adhesion on laboratory-made polyvinyl chloride (PVC) surfaces. The materials contained different plasticizers and microstructures. Both the quality and amount of plasticizers and the microstructure affected the cleanability of the PVC samples. The surface topography and structures were examined with a contact angle meter, atomic force microscopy (AFM) and a contact profilometer.

Keywords: PVC; Microstructure; Profilometer; AFM; Radiochemistry; ¹⁴; C; ⁵¹; Cr; Gammaspectrometry; Liquid scintillation counting; Contact angle measurement

Corrosive behavior of chromium carbide-based films formed on steel using a filtered cathodic vacuum arc system by Chun-Chun Lin; Ku-Ling Chang; Han C. Shih (pp. 5011-5016).

The formation of chromium carbide-based hard-coatings on steels using a 90°-bend filtered cathodic vacuum arc (FCVA) has extensive industrial applications; such coatings are free of macroparticles and exhibit excellent characteristics. In this investigation, a working pressure of C₂H₂/Ar was adopted to synthesize amorphous chromium carbide film (a-C:Cr) and crystalline chromium carbide film (cryst-Cr₃C₂) from a Cr target (99.95%) at 500°C under a substrate voltage of −50V. The corrosion behavior of a-C:Cr coated on steel (a-C:Cr/steel) and cryst-Cr₃C₂ coated on steel (cryst-Cr₃C₂/steel) were compared in terms of open-circuit potentials (OCP) and polarization resistance ( R_p) in an aerated 3.5wt% NaCl aqueous solution, as determined by electrochemical impedance spectroscopy (EIS). The XRD results indicated that the transformation of a-C:Cr to cryst-Cr₃C₂ is distinct as the working pressure declines from 1.2×10⁻² to 2.9×10⁻³Torr. The OCP of a-C:Cr/steel and cryst-Cr₃C₂/steel resemble each other and both assembly are nobler than uncoated steel. The R_p of the coatings exceeds that of the uncoated steel. The SEM observation and the EIS results demonstrate that the cryst-Cr₃C₂/steel more effectively isolates the defects than dose a-C:Cr/steel.

Keywords: Filtered cathodic vacuum arc; Chromium carbide; Electrochemical impedance spectroscopy; Corrosion

The absorptance of steels to Nd:YLF and Nd:YAG laser light at room temperature by D. Bergström; J. Powell; A.F.H. Kaplan (pp. 5017-5028).

The measurement of absorptance is important for the analysis and modelling of laser–material interactions. Unfortunately, most of the absorptance data presently available considers only polished pure metals rather than the commercially available (unpolished, oxidised) alloys, which are actually being processed in manufacturing. This paper presents the results of absorptance measurements carried out at room temperature on as-received engineering grade steels including hot and cold rolled mild steel and stainless steels of various types. The measurements were made using an integrating sphere with an Nd:YLF laser at two wavelengths (1053 and 527nm, which means that the results are also valid for Nd:YAG radiation at 1064 and 532nm). The absorptance results obtained differ considerably from existing data for polished, pure metals and should help improve the accuracy of laser–material interaction models. Some clear trends were identified; for all materials studied, the absorptance was considerably higher than the previously published values for the relevant pure metals with polished surfaces. For all 15 samples the absorptance was higher for the green than for the infrared wavelength. No clear trend correlating the absorptance with the roughness was found for mild steel in the roughness range Sa 0.4–5.6μm. A correlation between absorptance and roughness was noted for stainless steel for Sa values above 1.5μm.

Keywords: PACS; 42.62.-b; 42.82.-m; 78.66.Bz; 78.68.+mLaser material processing; Absorptance; Steels; Integrating sphere

Electron microscopic study on interfacial characterization of electroless Ni–W–P plating on aluminium alloy by Hu Yong-jun; Xiong Ling; Meng Ji-long (pp. 5029-5034).

The interface between electroless plating Ni–W–P deposit and aluminium alloy (Al) matrix at different temperature heated for 1h was studied using transmission electron microscope. The results show that the interface between as-deposited Ni–W–P deposit and Al matrix is clear. There are no crack and cavity. The bonding of Ni–W–P deposit and Al matrix is in good condition. The Ni–W–P plating is nanocrystalline phase (5–6nm) in diameter. After being heated at 200°C for 1h, the interface of Ni–W–P deposit and Al matrix is clear, without the appearance of the diffusion layer. There exist a diffusion layer and educts of intermetallic compounds of nickle and aluminium such as Al₃Ni, Al₃Ni₂, NiAl, Ni₅Al₃ and so on between Ni–W–P deposit and Al matrix after being heated at 400°C for 1h.

Keywords: PACS; 68.35.FxElectroless plating; Ni–W–P alloy; Interface; Diffusion

Electrical and optical properties of ZnO films prepared by sputtering of ZnO targets containing AlN by K. Kobayashi; Y. Kondo; Y. Tomita; Y. Maeda; S. Matsushima (pp. 5035-5039).

ZnO films prepared from the ZnO target containing 2% AlN are transparent irrespective of radio frequency (RF) power. The obtained ZnO films have the carrier density of 3.8×10²⁰cm⁻³ or less and the low mobility of 5.3–7.8cm²/(Vs). In the case of 5% AlN target, ZnO films prepared at 40, 60 and 80W are transparent, whereas ZnO films prepared at 100 and 120W are colored. As RF power increases from 40 to 120W, the carrier density increases straightforwardly up to 5.5×10²⁰cm⁻³ at 100W and is oppositely reduced to 3.2×10²⁰cm⁻³ at 120W. In the case of 10% AlN target, ZnO films prepared at 60W or more are colored, and have the carrier density of 4×10²⁰cm⁻³ or less. The N-concentration in these colored films is estimated to be 1% or less. The Al-concentration in the ZnO films prepared from the 5 and 10% AlN targets is higher than 2%. The carrier density of the ZnO films containing Al and N atoms is nearly equal to that of ZnO films doped with Al atoms alone. There is no evidence in supporting the enhancement of the carrier density via the formation of N-Al_xZn4−_x clusters (4≥ x≥2).

Keywords: PACS; 73.61.GaTransparent conductive oxide; Al-doped ZnO films; Sputtering; Cluster-doping; N atoms

Influence of the calcium phosphate content of the target on the phase composition and deposition rate of sputtered films by K. Ozeki; Y. Fukui; H. Aoki (pp. 5040-5044).

Calcium phosphate was coated from tetracalcium phosphate (TTCP), hydroxyapatite (HA), β-tricalcium phosphate (TCP), β-calcium pyrophosphate (CPP), and β-calcium metaphosphate (CMP) powder targets using radio frequency magnetron sputtering. The composition of the crystal phase of the coated films was changed, depending on the target materials, and the Ca/P molar ratios of the films varied from 0.74 to 2.54, increasing with the Ca/P molar ratio of the target. The solubility of the target, determined using a microwave-induced plasma-mass spectrometer was: TTCP≈β-CMP>β-TCP>β-CPP>HA, and the deposition rate from each target showed a similar order to the solubility: TTCP≈β-CMP>β-TCP>β-CPP≈HA.

Keywords: Sputtering; Target; Calcium phosphate; Hydroxyapatite; Crystal phase

Characteristic of microarc oxidized coatings on titanium alloy formed in electrolytes containing chelate complex and nano-HA by Daqing Wei; Yu Zhou; Yaming Wang; Dechang Jia (pp. 5045-5050).

Microarc oxidized (MAO) TiO₂-based coatings containing Ca and P on titanium alloy were formed in electrolytes containing nano-hydroxyapatite (nano-HA), calcium and phosphate salts. The effects of HA concentration on the thickness, micropore size and number of the MAO coatings were not pronounced. However, the surfaces of the MAO coatings become rough and the crystallinity of anatase increases with increasing HA concentration. In addition, the Ca and P concentrations on the surfaces of the MAO coatings decrease, since the chelate complex of CaY²⁻ (Y=[₂(OOC)NCH₂CH₂N(COO)₂]⁴⁻) and phosphate ions are hindered to be incorporated into the MAO coatings by HA. In vitro experiments indicate that the apatite-forming abilities of the MAO coatings decrease with increasing HA concentration. Furthermore, with increasing HA concentration, the solubility of Ca and P of the MAO coatings decreases, which could lower the supersaturation of the SBF with respect to apatite near the surfaces of the MAO coatings, further leading to the decreased apatite-forming ability. The results indicate that the HA addition in the electrolytes has an important effect on the structure and in vitro bioactivity of the MAO coatings.

Keywords: Coating; Microarc oxidation; Titanium alloy; Hydroxyapatite; Chelate complex; Apatite

Improvement of hydrophobic properties of silk and cotton by hexafluoropropene plasma treatment by Shen Li; Dai Jinjin (pp. 5051-5055).

Plasma surface-treatment of silk and cotton fabrics were carried out in a hexafluoropropene (C₃F₆) atmosphere under different experimental conditions. Analysis of the treated fibers by X-ray photoelectron spectroscopy (XPS) indicated about 50 at% fluorine atoms were incorporated in the surface structure of two fibers and confirmed the presence of –CF, –CF₂, –CF₃ groups on the surface. After water-washing and alcohol-extraction, though partial loss of fluorine from the surface has been observed, contact angle and wet-out time measurements on the fibers still show much improved hydrophobic properties. The other properties of the treated fabrics, such as water vapor permeability and tensile strength were also evaluated.

Keywords: PACS; 52.77.DqSilk; Cotton; Hexafluoropropene; Plasma treatment; Hydrophobic property

Current conduction mechanism in Al/p-Si Schottky barrier diodes with native insulator layer at low temperatures by Ş. Altındal; H. Kanbur; D.E. Yıldız; M. Parlak (pp. 5056-5061).

The forward bias current–voltage ( I– V) characteristics of Al/p-Si (MS) Schottky diodes with native insulator layer were measured in the temperature range of 80–300K. The obtained zero bias barrier height Φ_B0( I– V), ideality factor ( n) and series resistance ( R_s) determined by using thermionic emission (TE) mechanism show strong temperature dependence. There is a linear correlation between the Φ_B0( I– V) and n because of the inhomogeneties in the barrier heights (BHs). Calculated values from temperature dependent I– V data reveal an unusual behaviour such that the Φ_B0 decreases, as the n and R_s values are increasing with decreasing absolute temperature, and these changes are more pronounced especially at low temperatures. Such temperature dependence of BH is contradictory with the reported negative temperature coefficient of the barrier height. In order to explain this behaviour we have reported a modification in the expression reverse saturation current I_o including the n and the tunnelling factor ( αΧ^1/2 δ) estimated to be 15.5. Therefore, corrected effective barrier height Φ_bef.( I– V) versus temperature has a negative temperature coefficients ( α=−2.66×10⁻⁴eV/K) and it is in good agreement with negative temperature coefficients ( α=−4.73×10⁻⁴eV/K) of Si band gap. In addition, the temperature dependent energy distribution of interface states density N_ss profiles was obtained from the forward bias I– V measurements by taking into account the bias dependence of the Φ_e and n. The forward bias I– V characteristics confirm that the distribution of N_ss, R_s and interfacial insulator layer are important parameters that the current conduction mechanism of MS Schottky diodes.

Keywords: PACS; 73.30.+y: 73.40.Qv: 73.40.NsSeries resistance; Interface states; Native insulator layer; Conduction mechanisms; I; –; V; characteristics

Chemical characterization by XPS of Cu/Ge ohmic contacts to n-GaAs by M.C. López; B. Galiana; C. Algora; I. Rey-Stolle; M. Gabas; J.R. Ramos-Barrado (pp. 5062-5066).

Chemical composition of Cu/Ge layers deposited on a 1μm thick n-type GaAs epitaxial layer (doped with Te to a concentration of 5×10¹⁸cm⁻³) and its interface were examined ex situ by XPS combined with Ar⁺ sputtering. These measurements indicate a diffusion of Cu and Ge from the Cu/Ge layer towards GaAs and, also, an out-diffusion of Ga and As from the GaAs layer to the metallic films. The Auger parameter corrected Auger spectra and XPS spectra show only Cu and Ge metals in the in the Cu/Ge layer and in the interface.

Keywords: PACS; 73.61.Ey III–V semiconductors; 73.61.At metal and metallic alloys; 68.35.Fx diffusion; Interface formationXPS; Copper alloys; Semiconductor devices; Interface structure; Surface diffusion

Fabrication of Sb-doped p-type ZnO thin films by pulsed laser deposition by Xinhua Pan; Zhizhen Ye; Jiesheng Li; Xiuquan Gu; Yujia Zeng; Haiping He; Liping Zhu; Yong Che (pp. 5067-5069).

p-Type ZnO thin films have been realized via monodoping antimony (Sb) acceptor by using pulsed laser deposition. The obtained films with the best electrical properties show a hole concentration in the order of 10¹⁸cm⁻³ and resistivity in the range of 2–4Ωcm. X-ray diffraction measurements revealed that all the films possessed a good crystallinity with (002)-preferred orientation. Guided by X-ray photoemission spectroscopy analysis and a model for large-sized-mismatched group-V dopant in ZnO, an Sb_Zn–2V_Zn complex is believed to be the most possible acceptor in the Sb-doped p-type ZnO thin films.

Keywords: PACS; 61.72.V; 72.80.E; 73.61.G; 78.66.HZnO; Sb-doped; Pulsed laser deposition; X-ray photoemission spectroscopy

Diamond–DLC double layer used in corrosive protective coating by H.K. Csorbai; G. Kovách; G. Pető; P. Csíkvári; A. Karacs; A. Sólyom; Gy. Hárs; E. Kálmán (pp. 5070-5075).

Pinhole-free diamond layers can widely be used in sensor technology as resistive coating against electrolyte solutions. The diamond layers created with chemical vapour deposition technique (CVD) are pinhole-free only above a certain thickness (at least 2.4μm). Such layer thicknesses reduce the application possibilities. On the other hand, thin (∼200nm) diamond like carbon (DLC) layers deposited by pulsed laser deposition technique (PLD) are pinhole free but have adhesion or contiguity problems depending on layer thickness. Utilizing the advantages of these two techniques a combined method was developed in order to prepare a pinhole free thin diamond–DLC double layer, for corrosion protection coating. The effects of various deposition parameters (such as background gas, temperature, bias, layer thickness) on the protective properties of the layers have been studied.

Keywords: Diamond; Corrosion; DLC; Pinhole; Protective layer

Nanolayered multilayer coatings of CrN/CrAlN prepared by reactive DC magnetron sputtering by Harish C. Barshilia; B. Deepthi; N. Selvakumar; Anjana Jain; K.S. Rajam (pp. 5076-5083).

Single-phase CrN and CrAlN coatings were deposited on silicon and mild steel substrates using a reactive DC magnetron sputtering system. The structural characterization of the coatings was done using X-ray diffraction (XRD). The XRD data showed that both the CrN and CrAlN coatings exhibited B1 NaCl structure with a prominent reflection along (200) plane. The bonding structure of the coatings was characterized by X-ray photoelectron spectroscopy and the surface morphology of the coatings was studied using atomic force microscopy. Subsequently, nanolayered CrN/CrAlN multilayer coatings with a total thickness of approximately 1μm were deposited on silicon substrates at different modulation wavelengths ( Λ). The XRD data showed that all the multilayer coatings were textured along {200}. The CrN/CrAlN multilayer coatings exhibited a maximum nanoindentation hardness of 3125kg/mm² at a modulation wavelength of 72Å, whereas single layer CrN and CrAlN deposited under similar conditions exhibited hardness values of 2375 and 2800kg/mm², respectively. Structural changes as a result of heating of the multilayer coatings in air (400–800°C) were characterized using XRD and micro-Raman spectroscopy. The XRD data showed that the multilayer coatings were stable up to a temperature of 650°C and peaks pertaining to Cr₂O₃ started appearing at 700°C. These results were confirmed by micro-Raman spectroscopy. Nanoindentation measurements performed on the heat-treated coatings revealed that the multilayer coatings retained hardness as high as 2250kg/mm² after annealing up to a temperature of 600°C.

Keywords: CrN and CrAlN films; CrN/CrAlN nanolayered multilayers; Magnetron sputtering; Structural and mechanical properties; Thermal stability

Numerical simulation of deformation behavior of Al particles impacting on Al substrate and effect of surface oxide films on interfacial bonding in cold spraying by Wen-Ya Li; Hanlin Liao; Chang-Jiu Li; Hee-Seon Bang; C. Coddet (pp. 5084-5091).

In this study, a comprehensive examination of the deformation behavior of Al particles impacting on Al substrate was conducted by using the Arbitrary Lagrangian Eulerian (ALE) method to clarify the deposition characteristics of Al powder and the effect of surface oxide films in cold spraying. It was found that the deformation behavior of Al particles is different from that of Cu particles under the same impact conditions owing to its lower density and thus less kinetic energy upon impact. The results indicated that a higher velocity was required for Al particles to reach the same compression ratio as that of Cu particles. On the other hand, the numerical results showed that the oxide films at particle surfaces influenced the deformation and bonding condition between the particle and substrate. The inclusions of the crushed oxide films at the interfaces between the depostied particles inhibit the deformation.

Keywords: Cold spraying; Numerical simulation; Aluminum; Oxide film; Deformation behavior

XPS, XAES, and TG/DTA characterization of deposited carbon in methane dehydroaromatization over Ga–Mo/ZSM-5 catalyst by B.S. Liu; L. Jiang; H. Sun; C.T. Au (pp. 5092-5100).

The catalytic dehydroaromatization of methane over 3.0%Mo/HZSM-5 and 0.1%Ga–3%Mo/HZSM-5 catalysts were reported. The nature of deposited carbon was characterized by means of XPS, XAES, TG/DTG, HRTEM, and DTA techniques. In XAES study, the type of deposited carbon was characterized based on the fine structures of d N/d E spectra. The results confirm that the sp²/sp³ bonding ratio of coke species increases with on-stream time, suggesting that the deposition of heavier aromatic-type carbon is the main reason for catalyst deactivation. The addition of gallium to 3.0%Mo/HZSM-5 enhances the adsorption of CO_x species as well as the formation of alkene (such as ethylene). Therefore, the Ga-modified 3%Mo/HZSM-5 catalyst is more active and stable than the unmodified one.

Keywords: Ga–Mo/ZSM-5 catalyst; Carbon deposition; Suppression of coke; XPS; DTA; Derivative XAES

Changes in surface stress, morphology and chemical composition of silica and silicon nitride surfaces during the etching by gaseous HF acid by Johann Mertens; Eric Finot; Olivier Heintz; Marie-Hélène Nadal; Vincent Eyraud; Arnaud Cathelat; Guillaume Legay; Eric Bourillot; Alain Dereux (pp. 5101-5108).

HF acid attack of SiO₂ and Si₃N₄ substrates is analyzed to improve the sensitivity of a sensor based on microcantilever. Ex situ analysis of the etching using XPS, SIMS and AFM show significant changes in the anisotropy and the rate of the etching of the oxides on SiO₂ and Si₃N₄ surface. Those differences influence the kinetic evolution of the plastic bending deflection of the cantilever coated with SiO₂ and Si₃N₄ layer, respectively. The linear dependence between the HF concentration and the Si₃N₄ cantilever bending corresponds to a deep attack of the layer whereas the non-linear behavior observed for SiO₂ layer can be explained by a combination of deep and lateral etching. The cantilever bending is discussed in terms of free surface energy, layer thickness and grain size.

Keywords: Sensor; Cantilever; X-ray photoelectron spectroscopy (XPS); Secondary ion mass spectroscopy (SIMS); Hydrofluoric acid (HF); Silicon; Atomic force microscope (AFM)

Scanning tunneling microscopy/spectroscopy on Au nanoparticles assembled using lauryl amine (LAM) and octadecane thiol (ODT) by Suwarna Datar; Minakshi Chaudhari; Murali Sastry; C.V. Dharmadhikari (pp. 5109-5115).

In this report, we demonstrate scanning tunneling microscopy and spectroscopy on thin films of lauryl amine (LAM) and octadecane thiol (ODT) protected gold nanoparticles. We show that the zero current in the I– V curves (measure of Coulomb blockade (CB) of the nanoparticles) depends on the properties of the spacer molecule. In both the cases the gap voltage and the tunneling current at which the images are obtained are quite different which is further confirmed from the fitting performed based on the orthodox theory. The values for the capacitance and charging energy obtained from the fitting for ODT capped particles are comparable to the values obtained using spherical capacitor model. In contrast, values of these parameters were found to differ for LAM capped nanoparticles. While imaging, ODT capped nanoparticles were observed to drag along the scan direction leading to ordering of particles. Images of LAM capped gold nanoparticles show local ordering in self-assembly of particles although no evidence of large scale ordering in spatial Fourier transform was seen. These observations suggest that nanoparticles with larger CB would be imaged nonevasively in contrast to small CB systems for which tip induced effects will be dominant. In both the systems the current was found to rise faster than theoretical curves based on the orthodox theory suggesting that mechanism of charge transfer in this case may involve field emission rather than tunneling through a rectangular barrier. An attempt has been made to explain charge transfer based on Fowler–Nordheim (F–N) plots of the I– V curves.

Keywords: PACS; 07.79.Cz; 81.07.; −; bScanning tunneling microscopy (STM); Nanostructures

Electroless deposition of Ni–W–P coating on AZ91D magnesium alloy by W.X. Zhang; N. Huang; J.G. He; Z.H. Jiang; Q. Jiang; J.S. Lian (pp. 5116-5121).

Ternary Ni–W–P alloy coating was deposited directly on AZ91D magnesium alloy by using an alkaline-citrate-based baths. Nickel sulfate and sodium tungstate were used as metal ion sources, respectively, and sodium hypophosphite was used as a reducing agent. The pH value of the electroless bath was tailored for magnesium alloy. The coating was characterized for its structure, morphology, microhardness and the corrosion properties. SEM observation showed the presence of dense and coarse nodules in the ternary coating. EDS analysis showed that the content of tungsten in the Ni–W–P alloy was 4.5wt.%. Both the electrochemical analysis and the immersion test in 10% HCl solution revealed that the ternary Ni–W–P coating exhibited good corrosion resistance properties in protecting the AZ91D magnesium alloy.

Keywords: Electroless Ni–W–P coating; Magnesium alloy; Corrosion resistance

Poly( N-vinyl carbazole)-grafted multiwalled carbon nanotubes: Synthesis via direct free radical reaction and optical limiting properties by Hui-Xia Wu; Xue-Qiong Qiu; Rui-Fang Cai; Shi-Xiong Qian (pp. 5122-5128).

In this work, samples of poly( N-vinyl carbazole) (PVK)-grafted multiwalled carbon nanotubes (MWCNTs) were synthesized via free radical reaction. The ready-made PVK was allowed to react directly with MWCNTs at 70°C in the presence of azo-bis-isobutyronitrile (AIBN). The purified deep grey products, which can dissolve in common organic solvents such as chloroform and 1,2-dichlorobenzene (DCB), were then characterized by FTIR spectra, TEM, TGA, elemental analysis, XPS, UV–vis spectra and Raman spectra. It was confirmed that PVK chains were grafted onto the surface of the carbon nanotubes (CNTs). The optical limiting properties of these PVK-grafted MWCNTs samples were investigated by open-aperture z-scan method. All of the samples of PVK-modified carbon nanotubes in chloroform showed optical limiting behavior better than that of C₆₀ in toluene.

Keywords: PACS; 82.30.Cf; 82.35.−x; 78.67.ChCarbon nanotubes; Poly(; N; -vinyl carbazole); Free radical reaction; Optical limiting properties

Microstructure characterization of porous silicon as studied by positron annihilation measurements at low temperatures and high vacuum by Pallab Banerji (pp. 5129-5132).

Atomic scale properties of thin porous silicon (PSi) layers, characterized by the formation of positronium, are investigated using positron annihilation lifetime spectroscopy in the temperature range 20–300K under 10⁻⁷Torr vacuum. The longest orthopositronium as well as the shortest parapositronium components are found to have quite low intensities in the thin layer at room temperature. It is also found that at temperatures ≤240K, these two components do not show up in the spectrum. The reason for this absence of the longest lifetime component is suggested.

Keywords: Porous silicon; Positron annihilation; Low temperature; High vacuum

Fabrication of microrods and microtips of InP by electrochemical etching by Zhankun Weng; Aimin Liu; Yanhong Liu; Feng Xu; Guoqing Li; Xiaojuan Sun (pp. 5133-5136).

Here we presented a simple approach to fabricate the microstructures of InP by electrochemical etching. Microrods were formed while InP etched in 7M HCl solutions for 30s, and microtips were obtained while InP etched for 120s. In addition, with increasing applied potential the surface of the microrods became smoother. The formation mechanism was also discussed in this article.

Keywords: PACS; 81.05.Ea; 73.40.Mr; 82.45.Jn; 82.45.VpIndium phosphide; Microrods; Microtips; Electrochemical etching

Structural, optical properties and VCNR mechanisms in vacuum evaporated iodine doped ZnSe thin films by S. Venkatachalam; D. Mangalaraj; Sa.K. Narayandass (pp. 5137-5142).

Iodine doped ZnSe thin films were prepared onto uncoated and aluminium (Al) coated glass substrates using vacuum evaporation technique under a vacuum of 3×10⁻⁵Torr. The composition, structural, optical and electrical properties of the deposited films were analyzed using Rutherford backscattering spectrometry (RBS), X-ray diffraction (XRD), spectroscopic ellipsometry (SE) and study of I– V characteristics, respectively. In the RBS analysis, the composition of the deposited film is calculated as ZnSeI_0.003. The X-ray diffractograms reveals the cubic structure of the film oriented along (111) direction. The structural parameters such as crystallite size, strain and dislocation density values are calculated as 32.98nm, 1.193×10⁻³lin⁻²m⁻⁴ and 9.55×10¹⁴lin/m², respectively. Spectroscopic ellipsometric (SE) measurements were also presented for the prepared iodine doped ZnSe thin films. The optical band gap value of the deposited films was calculated as 2.681eV by using the optical transmittance measurements and the results are discussed. In the electrical studies, the deposited films exhibit the VCNR conduction mechanism. The iodine doped ZnSe films show the non-linear I– V characteristics and switching phenomena.

Keywords: ZnSe thin films; Vacuum evaporation; RBS; XRD; Optical; I; –; V

The influence of nonpolar organics adsorption on the electrochemical behaviour of powdered activated carbon electrodes in aqueous electrolytes by M. Pakula; S. Biniak; A. Swiatkowski; A. Derylo-Marczewska (pp. 5143-5148).

Adsorption and electrochemical studies were carried out on three activated carbon samples first oxidized, then heat-treated under vacuum (at 180, 500 and 900°C). The investigations were performed with aqueous electrolyte (Na₂HPO₄ and H₃PO₄) solutions containing selected nonpolar organics (benzene and n-hexane). Adsorption measurements were carried out on solution with a wide range of organics concentration (up to saturation point). Cyclovoltammetric curves of powdered electrodes prepared from the activated carbon samples were recorded for the organics in saturated solutions. The electric double layer capacities of the anodic and cathodic parts were estimated, and the surface anodic and cathodic charge was calculated both in absence and presence of organics in the electrochemical systems. The relative surface charge (in relation to systems without organics) was found to decrease with a reduction in the concentration of surface oxygen-containing groups. Other physicochemical parameters characterizing the degree of surface oxidation (total oxygen concentration, primary water adsorption centres) were also taken into consideration. The correlation between adsorption capacity towards the nonpolar organic compounds (obtained from adsorption isotherms) and change of surface charge was analyzed.

Keywords: Activated carbon; Modification; Cyclic voltammetry; Adsorption of organics; Surface chemistry

Thermally responsive wettability of self-assembled methylcellulose nanolayers by Shingo Yokota; Kana Matsuyama; Takuya Kitaoka; Hiroyuki Wariishi (pp. 5149-5154).

Thermo-responsive cellulosic nanolayers were prepared from methylcellulose (MC), which is known to have a unique lower critical solution temperature. Thiosemicarbazide (TSC) was selectively introduced into the MC reducing end groups, and the corresponding MC–TSC derivative was spontaneously chemisorbed on an Au substrate at 4°C to give MC self-assembled monolayers (SAMs). Linear MC chains were stably fixed onto the Au substrate, yielding an MC-SAM of thickness ca. 15nm with a root mean square value less than 1nm. The MC-SAM surface exhibited thermally responsive wetting characteristics; the water contact angle was found to rise and fall around 70°C, possibly due to the solid-state phase transition of the MC nanolayers resulting from the inherent gelation of MC molecules in water. Such wetting behavior was shown to be reversible following repeated heating and cooling. The MC-SAM immersed in salt solution revealed lower phase transition temperatures, and an increase in sodium chloride concentration ranging from 0.0 to 1.0M brought about a dramatic decrease in the apparent phase transition temperature from ca. 70 to 30°C. For the purposely designed MC nanolayers, such controllable wetting properties are expected to prompt growing interest in the applications of cellulosic biopolymer interfaces.

Keywords: PACS; 81.07.−b; 81.16.DhMethylcellulose; Self-assembled monolayer; Wetting property; Solid-state phase transition; Thermal responsibility

Preparation of the nickel foam/Ni–Ce–Co–O film electrode by thermal decomposition for oxygen evolution reaction by Fancai Chen; Chengcai Jiang; Jinfeng Liu; Deliang He; Xiaohua Zhang; Jiaxin Wen; Yaling Wang (pp. 5155-5160).

The Ni–Ce–Co–O film on nickel foam was prepared by thermal decomposition of acetates. The electrochemical activity of the film was affected by the temperature of thermal decomposition. Cerium ions introduced into the oxide film could increase the surface area and improve the oxygen evolution reaction (OER) activity of the electrode. Compared with thermal decomposition of nitrates, the OER activity of the film prepared with acetates was higher. When the nickel foam/Ni–Ce–Co–O film electrode prepared with acetates was used as the anode, in 30% KOH solution (88±2°C) at the current density of 4000A/m², the cell voltage was 250mV lower than that of the nickel foam anode. Furthermore, the film electrode exhibited good stability.

Keywords: PACS; 82.45.Cc; 82.45.Fk; 82.45.MpNi–Ce–Co–O film; Nickel foam; Thermal decomposition; OER activity

Realization of controllable etching for ZnO film by NH₄Cl aqueous solution and its influence on optical and electrical properties by Jingchang Sun; Jiming Bian; Hongwei Liang; Jianze Zhao; Lizhong Hu; Ziwen Zhao; Weifeng Liu; Guotong Du (pp. 5161-5165).

ZnO films were deposited on c-plane Al₂O₃ substrates by pulsed laser deposition. The etching treatments for as-grown ZnO films were performed in NH₄Cl aqueous solution as a function of NH₄Cl concentration and etching time. It was found that NH₄Cl solution is an appropriate candidate for ZnO wet etching because of its controllable and moderate etching rate. The influence of etching treatment on the morphology, optical and electrical properties of the ZnO films has been investigated systematically by means of X-ray diffraction, atomic force microscope, photoluminescence and Hall effect. The results indicated that the surface morphology and optical properties of the films were highly influenced by etching treatment.

Keywords: PACS; 78.55.Et; 81.15.Fg; 81.65.CfZnO; Controllable etching; NH; ₄; Cl aqueous solution

Fabrication of nanostructured CuInS₂ thin films by ion layer gas reaction method by Kajari Das; Subhendu K. Panda; S. Chaudhuri (pp. 5166-5172).

CuInS₂ thin films were prepared by a two-stage ion layer gas reaction (ILGAR) process in which the Cu and In precursors were deposited on glass substrate by using a simple and low-cost dip coating technique and annealed in H₂S atmosphere at different temperatures. The influence of the annealing temperature (250–450°C) on the particle size, crystal structure and optical properties of the CuInS₂ thin films was studied. Transmission electron microscopy revealed that the particle radii varied in the range 6–21nm with annealing. XRD and SAED patterns indicated polycrystalline nature of the nanoparticles. The optical band gap ( E_g) varied from 1.48 to 1.56eV with variation of particle size. The variation of Urbach tail with temperature indicated higher density of the defects for the films annealed at lower temperature. From the Raman study, it was observed that the FWHM of the A₁ mode at ∼292cm⁻¹ corresponding to the chalcopyrite phase of CuInS₂ decreased with increasing annealing temperature.

Keywords: PACS; 79.60.Dp; 79.60.Jv; 78.66.−wCuInS; ₂; ILGAR; Thin films; Nanoparticle

Biosensing of biophysical characterization by metal-aluminum nitride-metal capacitor by Chang-Chih Chen; Che-Tong Lin; Sheng-Yang Lee; Ling-Hung Lin; Chiung-Fang Huang; Keng-Liang Ou (pp. 5173-5178).

Aluminum nitride thin films were fabricated as stress biosensors for biosensing cell attachment. The features and capacitance of AlN films following cell culture were detected via leakage current density and biocompatibility testing. Analytical results demonstrate that the failure of the capacitors produced slit-like microvoids to form on the AlN film, following cell differentiation and proliferation. Slit-like microvoids incurred substantial current leaking of the cell cultured-capacitor, even at a low breakdown voltage. Stress variation during cell differentiation and proliferation were responsible for the formation of microvoids and the low breakdown voltage. The stress produced lattice distortion of the AlN film, resulting in a piezoelectric effect on the AlN film surface. Results of this study demonstrate that the piezoelectric AlN film is highly promising as a biosensing film.

Keywords: Aluminum nitride; Thin film; Biocompatibility; Differentiation; Proliferation

Structural, electrical and optical properties of Gd doped and undoped ZnO:Al (ZAO) thin films prepared by RF magnetron sputtering by Wei Lin; Ruixin Ma; Wei Shao; Bin Liu (pp. 5179-5183).

The influence of the gadolinium doping on the structural features and opto-electrical properties of ZnO:Al (ZAO) films deposited by radio frequency (RF) magnetron sputtering method onto glass substrates was investigated. X-ray analysis showed that the films were polycrystalline fitting well with a hexagonal wurtzite structure and have preferred orientation in [002] direction. The Gd doped ZAO film with a thickness of 140nm showed a high visible region transmittance of 90%. The optical band gap was found to be 3.38eV for pure ZnO film and 3.58eV for ZAO films while a drop in optical band gap of ZAO film was observed by Gd doping. The lowest resistivities of 8.4×10⁻³ and 10.6×10⁻³Ωcm were observed for Gd doped and undoped ZAO films, respectively, which were deposited at room temperature and annealed at 150°C.

Keywords: PACS; 81.05.−t; 81.05.Je; 81.15.CdZinc oxide; RF magnetron sputtering; Transparent conductive thin film; Optical and electronic properties

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Applied Surface Science (v.253, #11)

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Applied Surface Science (v.253, #11)