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Applied Surface Science (v.253, #12)

The formation of nanotubes and nanocoils of molybdenum disulphide by V. Lavayen; N. Mirabal; C. O’Dwyer; M.A. Santa Ana; E. Benavente; C.M. Sotomayor Torres; G. González (pp. 5185-5190).

This work reports the successful realization of MoS₂ nanotubes by a novel intercalation chemistry and hydrothermal treatment. An inorganic–organic precursor of hexadecylamine (HDA) and molybdenum disulphide (MoS₂) were used in synthesizing the nanocomposite comprising laminar MoS₂ with HDA intercalated in the interlaminar spacing. The formation of MoS₂ nanotubes occurred during hydrothermal treatment (HT) by a self-organized rolling mechanism. The nanotubes were observed to have dimensions 2–12μm in length and inner diameters typically in the range of 25–100 nm. We also report the formation of amorphous nanocoils of MoS₂ obtained during similar procedures.

Keywords: Chalcogenides; Transmission electron microscopy; Molybdenum; Nanotubes; Nanostructures

Internal structure transition of spin-on glass by electron beam irradiation by Makoto Araki; Jun Taniguchi; Nobuo Sawada; Takayuki Utsumi; Iwao Miyamoto (pp. 5191-5195).

The effects of electron beam (EB) irradiation on spin-on glass (SOG) were investigated using thermal desorption spectroscopy. We were able to employ heat treatment as a “development process”, since we discovered that heat treatment breaks different bonds in SOG depending on whether it is applied before or after EB irradiation of SOG. In the case, when heat treatment was applied before EB irradiation of SOG, it was possible to break the Si–C bond at about 500°C. In the case, when heat treatment was applied after EB irradiation of SOG, on the other hand, the –SiC bond could be broken at a lower temperature of about 400°C. Using this difference between the two bond-breaking temperatures, it was possible to develop SOG using thermal desorption development (TDD). Moreover, the bond-breaking mechanisms revealed that the organic components in SOG play an important role in TDD. Hence, in order to determine the influence of organic components on TDD, the development characteristics of SOG samples with 10% and 15% organic contents were investigated.

Keywords: PACS; 68.43.Vx; 68.43.RsSpin-on glass (SOG); Thermal desorption spectroscopy (TDS); Electron beam irradiation; Thermal desorption development (TDD)

Surface analysis of the nanostructured W–Ti thin film deposited on silicon by S. Petrović; N. Bundaleski; D. Peruško; M. Radović; J. Kovač; M. Mitrić; B. Gaković; Z. Rakočević (pp. 5196-5202).

The W–Ti thin films are deposited by the dc Ar⁺ sputtering of W(70%)–Ti(30%) a.t. target on silicon substrates. The surface composition and structure of the thin film, previously exposed to air, was carried out. The surface structure was undertaken using grazing incidence X-ray diffraction (GIXRD), and compared to that of the thin film interior. The surface morphology was determined by the Scanning Tunneling Microscopy (STM). The surface composition and chemical bonding of elements on the Ti–W film were analyzed by X-ray photoelectron spectroscopy (XPS) and Low Energy Ion Scattering (LEIS). The measurements show that the overlayer of metallic oxides TiO₂ and WO₃ is formed. The first atomic layer is occupied by TiO₂ only, and its thickness is estimated to about 3.2±0.4nm. The strong surface segregation of Ti is triggered by the surface oxidation, which is confirmed by the thermodynamical considerations.

Keywords: W–Ti thin films; Surface segregation; GIXRD; STM; XPS; LEIS

Plasma polymerization of styrene with carbon dioxide under glow discharge conditions by H.L. Luo; J. Sheng; Y.Z. Wan (pp. 5203-5207).

Plasma polymerization gains increasing interest for the deposition of films with functional properties suitable for a wide range of modern applications on account of its advantageous features. In this study, carbon dioxide (CO₂) was chosen as carrier gas at flow rates of 30 and 60sccm, respectively and styrene vapor was used as the monomer to prepare polystyrene films on glass substrates. The structure and composition of the plasma polymerized films were characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR) and compared with the film prepared by conventional thermal polymerization. The morphology information of the films was provided by optical microscopy. XPS and FT-IR results reveal that chemical composition of the plasma polymerized films is different from that of the thermal polymerized film and that oxygen content in the plasma polymerized films increases with the flow rate of CO₂. Furthermore, the presence of oxygen-containing groups on the surface of plasma polymerized polystyrene films is confirmed. It is also found that the composition and morphology of the plasma polymerized films are controlled by the flow rate of CO₂.

Keywords: PACS; 52.77Dq; 82.35.–xPlasma polymerization; Polystyrene film; Carbon dioxide

Modification of cycloolefin copolymer and poly(vinyl chloride) surfaces by superimposition of nano- and microstructures by Hanna-Kaisa Koponen; Inka Saarikoski; Tuulia Korhonen; Marjo Pääkkö; Risto Kuisma; Tuula T. Pakkanen; Mika Suvanto; Tapani A. Pakkanen (pp. 5208-5213).

Cycloolefin copolymer (COC) and poly(vinyl chloride) (PVC) surfaces were patterned with nanopillars or with microbumps on which nanopillars were superimposed. The area of patterned surfaces was several square centimeters. Patterning was achieved by applying nanoporous anodized aluminum oxide (AAO) membrane as a mask in injection molding or imprinting. Nanostructures superimposed on microstructures were achieved by patterning the AAO mask with microstructures before anodization. Micro- and nanometer-sized structures could then be transferred simultaneously to polymer surfaces. Structures were characterized by SEM, AFM, and contact profilometry. The effect of different-sized structures on properties of the polymer surface was studied by contact angle measurements. Relative to the smooth surface, the increase in water contact angle on a COC surface with nanostructures superimposed on microstructures was up to 50°.

Keywords: Poly(vinyl chloride) (PVC); Cycloolefin copolymer (COC); Anodized aluminum oxide (AAO); Nanostructure; Microstructure

Co-energy of surface and grain boundary in Ag film by Xiu-Mei Wei; Jian-Min Zhang; Ke-Wei Xu (pp. 5214-5217).

A model is proposed for calculating the co-energy of surface and grain boundary (GB) by the modified analytical embedded atom method (MAEAM). As example, the energy densities E_d of the two adjacent grains are obtained when their (001) twist GB meets the free surface ( h₁ k₁0)/( h₂ k₂0) of Ag film. The period along the boundary line on the surface is found and the energy density is calculated for the situations either with or without periodicity. The results show that, the energy value achieved via this model can be stable even for most grains with boundary line smaller than 100nm. Among the grains with ( h k0) surface, (100) grains should be favored and grow fastest when they meet (110) grains.

Keywords: Surface; Grain boundary; MAEAM

Electrical characteristics of UV photodetectors based on ZnO/diamond film structure by Jianmin Liu; Yiben Xia; Linjun Wang; Qingfeng Su; Weimin Shi (pp. 5218-5222).

Ultraviolet photodetectors based on ZnO/diamond film structure were fabricated. The properties of Au/ZnO contacts and effects of grain sizes on the electrical characteristics of photodetectors were discussed. Due to the bombardment with Au atoms and the annealing process, fine ohmic contacts were formed between Au electrodes and ZnO films. Dark currents and photocurrents of the photodetectors were related to sputtering time and the grain size of ZnO films. For the photodetector with a bigger grain size, a lower dark current and a higher photocurrent were obtained under 10V bias voltage. The time-dependent photocurrent confirmed the carrier trapping effect.

Keywords: PACS; 81.05.Dz; 61.80.Ba; 72.40.+wPhotodetector; ZnO/diamond film structure; Ohmic contact; Grain size; Photoresponse

Synthesis and characterization of tantalum nitride films prepared by cathodic vacuum arc technique by Erwu Niu; Li Li; Guohua Lv; Wenran Feng; Huan Chen; Songhua Fan; Size Yang; Xuanzong Yang (pp. 5223-5227).

Tantalum nitride films were deposited on silicon wafer and steel substrates by cathodic vacuum arc in N₂/Ar gas mixtures. The chemical composition, crystalline microstructure and morphology of the films were investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM), respectively. According to the results, film composition and microstructure depends strongly on the N₂ partial pressure and the applied negative bias ( V_s).

Keywords: Cathodic vacuum arc; Tantalum nitride

Atomic layer deposition of PbZrO₃ thin films by Jenni Harjuoja; Samuli Väyrynen; Matti Putkonen; Lauri Niinistö; Eero Rauhala (pp. 5228-5232).

In this paper, we report on the preparation of lead zirconate films for the first time using atomic layer deposition in an attempt to investigate some of the film properties and also to evaluate possible use of the precursor combination to prepare more complex lead titanate zirconate. In the depositions tetraphenyl lead (Ph₄Pb) was used as the lead and zirconium 2,2,6,6-tetramethyl-3,5-heptadionato (Zr(thd)₄) as the zirconium precursor, while ozone was used as the oxygen source. Film growth, stoichiometry and quality were studied using different pulsing ratios at deposition temperatures of 275 and 300°C. According to X-ray diffraction, the crystalline perovskite phase was observed when films deposited on SrTiO₃(100) were annealed at 600°C. Surface roughness was reduced for lead deficient films as well as in annealed samples.

Keywords: PACS; 68.37.Ps; 68.55.Jk; 68.55.Nq; 81.15.−z; 81.15.Gh; 82.80.YcAtomic layer deposition; ALD; Lead zirconate; X-ray diffraction; Atomic force microscopy; Rutherford backscattering spectroscopy

Diamond coating deposition by synergy of thermal and laser methods—A problem revisited by Gordana S. Ristić; Milan S. Trtica; Žarko D. Bogdanov; Nebojša Ž. Romčević; Šćepan S. Miljanić (pp. 5233-5239).

Diamond coatings were deposited by synergy of the hot filament CVD method and the pulse TEA CO₂ laser, in spectroactive and spectroinactive diamond precursor atmospheres. Resulting diamond coatings are interpreted relying on evidence of scanning electron microscopy as well as microRaman spectroscopy. Thermal synergy component (hot filament) possesses an activating agent for diamond deposition, and contributes significantly to quality and extent of diamond deposition. Laser synergy component comprises a solid surface modification as well as the spectroactive gaseous atmosphere modification. Surface modification consists in changes of the diamond coating being deposited and, at the same time, in changes of the substrate surface structure. Laser modification of the spectroactive diamond precursor atmosphere means specific consumption of the precursor, which enables to skip the deposition on a defined substrate location. The resulting process of diamond coating elimination from certain, desired locations using the CO₂ laser might contribute to tailoring diamond coatings for particular applications. Additionally, the substrate laser modification could be optimized by choice of a proper spectroactive precursor concentration, or by a laser radiation multiple pass through an absorbing medium.

Keywords: PACS; 81.05.Uw; 81.15.GhDiamond coating; Hot filament; CO; ₂; -laser; Chemical vapour deposition; Laser and hot filament synergy; Deposition tailoring

Synthesis and characterization of single- and co-doped SnO₂ thin films for optoelectronic applications by I. Saadeddin; B. Pecquenard; J.P. Manaud; R. Decourt; C. Labrugère; T. Buffeteau; G. Campet (pp. 5240-5249).

Doped SnO₂ thin films have been prepared by sputtering from two different targets: antimony doped tin oxide (ATO) and antimony and zinc doped tin oxide (AZTO). In the case of ATO ceramic, the antimony amount only reaches 0.012mol per formula unit due to its evaporation at high temperature while the presence of Zn²⁺ in AZTO prevents the antimony evaporation, greatly enhances the ceramic density and allows the deposition of thin films with a high deposition rate. Both types of thin films have a dense morphology with a smooth surface and they are polycrystalline. For post-annealed ATO thin films, the Drude model was applied to deduce the carrier concentration, the optical mobility as well as the resistivity. The carrier concentration is around ten times higher for ATO thin films compared to AZTO. The two combined effects (higher carrier concentration and mobility) for ATO thin films doped with 1.2% of Sb lead to the best optoelectronic performances, confirming previous results obtained with ceramics. Nevertheless, we have a better opportunity to modulate the conductivity in the case of AZTO thin films.

Keywords: Antimony and/or zinc-doped tin oxide; Sputtering; Transparent conducting film

Influence of surface treatment on the electroless nickel plating of textile fabric by C.W.M. Yuen; S.Q. Jiang; C.W. Kan; W.S. Tung (pp. 5250-5257).

The present study is performed with an objective to acquire a deeper understanding of the properties of nickel-plated polyester fabric after conducing low temperature plasma treatment. Low temperature plasma treatment with oxygen and argon gases was employed to render a hydrophilic property of woven polyester fabrics and facilitate the absorption of a palladium catalyst in order to provide a catalytic surface for electroless nickel plating. The properties of plasma-induced electroless nickel-plated polyester fabrics were evaluated by various standard testing methods in terms of both physical and chemical performances.

Keywords: Surface; Low temperature plasma; Electroless nickel plating; Polyester; Fibre

Laser removal of loose uranium compound contamination from metal surfaces by D.E. Roberts; T.S. Modise (pp. 5258-5267).

Pulsed laser removal of surface contamination of uranyl nitrate and uranium dioxide from stainless steel has been studied. Most of the loosely bound contamination has been removed at fluence levels below 0.5Jcm⁻², leaving about 5% fixed contamination for uranyl nitrate and 15% for uranium dioxide. Both alpha and beta activities are then sufficiently low that contaminated objects can be taken out of a restricted radiation area for re-use. The ratio of beta to alpha activity is found to be a function of particle size and changes during laser removal. In a separate experiment using technetium-99m, the collection of removed radioactivity in the filter was studied and an inventory made of removed and collected contamination.

Keywords: PACS; 42.62.Cf; 81.65.CfLaser; Decontamination; Uranium; Radioactive; Cleaning; Surface

Effect of aluminum on the corrosion behavior of NiTiAl thin films by K.T. Liu; J.G. Duh (pp. 5268-5273).

An electrochemical study for the evaluation of corrosion behavior using potentiodynamic and Tafel techniques was conducted in 0.9% NaCl solution on Ni-Ti and Ni-Ti-Al shape memory thin films. Atomic force microscopy (AFM) and electron probe microanalyzer (EPMA) were applied to observe morphology of the surface film and elemental distribution, respectively, prior to and after immersion in 0.9% NaCl solution. The concentration of dissolved Ni from Ni-Ti-Al thin films in the electrolyte, measured with inductively coupled plasma atomic emission spectrometer (ICP-AES), was significantly lower after immersion for 7 days, as compared to Ni-Ti thin film. This demonstrated that a better corrosion resistance and lower corrosion current density were revealed for Ni-Ti-Al thin films than that for Ni-Ti thin film. The improved corrosion performance of Ni-Ti-Al thin films would be potentially beneficial for related biological applications. This was attributed to the introduction of aluminum after exposure to an aqueous environment.

Keywords: Ni-Ti; Ni-Ti-Al; Potentiodynamic; Tafel; Thin films; Dissolution of nickel; ICP-AES; Corrosion resistance

A comparative study of the adsorption equilibrium of progesterone by a carbon black and a commercial activated carbon by Cristóbal Valenzuela-Calahorro; Antonio Navarrete-Guijosa; Mostafa Stitou; Eduardo M. Cuerda-Correa (pp. 5274-5280).

In this paper the adsorption process of a natural steroid hormone (progesterone) by a carbon black and a commercial activated carbon has been studied. The corresponding equilibrium isotherms have been analyzed according to a previously proposed model which establishes a kinetic law satisfactorily fitting the C versus t isotherms. The analysis of the experimental data points out the existence of two well-defined sections in the equilibrium isotherms. A general equation including these two processes has been proposed, the global adsorption process being fitted to such equation. From the values of the kinetic equilibrium constant so obtained, values of standard average adsorption enthalpy (ΔH°) and entropy (ΔS°) have been calculated. Finally, information related to variations of differential adsorption enthalpy (ΔH) and entropy (ΔS) with the surface coverage fraction (θ) was obtained by using the corresponding Clausius–Clapeyron equations.

Keywords: Adsorption; Equilibrium; Isotherms; Carbon blacks; Activated carbon; Progesterone

Ultrastructural organization of premature condensed chromosomes at S-phase as observed by atomic force microscopy by Fan Yihui; Zhang Xiaohong; Bai Jing; Mao Renfang; Zhang Chunyu; Lei Qingquan; Fu Songbin (pp. 5281-5286).

In this study, we used calyculin A to induce premature condensed chromosomes (PCC). S-phase PCC is as “pulverized” appearance when viewed by light microscopy. Then, we applied atomic force microscopy (AFM) to investigate the ultrastructual organization of S-phase PCC. S-phase PCC shows ridges and grooves as observed by AFM. After trypsin treatment, chromosome surface roughness is increased and chromosome thickness is decreased. At high magnification, the ridges are composed of densely packed 30nm chromatin fibers which form chromosome axis. Around the ridges, many 30nm chromatin fibers radiate from center. Some of the 30nm chromatin fibers are free ends. The grooves are not real “gap”, but several 30nm chromatin fibers which connect two ridges and form “grid” structure. There are four chromatin fibers detached from chromosome: two free straight 30nm chromatin fibers, one loop chromatin fiber and one straight combining with loop chromatin fiber. These results suggested that the S-phase PCC was high-order organization of 30nm chromatin fibers and the 30nm chromatin fibers could exist as loops and free ends.

Keywords: Calyculin A; Premature condensed chromosomes (PCC); Ultrastructual organization; Atomic force microscopy (AFM)

Properties of dc magnetron sputtered Cu₂O films prepared at different sputtering pressures by A. Sivasankar Reddy; S. Uthanna; P. Sreedhara Reddy (pp. 5287-5292).

The sputtering pressures maintained during the deposition of Cu₂O films, by dc reactive magnetron sputtering, influence the structural, electrical and optical properties. The crystalline orientation mainly depends on the sputtering pressure. The films deposited at a sputtering pressure of 4Pa showed single-phase Cu₂O films along (111) direction. The electrical resistivity of the films increased from 1.1×10¹Ωcm to 3.2×10³Ωcm. The transmittance of the films increased from 69% to 88% with the increase of sputtering pressure from 2.5Pa to 8Pa.

Keywords: Cuprous oxide; Magnetron sputtering; Structure; Electrical; Optical properties

Direct micropatterning of high dielectric BaTiO₃ films by laser-induced pyrolysis with a nano-crystalline seeding technique by Yoshio Kobayashi; Kenshi Miyajima; Daisuke Nagao; Akira Watanabe; Shinji Yamada; Takao Miwa; Mikio Konno (pp. 5293-5301).

A direct patterning method of dielectric BaTiO₃ (BT) films is proposed, which applies laser-induced pyrolysis in combination with nano-crystalline seeding technique. A precursor solution of a BT complex alkoxide containing BT nano-crystalline particles with polyvinylpyrollidone (PVP) as dispersion stabilizer was spin-coated on Pt substrate. An Ar⁺ laser beam was focused and scanned on spin-coated BT films, which induced pyrolysis and crystallization of the films with spatial selectivity. Micropatterns were obtained by striping laser-unirradiated regions on the films with HCl aqueous solution. Raman spectra of the micropattern confirmed that the structures were tetragonal crystalline BT. Clear micropatterns with a line width of ca. 3μm and an interval of 5μm were formed at PVP concentrations of 25 and 50kg/m³. The dielectric constant and dissipation factor of the film fabricated at a laser energy density of 27MW/cm² and a scanning speed of 25μm/s attained 76.2 and 0.07, respectively, for a measurement frequency of 100kHz.

Keywords: Micropattern; Laser-induced pyrolysis; BaTiO; ₃; Crystallization; Dielectric properties; Raman spectroscopy

Influence of bilayer periods on structural and mechanical properties of ZrC/ZrB₂ superlattice coatings by J. Yang; M.X. Wang; Y.B. Kang; D.J. Li (pp. 5302-5305).

ZrC/ZrB₂ multilayered coatings with bilayer periods ranging from 4.4 to 35.5nm were synthesized by r.f. magnetron sputtering. X-ray diffraction, scanning electron microscopy and nanoindention were employed to investigate the microstructure and mechanical properties of the nanoscale multilayers. The results indicated that all coatings had the clear multilayered structure with mixed ZrB₂(001), ZrB₂(002) and ZrC(111) preferred orientations. The maximum hardness (41.7GPa) was observed in the multilayer with 27.5-nm thick period, which is about 25% higher than the rule-of-mixture value of the monolithic ZrC and ZrB₂ coatings. It also exhibited the best adhesion. Its critical load was over 70mN. While through insert ZrB₂ into ZrC layer periodically, higher residual stress built in ZrC layer can be released.

Keywords: PACS; 68.65.Ac; 81.15.Cd; 81.65.Lp; 81.40.Npr.f. magnetron sputtering; ZrC/ZrB; ₂; multilayered coatings; Nanoscale

The resistance to wear and corrosion of laser-cladding Al₂O₃ ceramic coating on Mg alloy by Gao Ya-li; Wang Cun-shan; Yao Man; Liu Hong-bin (pp. 5306-5311).

The paper presents a study on the preparation of Al₂O₃ ceramic coating on AZ91HP Mg alloy by laser remelting plasma-sprayed coating. It was found that after laser remelting, the coating exhibited obvious layer-like characteristics due to influence of temperature distribution, thermophysical parameters and layer thickness. According to the microstructural difference, the coating can be divided into the melted zone with the α-Al₂O₃ column-like crystal, the sintered zone with flock-like structure, the residual plasma-sprayed zone with loosened structure. Because of the dense column-like crystal, the hardness, wear and corrosion resistance of the laser remelted coating are much higher than those of the plasma-sprayed coating and as-received Mg alloy.

Keywords: Magnesium alloy; Al; ₂; O; ₃; ceramic coating; Plasma spraying; Laser remelting

Titanium oxynitride thin films sputter deposited by the reactive gas pulsing process by Jean-Marie Chappé; Nicolas Martin; Jan Lintymer; Fabrice Sthal; Guy Terwagne; Jamal Takadoum (pp. 5312-5316).

DC reactive sputtering was used to successfully make thin films of titanium oxynitride using titanium metallic target, argon as plasma gas and nitrogen and oxygen as reactive gases. The nitrogen partial pressure was kept constant during every deposition whereas oxygen flow rate was pulsed using a square pattern. The study consisted in analysing the influence of the shape of the pulsed rate on physical properties of these films. In order to adjust the metalloid concentration to get films with a wide range of oxygen-to-nitrogen ratios, the reactive gas pulsing process (RGPP) was used. In this process, the oxygen flow switches “on” and “off” periodically according to a duty cycle α= t_ON/ T. Electrical conductivity of films measured against temperature was gradually modified from metallic ( σ_300K=4.42×10⁴Sm⁻¹) to semi-conducting behaviour ( σ_300K=7.14Sm⁻¹) with an increasing duty cycle. Mechanical properties like nanohardness ( H_n) and reduced Young's modulus ( E_r) of the films were investigated. Experimental values of H_n and E_r obtained by nanoindentation at 10% depth ranged from 15.8 to 5.2GPa and from 273 to 142GPa, respectively. Evolutions of H_n and E against duty cycle were similar. A regular decrease was observed for duty cycle α≤25% corresponding to the occurrence of TiO_xN_y phase. Higher duty cycles led to the smallest values of H_n and E and correlated with TiO₂ compound composition. At last, the colour variation of these titanium oxynitrides was investigated as a function of α in the L^* a^* b^* colour space. It was related to the chemical composition of the films.

Keywords: PACS; 81.15.-z 81.15.CdTitanium oxynitride; Thin films; Reactive sputtering; Reactive gas pulsing process

Synthesis of GaN phase by ion implantation by Vikas Baranwal; Richa Krishna; Fouran Singh; Ambuj Tripathi; Avinash C. Pandey; Dinakar Kanjilal (pp. 5317-5319).

GaN phase is synthesized using systemic implantation of nitrogen ions of multiple energies (290, 130 and 50keV) into Zn-doped GaAs (100) at room temperature and subsequent annealing at 850°C for 30min in Ar+H₂ atmosphere. The implanted doses of nitrogen ions are 5×10¹⁶ and 1×10¹⁷ions-cm⁻². Glancing angle X-ray diffraction studies show that hexagonal phase of GaN were formed. The photoluminescence studies show the emission from the band edge as well as from point defects.

Keywords: PACS; 61.72.Vv; 78.55.Cr; 81.05.Ea; 61.10.NzGaN; Ion implantation; Photoluminescence; X-ray diffraction

Tuning the wettability of calcite cubes by varying the sizes of the polystyrene nanoparticles attached to their surfaces by Yongjun He; Tanliang Li; Xiangyang Yu; Shiyong Zhao; Jianhua Lu; Jia He (pp. 5320-5324).

The wettability of calcite cubes was tuned by varying the sizes of the polystyrene nanoparticles attached to their surfaces via a dispersion polymerization. The products were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersion spectrum (EDS) and Fourier transformation infrared spectrum (FTIR). The results showed that the hydrophobicity of the calcite cubes was enhanced with the increase of the size of the polystyrene nanoparticles attached. Using polystyrene nanoparticle-attached calcite cubes (PNACC) as emulsifiers, stable water-in-tricaprylin Pickering emulsions were produced. By gelling the water droplets of the Pickering emulsions, the hierarchical structures of polystyrene nanoparticle-attached calcite cube-armored microspheres were obtained. The polystyrene nanoparticle-attached calcite cubes were expected to have novel surface properties similar neither to traditional Pickering particles, nor to macroscopically asymmetrical Janus particles.

Keywords: PACS; 81.16Wettability; Calcite cubes; Polystyrene; Nanoparticles; Pickering emulsions

Surface sensitive probe of the morphological and structural aspects of CdSe core–shell nanoparticles by Himani Sharma; Shailesh N. Sharma; Sukhvir Singh; Ram Kishore; Gurmeet Singh; S.M. Shivaprasad (pp. 5325-5333).

The promising technological applications of colloids of CdSe nanoparticles in solid state devices is hampered due to issues related to their stoichiometry, agglomeration effects and core–shell relationship. Due to the short inelastic mean free path of core-level electrons, X-ray photoelectron spectroscopy is the most reliable method for analysis at the nanometer depth scale, and in conjunction with layer by layer ion beam erosion it can provide valuable information regarding distribution of elements along the depth of the sample. In this work, we address the issue of synthesis of CdSe nanoparticles and probing them by XPS and conventional techniques such as like transmission electron microscopy (TEM) and X-ray diffraction (XRD). Cd/Se input precursor ratio is varied to form colloidal TOP/TOPO capped CdSe nanoparticles. An optimum input precursor ratio is determined where stoichiometric yield, efficiently capped smallest sized (∼5nm) CdSe nanoparticles with superior optical, structural and morphological properties are obtained. Electron diffraction and deconvolution of XPS-core-levels enables the identification of the different compositional regimes of CdSe nanocrystallites. For non-optimal precursor ratios, the presence of Cd- and Se-related oxides are observed. This multi-technique approach has enabled us to pictorially model the compositional, structural and morphological aspects of TOP/TOPO capped CdSe nanoparticles.

Keywords: CdSe nanoparticles; XPS; TEM; TOP/TOPO capping

Hydrogen induced voids in hydrogenated amorphous silicon carbon (a-SiC:H): Results of effusion and diffusion studies by Rosari Saleh; Lusitra Munisa; Wolfhard Beyer (pp. 5334-5340).

The void formation in Si-rich a-SiC:H films deposited with dc magnetron sputtering is studied by effusion measurements of hydrogen and of implanted rare gases and secondary ion mass spectrometry (SIMS). Rare gas atoms were incorporated into the material by ion implantation. The results suggest a widening of the network openings with increasing alloy concentration. However, the void formation is mainly attributed not to an increase in carbon concentration but to an increase in hydrogen incorporation.

Keywords: Amorphous alloys; SIMS; Implantation

Electrical properties of purified solar grade silicon substrates using a combination of porous silicon and SiCl₄ by M. Hajji; M. Hassen; H. Ezzaouia; A. Selmi; H. Bouchriha (pp. 5341-5344).

This work investigates the photo-thermal treatment of solar grade (SG) silicon to reduce impurities to a low level suitable for high efficiency low-cost solar cells application. It describes experiment carried out by using a tungsten lamps furnace (rapid thermal processing, RTP) to purify solar grade silicon wafers using a combination of porous silicon (PS) and silicon tetrachloride. This process enables to attract the impurities towards the porous layer where they react with SiCl₄ to form metallic chlorides. The gettering effect was studied using the Hall Effect and the Van Der Pauw methods to measure the resistivity, the majority carrier concentration and mobility. We have obtained a significant improvement of the majority carrier mobility after such thermo-chemical treatment. The gettering efficiency is also evaluated by the relative increase of the minority carrier diffusion length L, measured by the light beam induced current (LBIC) technique.

Keywords: Silicon; Porous silicon; Silicon tetrachloride; Gettering

Built-in electric field effect on hydrogenic impurity in wurtzite GaN/AlGaN quantum dot by C.X. Xia; S.Y. Wei; X. Zhao (pp. 5345-5348).

The binding energy of a hydrogenic donor impurity in a wurtzite (WZ) GaN/AlGaN quantum dot (QD) is investigated, including the strong built-in electric field effect due to the spontaneous and piezoelectric polarizations. Numerical results show that the strong built-in electric field induces an asymmetrical distribution of the donor binding energy with respect to the center of the QD. The donor binding energy is insensitive to dot height when the impurity is located at the right boundary of the QD with large dot height.

Keywords: PACS; 73.21.La; 71.55.; −; i; 77.65.LyQuantum dot; Hydrogenic impurity; Built-in electric field

Microstructure evolution occurring in the modified surface of 316L stainless steel under high current pulsed electron beam treatment by Shengzhi Hao; Pingsheng Wu; Jianxin Zou; Thierry Grosdidier; Chuang Dong (pp. 5349-5354).

High current pulsed electron beam (HCPEB) surface treatment of 316L stainless steel (SS) was carried out with a wide spectrum of treating parameters. Microstructure changes occurring in the modified surface were characterized with microscopy, X-ray diffractometry and electron backscatter diffractometry (EBSD) techniques. The evolution regularities of surface craters and microstructure refinement, as well as preferred orientation of (111) crystal planes were discussed on considering the coupled temperature-stress fields formed in surface layers after an absorption of HCPEB energy.

Keywords: PACS; 61.80.Fe; 81.65.–b; 61.66.–fHigh current pulsed electron beam (HCPEB); Surface treatment; 316L stainless steel; Microstructure

Effect of accelerated weathering on surface chemistry of modified wood by Ali Temiz; Nasko Terziev; Morten Eikenes; Jonas Hafren (pp. 5355-5362).

In this study, the effects of UV-light irradiation and water spray on colour and surface chemistry of scots pine sapwood samples were investigated. The specimens were treated with chromated copper arsenate (CCA), a metal-free propiconazol-based formulation, chitosan, furfuryl alcohol and linseed and tall oils. The weathering experiment was performed by cycles of 2h UV-light irradiation followed by water spray for 18min. The changes at the surface of the weathered samples were characterised by Fourier transform infrared spectroscopy (FT-IR); colour characterizations were performed by measuring CIELab parameters.The results show that all treatment methods except chitosan treatment provided lower colour changes than the control groups after 800h exposure in weathering test cycle, but differences between chitosan and control were also small. The lowest colour changes were found on linseed oil (full cell process) and CCA treated wood. FT-IR results show that oil treatment (linseed and tall oil) decreased the intensities of a lignin specific peak (1500–1515cm⁻¹). Absorption band changes at 1630–1660cm⁻¹ were reduced by all treatments.

Keywords: Chitosan; Colour changes; FT-IR; Furfurylation; Linseed oil; Tall oil; Weathering; Wood modification

Strengthening sapphire at elevated temperatures by SiO₂ films by Li-Ping Feng; Zheng-Tang Liu; Qiang Li (pp. 5363-5367).

SiO₂ films have been prepared on sapphire by radio frequency magnetron reactive sputtering in order to increase the optical and mechanical properties of infrared windows and domes of sapphire at elevated temperatures. Infrared transmission and flexural strength of uncoated and coated sapphires have been investigated at different temperatures. SiO₂ films were shown to have apparent antireflective effect on sapphire substrate at room temperature. With increasing temperature, the coated sapphires have larger average transmission than the uncoated ones. The temperature was proven to only weakly affect the absorption coefficient and antireflection capability of the deposited films. It is also indicated that the flexural strengths of the c-axis sapphire samples coated with SiO₂ films are increased by 1.2 and 1.5 times than those of uncoated at 600 and 800°C, respectively.

Keywords: PACS; 68.35.Ct; 78.30.−j; 81.15.Cd; 81.65.−bTransmission; Flexural strength; Sapphire; SiO; ₂; films

Growth and surface characterization of sputter-deposited molybdenum oxide thin films by C.V. Ramana; V.V. Atuchin; V.G. Kesler; V.A. Kochubey; L.D. Pokrovsky; V. Shutthanandan; U. Becker; R.C. Ewing (pp. 5368-5374).

Molybdenum oxide thin films were produced by magnetron sputtering using a molybdenum (Mo) target. The sputtering was performed in a reactive atmosphere of an argon–oxygen gas mixture under varying conditions of substrate temperature ( T_s) and oxygen partial pressure ( pO₂). The effect of T_s and pO₂ on the growth and microstructure of molybdenum oxide films was examined in detail using reflection high-energy electron diffraction (RHEED), Rutherford backscattering spectrometry (RBS), energy-dispersive X-ray spectrometry (EDS), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) measurements. The analyses indicate that the effect of T_s and pO₂ on the microstructure and phase of the grown molybdenum oxide thin films is remarkable. RHEED and RBS results indicate that the films grown at 445°C under 62.3% O₂ pressure were stoichiometric and polycrystalline MoO₃. Films grown at lower pO₂ were non-stoichiometric MoO_x films with the presence of secondary phase. The microstructure of the grown Mo oxide films is discussed and conditions were optimized to produce phase pure, stoichiometric, and highly textured polycrystalline MoO₃ films.

Keywords: MoO; ₃; thin films; Sputter deposition; Substrate temperature; Oxygen pressure; Growth; Microstructure

Laser activation-modification of semiconductor surfaces (LAMSS) of 1-alkenes on silicon: A ToF-SIMS, chemometrics, and AFM analysis by Lei Pei; Guilin Jiang; Robert C. Davis; Jeremy M. Shaver; Vincent S. Smentkowski; Matthew C. Asplund; Matthew R. Linford (pp. 5375-5386).

Laser-activation-modification of semiconductor surfaces (LAMSS) was carried out on silicon with a series of 1-alkenes. These laser spots were studied by time of flight secondary ion mass spectrometry (ToF-SIMS). The resulting spectra were analyzed using the multivariate curve resolution (MCR) method within the Automated eXpert Spectral Image Analysis (AXSIA) toolkit, and also by MCR and cluster analysis using commercially available toolboxes for Matlab: the PLS_Toolbox and the MIA_Toolbox, respectively. AXSIA based MCR generally finds three components for the spectral images: one for the background and two for the laser-activated spots, for both the positive and negative ion images. The negative ion component spectra from the spots show increased carbon and hydrogen signals compared to oxygen. They also show reduced chlorine and fluorine (contamination) peaks. In order to compare AXSIA–MCR results from different images, the AXSIA component spectra of different spots were further analyzed by principal components analysis (PCA). PCA of all of the negative ion components shows that component 1 is chemically distinct from components 2 and 3. PCA of all of the positive ion components yields the same result. The loadings plots of this PCA analysis confirm that component 1 generally contains fragments expected from the substrate, while components 2 and 3 contain fragments expected from an overlayer composed of alkyl chains in the spots. A comparison of the two MCR analyses suggests that roughly the same information can be obtained from AXSIA, which is not commercially available, and the PLS_Toolbox. Cluster analysis of the data also clearly separates the spots from the backgrounds. A key finding from these analyses is that the degree of surface functionalization in a LAMSS spot appears to decrease radially from the center of the spot. Finally, a comparison of atomic force microscopy (AFM) of the spots versus the AXSIA analysis of the ToF-SIMS data produced another important result, which is that the surface morphology is only weakly correlated with the LAMSS chemistry.

Keywords: ToF-SIMS; Chemometrics; Laser; Silicon; MCR

Adsorption on nanostructured chiral surfaces studied by the Monte Carlo method by Paweł Szabelski (pp. 5387-5392).

A Monte Carlo (MC) lattice gas model of adsorption of a racemic mixture of enantiomers of 1,2-dimethylcyclopropane on a chiral surface with different spatial distribution of active sites was proposed. The calculations were performed on a square lattice for both stepped chiral surfaces and smooth surfaces with chiral patterns of active sites. The adsorbing molecules were assumed to be rigid structures of two types being mirror images one of another. Regardless of the enantiomer type, each molecule was composed of four segments occupying four lattice sites. The chiral surfaces were exposed to equimolar mixture of enantiomers whose individual equilibrium adsorption isotherms were calculated using standard Grand Canonical MC technique. The major purpose of the simulation was to examine how the structure of the surface affects separation of enantiomers, that is, to determine enantioselectivity defined as the ratio of their adsorbed amounts. Additionally, comparison of the enantioselectivities corresponding to the stepped and smooth surfaces was made.

Keywords: PACS; 68.43.-h; 68.43.De; 68.03.HjChiral surfaces; Adsorption; Monte Carlo simulation; Enantioseparation

Investigation of monolayer dispersion of benzoic acid supported on the surface of H-titanate nanotubes by Wei Wang; Jingwei Zhang; Huizhong Huang; Zhishen Wu; Zhijun Zhang (pp. 5393-5399).

Benzoic acid (BA) can disperse spontaneously onto the surface of H-titanate nanotubes (HTNTs) in a sub-monolayer state by heating mechanical mixtures method. The structure of BA–HTNTs system has been characterized by X-ray diffraction (XRD), thermogravimetric (TG), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) in detail. The results show that the H-bond association structure among BA molecules collapses and the carboxyl groups react with the surface hydroxyl group of HTNTs to form a salt-like structure on the surface after dispersion. The monolayer dispersion capacity determined by XRD is ca. 0.305g BAg⁻¹ HTNTs, which is lower than the utmost monolayer dispersion capacity 0.550g BAg⁻¹ HTNTs calculated according to a model that the benzene ring in BA molecules is perpendicular to the surface of HTNTs. At the same time, the dispersion capacity is also measurement by the fit of C 1s XPS peak at various BA loadings at first time.

Keywords: Monolayer dispersion; Threshold; XPS; H-titanate nanotubes; Benzoic acid

Photoelectron-spectroscopic and reactivity investigation of thin Pd–Sn films prepared by magnetron sputtering by T. Skála; K. Veltruská; L. Sedláček; K. Mašek; I. Matolínová; V. Matolín (pp. 5400-5403).

We have studied Pd–Sn layers with different composition prepared by magnetron sputtering. Layers were sputtered onto Al₂O₃ and SiO₂ substrates and studied by X-ray photoelectron spectroscopy (XPS). Spectra confirmed that after vacuum annealing residual oxygen and carbon have been removed and bimetallic bonds have been created. The shift of Pd 3d_5/2 core level to higher binding energy followed by the peak narrowing in dependence on the composition was observed, accompanied by the shift of the Pd 4d in the valence band region, induced by hybridization of Pd-d and Sn-s,p states. Experiments carried out on a gas-flow reactor indicate increasing temperature of the CO oxidation with tin ratio in the alloy.

Keywords: PACS; 81.15.Cd; 81.05.Bx; 61.43.Dq; 79.60.Dp; 33.60.FyPalladium; Tin; Alloys; XPS; Magnetron sputtering; CO oxidation

Patterning of amorphous and polycrystalline Ni₇₈B₁₄Si₈ with a focused-ion-beam by Wuxia Li; Roussi Minev; Stefan Dimov; Georgi Lalev (pp. 5404-5410).

The machining response of amorphous and crystalline Ni₇₈B₁₄Si₈ was investigated when structuring substrates using focused-ion-beam (FIB) milling. In particular, the sputtering yield as a function of the scan speed, and the effects of ion fluence and scan speed on the milled depth were studied. The ion fluence dependent evolution of the cross-sectional profiles of trenches was examined by atomic force microscopy (AFM). When milling amorphous Ni₇₈B₁₄Si₈, it was found that the sputtering yield first decreased with increasing the beam scan speed, then kept constant within the scan speed range, up to 710nm/s, investigated in this work; it was also found that the milled depth was almost proportional to the ion beam fluence. The patterning of polycrystalline Ni₇₈B₁₄Si₈ resulted in anisotropic milling-rates due to the varying orientation of the grains in the material. The analysis of the profile evolution in both materials indicated that the surface finish of trenches was scan speed, ion beam fluence and scan strategy dependent. The study demonstrated that direct patterning by FIB could be used for producing masters in amorphous Ni-based alloys for injection moulding and hot embossing.

Keywords: PACS; 89.20.-a; 81.20.Wk; 81.16.Rf; 61.82.MsFocused-ion-beam; Patterning; Ni; ₇₈; B; ₁₄; Si; ₈; alloys; Micro/nano-tooling

Nitridation of the SiO₂/4H–SiC interface studied by surface-enhanced Raman spectroscopy by S.H. Choi; D. Wang; J.R. Williams; M. Park; W. Lu; S. Dhar; L.C. Feldman (pp. 5411-5414).

We employ surface-enhanced Raman spectroscopy (SERS) to investigate the effect of nitridation on interfacial carbon at the SiO₂/4H–SiC interface. These results demonstrate that the interfacial carbon clusters are strongly modified by post-nitridation process and the nitrogen take-up correlates with the reduction in the interface state density.

Keywords: SERS; 4H–SiC

Effect of laser-etched indium tin oxide on optoelectrical properties of organic light-emitting diodes by Jian-Feng Li; Shui-Hsiang Su; Kao-Shing Hwang; Meiso Yokoyama (pp. 5415-5418).

This study investigated how laser and wet etching methods of ITO substrates affect the optoelectrical properties of OLEDs. Experimental results indicated that the OLED with a laser-etched ITO substrate has a lower driving voltage than that with a wet-etched ITO substrate. According to scanning electron microscopy (SEM) and atomic force microscopy (AFM) measurements, the ITO etching methods yielded different surface morphologies of ITO pattern edges. The lower luminance of the OLED with a laser-etched ITO substrate is attributable to the fringe at the edge of ITO pattern, which causes a high local electric field resulting in the recrystallization of organic materials.

Keywords: PACS; 81.65.Cf; 85.60.Bt; 72.80.Le; 78.60.FiOrganic light-emitting diode; Indium tin oxide; Laser-etched; Recrystallization

Influence of pH value on the quality of sol–gel derived ZnO films by Parmod Sagar; P.K. Shishodia; R.M. Mehra (pp. 5419-5424).

In sol–gel derived ZnO films the pH value of the sol plays an important role in controlling their properties. In this study, the influence of adding monoethanolamine to zinc acetate solution in methanol on structural, surface morphology and optical properties has been investigated. Addition of monoethanolamine to zinc acetate solution transforms the nature of the sol from acidic to alkaline by changing the pH value from 6.4 to 10.6. The investigations indicate that high quality ZnO films are obtained by using sol having monoethanolamine to zinc acetate ratio of 1:1 and pH value of 10.6.

Keywords: PACS; 71.55.Gs; 78.55.Et; 81.20.FwZinc oxide; Thin films; Sol–gel; MEA; pH; Photoluminescence

Phase transformation of graphite irradiated by high-intensity pulsed ion beams by X.G. Han; S.M. Miao; X.P. Zhu; M.K. Lei (pp. 5425-5430).

The microstructure and morphology of graphite irradiated by high-intensity pulsed ion beams (HIPIB) has been studied by varying the ion current density as 200, 350 and 1500A/cm² with one to five shots. Phase transformation from graphite to diamond-like carbon (DLC) on the HIPIB-irradiated graphite was confirmed by Raman spectroscopy where a typical broadened asymmetric peak appeared in the wavenumber range of 1100–1700cm⁻¹. Formation of DLC on the irradiated graphite strongly depended on the HIPIB parameters and preferably took place at the medium ion current density of 350A/cm² up to five shots. Numerical simulation of ablation process was performed to explore the transformation mechanism of DLC from graphite irradiated by HIPIB. The calculation showed that the temperature profile in irradiated graphite at 350A/cm² is almost identical to that at 200A/cm², showing a deeper heat-affected zone in comparison with that of 1500A/cm². Moreover, the ablation depth per shot is around 0.8μm at 350A/cm², higher than that of 0.4μm at 200A/cm² and much lower than that of 8.4μm at 1500A/cm², respectively. The experimental and numerical results indicate that a proper temperature and pressure repetitively created in the top layer of ablated graphite during HIPIB irradiation facilitates the phase transformation.

Keywords: High-intensity pulsed ion beam; DLC; Graphite; Ablation

Structure and RT ferromagnetism of Fe-doped AlN films by X.D. Gao; E.Y. Jiang; H.H. Liu; W.B. Mi; Z.Q. Li; P. Wu; H.L. Bai (pp. 5431-5435).

Al1−_xFe_xN1−_δ thin films with 0≤ x≤13.6% were deposited by dc magnetron co-sputtering at room temperature (RT). It is found that Fe atom will substitutes the Al atom in the lattice when x≤1.2%, while it will embed into the interstice of the lattice at larger Fe content. RT ferromagnetism was observed in all doped samples. A maximum saturated magnetization 2.81emu/cm³ of the film is found to be induced by AlFeN ternary alloy when x=1.2%.

Keywords: PACS; 68.55.−a; 75.50. Pp; 75.70. Ak; 81.15.Cd; 71.20.NrFe-doped AlN film; Semiconductors–ferromagnetic; RT ferromagnetism

Surface modification of poly(propylene carbonate) by oxygen ion implantation by Jizhong Zhang; Jiachen Kang; Ping Hu; Qingli Meng (pp. 5436-5441).

Poly(propylene carbonate) (PPC) was implanted by oxygen ion with energy of 40keV. The influence of experimental parameters was investigated by varying ion fluence from 1×10¹² to 1×10¹⁵ions/cm². XPS, SEM, surface roughness, wettability, hardness, and modulus were employed to investigate structure and properties of the as-implanted PPC samples. Eight chemical groups, i.e., carbon, CH, COC, CO, OCO, CO, ▪, and ▪ groups were observed on surfaces of the as-implanted samples. The species and relative intensities of the chemical groups changed with increasing ion fluence. SEM images displayed that irradiation damage was related strongly with ion fluence. Both surface-recovering and shrunken behavior were observed on surface of the PPC sample implanted with fluence of 1×10¹⁵ions/cm². As increasing ion fluence, the surface roughness of the as-implanted PPC samples increased firstly, reached the maximum value of 159nm, and finally decreased down the minimum value. The water droplet contact angle of the as-implanted PPC samples changed gradually with fluence, and reached the minimum value of 70° with fluence of 1×10¹⁵ions/cm². The hardness and modulus of the as-implanted PPC samples increased with increasing ion fluence, and reached their corresponding maximum values with fluence of 1×10¹⁵ions/cm². The experimental results revealed that oxygen ion fluence closely affected surface chemical group, morphology, surface roughness, wettability, and mechanical properties of the as-implanted PPC samples.

Keywords: PACS; 61.41.+e; 61.72.Ww; 61.80.JhPoly(propylene carbonate); Oxygen ion implantation; Surface modification

Synthesis and fine patterning of organic–inorganic composite SiO₂–Al₂O₃ thick films by Q.L. Liang; G.Y. Zhao; J.G. Lu (pp. 5442-5446).

Organic–inorganic composite SiO₂–Al₂O₃ films have been prepared by sol–gel using methacryloxypropyl trimethoxysilane and aluminum sec-butoxide as the precursors. By introduction of organic groups into the inorganic backbone, the smooth and crack-free films could be readily achieved by a one-step dip-coating process, with the thickness up to 4.6μm after being post-baked at 200°C for 2h. The films presented in an amorphous phase with an acceptable chemical homogeneity. Owing to the formation of chelate rings, the gel films showed a strong photosensitivity to ultraviolet light at 325nm. The uniform fine patterns of SiO₂–Al₂O₃ thick films could be well defined by ultraviolet light imprinting simply using a mask. These performances of SiO₂–Al₂O₃ films indicate the potential for integrated optical systems.

Keywords: PACS; 61.43.Er; 78.66.Sq; 81.65.Cf; 81.20.FwSiO; ₂; –Al; ₂; O; ₃; thick film; Fine patterning; Sol–gel process

Fabrication of metal nano-structures using anodic alumina membranes grown in phosphoric acid solution: Tailoring template morphology by R. Inguanta; M. Butera; C. Sunseri; S. Piazza (pp. 5447-5456).

The influence of experimental parameters on the morphology of the porous structure and on the formation kinetics has been investigated for anodic alumina membranes (AAM) grown in aqueous H₃PO₄ at 160V. It was found that pore aspect ratio and membrane porosity on the solution-side surface are influenced by tensiostatic charge, bath temperature and the presence of Al³⁺ ions in solution. Morphological and kinetic data, recorded in different conditions, give useful information on the growth mechanism of pore channels in phosphoric acid solution.Nickel nano-structures have been fabricated using AAM as template. Electroless deposition, performed by adding the reducing agent to a suitable bath in several steps, resulted in the formation of short metal nanotubes (about 5μm long) in the upper part of the channels. Long Ni nanowires (up to 25μm) with aspect ratio higher than 100 were obtained by pulsed unipolar electrodeposition from a Watt bath. In this case, both the influence of some experimental parameters on the nanowires growth and the fast current transients during the electrodeposition steps were analyzed.

Keywords: PACS; 82.45.Mp; 81.15.−z; 81.07.DeAlumina membranes; Nickel; Nanowires; Electrodeposition

Observation of triangle pits in PbSe grown by molecular beam epitaxy by T.N. Xu; H.Z. Wu; J.X. Si; C.F. Cao (pp. 5457-5461).

PbSe thin films on BaF₂ (111) were grown by molecular beam epitaxy with different selenium beam flux. Evolution of PbSe surface morphologies with Se/PbSe beam flux ratio ( R_f) has been studied by atomic force microscopy and high-resolution X-ray diffraction. Growth spirals with monolayer steps on PbSe surface are obtained using high beam flux ratio, R_f≥0.6. As R_f decreases to 0.3, nano-scale triangle pits are formed on the surface and the surface of PbSe film changes to 3D islands when R_f=0. Glide of threading dislocations in 〈110〉{100}-glide system and Pb-rich atom agglomerations are the formation mechanism of spiral steps and triangle pits. The nano-scale triangle pits formed on PbSe surface may render potential applications in nano technology.

Keywords: PACS; 68.55.Jk; 68.37.Ps; 81.05.HdPbSe; Triangle pits; Growth spirals

Deposition of superhydrophobic nanostructured Teflon-like coating using expanding plasma arc by A. Satyaprasad; V. Jain; S.K. Nema (pp. 5462-5466).

A novel approach was used to grow nanostructured Teflon-like superhydrophobic coatings on stainless steel (SS). In this method Teflon tailings were pyrolyzed to generate fluorocarbon precursor molecules, and an expanding plasma arc (EPA) was used to polymerize these precursors to deposit Teflon-like coating. The coating shows super hydrophobic behavior with water contact angle (WCA) of 165°. The coating was observed to be uniform. It consists of nanostructured (∼80–200nm) features, which were confirmed by scanning electron microscopy. The chemical bond state of the film was determined by XPS and FTIR, which indicate the dominance of –CF₂ groups in the deposited coating. The combination of nanofeature induced surface roughness and the low surface energy imparted by Teflon-like coating is responsible for the observed superhydrophobic nature.

Keywords: Teflon-like coating; Superhydrophobicity; Expanding plasma arc; Contact angle; Nanostructure

Molecular dynamics simulation of deposition and etching of Si bombarding by energetic SiF by F. Gou (pp. 5467-5472).

In this study, SiF interaction with amorphous Si surface at normal incidence was investigated using molecular dynamics simulation at 300 and 600K. The incident energies of 50, 100 and 200eV were used. The results show that the deposition rate is not sensitive to the incident energy, while with increasing the surface temperature, the deposition rate decreases. The etch yield is sensitive to the incident energy and the surface temperature. The etch yield increases with increasing incident energy and temperature. After bombarding, a Si_xF_y interfacial layer is formed. The interfacial layer thickness increases with increasing incident energy mainly through enhanced penetration of the silicon lattice. In the interfacial layer, for SiF_x ( x=1–3) species, SiF is dominant and only little SiF₃ is present. At the outmost and innermost of the interfacial layer, SiF species is dominant. Most of SiF₃ species is concentrated above the initial surface.

Keywords: PACS; 52.65.Yy; 81.65.Cf; 52.77.DqMolecular dynamics methods; Surface etching; Plasma-based ion implantation and deposition

Surface modification of ZnO nanocrystals by Y.L. Wu; A.I.Y. Tok; F.Y.C. Boey; X.T. Zeng; X.H. Zhang (pp. 5473-5479).

Nano-crystalline ZnO particles were synthesized using alcoholic solutions of zinc acetate dihydrate through a colloidal process. Five types of capping agents: 3-aminopropyl trimethoxysilane (Am), tetraethyl orthosilicate (TEOS), mercaptosuccinic acid (Ms), 3-mercaptopropyl trimethoxysilane (Mp) and polyvinylpyrrolidone (Pv) were added at the first ZnO precipitation time (first PPT) to limit the particle growth. The first three capping agents effectively capped the ZnO nanoparticles and limited the growth of the particles, while the last two capping agents caused agglomeration or larger clusters in the solutions. Particles synthesized were in the size range of 10–30nm after capping, and grew to 60 and 100nm in 3 and 6 weeks, respectively, during storage at ambient conditions. Refluxing time was found to only affect the first PPT time. Washing by ethanol and slow drying were very important in converting Zn(OH)₂ into ZnO. XRD analyses revealed single phase ZnO Wurtzite crystal structure. Photoluminescence (PL) spectra showed high-intensity in UV emission and very low intensity in the visible emission, which indicates a good surface morphology of the ZnO nanoparticles with little surface defects. Optical absorption spectra showed a blue shift by the capped ZnO due to the quantum confinement effect by the single crystal size of 5–6nm as analysed by TEM. Capping effectiveness of each agent is discussed through possible capping mechanism and chemical reaction of each capping agent. This synthesis process is a low cost, high purity, easy to control method using only bio-compatible materials.

Keywords: ZnO; Nanocrystal; Surface; Capping agent; Photoluminescence; Colloidal

Low-macroscopic field emission from silicon-incorporated diamond-like carbon film synthesized by dc PECVD by Sk.F. Ahmed; M.K. Mitra; K.K. Chattopadhyay (pp. 5480-5484).

Silicon-incorporated diamond-like carbon (Si–DLC) films were deposited via dc plasma-enhanced chemical vapor deposition (PECVD), on glass and alumina substrates at a substrate temperature 300°C. The precursor gas used was acetylene and for Si incorporation, tetraethyl orthosilicate dissolved in methanol was used. Si atomic percentage in the films was varied from 0% to 19.3% as measured from energy-dispersive X-ray analysis (EDX). The binding energies of C 1s, Si 2s and Si 2p were determined from X-ray photoelectron spectroscopic studies. We have observed low-macroscopic field electron emission from Si–DLC thin films deposited on glass substrates. The emission properties have been studied for a fixed anode–sample separation of 80μm for different Si atomic percentages in the films. The turn-on field was also found to vary from 16.19 to 3.61V/μm for a fixed anode–sample separation of 80μm with a variation of silicon atomic percentage in the films 0% to 19.3%. The turn-on field and approximate work function are calculated and we have tried to explain the emission mechanism there from. It was found that the turn-on field and effective emission barrier were reduced by Si incorporation than undoped DLC.

Keywords: PACS; 81.05.Uw; 81.05.Gc; 79.70.+q; 82.80.PvSi–DLC; EDX; XPS; Field emission; Low-threshold

An aqueous route to organically functionalized silica diatom skeletons by Christabel E. Fowler; Catherine Buchber; Bénédicte Lebeau; Joël Patarin; Cyril Delacôte; Alain Walcarius (pp. 5485-5493).

Diatomaceous earth was functionalized by grafting organotrialkoxysilane precursors onto the surface of the porous silica cell walls of this biomineral. Vinyl- and mercapto-containing structures were prepared in aqueous media without disruption of the diatomic architecture. Successful grafting of the organic moieties was confirmed using solid state²⁹Si MAS NMR spectroscopy, and the presence of the intact diatom framework by scanning electron microscopy. The sorption properties of mercaptopropyl-functionalized diatoms towards heavy metals was studied by measuring the accessibility and diffusion rates of mercury(II) species to the binding sites (-SH) by the means of electrochemical methods.

Keywords: Diatom; Functionalization; Grafting; Metal uptake

Different responses of several kinds of copolymerized polyimide films to ultraviolet irradiation by Xianqiang Pei; Qihua Wang (pp. 5494-5500).

The surfaces of three kinds of copolymerized polyimide films were irradiated by ultraviolet (UV) light. The chemical composition changes of the films after irradiation were investigated by X-ray photoelectron spectroscopy (XPS), while their topographical changes were studied by atomic force microscopy (AFM). Besides, the surface topographical variation induced changes in friction behavior were recorded on a DF·PM unidirectional friction and wear test rig in a ball on block contact configuration. It was found that photodegradation took place, which induced the chain scission of the polyimide molecules and formation of low molecular weight oxidized material (LMWOM). Due to different photostability of the three kinds of polyimide, different chemical composition changes and forms of “LMWOM” were observed. Also, different friction behavior variations of the three kinds of polyimide films were recorded. It is thought that the polyimide film of PI (PPA+PMDA) with rod-like structures might have stronger photo-resistance, whose form of “LMWOM” was “nodules” and whose friction coefficient increased at 2h of irradiation possibly due to cross-linking. In the case of PI (OPA+PMDA) and PI (MPA+PMDA) films, they mainly underwent photodegradation, which might soften the surfaces and increased the friction coefficients with increasing irradiation time.

Keywords: PACS; 94.05.Dd (Radiation processes)Polyimide film; X-ray photoelectron spectroscopy; Atomic force microscopy; Surface topography; Friction behavior; Photochemistry

Ar⁺ irradiation of Si nanocrystal-doped SiO₂: Evolution of photoluminescence by Zhi-Qiang Xie; Zheng-Hao Li; Wen-Bin Fan; Dan Chen; You-Yuan Zhao; Ming Lu (pp. 5501-5505).

We report the evolution of photoluminescence (PL) of Si nanocrystals (nc-Si) embedded in a matrix of SiO₂ during Ar⁺ ion bombardment. The integrated intensity of nc-Si PL falls down drastically before the Ar⁺ ion fluence of 10¹⁵ionscm⁻², and then decreases slowly with the increasing ion fluence. At the meantime, the PL peak position blueshifts steadily before the fluence of 10¹⁵ionscm⁻², and then changes in an oscillatory manner. Also it is found that the nc-Si PL of the Ar⁺-irradiated sample can be partly recovered after annealing at 800°C in nitrogen, but can be almost totally recovered after annealing in oxygen. The results confirm that the ion irradiation-induced defects are made up of oxygen vacancies, which absorb light strongly. The oscillatory peak shift of nc-Si can be related to a size-distance distribution of nc-Si in SiO₂.

Keywords: PACS; 79.20.−m; 78.67.Bf; 78.55.−m; 61.72.CcSi nanocrystal; Ion bombardment; Photoluminescence

Study by XPS of the chlorination of proteins aggregated onto tin dioxide during electrochemical production of hypochlorous acid by Catherine Debiemme-Chouvy; Sanae Haskouri; Hubert Cachet (pp. 5506-5510).

In solution, hypochlorous acid (HOCl) reacts with organic matter and notably with protein side-chains. In this study, HOCl was produced by an electrochemical way, by oxidation of chloride ions at a transparent tin dioxide electrode in the presence of a protein, the bovine serum albumin (BSA). A thick irregular layer is formed at the electrode when HOCl is produced at the SnO₂ surface. Indeed, SEM analyses show that an important deposit is formed during the anodic polarization of SnO₂ in the presence of chloride ions and proteins. Actually, two phenomena take place on the one hand the chlorination of the proteins due to the reaction of HOCl with some protein side-chains and on the other hand the aggregation of proteins onto the SnO₂ surface. The present X-ray photoelectron spectroscopy study points out the cross-linking of BSA molecules via formation of inter molecular sulfonamide groups. It also shows that the BSA chlorination is due on the one hand to the formation of sulfonyl chloride groups (–SO₂Cl) and on the other hand to formation of chloramine groups (N–Cl). The Cl2p and S2p photo-peak intensities allowed us to quantify the chloramines. It is found that, one BSA entity immobilized onto the SnO₂ surface contains about 50 chloramine groups.

Keywords: SnO; ₂; HClO; BSA; Protein aggregation; Chloramine; XPS; S2p; Cl2p

Accurate detection of interface between SiO₂ film and Si substrate by H.X. Qian; W. Zhou; X.M. Li; J.M. Miao; L.E.N. Lim (pp. 5511-5515).

Accurate end point detection of interface for multilayers using focused ion beam (FIB) is important in nanofabrication and IC modification. Real-time end point graph shows sample absorbed current as a function of sputtering time during FIB milling process. It is found that sample absorbed current increases linearly with ion beam current for the same material and changes when ion beam is milling through a different material. Investigation by atomic force microscope (AFM) and FIB cross-sectioning shows that accurate SiO₂/Si interface occurs to where the maximum sample absorbed current occurs. Since sample absorbed current can be real-time monitored in focused ion beam machine, the paper provides a viable and simple method for accurately determining the interface during FIB milling process for widely used SiO₂/Si system.

Keywords: PACS; 79.20.Rf; 81.20.Wk; 87.64.Dz; 07.60.PbFocused ion beam; End point; Sample absorbed current; Interface

Effect of tin-doped indium oxide film as capping layer on the agglomeration of copper film and the appearance of copper silicide by W.L. Liu; W.J. Chen; T.K. Tsai; S.H. Hsieh; C.M. Liu (pp. 5516-5520).

In this work, the effect of tin-doped indium oxide (ITO) film as capping layer on the agglomeration of copper film and the appearance of copper silicide was studied. Both samples of Cu 100nm/ITO 10nm/Si and ITO 20nm/Cu 100nm/ITO 10nm/Si were prepared by sputtering deposition. After annealing in a rapid thermal annealing (RTA) furnace at various temperatures for 5min in vacuum, the samples were characterized by four probe measurement for sheet resistance, X-ray diffraction (XRD) analysis for phase identification, scanning electron microscopy (SEM) for surface morphology and transmission electron microscopy (TEM) for microstructure.The results show that the sample with ITO capping layer is a good diffusion barrier between copper and silicon at least up to 750°C, which is 100°C higher than that of the sample without ITO capping layer. The failure temperature of the sample with ITO capping layer is about 800°C, which is 100°C higher than that of the sample without ITO capping layer. The ITO capping layer on Cu/ITO/Si can obstacle the agglomeration of copper film and the appearance of Cu₃Si phase.

Keywords: Tin-doped indium oxide; Diffusion barrier; Capping layer; Silicon substrate; Copper metallization

Graft copolymerization of acrylic acid onto polyamide fibers by Chahira Makhlouf; Stéphane Marais; Sadok Roudesli (pp. 5521-5528).

The grafting of acrylic acid (AA) monomer (CH₂CHCOOH) on polyamide 6.6 monofilaments (PA 6.6) using benzoyl peroxide (BPO) as initiator was carried out in order to enhance the hydrophilic nature of fibers. The grafting rate depends on the AA concentration, the BPO concentration, the time and the temperature of reaction.The best conditions for optimum rate of grafting were obtained with a AA concentration of 0.5M, a BPO concentration of 0.03M, a reaction temperature of T=85°C and a reaction time of 120mn.The fiber surface has been investigated by many experimental techniques of characterization such as Fourier transform infrared spectroscopy (FTIR), calorimetric analysis (DSC), scanning electron microscopy (SEM), and contact angle measurements.The effect of grafting of acrylic acid onto PA 6.6 fibers on their moisture and mechanical resistances was analyzed from water sorption and elongation at break measurements.The analysis of the experimental data shows clearly the efficiency of the grafting reaction used, leading to a significant increase of the hydrophilic character of the PA 6.6 surface.

Keywords: Graft copolymerization; Polyamide 6.6 fibers; Fourier transform infrared spectroscopy; Thermal analysis; Scanning electron microscopy; Moisture regain; Elongation at break; Contact angle measurements

Optimum designs for multi-layered film structures based on the knowledge on residual stresses by X.C. Zhang; B.S. Xu; H.D. Wang; Y.X. Wu (pp. 5529-5535).

Residual stresses are inevitably generated within the multi-layered film structures due to the mismatches of material properties between the adjacent layers. Using the force and moment equilibrium conditions and beam bending theory, the residual stresses in each layer can be predicted and expressed as σ_i( z)= E_i[ ɛ′+ K( z+ δ)], where E_i is the elastic modulus of the layer, ɛ′ the strain due to the in-plane force resulting from the misfit strain, K( z+ δ) characterizes the bending contribution. For a bilayer system, the expression of the residual stress in the film is relatively simple. If the each layer thickness is much less than the substrate thickness, Stoney's equation will be derived. The assumption of a constant elastic modulus throughout the system is only applicable when the film and the substrate thickness ratio is less than 0.1. Specific analyses are performed for the thermal stresses in ZrO₂/NiCoCrAlY thermal barrier coatings (TBCs) to illustrate the implementation of the analytical model. Moreover, the effects of single interlayer and graded interlayer inserted between the metallic layer and the ceramic layer on the residual stress distributions in TBCs are investigated. Additionally, the zero-deflection design is also discussed for typically duplex-layer TBC system.

Keywords: PACS; 05.70.−a; 62.20.−x; 65.70.+yResidual stress; Optimum design; Multi-layered film structure; Interlayer; Zero-deflection design

Evaluation of a bioluminescence method, contact angle measurements and topography for testing the cleanability of plastic surfaces under laboratory conditions by I. Redsven; H.-R. Kymäläinen; E. Pesonen-Leinonen; R. Kuisma; T. Ojala-Paloposki; M. Hautala; A.-M. Sjöberg (pp. 5536-5543).

Detection of adenosine triphosphate (ATP) by bioluminescence is used, for instance, in the food industry and in hospitals to assess the hygiene status of surfaces. The aim of this laboratory study was to investigate the feasibility of the ATP method for estimating the cleanability of resilient floor coverings from biological soil. The surfaces were worn using a Soiling and Wearing Drum Tester, and soiled and cleaned with an Erichsen Washability and Scrubbing Resistance Tester. In the laboratory test carried out with the bioluminescence method, most of the new and worn floor coverings that were biologically soiled were cleaned efficiently. According to this study, the semiquantitative ATP screening method can be used for hygiene monitoring of flooring materials. No correlation was found between cleanability and contact angles or surface topography measured using a profilometer. However, by revealing local irregularities and damage on surfaces, scanning electron micrographs appeared useful in explaining differences in cleanability.

Keywords: Cleanability; Resilient floor coverings; Hygiene monitoring; Advancing contact angle; Topography

Cemented carbide cutting tool: Laser processing and thermal stress analysis by B.S. Yilbas; A.F.M. Arif; C. Karatas; M. Ahsan (pp. 5544-5552).

Laser treatment of cemented carbide tool surface consisting of W, C, TiC, TaC is examined and thermal stress developed due to temperature gradients in the laser treated region is predicted numerically. Temperature rise in the substrate material is computed numerically using the Fourier heating model. Experiment is carried out to treat the tool surfaces using a CO₂ laser while SEM, XRD and EDS are carried out for morphological and structural characterization of the treated surface. Laser parameters were selected include the laser output power, duty cycle, assisting gas pressure, scanning speed, and nominal focus setting of the focusing lens. It is found that temperature gradient attains significantly high values below the surface particularly for titanium and tantalum carbides, which in turn, results in high thermal stress generation in this region. SEM examination of laser treated surface and its cross section reveals that crack initiation below the surface occurs and crack extends over the depth of the laser treated region.

Keywords: Laser; Cemented tool; Thermal stress; Model

Structure, electrochromic and optical properties of WO₃ film prepared by dip coating-pyrolysis by Haitao Yang; Fuliang Shang; Ling Gao; Haitao Han (pp. 5553-5557).

The tungsten oxide (WO₃) film was grown by dip coating-pyrolysis method with the PEG-400 as the structure-directing agent. Microstructure of the WO₃ film was characterized by TG-DSC, XRD and SEM techniques. It was found that the film annealed at 350°C for 2h comprised cubic WO₃ and orthorhombic WO₃. The measurements of the cyclic voltammetry (CV) and UV–vis spectrum suggested that the WO₃ film had a good electrochromic reversibility performance. The film possessed excellent modulation to the visible light and the maximal average transmittance modulation reached 70.06%.

Keywords: WO; ₃; Film; Structure; Electrochromism; Transmittance

Passivation of the surface of aluminum nanopowders by protective coatings of the different chemical origin by Young-Soon Kwon; Alexander A. Gromov; Julia I. Strokova (pp. 5558-5564).

The results of investigation and analysis of electro-exploded aluminum nanopowders, whose surface were passivated with the following substances: liquids – nitrocellulose (NC), oleic acid (C₁₇H₃₃COOH) and stearic acid (C₁₇H₃₅COOH), suspended in kerosene and ethanol, fluoropolymer; solids – boron and nickel; gases – N₂, CO₂ and air (for a comparison) are discussed. The surface protection for the aluminum nanopowders by coatings of different chemical origins leads to the some advantages of the powders properties for an application in energetic systems, e.g. solid propellants and “green” propellants (Al–H₂O). Aluminum nanopowders with a protected surface showed the increased stability to oxidation in air during the storage period and higher reactivity by heating. The TEM-visual diagram of the formation and stabilization of the coatings on the particles has been proposed on the basis of experimental results. The kinetics of the interaction of aluminum nanopowders with air has been discussed. The recommendations concerning an efficiency of the protective “non-Al₂O₃” layers on aluminum nanoparticles were proposed.

Keywords: Abbreviations; ALEX; aluminum explosive (TM); EEW; electrical explosion of wires; ANP; aluminum nanopowder; S; _sp; area of the specific surface (m2/g); a; _s; mean-surface particle diameter (nm); TEM; transmission electron microscopy; C; _Al; metal aluminum content (wt. %); TG; thermogravimetry; DSC; differential scanning calorimetry; UDP; ultra dispersed powder; EDS; energy dispersive X-ray spectrometry; XRD; X-ray diffractionAluminum; Nanopowder; Surface passivation; Oxidation; Stability; Coating; DTA–DSC–TG; TEM

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Applied Surface Science (v.253, #12)

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Applied Surface Science (v.253, #12)