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Applied Surface Science (v.253, #5)

Improving electroless Cu via filling with optimized Pd activation by P.P. Lau; C.C. Wong; L. Chan (pp. 2357-2361).

To improve the via fill capability of electroless (EL) Cu, we explored the influence of the Pd activation process prior to EL Cu deposition. We found that EL Cu roughness is closely related to the Pd nuclei size range and density, which are functions of Pd activation time. With activation time, Pd deposition goes through the sequential stages of growth, secondary nucleation, and ripening. The smoothest EL Cu film can be achieved with a Pd nucleation time that corresponds to the beginning of the ripening stage. A Pd activation process that leads to the smoothest EL Cu deposit also yields the most conformal via filling.

Keywords: PACS; 61.46.-w; 68.55.AcPalladium activation; Electroless copper; Via filling

Study of corrosion–erosion behaviour of stainless alloys in industrial phosphoric acid medium by Abdellah Guenbour; Mohamed-Adil Hajji; El Miloudi Jallouli; Ali Ben Bachir (pp. 2362-2366).

The corrosion and corrosion-abrasion resistance of some stainless steels in industrial phosphoric acid 30% P₂O₅ has been studied using electrochemical techniques. The corrosion rate of materials increases with the increase of temperature. Alloys which contain chromium, molybdenum and nitrogen in sufficient quantities present the best behaviour.In the abrasion-corrosion conditions, the experimental device set up allowed to follow continually samples electrochemical behaviour. Under dynamic conditions and without solid particles, the increase of acid projection speed has no effect on the alloys corrosion behaviour. The adding of abrasive leads to a general increase of corrosion rate and to a decrease of material resistance. Under these conditions, materials attack is controlled by synergistic effect between the abrasion and the impurities. The cast 30% Cr shows good resistance according to his high chromium content.

Keywords: Corrosion-abrasion; Dynamic conditions; Stainless steel; Phosphoric acid

Synergistic effect between 4-(2-pyridylazo) resorcin and chloride ion on the corrosion of cold rolled steel in 1.0M phosphoric acid by Libin Tang; Xueming Li; Guannan Mu; Lin Li; Guangheng Liu (pp. 2367-2372).

The synergistic inhibition between 4-(2-pyridylazo) resorcin (PAR) and chloride ion on the corrosion of cold rolled steel in 1.0M phosphoric acid was studied using weight loss and potentiodynamic polarization method. Results obtained revealed that single PAR is not an effective inhibitor for steel corrosion in phosphoric acid, but in the presence of chloride ion, PAR may act as a good inhibitor due to the synergism. It is found that the adsorption of PAR accords with the Langmuir adsorption isotherm in the absence and presence of chloride ion. Potentiodynamic polarization studies show that PAR is an anodic inhibitor for steel in 1.0M phosphoric acid, and with addition of chloride ion PAR acts as a mixed type inhibitor. The experimental temperature ranges from 30 to 45°C. The kinetic data such as apparent activation energies and pre-exponential factors at different concentrations of the inhibitor were calculated, and the effect of the apparent activation energies and pre-exponential factors on the corrosion rates of cold rolled steel was discussed. The inhibitive action was satisfactorily explained by using kinetic models.

Keywords: PAR; Synergism; Corrosion inhibition; Cold rolled steel; Phosphoric acid

Fabrication of nanostructures on Si(100) and GaAs(100) by local anodic oxidation by Jiří Červenka; Radek Kalousek; Miroslav Bartošík; David Škoda; Ondřej Tomanec; Tomáš Šikola (pp. 2373-2378).

Atomic force microscopes have become useful tools not only for observing surface morphology and nanostructure topography but also for fabrication of various nanostructures itself. In this paper, the application of AFM for fabrication of nanostructures by local anodic oxidation (LAO) of Si(100) and GaAs(100) surfaces is presented. A special attention is paid to finding relations between the size of oxide nanolines (height and half-width) and operational parameters as tip-sample voltage and tip writing speed. It was demonstrated that the formation of silicon oxide lines obeys the Cabrera–Mott theory, i.e. the height of the lines grow, linearly with tip-sample voltage and is inversely proportional to logarithm of tip writing speed. As for GaAs substrates, the oxide line height grows linearly with tip-sample voltage as well but LAO exhibits a certain deviation from this theory. It is shown that the selective chemical etching of Si or GaAs ultrathin films processed by LAO makes it possible to use these films as nanolithographic masks for further nanotechnologies, e.g. fabrication of metallic nanostructures by ion-beam bombardment. The ability to control LAO and tip motion can be utilized in fabrication of complex nanostructures finding their applications in nanoelectronic devices, nanophotonics and other high-tech areas.

Keywords: PACS; 81.16.Nd; 81.16.PrNanotechnology; Nanostructure fabrication; Local anodic oxidation; AFM

Deposition conditions in tailoring the morphology of highly porous reticular films prepared by electrostatic spray deposition (ESD) technique by J.L. Shui; Y. Yu; C.H. Chen (pp. 2379-2385).

Spongy-like reticular structure is a unique morphology fabricated by electrostatic spray deposition (ESD) technique. The effects of solvent, substrate temperature, precursor feeding rate, static electric field strength, and deposition time on tailoring the reticular structure were investigated. Scanning electron microscopy was used to observe the film morphology. MnO_x or LiMn₂O₄ were selected as the model materials. It is found that in addition to the conventional solvent butyl carbitol, other kinds of solvents such as ethylene glycol and propylene glycol can also be used to obtain reticular films at a suitable substrate temperature. Porous films with a low cross-linking degree pore structure can be prepared by increasing precursor feeding rate or decreasing substrate temperature. Increasing the deposition time or the electric field strength helps to obtain reticular films with more homogeneous pore size distribution. In addition, the addition of a high boiling-point solvent in mixed alcohol solvent results in the increase of proper substrate temperature. It is concluded that the fluidity of the spray droplets on the surface of a hot substrate is an important factor to form a reticular film.

Keywords: Electrostatic spray deposition; Solvent; Static electric field; Porosity; Lithium batteries

Steady-state mechanism for polymer ablation by a free-running Er:YAG laser by D.M. Bubb; A.O. Sezer; D. Harris; F. Rezae; S.P. Kelty (pp. 2386-2392).

A free-running Er:YAG laser is used to ablate polyethylene glycol and the ablation yield is studied as a function of molecular weight (1000–10,000g/mol) and laser fluence (8–25J/cm²). A steady-state ablation mechanism is proposed which includes recoil-induced expulsion as the primary contributor to the ablation yield. It is also proposed that the formation of a molten layer is a necessary part of the ablation mechanism because the calculated tensile strengths for the solid polymer are too large to permit fracture of the target due to the laser-induced stress transient. The ablation yield is found to depend in a sigmoidal fashion upon laser fluence, thus implying a variable ablation enthalpy. Finally, the current results are compared with that obtained previously with a free electron laser.

Keywords: PACS; 61.41.+e; 78.30.−j; 81.05.Lg; 81.15.FgLaser ablation; Steady-state; Ablation mechanism; Pulsed laser deposition; Polymer ablation; Physical vapor deposition

Fabricating tunable nanoparticle density gradients with the contact printing based approach by Feng Song; Yangjun Cai; Bi-min Zhang Newby (pp. 2393-2398).

Recently, the generation of spatial gradient nanoparticle assemblies has attracted much attention. Such assemblies can be intriguing templates for building novel molecular architectures, and be employed as a combinatorial tool for quick determination of interaction selectivity for nanoparticles. In this communication, we report on convenient contact printing based techniques for generating lateral gradients containing nanoparticles with tunable geometry, scale and steepness. In the first method, octadecyltrichlorosilane (OTS) gradient surfaces were generated via the contact printing approach, and then spaces un-occupied by OTS molecules were back-filled with an amine-terminated silane, which allows the grafting of nanoparticles that were surface functionalized with carboxylic acid. By varying the size and geometry of the stamp, different geometrical gradients were generated. In addition, by changing the stamping procedures, either well-defined stepwise gradients or continuous gradients can be achieved. Furthermore, the contact printing based technique can be utilized in combination with diffusion of the aminosilane molecules to directly create its gradient, and consequently a nanoparticle density gradient.

Keywords: Gradient assemblies; Nanoparticles; Contact-printing

Details of crystalline growth in co-deposited electroplated nickel films with hard (nano)particles by Thomas Lampke; Bernhard Wielage; Dagmar Dietrich; Annette Leopold (pp. 2399-2408).

Electroplated nickel dispersion films with incorporated hard particles, primarily titanium oxide, were studied. A sufficient dispersion of nanometre-scaled particles in Watts solution was reached by application of ultrasonic energy to the galvanic bath. Crystal morphology, mean grain size and formation of textures were examined by electron backscattering diffraction (EBSD), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The typical columnar structure of pure Ni films was refined by means of ultrasound. Incorporation of micron-sized TiO₂ particles generates additional nucleation surfaces in contrast to SiC particles. Textures of the subsequent columnar nickel crystals change from 〈211〉 (silent condition) or 〈110〉 (ultrasonic condition) fibre textures in growth direction to 〈100〉 and 〈111〉 textures under the influence of nanoparticle incorporation. Moreover, nanoparticles remarkably decrease the grain size and grain aspect ratio. Their incorporation takes place inside the crystals as well as between grains.

Keywords: PACS; 81.15.Pq; 81.07.−b; 61.46.Df; 61.14.−xElectroplating; Nickel dispersion films; Crystal growth; Nanoparticles; EBSD; XRD; TEM

Structural, electrical and optical properties of ZnS films deposited by close-spaced evaporation by Y.P. Venkata Subbaiah; P. Prathap; K.T. Ramakrishna Reddy (pp. 2409-2415).

ZnS films have been deposited on glass substrates by close-spaced evaporation (CSE) technique. The films were grown at different temperatures in the range, 200–350°C. The layers have been characterized with X-ray diffractometer (XRD), atomic force microscope (AFM), energy dispersive analysis of X-rays (EDAX) and optical spectrophotometer to evaluate the quality of the layers for photovoltaic applications. The studies showed that the optimum substrate temperature for the growth of ZnS layers was 300°C. The films grown at these temperatures exhibited cubic structure with nearly stoichiometric composition. The AFM data revealed that the films had nano-sized grains with a grain size of ∼40nm. The optical studies exhibited direct allowed transition with an energy band gap of 3.61eV. The other structural and optical parameters such as lattice stress, dislocation density, refractive index and extinction coefficient were also evaluated. The temperature-dependent conductivity measured in the range, 303–523K showed a change in the conduction mechanism at 120°C. The activation energy values evaluated using the temperature dependence of electrical conductivity are 7 and 29meV at low and high temperature regions, respectively.

Keywords: PACS; 68.55.J; 81.15.E; 73.61.G; 78.66.FZnS films; Close-spaced evaporation; Structure; Optical properties

Thermal oxidation temperature dependence of 4H-SiC MOS interface by Hirofumi Kurimoto; Kaoru Shibata; Chiharu Kimura; Hidemitsu Aoki; Takashi Sugino (pp. 2416-2420).

The thermal oxidation temperature dependence of 4H-silicon carbide (SiC) is systematically investigated using X-ray photoelectron spectroscopy (XPS) and capacitance–voltage ( C– V) measurements. When SiC is thermally oxidized, silicon oxycarbides (SiC_xO_y) are first grown and then silicon dioxide (SiO₂) is grown. It is identified by XPS that the SiO₂ films fall into two categories, called SiC-oxidized SiO₂ and Si-oxidized SiO₂ in this paper. The products depend on thermal oxidation temperature. The critical temperature is between 1200 and 1300°C. The interface trap density ( D_it) of the sample possessing Si-oxidized SiO₂, at thermal oxidation temperature of 1300°C, is lower than SiC-oxidized SiO₂ at and below 1200°C, suggesting that a decrease of the C component in SiO₂ film and SiO₂/SiC interface by higher oxidation temperature improves the metal-oxide–semiconductor (MOS) characteristics.

Keywords: PACS; 81.65.Mq; 77.55.+f; 65.90.+iSilicon carbide; Silicon oxide; Oxidation; Metal-oxide–semiconductor structures; X-ray photoelectron spectroscopy

Electrical property of HfO_xN_y–HfO₂–HfO_xN_y sandwich-stack films by Ran Jiang; Erqing Xie; Zhiyong Chen; Zhenxing Zhang (pp. 2421-2424).

The effects of HfO_xN_y on the electrical property of HfO_xN_y–HfO₂–HfO_xN_y sandwich-stack (signed as SS) films were investigated. Excellent electrical performances were achieved in SS films, with a high dielectric constant of 16 and a low leakage current of ∼2×10⁻⁸A/cm² at 1MV/cm. Schottky (SK) emission and Frenkel–Poole (PF) emission are found to be the dominant mechanisms for the current conduction behavior. After a long time stress, the flat-band voltage shift in the SS film is much smaller than that in a pure HfO_xN_y film indicating fewer charge traps existed in the SS film. Based on the experiments, the new SS structure is more favorable for the improvement of electrical performances than a pure HfO_xN_y or HfO₂ structure.

Keywords: Hafnium oxynitride; Dielectrics; Diffusion; Electrical properties; Permittivity

Ethanol and methanol induced changes in phospholipid monolayer by M. Weis; M. Kopáni; J. Jakubovský; Ľ. Danihel (pp. 2425-2431).

The main components of cell membranes are phospholipids and proteins. The aim of our study was to examine structural changes of dipalmitoyl-phosphatidylcholine (DPPC) monolayer as a simple model system of a cell membrane in different environments. Pure water, ethanol and methanol solutions were used as subphases of Langmuir films as a membrane models. For detection of changes in charge states of the molecules as well as relation with structural and conformational changes, a contactless method Maxwell's displacement currents (MDC) was used. Behaviour of DPPC molecules on two different subphases is substantialy different. In DPPC monolayer on the subphase of methanol–water, a gradual absorption (incorporation, penetration) of methanol molecules into the layer can appear. In DPPC monolayer on the subphase of ethanol–water adsorption of ethanol molecules on the layer can be observed. The membrane permeability might change. At both subphases (ethanol–water and methanol–water) the elasticity modulus of the monolayer decreases leading to the loss of membrane elasticity.

Keywords: PACS; 68.08.−p Liquid–solid interfaces; 68.18.−g Langmuir–Blodgett films on liquidsMaxwell displacement current; Conformation; Membrane; Ethanol; Methanol; Permeability

Dependence of the strain energies on grain orientations in HCP metal films by Jian-Min Zhang; Yan Zhang; Ke-Wei Xu; Vincent Ji (pp. 2432-2436).

A thin polycrystalline film bonded tightly to a thick substrate of different thermal expansion coefficients will experience thermal strain when the temperature is changed. Calculations of the strain energies for grains having various crystallographic orientations ( h k l) relative to the film surface were made for a polycrystalline film composed of the close-packed hexagonal (HCP) metal Be, Cd, Co, Hf, Mg, Re, Ru, Sc, Ti, Y, Zr and Zn, respectively. From strain energy minimization, the (001), (013), (045), (123), (258), (057), (035), (057), (010), (558), (147) and (001) textures should be favorable in Be, Cd, Co, Hf, Mg, Re, Ru, Sc, Ti, Y, Zr and Zn film, respectively.

Keywords: PACS; 65.40.-b; 65.40.De; 68.35.Gy; 81.40.JjHCP films; Texture; Strain energy; Calculation

Yttrium ion implantation on the surface properties of magnesium by X.M. Wang; X.Q. Zeng; G.S. Wu; S.S. Yao (pp. 2437-2442).

Owing to their excellent physical and mechanical properties, magnesium and its alloys are receiving more attention. However, their application has been limited to the high reactivity and the poor corrosion resistance. The aim of the study was to investigate the beneficial effects of ion-implanted yttrium using a MEVVA ion implanter on the surface properties of pure magnesium. Isothermal oxidation tests in pure O₂ at 673 and 773K up to 90min indicated that the oxidation resistance of magnesium had been significantly improved. Surface morphology of the oxide scale was analyzed using scanning electron microscope (SEM). Auger electron spectroscopy (AES) and X-ray diffraction (XRD) analyses indicated that the implanted layer was mainly composed of MgO and Y₂O₃, and the implanted layer with a duplex structure could decrease the inward diffusion of oxygen and reduce the outward diffusion of Mg²⁺, which led to improving the oxidation resistance of magnesium. Potentiodynamic polarization curves were used to evaluate the corrosion resistance of the implanted magnesium. The results show yttrium implantation could enhance the corrosion resistance of implanted magnesium compared with that of pure magnesium.

Keywords: Magnesium; Implantation; Oxidation; Corrosion

Comparative studies of Zr-based MCM-41 and MCM-48 mesoporous molecular sieves: Synthesis and physicochemical properties by L.F. Chen; X.L. Zhou; L.E. Noreña; J.A. Wang; J. Navarrete; P. Salas; A. Montoya; P. Del Angel; M.E. Llanos (pp. 2443-2451).

Two surfactant-templated synthetic routes are developed for the preparation of new types of mesoporous molecular sieves, Zr-MCM-41 and Zr-MCM-48, using different Si sources but keeping the same zirconium precursor (zirconium- n-propoxide). When fumed silica was used as Si precursor, a Zr-MCM-48 material of cubic structure was formed with a surface area of 654.8m²/g and an unimodal pore diameter distribution. It shows low stability: after calcination at 600°C, the ordered structure was transformed into a relatively disordered worm-like mesostructure with many defects and silanol groups. The use of tetraethyl orthosilicate as Si source led to the formation of a Zr-MCM-41 mesoporous solid, which had good thermal stability and a highly ordered hexagonal arrangement, with a surface area 677.9m²/g and an uniform pore diameter distribution. Fourier transform infrared (FT-IR) characterization and²⁹Si NMR analysis confirm that zirconium ions indeed incorporated into the framework of the solid. The in situ FT-IR spectroscopy of pyridine adsorption reveals that both, Lewis and Brönsted acid sites, were formed on the surface of these mesoporous materials. The strength and number of the Brönsted acid sites of the Zr-MCM-48 solid were greater than those of the Zr-MCM-41, due to a lower degree of condensation reaction during the synthesis that led to more structural defects in the framework and more silanol groups stretching from the solid surface.

Keywords: Mesoporous solid; Zr-MCM-41; Zr-MCM-48; Surface acidity; Templated synthesis

Effect of Al incorporation on the AlGaN growth by metalorganic chemical vapor deposition by D.G. Zhao; Z.S. Liu; J.J. Zhu; S.M. Zhang; D.S. Jiang; Hui Yang; J.W. Liang; X.Y. Li; H.M. Gong (pp. 2452-2455).

The effect of Al incorporation on the AlGaN growth by metalorganic chemical vapor deposition is investigated. With the increase of trimethylalluminum (TMAl) flux, the crystal quality becomes worse, and the epilayer surface becomes rougher. An interesting phenomenon is that the growth rate of AlGaN decrease with increasing TMAl flux, which is opposite to the AlN growth rate dependence on the TMAl flux. All these effects are attributed to the different properties of Al atoms due to the higher bond strength of Al–N compared with Ga–N, which lead to lower surface mobility and stronger competitive ability of Al atoms during the growth. The enhancement of the surface mobility of Al is especially important for improving the quality of AlGaN.

Keywords: PACS; 81.15.Gh; 61.10.–i; 73.61.EyAl incorporation; MOCVD; AlGaN

Scanning tunneling microscopy investigation of leucine and asparagine adsorbed on Cu(111) by S.P. Ge; C. Lü; R.G. Zhao; Q. Chen (pp. 2456-2459).

Adsorption of leucine and asparagine on Cu(111) surface has been studied by means of scanning tunneling microscopy (STM) in ultra-high vacuum (UHV) conditions. It has been found that leucine can form (3×2) superstructure on Cu(111) and copper steps facet to 〈110〉 directions. On the basis of our STM images, model has been proposed for the Cu(111)(3×2)–leucine superstructure. The model explains quite naturally the motivation behind the step faceting process. On the other hand, asparagine cannot form any ordered superstructure on Cu(111) and no copper step faceting can be observed either. The role of amino group in the side chain played in asparagine adsorption geometry is discussed in this paper.

Keywords: PACS; 82.65.My; 68.35.Bs; 61.16.ChScanning tunneling microscopy; Leucine; Asparagine; Cu(1; 1; 1)

Selective growth of carbon nantoubes on SiO₂/Si substrate by J.M. Cao (pp. 2460-2464).

Three-step raising temperature process was employed to fabricate carbon nanotubes by pyrolysis of ferrocene/melamine mixtures on silica and single crystalline silicon wafers respectively. Then the morphologies, structures and compositions of obtained carbon nanotubes are investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscope (EDX) and electron energy-loss spectroscopy (EELS). TEM and SEM observation shows that on silica substrate, high-oriented carbon nanotube can grow compactly to form continuous film on both frontal and cross-section surfaces, but on silicon substrate, only can form on cross-section surface. These carbon nanotubes have much irregular cup-like structure, and with outer diameter varying from 25nm to 35nm. At the top end of carbon nanotube there is a catalyst particle. EDX analysis reveals that the particle are iron cluster, and EELS spectrum indicates that the nanotube is composed of pure carbon. Finally, the effect of substrate surface roughness on the growth behavior of carbon nanotubes has been discussed.

Keywords: PACS; 81.05.Uw; 85.35.Kt; 68.49.UvCarbon nanotube; Pyrolysis; EELS

ZrB₂/Pt/Au Ohmic contacts on bulk, single-crystal ZnO by J.S. Wright; Rohit Khanna; K. Ramani; V. Cranciun; R. Singh; D.P. Norton; S.J. Pearton; F. Ren; I.I. Kravchenko (pp. 2465-2469).

There is a strong interest in developing thermally stable metallization schemes for ZnO and boride-based contact stacks are expected to have potential because of their thermodynamic stability. The contact characteristics on bulk single-crystal n-ZnO of a ZrB₂/Pt/Au metallization scheme deposited by sputtering are reported as a function of annealing temperature in the range 300–800°C. The contacts were rectifying for anneal temperatures <500°C but exhibited Ohmic behavior at higher temperatures and exhibit a minimum specific contact resistivity of 9×10⁻³Ωcm after 700°C anneals. The contact stack reverts to rectifying behavior after annealing above 800°C, coincident with a degraded surface morphology and intermixing of the Au, Pt and ZrB₂. The boride-based contacts exhibit higher thermal stability but poorer specific contact resistivity than conventional Ti/Au metal stacks on ZnO.

Keywords: ZnO; Contacts; Borides

The significance of carbon on the microstructure of TiAlNC coatings deposited by reactive magnetron sputtering by Y.Z. Huang; M. Stueber; P. Hovsepian (pp. 2470-2473).

A series of TiAlCN coatings with different carbon contents have been deposited by a reactive sputtering of TiAl target under an environment with a mixture of Ar, N₂ and CH₄ gases. Microstructural changes, starting from pure TiAlN and then into TiAlCN with the increase of the carbon content, have been clearly demonstrated. This occurrence is due to the carbon atom substitution that results in a small alternation of the interplannar lattice parameter. The coating initially shows a strong preferred (111) texture in the pure TiAlN but becomes more randomly oriented at the higher carbon contents. Evidence was found for the presence of a free carbon phase, which provides the possibility to accomplish the self-lubricant coating.

Keywords: Carbon; TiAlNC; Coating

Electroless Ni–P coating preparation of conductive mica powder by a modified activation process by Hongbin Dai; Hongxi Li; Fuhui Wang (pp. 2474-2480).

A modified activation process was developed for electroless Ni–P coating preparation of conductive mica powder. The electroless Ni–P coating process was modified by replacing the conventional sensitization and activation steps only using activation step with a Pd(II)–APTHS activator, which is a complex of Pd(II) ion with a derivate γ-aminopropyltrihydroxysilane (APTHS) from the hydrolysis of γ-aminopropyltriethoxysilane (APTES). The activated reaction progress and resulted Ni–P coating were characterized by XPS, SEM/EDX and TEM. Electroless nickel deposition was successfully initiated by this activation process. This activation process is very simple, and the obtained Ni–P deposits have the advantages of uniformity, continuity and densification. The average specific resistivity for the Ni–P coated mica powder was 4.85×10⁻²Ωcm.

Keywords: Electroless Ni–P coating; Conductive powder; Mica; Activation

Different effects of cerium ions doping on properties of anatase and rutile TiO₂ by Guangqin Li; Chunyan Liu; Yun Liu (pp. 2481-2486).

Pure and Ce⁴⁺ doped anatase and rutile TiO₂ were prepared by hydrothermal methods and characterized by XRD, TEM, UV–vis diffusion spectroscopy, and XPS measurements. The photocatalytic reactivity of the catalysts was evaluated by the photodegradation of Rhodamine B (RB) under ultraviolet irradiation. The photocatalytic efficiency of the rutile sample doped with an appropriate amount of Ce⁴⁺ was enhanced while all Ce⁴⁺ doped anatase samples showed a much lower activity than pure anatase. The reasons were discussed

Keywords: Cerium ions; Doping; Anatase; Rutile; TiO; ₂

Synthesis evaluation and adsorption studies of anionic copolymeric surfactants based on fatty acrylate ester by W.I.A. El-Dougdoug; E.H. El-Mossalamy (pp. 2487-2492).

A series of anionic copolymeric surfactants based on n-dodecylacrylate ester (M₁) as hydrophobe, and oxypropylated acrylate ester (MA_4,6) as hydrophiles, were prepared by copolymerization of n-dodecylacrylate (M₁) and oxypropylated acrylate ester (MA_4,6) with molar ratio's (0.3:0.7, 0.4:0.6 and 0.5:0.5, respectively) in presence of benzoyl peroxide as initiator followed by sulfation and neutralization to afforded [(PAS₄), and (PAS₆)]_a–c, as anionic copolymeric surfactant in suitable yield. These derivatives were purified and characterized by IR and¹H NMR spectral studies. Surface activity, and biodegradability were evaluated. Adsorption of some copolymeric surfactant on salary sand was investigated to assess possibility of treating waste water streams for removal of Pb²⁺ and Hg²⁺ toxic minerals. The effect of several factors governing the adsorption such as initial concentration, temperature, pH, have been studied.

Keywords: Dodecylacrylate; Oxypropylation; Copolymerization reaction; Salary sand and adsorption

Formation of periodic structures by surface treatments of polyamide fiber by Joanne Yip; Kwong Chan; Kwan Moon Sin; Kai Shui Lau (pp. 2493-2497).

The processes of low temperature plasma treatment of polyamide fiber were systemically studied. Ripple-like structures in sub-micron size perpendicular to fiber axis were observed under particular treatment parameters. Suggested explanations were given of the mechanisms that produce the structure after the processes of plasma treatment. The fundamental approach used in modelling was considered the temperature profile of the material during the treatment. The morphological study results showed that the stress-field inside the fiber and the degree of crystallinity are essentially important in contributing to structure formation.

Keywords: Surface treatment; Low temperature plasma; Polyamide fiber

Electric field dependence of topography in ferroelectric P(VDF/TrFE) films by Guodong Zhu; Jing Xu; Zhigang Zeng; Li Zhang; Xuejian Yan; Jie Li (pp. 2498-2501).

The effect of electric fields on the topography and structures in P(VDF/TrFE) ferroelectric films was studied. The morphological changes after poling treatment at 25°C, from previously chrysanthemum-like structures to regular and parallel slug-like domains, were observed by scanning probe microscope. Poling process at higher temperature induced even greater morphological changes. Imaging of local electrical properties showed that these changes could not be attributed to the influence of local charges injected into film surface during poling process. It was believed that this new morphology came from the reform of film structures induced by electric fields.

Keywords: PACS; 68.55.Jk; 77.84.Jd; 68.37.PsP(VDF/TrFE); SPM; EFM; Electric field; Topography

On 308nm photofragmentation of the silver nanoparticles by Y. Badr; M.G. Abd El Wahed; M.A. Mahmoud (pp. 2502-2507).

Silver nanoparticles (Ag NPs) were prepared by different chemical methods possessing different sizes 3±2, 8±2, and 20±5nm. The influence the size of Ag NPs was demonstrated by the absorption and fluorescence spectra, the maximum absorption of Ag NPs increases as the particle size increases. When Ag NPs irradiated with 308nm excimer laser; the maximum absorption and the full width at half maximum decreased as the number of pulses increased up to 100,000 pulse; due to the size reduction. The fluorescence spectra of Ag NPs and irradiated Ag NPs with 308nm excimer laser were recorded after excitation at 441.5nm He–Cd laser, showing a red shift increasing as the particle size is increased.

Keywords: Photodegradation; Laser flouresence; Silver nanoparticles

Al-pillared clays supported rare earths and palladium catalysts for deep oxidation of low concentration of benzene by Shufeng Zuo; Renxian Zhou (pp. 2508-2514).

Al-pillared clays supported rare earths (RE/Al-PILC) are prepared and used as supports of palladium catalysts for deep oxidation of low concentrations of benzene (130–160ppm). The supports and catalysts are characterized by X-ray powder diffraction (XRD), FT-IR, BET, transmission electron microscopy (TEM) and temperature-programmed reduction (H₂-TPR). The results show that Al-pillaring results in a strong increase in the basal spacing ( d00₁) from about 1.2 to 1.8nm, and an increase in the BET surface area from 63.6 (±3.2) to 238.8 (±11.9)m²/g. Activity tests of deep oxidation of low concentration benzene show catalysts supported on Al-PILC and RE/Al-PILC are obviously more active than that on raw clay. Pd/6% Ce/Al-PILC, in particular, can catalyze the complete oxidation of low concentration benzene at a temperature as low as about 290°C.

Keywords: Al-pillared clays (Al-PILC); Palladium catalyst; Rare earths (RE); Benzene; Catalytic deep oxidation

Study on the bonding state for carbon–boron nitrogen with different ball milling time by Y.H. Xiong; C.S. Xiong; S.Q. Wei; H.W. Yang; Y.T. Mai; W. Xu; S. Yang; G.H. Dai; S.J. Song; J. Xiong; Z.M. Ren; J. Zhang; H.L. Pi; Z.C. Xia; S.L. Yuan (pp. 2515-2521).

The varied bonding state and microstructure characterization were discussed for carbon–boron nitrogen (CBN) with abundant phase structure and nanostructure, which were synthesized directly by mechanical alloying technique at room temperature. According to the results of SEM and X-ray photoelectron spectroscopy (XPS) of CBN with different ball milling time, it is substantiated that the bonding state and microstructure for CBN were closely related to the ball milling time. With the increase of the ball milling time, some new chemical bonding states of CBN were observed, which implies that some new bonding state and microstructures have been formed. The results of XPS are accordance with that of X-ray diffraction of CBN.

Keywords: PACS; 61.14.Qp; 81.20.Ev; 81.05.JeX-ray photoelectron spectroscopy; Bonding state; Mechanical alloying; Carbon–boron nitrogen nano-structure

Effects of hole injection layer thickness on the luminescent properties of white organic light-emitting diodes by Jian-Feng Li; Shih-Fang Chen; Shui-Hsiang Su; Kao-Shing Hwang; Meiso Yokoyama (pp. 2522-2524).

This work investigates how the thickness of the hole injection layer (HIL) influences the luminescent characteristics of white organic light-emitting diodes (WOLED). Experimental results indicate that inserting a thin HIL (<200Å) into a WOLED without an HIL reduces the brightness and clearly changes the chromaticity because the surface of the 4,4′,4″-tris{ N,-(3-methylphenyl)- N-phenylamino}-triphenylamine) (m-MTDATA) film is extremely rough. In contrast, a dense film structure and the fine surface morphology of m-MTDATA of moderate thickness (350–650Å) provides a uniform conducting path on which holes cross the indium tin oxide (ITO)/HIL interface, improving luminescent performance, associated with the relatively stable purity of the color of the emission, with Commission Internationale 1′Eclairage (CIE) coordinates of ( x=0.40, y=0.40). However, inserting a thick HIL (>650Å) reduces the luminescent performance and causes red-shift, because the holes and electrons in the effective emissive confinement region become less optimally balanced. Moreover, optimizing the device structure enables a bright WOLED with CIE coordinates of ( x=0.34, y=0.33) to reach a luminance of 7685cd/m² at a current density of 100mA/cm², with a maximum luminous efficiency of 1.72lm/W at 5.5V.

Keywords: Hole injection layer; White organic light-emitting diodes; Surface morphology; Luminescent

Benzene adsorption on carbonaceous materials: The influence of pore structure on the state of the adsorbate by Piotr A. Gauden /; Artur P. Terzyk; Magda S. Ćwiertnia; Gerhard Rychlicki; Gayle Newcombe; Piotr Kowalczyk (pp. 2525-2539).

Experimental nitrogen ( T=77K) and as benzene ( T=298K) adsorption isotherms measured on eight carbons possessing various porous structure are used to evaluate the parameters characterizing the geometric heterogeneity. Additionally, the experimental energetic measurements, i.e. the enthalpy and adsorption and related entropy of adsorbed benzene, are taken into considerations. The analysis of experimental data leads to the conclusion that the entropy of C₆H₆ adsorbed in strictly microporous materials approaches the value characteristic of quasi-solid (a partially ordered structure). On the other hand, for adsorbents possessing wider pores (i.e. the contribution of mesopores to the total porosity is significant) the differential entropy approaches to the value characteristic of liquid. We test a key assumption of the theoretical models describing the mechanism of adsorption, that the adsorbed phase is considered as liquid. This verification leads to the conclusion that the various orientation of the adsorbate in the pore space should be taken into consideration in the theoretical assumptions of a model and in its thermodynamic verification. The significant improvement in the description of benzene experimental data for microporous adsorbents is observed if the “correction term�? in the enthalpy of adsorption is considered. This term is correlated with the average pore diameter of studied solids. Our results of the critical pore diameter where the system undergoes an order-disorder transition are very close to obtained by Chakrabarti and Kerkhof via the computer simulation experiments.

Keywords: Benzene adsorption; Thermodynamics; Porosity; Solidlike and liquidlike structure

Infrared reflection absorption study of carbon monoxide adsorption on Pd/Cu(111) by T. Wadayama; K. Abe; H. Osano (pp. 2540-2546).

Pd–Cu bimetallic surfaces formed through a vacuum-deposition of Pd on Cu(111) have been discussed on the basis of carbon monoxide (CO) adsorption: CO is used as a surface probe and infrared reflection absorption (IRRAS) spectra are recorded for the CO-adsorbed surfaces. Low energy electron diffraction (LEED) patterns for the bimetallic surfaces reveal six-fold symmetry even after the deposition of 0.6nm. The lattice spacings estimated by the separations of reflection high-energy electron diffraction (RHEED) streaks increase with increasing Pd thickness. Room-temperature CO exposures to the bimetallic surfaces formed by the Pd depositions less than 0.3nm thickness generate the IRRAS bands due to the three-fold-hollow-, bridge- and linear-bonded CO to Pd atoms. In particular, on the 0.1nm-thick Pd surface, the linear-bonded CO band becomes apparent at an earlier stage of the exposure. In contrast, the bridge-bonded CO band dominates the IRRAS spectra for CO adsorption on the 0.6nm-thick Pd surface, at which the lattice spacing corresponds to that of Pd(111). A 90K-CO exposure to the 0.1nm-thick Pd surface leads to the IRRAS bands caused not only by CO–Pd but also by CO–Cu, while the Cu-related band is almost absent from the spectra for the 0.3nm-thick Pd surface. The results clearly reveal that local atomic structures of the outermost bimetallic surface can be discussed by the IRRAS spectra for the probe molecule.

Keywords: PACS; 78.30.−j; 61.14.Hg; 68.43.−h; 68.55.−aPalladium; Copper; Infrared reflection absorption spectroscopy; RHEED; LEED; Carbon monoxide; Bimetallic surfaces; Surface alloys

Water electrolysis-induced optical degradation of aluminum-doped zinc oxide films by Linggang Fang; Guojia Fang; Wanping Chen; Chun Li; Su Sheng; Shuang Ma; Xingzhong Zhao (pp. 2547-2550).

A type of optical degradation of aluminium-doped zinc oxide (AZO) films due to water electrolysis-induced reduction reaction was reported. An experiment was designed in which AZO films were immersed in a 0.01M NaOH aqueous solution as cathode to electrolyze water. Significant decreases in the optical transmission of the treated samples were observed. Studies by X-ray diffraction and scanning electron microscope showed that the degradation of AZO films was due to compositional and structural changes with the treatment of water electrolysis, which resulted from the reduction reaction of atomic hydrogen generated in the electrolysis of water. This optical degradation reflects the stability degradation of AZO films under water electrolysis environment.

Keywords: PACS; 81.05. Dz; 81.40−zAluminum-doped zinc oxide; Electrolysis of water; Optical degradation; Stability

Surface modifications of a titanium implant by a picosecond Nd:YAG laser operating at 1064 and 532nm by Milan Trtica; Biljana Gakovic; Dimitri Batani; Tara Desai; Peter Panjan; Bojan Radak (pp. 2551-2556).

Interaction of an Nd:YAG laser, operating at 1064 or 532nm wavelength and pulse duration of 40ps, with titanium implant was studied. Surface damage thresholds were estimated to 0.9 and 0.6J/cm² at wavelengths 1064 and 532nm, respectively. The titanium implant surface modification was studied by the laser beam of energy density of 4.0 and 23.8J/cm² (at 1064nm) and 13.6J/cm² (at 532nm). The energy absorbed from the Nd:YAG laser beam is partially converted to thermal energy, which generates a series of effects, such as melting, vaporization of the molten material, shock waves, etc. The following titanium/implant surface morphological changes were observed: (i) both laser wavelengths cause damage of the titanium in the central zone of the irradiated area, (ii) appearance of a hydrodynamic feature in the form of resolidified droplets of the material in the surrounding outer zone with the 1064nm laser wavelength and (iii) appearance of wave-like microstructures with the 532nm wavelength. Generally, both laser wavelengths and the corresponding laser energy densities can efficiently enhance the titanium/implant roughness. This implant roughness is expected to improve its bio-integration. The process of the laser interaction with titanium implant was accompanied by formation of plasma.

Keywords: Titanium implant surface modification; Picosecond Nd:YAG laser; Laser-induced damage

Droplets from the metal surfaces irradiated by a high-intensity pulsed ion beam by Z.H. Dong; Z. Zhang; C. Liu; X.P. Zhu; M.K. Lei (pp. 2557-2564).

Droplet behavior from the surfaces of pure metals Ti and Al ablated by high-intensity pulsed ion beam (HIPIB) with an ion current density from 30 to 200A/cm² has been investigated to explore the mechanism of mass transfer on HIPIB-irradiated materials. Droplet ejection on the ablated metal surface is studied by scanning electron microscope observation, energy dispersive X-ray spectroscopy analysis and profilometer measurement. The presence of ejected droplets from the irradiated surfaces is detected on both the surfaces of irradiated metals and substrates locating adjacent to the ablated surfaces. Moreover, the number density of droplets observed on both the surfaces tends to increase with increasing the ion current density. This phenomenon correlates to the fact that higher ion-beam intensity led to a more intense ablation, i.e. a severer droplet ejection. In addition, surface roughness ( R_a) for the respective metals is continuously increased with increasing the ion current density, indicating a more significant disturbance on the melted surfaces caused by the correspondingly severer droplet ejection. Combined with the previous finding of selective ablation on titanium, it is concluded that the droplet ejection is the efficient cause of cratering and disturbance on HIPIB-ablated surfaces.

Keywords: High-intensity pulsed ion beam; Metal; Droplet; Ablation; Surface morphology

Degradation formula and working lifetime prediction for high-temperature coating by W. Zhou; Y.G. Zhao; W. Li; Q.D. Qin; S.W. Hu; B. Tian (pp. 2565-2571).

A model for predicting the degradation mode of high-temperature coating is developed in this paper based on Fick's law. The degradation formula is deduced according to this model and then used for predicting the working lifetime of the coating on the basis of the dependent relation among the effective thickness of the coating, the oxidation time and the thickness of the degradation layer resulting from oxidation and coating–substrate interdiffusion. Finally combination of the dominant degradation mode and formula gives the possible measures taken to improve the oxidation-resistant property of the coating.

Keywords: Degradation; Coating; Oxidation; Diffusion

High temperature annealing effect on structural and magnetic properties of Ti/Ni multilayers by Pramod Bhatt; V. Ganeshan; V. R. Reddy; S. M. Chaudhari (pp. 2572-2580).

High temperature annealing effect on structural and magnetic properties of Ti/Ni multilayer (ML) up to 600°C have been studied and reported in this paper. Ti/Ni multilayer samples having constant layer thicknesses of 50Å each are deposited on float glass and Si(111) substrates using electron-beam evaporation technique under ultra-high vacuum (UHV) conditions at room temperatures. The micro-structural parameters and their evolution with temperature for as-deposited as well as annealed multilayer samples up to 600°C in a step of 100°C for 1h are determined by using X-ray diffraction (XRD) and grazing incidence X-ray reflectivity techniques. The X-ray diffraction pattern recorded at 300°C annealed multilayer sample shows interesting structural transformation (from crystalline to amorphous) because of the solid-state reaction (SSR) and subsequent re-crystallization at higher temperatures of annealing, particularly at ≥400°C due to the formation of TiNi₃ and Ti₂Ni alloy phases. Sample quality and surface morphology are examined by using atomic force microscopy (AFM) technique for both as-deposited as well as annealed multilayer samples. In addition to this, a temperature dependent dc resistivity measurement is also used to study the structural transformation and subsequent alloy phase formation due to annealing treatment. The corresponding magnetization behavior of multilayer samples after each stage of annealing has been investigated by using Magneto-Optical Kerr Effect (MOKE) technique and results are interpreted in terms of observed micro-structural changes.

Keywords: Ti/Ni multilayer structure; Annealing effect; Interfaces properties; Magnetization measurements; Resistivity measurements

Structure and composition of the segregated Cu in V₂O₅/Cu system by M.M. Ahadian; A. Iraji zad (pp. 2581-2588).

We have investigated segregation of copper at the surface of V₂O₅ films deposited onto Cu substrate by employing surface analysis techniques. X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) confirmed that the Cu is segregated at the surface and its chemical state is Cu₂O. According to secondary ion mass spectroscopy (SIMS) and glow discharge spectroscopy (GDS), the Cu concentration inside the deposited V₂O₅ layer is low. Ultraviolet photoelectron spectroscopy (UPS) and scanning tunneling spectroscopy (STS) revealed the segregation alters the surface local density of states. Surface analysis of deposited samples in ultra high vacuum (UHV) condition verified that the segregation occurs during the deposition. We have extended kinetic tight binding Ising model (KTBIM) to explain the surface segregation during the deposition. Simulation data approve the possibility of surface segregation during room temperature deposition. These results point out that on pure Cu substrate, oxidation occurs during the segregation and low surface energy of Cu₂O is the original cause of the segregation.

Keywords: PACS; 64.75; 81.15.Aa; 66.30.-h; 68.35.DvSurface segregation; Copper; Vanadium pentoxide; Thin film deposition

Magnetic structure and collective Jahn–Teller distortions in nanostructured particles of CuFe₂O₄ by I. Nedkov; R.E. Vandenberghe; Ts. Marinova; Ph. Thailhades; T. Merodiiska; I. Avramova (pp. 2589-2596).

The aim of the present work is to compare the structural, the composition and chemical state of the surface and magnetic properties of different nanosized CuFe₂O₄ powders exhibiting collective Jahn–Teller effect. The samples under examination consist of edged nanosized particles (needle like) with average length 1300±20nm and diameter 300±20nm obtained after high temperature synthesis, and superparamagnetic (at room temperature) spherical particles ( d=6±2nm), obtained by soft chemistry techniques. The surface composition of the particles was investigated by X-ray photoelectron spectroscopy (XPS). Mössbauer spectroscopy (MöS), including at high magnetic field up to 5T and 4.2K, was used for characterization of cation distribution in the samples. The data yielded by the XPS and MöS analyses for spherical nanosized particles led us to the assumption for the existence of a Jahn–Teller effect gradient—from the B-sublattice on the surface to a compensation of the tetragonal distortion in the two sublattices in the core. The analysis of the contribution of the anisotropy energy in edged and spherical nanoparticles shows that it must be considered as an effective value reflecting the influence of the individual factors depending on the particle shape and surface.

Keywords: PACS; 73.22.-f; 71.70.Ej; 71.45.-dNanostructured particles; Copper ferrite; Surface effects; Collective Jahn–Teller effect; Magnetism; XPS; Mössbauer spectroscopy

Observation of metastable erbium trihydride by Craig R. Tewell; Saskia H. King (pp. 2597-2602).

The γ phase of the erbium–hydrogen system is a hexagonal trihydride that is not predicted to be stable at room temperature without an overpressure of hydrogen gas. Herein, we report the creation of both, a thin film and powder of erbium trihydride that is metastable at ambient conditions. The presence of the hexagonal γ phase was determined by X-ray diffraction (XRD). The ratio of the total moles of hydrogen isotopes (hydrogen and deuterium) to moles of erbium, (H+D):Er, have been confirmed by elastic recoil detection (ERD)/Rutherford backscattering spectroscopy (RBS). Auger electron spectroscopy (AES) depth profiles and X-ray photoelectron spectroscopy (XPS) revealed the presence of an oxide layer that may account for the metastable behavior of the thin film.

Keywords: Hydrogen storage materials; Surfaces and interfaces; Thin films; Gas–solid reactions; Photoelectron spectroscopy

Characterization and ion-induced degradation of cross-linked poly(methyl methacrylate) studied using time of flight secondary ion mass spectrometry by M.S. Wagner; K. Lenghaus; G. Gillen; M.J. Tarlov (pp. 2603-2610).

In this study, a series of random copolymers of methyl methacrylate (MMA) and ethylene glycol dimethacrylate (EGDMA) were prepared as surface-initiated polymer (SIP) films on silicon substrates using atom transfer radical polymerization. Positive and negative ion static time-of-flight secondary ion mass spectrometry (ToF-SIMS) was used to characterize SIP films with different MMA/EGDMA monomer ratios in an attempt to quantify their surface composition. However, matrix effects in the positive and negative ion modes led to preferential secondary ion generation from the EGDMA monomer and suppression of secondary ions characteristic of the MMA monomer, precluding accurate quantification using standard linear quantification methods. Ion-induced degradation of these films under 5keV SF₅⁺ bombardment was also examined to determine the effect of cross-linking on the accumulation of ion-induced damage. Increasing incorporation of the EGDMA cross-linker in the SIP films decreased the sputter rate and increased the rate of damage accumulation under extended (>10¹⁴ions/cm²) 5keV SF₅⁺ bombardment. Comparison of the ion bombardment data with thermal degradation of cross-linked PMMA suggests that the presence of the cross-linker impedes degradation by depolymerization, resulting in ion-induced damage accumulation. The increased rate of ion-induced damage accumulation with increased cross-link density also suggests that polymers that can form cross-links during ion bombardment are less amenable to depth profiling using polyatomic primary ions.

Keywords: Ethylene glycol dimethacrylate; Methyl methacrylate; Depth profiling; SF; ₅; ⁺; ToF-SIMS

Oleic acid coating on the monodisperse magnetite nanoparticles by Ling Zhang; Rong He; Hong-Chen Gu (pp. 2611-2617).

Monodisperse magnetite nanoparticles provide a more factual model to study the interface interactions between the surfactants and magnetic nanoparticles. Monodisperse magnetite nanoparticles of 7 and 19nm coated with oleic acid (OA) were prepared by the seed-mediated high temperature thermal decomposition of iron(III) acetylacetonate (Fe(acac)₃) precursor method. Fourier transform infrared spectra (FTIR) and X-ray photoelectron spectroscopy (XPS) reveal that the OA molecules were adsorbed on the magnetic nanoparticles by chemisorption way. Analyses of transmission electron microscopy (TEM) shows the OA provided the particles with better isolation and dispersibility. Thermogravimetric analysis (TGA) measurement results suggest that there were two kinds of different binding energies between the OA molecules and the magnetic nanoparticles. The cover density of OA molecules on the particle surface was significantly various with the size of magnetite nanoparticles. Magnetic measurements of the magnetite nanoparticles show the surface coating reduced the interactions among the nanoparticles.

Keywords: PACS; 73.20Monodisperse; Magnetite nanoparticles; Oleic acid; Chemisorption

The comparative study of thermal fatigue behavior of laser deep penetration spot cladding coating and brush plating Ni–W–Co coating by Jiang Xu; Zhengyang Li; Wenhui Zhu; Zili Liu; Wenjin Liu (pp. 2618-2624).

For improving the thermal fatigue behavior of hot work die steel in engineering application, the present work compare the influence of thermal fatigue resistance by the two different surface modified processes, the laser deep penetration spot cladding (LDPSC) and brush plating on the Cr12MoNi hot rolling tool steel. The thermal fatigue tests were fulfilled by heating and quenching in water at a cycle period of 2min. Before and after thermal fatigue testing, the microhardness distribution profile and microstructure of LDPSC have been investigated. The results show that the LDPSC can be divided to three zones: cladding zone, alloying zone and heat affected zone. The major phases in cladding zone consist of Fe₃C, Cr₇C₃, Cr₂₃C₆ and martensite. The oxidation resistance and thermal stability of brush plating Ni–W–Co coating and reference materials has been determined. The results of thermal fatigue testing show that LDPSC and brush plating Ni–W–Co coating can improve thermal fatigue resistance as compared to the reference material. The brush plating Ni–W–Co coating is more effective than the former owing to its higher thermal stability, oxidation resistance, superfine grain, high-density dislocation in microstructure and combination of strength and ductility.

Keywords: Thermal fatigue; Spot cladding; Brush plating; Cr12MoNi hot rolling steel; Thermal stability

A crude protective film on historic stones and its artificial preparation through biomimetic synthesis by Qiang Liu; Bingjian Zhang; Zhongyue Shen; Huanming Lu (pp. 2625-2632).

A biomimetic film has been found on the surface of the historic stone buildings and monuments. The stone inscriptions under the film are preserved so well that has not been damaged for more than 1000 years. Samples of the crude film have been analyzed by XRD, FTIR, PLM, EDA, SEM and TEM. The results show that it consists mainly of calcium oxalate monohydrate. On the basis of the existence of the organism debris, it is concluded that the film should be a product of biomineralization. According to this hypothesis, a similar film has been prepared on the stone surface through biomimetic synthesis in our laboratory. The preliminary analysis shows that the artificial protective film functions well.

Keywords: Protective film; Biomineralization; Biomimetic synthesis; Surface; Substrate; Stone conservation

Fabrication of an optically transparent super-hydrophobic surface via embedding nano-silica by Changhong Su; Jun Li; Hongbin Geng; Qingjun Wang; Qingmin Chen (pp. 2633-2636).

Super-hydrophobic thin films were prepared on glass by combining embedded nano-silica, subsequent fluoroalkylsilane coating. The hydrophobic capability of film depended on the concentration of nano-silica suspension. And the super-hydrophobic thin film shows the high transmittance in visible light wavelength.

Keywords: Super-hydrophobic; Nano-silica; Optically transmittance

Formation of periodic structures by surface treatments of polyamide fiber by Joanne Yip; Kwong Chan; Kwan Moon Sin; Kai Shui Lau (pp. 2637-2643).

The processes of UV excimer laser irradiation (both high- and low-fluence) of polyamide fiber were systemically studied, including the surface temperature of the material during the treatment and possible mechanisms for the structure formation. The fluence applied in the high-fluence laser irradiation was above the ablation threshold of the material. The ablation of polymer can be described on the basis of photo-thermal bond breaking within the bulk material. The fluence applied in the low-fluence laser irradiation was far below the ablation threshold of the material. The development of low-fluence laser-induced structures is closely related to the absorption coefficient of the material, the laser fluence used, the polarization of the laser beam, the angle of incidence, and the number of laser pulses applied.

Keywords: Surface treatment; UV excimer laser; High-fluence; Low-fluence

XPS and bioactivity study of the bisphosphonate pamidronate adsorbed onto plasma sprayed hydroxyapatite coatings by Kate McLeod; Sunil Kumar; Roger St.C. Smart; Naba Dutta; Nicolas H. Voelcker; Gail I. Anderson; Ron Sekel (pp. 2644-2651).

This paper reports the use of X-ray photoelectron spectroscopy (XPS) to investigate bisphosphonate (BP) adsorption onto plasma sprayed hydroxyapatite (HA) coatings commonly used for orthopaedic implants. BPs exhibit high binding affinity for the calcium present in HA and hence can be adsorbed onto HA-coated implants to exploit their beneficial properties for improved bone growth at the implant interface. A rigorous XPS analysis of pamidronate, a commonly used nitrogenous BP, adsorbed onto plasma sprayed HA-coated cobalt–chromium substrates has been carried out, aimed at: (a) confirming the adsorption of this BP onto HA; (b) studying the BP diffusion profile in the HA coating by employing the technique of XPS depth profiling; (c) confirming the bioactivity of the adsorbed BP. XPS spectra of plasma sprayed HA-coated discs exposed to a 10mM aqueous BP solution (pamidronate) for periods of 1, 2 and 24h showed nitrogen and phosphorous photoelectron signals corresponding to the BP, confirming its adsorption onto the HA substrate. XPS depth profiling of the 2h BP-exposed HA discs showed penetration of the BP into the HA matrix to depths of at least 260nm. The bioactivity of the adsorbed BP was confirmed by the observed inhibition of osteoclast (bone resorbing) cell activity. In comparison to the HA sample, the HA sample with adsorbed BP exhibited a 25-fold decrease in primary osteoclast cells.

Keywords: X-ray photoelectron spectroscopy (XPS); Adsorption; Hydroxyapatite; Bisphosphonate

Effects of in situ thermal annealing on the structural, optical, and electrical properties in Hg_0.7Cd_0.3Te epilayers grown on CdTe buffer layers by Y.S. Ryu; T.W. Kang; T.W. Kim (pp. 2652-2656).

Scanning electron microscopy (SEM), Fourier transform infrared (FTIR) transmission, and Hall effect measurements were performed to investigate the structural, optical, and electrical properties of as-grown and in situ-annealed Hg_0.7Cd_0.3Te epilayers grown on CdTe buffer layers by using molecular beam epitaxy. After the Hg_0.7Cd_0.3Te epilayers had been annealed in a Hg-cell flux atmosphere, the SEM images showed that the surface morphologies of the Hg_0.7Cd_0.3Te thin films were mirror-like with no indication of pinholes or defects, and the FTIR spectra showed that the transmission intensities had increased in comparison to that of the as-grown Hg_0.7Cd_0.3Te epilayer. Hall-effect measurements showed that n-Hg_0.7Cd_0.3Te epilayers were converted to p-Hg_0.7Cd_0.3Te epilayers. These results indicate that the surface, optical, and electrical properties of the Hg1−_xCd_xTe epilayers are improved by annealing and that as-grown n-Hg1−_xCd_xTe epilayers can be converted to p-Hg1−_xCd_xTe epilayers by in situ annealing.

Keywords: PACS; 68. 55. Bd; 81. 15. Ef; 81. 40. EfThermal annealing effect; Molecular beam epitaxy; Optical properties; Semiconductors; Surface morphology

Mechanical properties of InAs/InP semiconductor alloys by R. Navamathavan; D. Arivuoli; G. Attolini; C. Pelosi; Chi Kyu Choi (pp. 2657-2661).

The microindentation studies have been reported for undoped and doped InAs/InP semiconductor alloys grown by metal organic vapor phase epitaxy (MOVPE). It was found that the microhardness value increases with increase of applied load and attains a constant value for further increase in the load. The mechanical properties like, fracture toughness, brittleness index, fracture surface energy and indentation size effect coefficient were determined using the microhardness value. The indented samples were etched in H₂SO₄:H₂O₂:H₂O of the ratio of (1:1:1) for 30s. This reveals the dislocation rosette patterns generated around the edges of the indentation on subsequent etching process.

Keywords: PACS; 71.55.Eq; 62.20.Fe; 46.55.+d; 62.25.+g; 62.20.-x; 62.20.QpMicroindentation; InAs/InP; Vicker's hardness; Mechanical properties

Surface roughening and erosion rate change at low energy SIMS depth profiling of silicon during obliqueO2+ bombardment by B. Fares; B. Gautier; Ph. Holliger; N. Baboux; G. Prudon; J.-Cl. Dupuy (pp. 2662-2670).

Surface roughening of boronδ-doped Si samples under low energy (0.5 keV/O2+, 44° and 54°, and 1.0 keV/O2+, 48°)O2+ bombardment at oblique incidence with and without oxygen flooding was studied with atomic force microscopy (AFM) and secondary ion mass spectrometry (SIMS). The erosion rate, the surface topography and the depth resolution as a function of depth have been measured. Changes in secondary ion yields have been correlated with changes in surface topography.It is found that the surface roughness depends on impact energy and incidence angle without flooding. The roughness decreases with decreasing impact energy. For the same energy (0.5 keV/O2+), the wavelength increases slightly with increasing angle of incidence and the roughness increases with increasing angle of incidence.With flooding, the roughness can be efficiently avoided. The best conditions to avoid roughness when analysing ultra shallow profiles with our magnetic sector instrument is 0.5 keV/O2+, 44° with flooding.A procedure for the depth calibration of the profiles revealed that surface roughness causes an erosion rate change as measured using the shift of the position of the measured B peaks with and without flooding. The consequences of the roughness in terms of depth resolution of the profiles are analysed with and without flooding. Moreover, we show that the value of the Gaussian broadening parameter of the depth resolution function is closely related to the final dispersion of the heights in the crater bottom.

Keywords: SIMS; AFM; δ; -Doped; RMS roughness; Depth resolution

Laser-induced thermoelectric voltage in normal state MgB₂ thin films by Songqing Zhao; Yueliang Zhou; Kun Zhao; Shufang Wang; Zhenghao Chen; Kui-juan Jin; Huibin Lü; Bolin Cheng; Guozhen Yang (pp. 2671-2673).

Laser-induced voltage has been observed in c-axis oriented MgB₂ thin film at room temperature. The amplitude of the signal is approximately proportional to the film thickness. For the film with the thickness of 150nm, a very fast response has been detected when the film was irradiated by a 308nm pulsed laser of 20ns duration. The rise time and full width at half-maximum of the signal are about 3 and 25ns, respectively. The physical origin of the laser-induced voltage can be attributed to a transverse thermoelectricity due to the anisotropic thermopower in MgB₂.

Keywords: PACS; 73.50.Pz; 74.78.–w; 81.15.GhMgB; ₂; thin films; Laser-induced voltage; Thermoelectric effect

The optical properties of planar waveguides in LiB₃O₅ crystals formed by Cu⁺ implantation by Yi Jiang; Chuan-Lei Jia; Lei Wang; Xue-Lin Wang; Feng Chen; Ke-Ming Wang; Qing-Ming Lu; Hong-Ji Ma; Ding-Yu Shen (pp. 2674-2677).

A planar optical waveguide has been formed in a LiB₃O₅ crystal using 6.0MeV Cu⁺-ions with a dose of 1×10¹⁵ions/cm² at room temperature. Possible propagating modes were measured at a wavelength of 633nm using the prism-coupling method. The refractive index profiles of the waveguide were reconstructed by an effective refractive index method and the beam propagation method was used to investigate the properties of the propagation modes in the formed waveguide. The results suggest that the fundamental TE₀ and TM₀ modes may be well-confined and propagate a longer distance inside the waveguide. The implantation process was also simulated using the transport of ions in matter code (TRIM), which indicates that the nuclear energy deposition may be the main factor for the refractive index change.

Keywords: PACS; 61.72.Ww; 61.72.Dd; 42.82.EtIon-implantation; Optical waveguide; LiB; ₃; O; ₅; crystal

Preparation and characterization of novel Pd/SiO₂ and Ca–Pd/SiO₂ egg-shell catalysts with porous hollow silica by Ji-Rui Song; Li-Xiong Wen; Lei Shao; Jian-Feng Chen (pp. 2678-2684).

Novel egg-shell structured monometallic Pd/SiO₂ and bimetallic Ca–Pd/SiO₂ catalysts were prepared by an impregnation method using porous hollow silica (PHS) as the support and PdCl₂ and Ca(NO₃)₂·4H₂O as the precursors. It was found from transmission electron microscope (TEM), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) that Pd was loaded on PHS with a particle size of 5–12nm in Pd/SiO₂ samples and the Pd particle size in Ca–Pd/SiO₂ was smaller than that in Pd/SiO₂ since Ca could prevent Pd particles from aggregating. X-ray photoelectron spectroscopy (XPS) analyses exhibited that Pd 3d_5/2 binding energies of Pd/SiO₂ and Ca–Pd/SiO₂ were 0.2 and 0.9eV lower than that of bulk Pd, respectively, as a result of the shift of the electron cloud from Pd to oxygen in Pd/SiO₂ and to both oxygen and Ca in Ca–Pd/SiO₂. The activity of Ca–Pd/SiO₂ egg-shell catalyst for CO hydrogenation and the selectivity to methanol, with a value of 36.50mmol_COmol⁻¹_Pds⁻¹ and 100%, respectively, were much higher than those of the catalysts prepared with traditional silica gel as the support, owing to the porous core-shell structure of the PHS support.

Keywords: Porous hollow silica; Egg-shell catalyst; Pd/SiO; ₂; Ca–Pd/SiO; ₂; Characterization

Identification of ionic aggregates in PVDF- g-PSSA membrane by tapping mode AFM and HADDF STEM by H.S. Huang; C.Y. Chen; S.C. Lo; C.J. Lin; S.J. Chen; L.J. Lin (pp. 2685-2689).

Previous literature has shown that poly(vinylidene fluoride)- graft-poly(styrene sulfonated acid) (PVDF- g-PSSA) exhibits a lower methanol permeability than commercial Nafion and so is better suited to use as a proton exchange membrane (PEM) in direct methanol fuel cells (DMFCs). A number of studies have suggested that the microstructures of ionic aggregates explain their lower methanol permeability, but few direct morphological observations have been reported. In this study, the use of a tapping mode atomic force microscope (AFM) and a high-angle annular dark-field (HAADF) scanning transmission electron microscope (STEM) has identified the phase separation of PVDF and sulfonated PS, and ionic sulfonic aggregates, 3–5nm, in sulfonated PS regions. An experiment to elucidate the microstructural changes in the membrane with and without methanol immersion shows that PVDF- g-PSSA has ionic aggregates with a more stable microstructure than Nafion.

Keywords: PACS; 84.60.D; 82.65.F; 61.16.C; 61.16.BIonic aggregate; PVDF-; g; -PSSA; Methanol crossover; Atomic force microscopy (AFM); High-angle annular dark-field (HAADF) scanning transmission electron microscopy (STEM)

Control over the wettability of amorphous carbon films in a large range from hydrophilicity to super-hydrophobicity by Y. Zhou; B. Wang; X. Song; E. Li; G. Li; S. Zhao; H. Yan (pp. 2690-2694).

Control of wettability is of significance in industry as well as our daily live. Amorphous carbon (a-C) films with nanostructured surface were deposited on silicon and glass substrates at different substrate temperatures through a magnetron sputtering technique. The microstructures of the a-C films were studied by SEM and XPS, which indicate that the surface of the a-C films deposited at room temperature are smooth due to their much dense sp³-bonded carbon, while they turn to be more porous graphite-like structure with elevated deposition temperature. The water contact angle (CA) measurements show that these pure carbon films exhibit different wettability, ranging from hydrophilicity with CA less than 40° to super-hydrophobicity with CA of 152°, which reveal that the surface wettability of a-C films can be controlled well by using nanostructures with various geometrical and carbon state features. The graphite-like carbon film deposited at 400°C without any modification exhibits super-hydrophobic properties, due to the combining microstructures of spheres with nanostructures of protuberances and interstitials. It may have great significance on the study of wettability and relevant applications.

Keywords: PACS; 61.30.HnWettability; Amorphous carbon films; Microstructure; Super-hydrophobic

Surface modification of polyacrylonitrile-based carbon fiber and its interaction with imide by Bing Xu; Xiaoshu Wang; Yun Lu (pp. 2695-2701).

In this work, sized polyacrylonitrile (PAN)-based carbon fibers were chemically modified with nitric acid and maleic anhydride (MA) in order to improve the interaction between carbon fiber surface and polyimide matrix. Bismaleimide (BMI) was selected as a model compound of polyimide to react with modified carbon fiber. The surface characteristic changing after modification and surface reaction was investigated by element analysis (EA), scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and surface enhanced Raman scattering (SERS). The results indicated that the modification of carbon fiber surface with MA might follow the Diels Alder reaction mechanism. In the surface reaction between modified fibers and BMI, among the various surface functional groups, the hydroxyl group provided from phenolic hydroxyl group and bridged structure on carbon fiber may be the most effective group reacted with imide structure. The results may shed some light on the design of the appropriate surface structure, which could react with polyimide, and the manufacture of the carbon fiber-reinforced polyimide matrix composites.

Keywords: Carbon fiber; Surface modification; Interfacial interaction; Imide structure

Spray pyrolytic deposition of solid electrolyte Bi₂V_0.9Cu_0.1O_5.35 films by R.K. Nimat; C.A. Betty; S.H. Pawar (pp. 2702-2707).

Copper substituted bismuth vanadate films have been successfully deposited first time by spray pyrolysis technique on glass substrates suitable for low temperature solid oxide fuel cells. Desired phase formation of polycrystalline Bi₂V_0.9Cu_0.1O_5.35 (BICUVOX.10) was confirmed by X-ray diffraction technique. These films were further studied with EDAX and SEM techniques for their compositional and morphological characterization. Electrical conductivity of BICUVOX.10 is found to be 5.7×10⁻²(Ωcm)⁻¹ at 698K, predicts the onset temperature for ionic contribution suitable for low temperature SOFC applications. Room temperature complex impedance plot reveals that electrical process arises due to contribution from the grain interior.

Keywords: Spray pyrolysis; BICUVOX.10; SOFC; Thin film; Oxide ion conductor; Impedance spectroscopy

Effect of C layer on the structures and magnetic properties of (001)-oriented [C/CoPt] n/Ag films by Tao Jin; Xiao-Hong Xu; Feng-Xian Jiang; Xiao-Li Li; Fang Wang; Xiao-Hua Shen; Rui-Qiang Zhang; Hai-Shun Wu (pp. 2708-2712).

CoPt/Ag and [C/CoPt] n/Ag thin films have been prepared onto the glass substrates by magnetron sputtering. We investigated the evolution of texture and magnetic properties of CoPt/Ag and [C/CoPt] n/Ag films. The results show that C-doping plays an important role in improving (001) texture, improving the order parameter S, reducing the intergrain interactions, and making the magnetization reversal mechanism more close to Stoner–Wolfarth rotational mechanism. The growth mechanism of (001) texture also seems to be related strongly to the films thickness. Our results show that the highly (001)-oriented films with ordered fct phase have a significant potential for the perpendicular media of extremely high-density recording.

Keywords: PACS; 75.30.Gw; 75.50.Ss; 75.70.Cn; 61.10.NzCoPt films; (0; 0; 1) Texture; C matrix

Surface enhanced Raman scattering of organic sample powders spread over vacuum-evaporated silver thin film by T. Wadayama; M. Oishi; A. Hatta (pp. 2713-2717).

Surface enhanced Raman scattering (SERS) from samples prepared by spreading para-nitrobenzoic acid (PNBA) and adenosine powders over silver thin films was achieved. The SERS intensities of the ionized PNBA on the silver film increase with increased applied pressure through a cover-glass and reach a maximum at 0.6MPa. In contrast, the signals caused by adenosine remain nearly unchanged under applied pressures of 0–0.6MPa. Beyond 0.6MPa, the signals attributable to samples decrease in intensity. Atomic force microprobe images reveal that nanometer-scale surface morphology is changed by 0.8MPa pressure, suggesting that the decrease in SERS intensity is related to pressure-induced morphological changes. Results obtained in this study indicate that SERS spectra are obtainable easily, without solvents, under ambient conditions using dispersion of the sample powder.

Keywords: PACS; 78.30.-j; 68.37.Ps; 68.43.-hSurface enhanced Raman scattering; Silver; para; -Nitrobenzoic acid; Adenosine; Atomic force microprobe

Correlation between optical properties and Si nanocrystal formation of Si-rich Si oxide films prepared by plasma-enhanced chemical vapor deposition by X.Y. Chen; Y.F. Lu; Y.H. Wu; B.J. Cho; L.J. Tang; D. Lu; J.R. Dong (pp. 2718-2726).

We have investigated the phase separation and silicon nanocrystal (Si NC) formation in correlation with the optical properties of Si suboxide (SiO_x, 0< x<2) films by thermal annealing in high vacuum. The SiO_x films were deposited by plasma-enhanced chemical vapor deposition at different nitrous oxide/silane (N₂O/SiH₄) flow ratios. The as-deposited films show increased Si concentration with decreasing N₂O/SiH₄ flow ratio, while the deposition rate and surface roughness have strong correlations with the flow ratio in the N₂O/SiH₄ reaction. After thermal annealing at temperatures above 1000°C, Fourier transform infrared spectroscopy, Raman spectroscopy, and transmission electron microscopy manifest the progressive phase separation and continuous growth of crystalline-Si (c-Si) NCs in the SiO_x films with increasing annealing temperature. We observe a transition from multiple-peak to single peak of the strong red-range photoluminescence (PL) with increasing Si concentration and annealing temperature. The appearance of the single peak in the PL is closely related to the c-Si NC formation. The PL also redshifts from ∼1.9 to 1.4eV with increasing Si concentration and annealing temperature (i.e., increasing NC size). The good agreements of the PL evolution with NC formation and the PL peak energy with NC size distribution support the quantum confinement model.

Keywords: PACS; 78.67.Bf; 81.05.Cy; 81.07.−b; 81.15.GhPlasma-enhanced chemical vapor deposition; Silicon nanocrystals; Silicon oxide; Optical properties

Modifier effects on chemical reduction synthesis of nanostructured copper by Xiaonong Cheng; Xifeng Zhang; Hengbo Yin; Aili Wang; Yiqing Xu (pp. 2727-2732).

Size-controlled chemical reduction synthesis of nanostructured Cu was studied in the presence of a single modifier such as polyethylene glycols, sodium dodecyl benzene sulfonate, sodium dodecyl sulfate or a mixture of two different types of modifiers. The Cu nanoparticles were characterized by powder X-ray diffraction, transmission electron microscopy, selected area electron diffraction and Fourier transform infrared spectroscopy. The average particle size and particle size distribution of the nanostructured Cu depend upon the type of modifiers and the modifier effect follows the order: PEG-2000>SDBS>PEG-600>SDS>PEG-6000. The experimental results indicate that due to the existence of a synergistic action, a mixture of two types of modifiers has a significant effect on the particle size and the size distribution of Cu nanoparticles.

Keywords: Copper; Nanoparticles; Chemical reduction synthesis; Modifier; Synergistic action; Transmission electron microscopy (TEM); X-ray diffraction (XRD); Fourier transform infrared (FTIR) spectroscopy

Structure and mechanical properties of Al/AlN multilayer with different AlN layer thickness by Z.G. Wu; G.A. Zhang; M.X. Wang; X.Y. Fan; P.X. Yan; T. Xu (pp. 2733-2738).

Nanometer scale Al/AlN multilayers have been prepared by dc magnetron sputtering technique with a columnar target. A set of Al/AlN multilayers with the Al layer thickness of 2.9nm and the AlN layer thickness variation from 1.13 to 6.81nm were determined. Low angle X-ray diffraction (LAXRD) was used to analyze the layered structure of multilayers. The phase structure of the coatings was investigated with grazing angle XRD (GAXRD). Mechanical properties of these multilayers were thoroughly studied using a nanoindentation and ball-on-disk micro-tribometer. It was found that the multilayer hardness and reduced modulus showed no strong dependence on the AlN layer thickness. Al2.9nm/AlN1.13nm multilayer had more excellent tribological properties than single layers and other proportion multilayers with a lowest friction coefficient of 0.15. And the tribological properties of all the multilayers are superior to the AlN single layer.

Keywords: dc magnetron sputtering; Al/AlN multilayer; Structure; Mechanical properties; Tribology

Effect of substrate temperature and annealing temperature on the structural, electrical and microstructural properties of thin Pt films by rf magnetron sputtering by Monjoy Sreemany; Suchitra Sen (pp. 2739-2746).

Influence of both substrate temperature, T_s, and annealing temperature, T_a, on the structural, electrical and microstructural properties of sputtered deposited Pt thin films have been investigated. X-ray diffraction results show that as deposited Pt films ( T_s=300, 400°C) are preferentially oriented along (111) direction. A little growth both along (200) and (311) directions are also noticed in the as deposited Pt films. After annealing in air ( T_a=500–700°C), films become strongly oriented along (111) plane. With annealing temperature, average crystallite size, D, of the Pt films increases and micro-strain, e, and lattice constant, a₀, decreases. Residual strain observed in the as deposited Pt films is found to be compressive in nature while that in the annealed films is tensile. This change in the strain from compressive to tensile upon annealing is explained in the light of mismatch between the thermal expansion coefficients of the film material and substrate. Room temperature resistivity of Pt films is dependant on both the T_s and T_a of the films. Observed decrease in the film resistivity with T_a is discussed in terms of annihilation of film defects and grain-boundary. Scanning electron microscopic study reveals that as the annealing temperature increases film densification improves. But at an annealing temperature of ∼600°C, pinholes appear on the film surface and the size of pinhole increases with further increase in the annealing temperature. From X-ray photoelectron spectroscopic analysis, existence of a thin layer of chemisorbed atomic oxygen is detected on the surfaces of the as deposited Pt films. Upon annealing, coverage of this surface oxygen increases.

Keywords: PACS; 81.15.Cd; 68.55.Jk; 68.37.Hk; 79.60.DpPt thin films; Preferred orientation; Strain; Microstructure; Chemisorbed atomic oxygen

The effect of thermal annealing and laser irradiation on the microstructure of vanadium oxide nanotubes by Xueqin Liu; Chunming Huang; Jiawen Qiu; Yinyue Wang (pp. 2747-2751).

The microstructure of vanadium oxide nanotubes (VONTs) have been characterized using FTIR spectroscopy and Raman spectroscopy. The temperature effects on the VONTs were studies by changing the laser irradiation power and thermal annealing temperature in air. Raman spectroscopy studies showed that the VONTs could be decomposed even at low laser power irradiation. Also, together with scanning electron microscopy, it was found that thermal annealing in air could lead to the collapse of the tubular structure and convert the nanotubes into V₂O₅ nanoparticle. It was found that the thermal stability of VONTs was relatively low and the tubular morphology was destroyed at temperatures higher than 300°C. The spectroscopic analyses showed that the Raman signature of the VONTs could be established for probing tubular structure.

Keywords: PACS; 36.20.Ng; 61.46.Fg; 65.80.+n; 81.40.−zVanadium oxide; Nanotubes; Raman spectroscopy; FTIR spectroscopy; Microstructure

High-density plasma etching of indium–zinc oxide films in Ar/Cl₂ and Ar/CH₄/H₂ chemistries by W.T. Lim; L. Stafford; Ju-Il Song; Jae-Soung Park; Y.W. Heo; Joon-Hyung Lee; Jeong-Joo Kim; S.J. Pearton (pp. 2752-2757).

The dry etching characteristics of transparent and conductive indium–zinc oxide (IZO) films have been investigated using an inductively coupled high-density plasma. While the Cl₂-based plasma mixture showed little enhancement over physical sputtering in a pure argon atmosphere, the CH₄/H₂/Ar chemistry produced an increase of the IZO etch rate. On the other hand, the surface morphology of IZO films after etching in Ar and Ar/Cl₂ discharges is smooth, whereas that after etching in CH₄/H₂/Ar presents particle-like features resulting from the preferential desorption of In- and O-containing products. Etching in CH₄/H₂/Ar also produces formation of a Zn-rich surface layer, whose thickness (∼40nm) is well-above the expected range of incident ions in the material (∼1nm). Such alteration of the IZO layer after etching in CH₄/H₂/Ar plasmas is expected to have a significant impact on the transparent electrode properties in optoelectronic device fabrication.

Keywords: Indium–zinc oxide; Dry etching

Surface characteristics of PLA and PLGA films by Thanki Paragkumar N; Dellacherie Edith; Six Jean-Luc (pp. 2758-2764).

Surface segregation and restructuring in polylactides (poly(d,l-lactide) and poly(l-lactide)) and poly(d,l-lactide-co-glycolide) (PLGA) films of various thicknesses were investigated using both attenuated total reflection FTIR (ATR-FTIR) and contact angle relaxation measurements. In case of poly(d,l-lactide) (DLPLA), it was observed that the surface segregation and the surface restructuring of methyl side groups are influenced by the polymer film thickness. This result has been confirmed by X-ray photoelectron spectroscopy (XPS). In the same way, PLGA thick films were also characterized by an extensive surface segregation of methyl side groups. Finally, surface restructuring was investigated by dynamic contact angle measurements and it was observed when film surface comes into contact with water.In parallel, we also found that poly(l-lactide) (PLLA) thin and clear films with thickness ∼15μm undergo conformational changes on the surface upon solvent treatment with certain solvents. The solvent treated surface of PLLA becomes hazy and milky white and its hydrophobicity increases compared to untreated surface. FTIR spectroscopic analysis indicated that polymer chains at the surface undergo certain conformational changes upon solvent treatment. These changes are identified as the restricted motions of C–O–C segments and more intense and specific vibrations of methyl side groups. During solvent treatment, the change in water contact angle and FTIR spectrum of PLLA is well correlated.

Keywords: Polylactide; PLGA; XPS; Thickness; Surface analysis; ATR-FTIR; Contact angle; Wettability

Structure and properties of ZnO films grown on Si substrates with low temperature buffer layers by Wei Zheng; Yuan Liao; Li Li; Qingxuan Yu; Guanzhong Wang; Yongping Li; Zhuxi Fu (pp. 2765-2769).

Zinc oxide (ZnO) thin films were grown on Si (100) substrates by pulsed laser deposition (PLD) using two-step epitaxial growth method. Low temperature buffer layer (LTBL) was initially deposited in order to obtain high quality ZnO thin film; the as-deposited films were then annealed in air at 700°C. The effects of LTBL and annealing treatment on the structural and luminescent properties of ZnO thin film were investigated. It was found that tensile strain was remarkably relaxed by employing LTBL and the band-gap redshifted, correspondingly. The shift value was larger than that calculated from band-gap theories. After annealing treatment, it was found that the annealing temperature with 700°C has little influence on strains of ZnO films with LTBLs other than directly deposited film in our experiments. Interestingly, the different behaviors in terms of the shift of ultraviolet (UV) emission after annealing between films with and without buffer were observed, and a tentative explanation was given in this paper.

Keywords: PACS; 78.55.Et; 78.66.Hf; 81.40.GhZnO; PLD; Buffer layer; Photoluminescence; Blueshift; Strain

X-ray photoemission and X-ray absorption studies of Hf-silicate dielectric layers by R. O’Connor; G. Hughes; P.-A. Glans; T. Learmonth; K.E. Smith (pp. 2770-2775).

Photoelectron spectroscopy and X-ray absorption spectroscopy (XAS) measurements have been performed on HfSi_xO_y and HfSi_xO_yN_z dielectric layers, which are potential candidates as high- k transistor gate dielectrics. The hafnium silicate layers, 3–4nm thick, were formed by codepositing HfO₂ and SiO₂ (50%:50%) by MOCVD at 485°C on a silicon substrate following an IMEC clean. Annealing the HfSi_xO_y layer in a nitrogen atmosphere at 1000°C resulted in an increase in the Si⁴⁺ chemical shift from 3.5 to 3.9eV with respect to the Si⁰ peak. Annealing the hafnium silicate layer in a NH₃ atmosphere at 800°C resulted in the incorporation of 10% nitrogen and the decrease in the chemical shift between the Si⁴⁺ and the Si⁰ to 3.3eV. The results suggest that the inclusion of nitrogen in the silicate layer restricts the tendency of the HfO₂ and the SiO₂ to segregate into separate phases during the annealing step. Synchrotron radiation valence band photoemission studies determined that the valence band offsets were of the order of 3eV. X-ray absorption measurements show that the band gap of these layers is 4.6eV and that the magnitude of the conduction band offset is as little as 0.5eV.

Keywords: PACS; 79.60JvHafnium silicate; X-ray absorption; Soft X-ray photoemission; Band offsets

Influence of epitaxial strain on the terrace and inter-layer diffusions in metal epitaxy by Ki-Ha Hong; Jong-Kyu Yoon; Pil-Ryung Cha (pp. 2776-2784).

The influence of epitaxial strain on the surface and inter-layer diffusions are investigated using molecular statics and transition state theory with several types of embedded atom method potentials for Ag and Ni. Quantitatively to analyze the competition of the surface and inter-layer diffusions in the instability to the multi-layer growth, Ehrlich–Schwoebel barrier and the attempt frequencies of the surface and inter-layer diffusions by both hopping and exchange mechanisms are considered simultaneously. The attempt frequencies of exchange mechanism are larger by order one than those of hopping mechanism and especially, the difference becomes more severe for the inter-layer diffusion. Considering both the attempt frequency and activation energy barrier shows that the layer-by-layer growth is enhanced by compressive strain for Ag(0 0 1), which is confirmed by the existing linear stability theory and kinetic Monte Carlo simulations.

Keywords: PACS; 81.15.Aa; 81.15.; −; z; 68.43.JkEhrlich–Schwoebel barrier; Jumping frequency; Epitaxial strain; Multi-layer growth

Preparation and characterization of C54 TiSi₂ nanoislands on Si (111) by laser deposition of TiO₂ by Fengzhou Zhao; Xuefeng Cui; Bing Wang; J.G. Hou (pp. 2785-2791).

We present the preparation of C54 TiSi₂ nanoislands on Si (111) with a method of the pulsed laser deposition of titanium oxide thin films. The TiO₂ thin films with nominal thicknesses of 1nm on Si (111) were annealed at 850°C for about 4h in situ. The X-ray diffraction patterns and the X-ray photoelectron spectra indicate that the nanoislands are in C54 TiSi₂ phase. The characterization using a scanning tunneling microscope shows that the nanoislands with triangular, polygonal and rod-like shapes on Si (111) exhibit the Volmer–Weber growth mode. The sizes of the polygonal islands distribute in two separated ranges. For the small islands, they have a narrow lateral size distribution centered at 4nm and a height range in 0.6–3.6nm, while for the large islands, their lateral sizes are in the range of 12–40nm and the heights in the range of 4–9nm. The sizes of the well-shaped triangular islands are intermediate with the lateral sizes in range of 5–20nm and the heights of 2–3.5nm. The rod-like islands are about 50–200nm in length, 5nm in height and about 15–20nm in width. The origination of the various shapes of the nanoislands is attributed to the symmetry of Si (111) substrate and the lattice mismatch between the C54 TiSi₂ and the Si (111) surface.

Keywords: PACS; 81.07.-b; 61.46.+w; 68.37.Ef; 81.16.MkNanostructure; Titanium silicide; Scanning tunneling microscopy; Laser ablation

Microstructure of laser melted Al₁₈B₄O₃₃w/2024Al composite by Jin Hu; Gang Liu; Jixiu Zhang; Lingchao Kong; Weidong Fei (pp. 2792-2795).

The microstructure of a laser treated Al₁₈B₄O₃₃w/2024Al composite has been investigated using transmission electron microscope (TEM), low-angle (glancing angle) X-ray diffraction (XRD) techniques. Various surface microstructures were observed in the laser treated composite. The Al₁₈B₄O₃₃ whisker on the surface of the composite was decomposed during laser surface melting, various decomposition products were studied in the laser treated composite. Eutectic phases and the precipitation in the matrix of the composite with laser-treated were observed. The main phases detected in the molten zone were aluminum and decomposition products Al₂O₃. The effect of laser treatment on the hardness of the composite was also examined. A surface hardness of 400Hv was noted.

Keywords: Al; ₁₈; B; ₄; O; ₃₃; w/2024Al composite; Laser treatment; Microstructure; Hardness

Backside etching of fused silica with Nd:YAG laser by K. Zimmer; R. Böhme; S. Pissadakis; L. Hartwig; G. Reisse; B. Rauschenbach (pp. 2796-2800).

The laser-induced backside etching of fused silica with gallium as highly absorbing backside absorber using pulsed infrared Nd:YAG laser radiation is demonstrated for the first time. The influence of the laser fluence, the pulse number, and the pulse length on the etch rate and the etched surface topography was studied. The comparable high threshold fluences of about 3 and 7J/cm² for 18 and 73ns pulses, respectively, are caused by the high reflectivity of the fused silica–gallium interface and the high thermal conductivity of gallium. For the 18 and 73ns long pulses the etch rate rises almost linearly with the laser fluence and reaches a value of 350 and 300nm/pulse at a laser fluence of about 12 and 28J/cm², respectively. Incubation processes are almost absent because etching is already observed with the first laser pulse at all etch conditions and the etch rate is constant up to 30 pulses.The etched grooves are Gaussian-curved and show well-defined edges and a smooth bottom. The roughness measured by interference microscopy was 1.5nm rms at an etch depth of 0.6μm. The laser-induced backside etching with gallium is a promising approach for the industrial application of the backside etching technique with IR Nd:YAG laser.

Keywords: PACS; 81.65.C; 81.05.J; 79.20.D; 61.80.B; 42.55.LLaser; Fused silica; Gallium; Etching; Nd:YAG; Material processing

Nanocomposites with fumed silica/poly(vinyl pyrrolidone) prepared at a low content of solvents by V.M. Gun’ko; E.F. Voronin; L.V. Nosach; E.M. Pakhlov; O.E. Voronina; N.V. Guzenko; O.A. Kazakova; R. Leboda; J. Skubiszewska-Zięba (pp. 2801-2811).

Highly disperse nanocomposites with fumed silica/poly(vinyl pyrrolidone) (PVP) prepared using different methods were studied by infrared spectroscopy, adsorption, and quantum chemistry methods. Low amounts of water or ethanol (30wt.% with respect to the silica content) promote appropriate distribution of PVP on silica particles. The use of ethanol leads to a smaller loss of the specific surface area ( S_BET) than in the case of water used as a solvent. On PVP distribution on a silica surface, treatment of the system in a pseudo-liquid state reactor (PLSR) provides slightly better results (a lower loss in S_BET) in comparison with mechanochemical activation (MCA) in a ball mill at the PVP monolayer coverage. An increase in the activation time to 6–9h leads to an increase in the |Δ S_BET/ S_BET| value to 0.29–0.35 for both treatment methods.

Keywords: Fumed silica; Poly(vinyl pyrrolidone); Hexamethyldisilazane; IR spectroscopy; Adsorption; Structural characteristics; Solvent effect; Quantum chemical calculation

Characterization of iron surface modified by 2-mercaptobenzothiazole self-assembled monolayers by Yuanyuan Feng; Shenhao Chen; Honglin Zhang; Ping Li; Ling Wu; Wenjuan Guo (pp. 2812-2819).

A self-assembled monolayer of 2-mercaptobenzothiazole (MBT) adsorbed on the iron surface was prepared. The films were characterized by electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared reflection spectroscopy (FT-IR) and scanning electron microscopy (SEM). Besides, the microcalorimetry method was utilized to study the self-assembled process on iron surface and the adsorption mechanism was discussed from the power–time curve. The results indicated that MBT was able to form a film spontaneously on iron surface and the presence of it could protect iron from corrosion effectively. However, the assembling time and the concentration influence the protection efficiency. Quantum chemical calculations, according to which adsorption mechanism was discussed, could explain the experimental results to some extent.

Keywords: Iron; EIS; XPS; SEM; 2-Mercaptobenzothiazole; Microcalorimetry

Chemical characterization of gallium droplets grown by LP-MOCVD by L. Imhoff; O. Heintz; V. Gauthier; C. Marco de Lucas; S. Bourgeois (pp. 2820-2824).

This study is concerned with the chemical characterization of metallic gallium droplets, obtained on silicon (100) substrates with a single growth step, by the LP-MOCVD technique with TMGa like precursor. These structures are characterized by SIMS, XPS and TEM. The analyses results lead to a structure proposition for the droplets. The core is composed of metastable metallic gallium with a non-negligible carbon quantity probably coming from incomplete precursor decomposition. The outer part, composed of gallium oxide maintains the structure stability. Covering of the substrate by a thin gallium layer of gallium compounds is observed.

Keywords: PACS; 68.90.+g; 81.15.Gh; 82.80.Ms; 82.80.Pv; 68.37.LpGallium droplets; MOCVD; SIMS; XPS; TEM

Native oxidation of ultra high purity Cu bulk and thin films by J. Iijima; J.-W. Lim; S.-H. Hong; S. Suzuki; K. Mimura; M. Isshiki (pp. 2825-2829).

The effect of microstructure and purity on the native oxidation of Cu was studied by using angle-resolved X-ray photoelectron spectroscopy (AR-XPS) and spectroscopic ellipsometry (SE). A high quality copper film prepared by ion beam deposition under a substrate bias voltage of −50V (IBD Cu film at V_s=−50V) showed an oxidation resistance as high as an ultra high purity copper (UHP Cu) bulk, whereas a Cu film deposited without substrate bias voltage (IBD Cu film at V_s=0V) showed lower oxidation resistance. The growth of Cu₂O layer on the UHP Cu bulk and both types of the films obeyed in principle a logarithmic rate law. However, the growth of oxide layer on the IBD Cu films at V_s=0 and −50V deviated upward from the logarithmic rate law after the exposure time of 320 and 800h, respectively. The deviation from the logarithmic law is due to the formation of CuO on the Cu₂O layer after a critical time.

Keywords: Copper; Thin films; Oxidation; Thickness; Ion beam

Surface characterization study of a Pd/Co₃O₄ methane oxidation catalyst by Gar B. Hoflund; Zhenhua Li (pp. 2830-2834).

A surface characterization study using X-ray photoelectron spectroscopy (XPS) and ion scattering spectroscopy (ISS) has been performed on a 5wt.% Pd/Co₃O₄ methane oxidation catalyst before and after exposure to a mixture of CH₄ and O₂ in N₂ at 250°C for a period of 6 days. The primary peaks observed in the XPS survey spectra are the Co 2p, Pd 3d, O 1s and C 1s, along with Co, Pd and O Auger peaks. High-resolution Pd 3d spectra reveal that Pd exists on the surface predominantly as PdO, with no apparent change in chemical state during reaction. High-resolution XPS Co 2p and O 1s spectra reveal an accumulation of CoOOH and a depletion of CoO in the near-surface region during reaction. ISS analysis with intermittent 1-keV Ar⁺ sputtering was used to obtain depth profiles from the catalyst before and after reaction. The results indicate that the Pd/Co concentration ratio decreases with sputtering and that this ratio is larger for the as-prepared catalyst indicating that morphological changes occur during reaction. The ISS depth profile spectra obtained from the catalyst after reaction indicates the presence of an oxyhydroxide layer throughout the near-surface region. This observation is consistent with the XPS data indicating accumulation of hydroxide and oxyhydroxide species at the surface during reaction.Based on these data and the results of related studies, a reaction mechanism is proposed. In this mechanism, methane dissociatively chemisorbs to form a surface methoxy species and CoOOH. The remaining hydrogen atoms are stripped from the methoxy species leaving an active adsorbed C species which reacts with surface oxygen and a hydroxyl group to form an adsorbed bicarbonate ion which then decomposes to form CO₂ and a surface hydroxyl group. These hydroxyl groups also react to form H₂O and then more O₂ adsorbs dissociatively at the vacant sites.

Keywords: PACS; 82.30.-bPd/Co; ₃; O; ₄; catalysts; Catalytic methane oxidation; Surface characterization by XPS and ISS

Vapor phase modification of sol–gel derived titania (TiO₂) surfaces by Ireneusz Piwoński; Aneta Ilik (pp. 2835-2840).

Chemical vapor deposition (CVD) method was used in titania surface modification. Titania layers were obtained in sol–gel process and prepared as thin films on silicon wafers in dip-coating method. In order to define the influence of modification on titania surface properties (e.g., friction), various types of fluoroalkylsilanes were used. The effectiveness of the modification was monitored by FT-IR spectroscopy. The topography and frictional measurements were investigated with the use of atomic force microscopy (AFM).

Keywords: TiO; ₂; Thin films; AFM; CVD

Composition of Ta₂O₅ stacked films on N₂O- and NH₃-nitrided Si by E. Atanassova; D. Spassov; A. Paskaleva; K. Kostov (pp. 2841-2851).

The composition and microstructure of rf sputtered 20nm Ta₂O₅ on N₂O or NH₃ Rapid Thermal Nitrided (RTN) Si substrates have been investigated by X-ray photoelectron spectroscopy. RTN at 800 and 850°C is effective to suppress active oxidation of Si. There is no evidence for the presence of SiO₂ at Si interface. A lightly nitrided surface is established in both cases without a formation of detectable oxynitride layer at Si. A layered nature of the films is observed, with stoichiometric tantalum pentoxide at and close to the films’ surface. In the depth, the films are mixed ones whose composition depends on the nitridation ambient. N₂O treatment stimulates oxidation processes during the film deposition while NH₃ nitridation results to a less effective oxidation and produces Ta-silicate like film. The correlation between the composition of the interfacial regions and the nitridation gas is also discussed. The results suggest that hydrogen, as a component of nitridation ambient, plays significant role in the reactions controlling the exact composition of the deposited Ta₂O₅, activating reactions with nitrogen. Nitrogen related reactions likely occur with NH₃ processing but do not with N₂O one. The presence of nitrogen feature is not detected in N₂O-samples spectra at all. In the integration perspective, preliminary RTN of Si in N₂O or NH₃ could be a suitable way to produce layered Ta₂O₅-based films with more or less presence of tantalum silicate with a trace of nitrogen, either only at the interface with Si (N₂O-process) or in the whole film (NH₃-process).

Keywords: PACS; 77.55.+f; 79.60.Bm; 79.60JvTantalum pentoxide; XPS; Depth profiles; Silicon nitridation

On high velocity impact of micro-sized metallic particles in cold spraying by Wen-Ya Li; Hanlin Liao; Chang-Jiu Li; Gang Li; Christian Coddet; Xiaofang Wang (pp. 2852-2862).

In this study, a systematic examination of particle deformation behaviour in cold spraying was conducted for Cu particle using both the Lagrangian and Arbitrary Lagrangian Eulerian (ALE) methods. It is found that the meshing size in modelling by Largrangian method influences significantly the localized shear instability at interface areas. With refining the meshing size the onset velocity for interface shear instability decreases. The extrapolation of these results yields a reasonable critical velocity comparable to the actual one in cold spray practice. The results indicate that both the flattening ratio and compression ratio of the deformed particles increase with the increase in particle velocity, which are in good agreement with the experiment results. The ALE method provides a suitable way to examine the particle deformation in cold spraying. Moreover, the numerical results also show that there exists the similarity for the deformation of particles of different diameters.

Keywords: Cold spraying; Numerical simulation; High velocity impact; Copper particle; Deformation behaviour

Superconducting molybdenum nitride epitaxial thin films deposited on MgO and α-Al₂O₃ substrates by molecular beam epitaxy by Kei Inumaru; Kazuya Baba; Shoji Yamanaka (pp. 2863-2869).

Molybdenum nitride Mo₂N_x films were grown on MgO(001) and on α-Al₂O₃(001) substrates by molecular beam epitaxy under nitrogen radical irradiation. X-ray photoelectron spectroscopy revealed that the composition of the film varied in the range of Mo₂N_1.4–Mo₂N_2.8 depending on the growth temperature. The deposition at 973K gave well-crystallized films on both substrates. The high-resolution reciprocal space mapping by X-ray diffraction showed that the nitrogen-rich γ-Mo₂N crystalline phase (the composition: Mo₂N_1.4) was epitaxially grown on MgO at 923K with a slight tetragonal distortion ( a=0.421 and c=0.418nm) to fit the MgO lattice ( a=0.421nm). On α-Al₂O₃(001), nitrogen-rich γ-Mo₂N (Mo₂N_1.8) was grown at 973K with (111) planes parallel to the substrate surface. X-ray diffraction analysis with a multi-axes diffractometer revealed that the γ-Mo₂N on α-Al₂O₃(001) had a slight rhombohedral distortion ( a=0.4173(2) and α=90.46(3)°). Superconductivity was observed below 2.8–3K for the films grown at 973K on MgO and on α-Al₂O₃(001).

Keywords: PACS; 74.78.−w; 81.15.FgMolybdenum nitride; X-ray diffraction; Molecular beam epitaxy; Superconductivity

Studies of the adsorption state of activated carbon by surface-enhanced Raman scattering by Zhi-Mei Li; Ning Zhang; Feng-Ting Li (pp. 2870-2874).

The adsorption behaviors of Alizarins and Reactive blue X-BR on both activated carbon covered with colloidal silver were studied using the surface-enhanced Raman scattering (SERS). The adsorptive mechanisms of both Alizarins and Reactive blue X-BR were discussed. The results indicated that colloidal silver can greatly enhance Raman scattering responses and colloidal silver was adsorbed on activated carbon through electrostatic force and Van der Waals forces while both the Reactive blue X-BR and Alizarins were adsorbed on silver collide mainly through chemical absorptions.

Keywords: Surface-enhanced Raman scattering; Reactive blue X-BR; Alizarins; Colloidal silver; Activated carbon

Electrochemical impedance spectroscopy and linear polarization applied to evaluation of porosity of phosphate conversion coatings on electrogalvanized steels by Vanessa de Freitas Cunha Lins; Geraldo Francisco de Andrade Reis; Carlos Roberto de Araujo; Tulio Matencio (pp. 2875-2884).

In this work, electrochemical impedance spectroscopy and linear polarization are used in determining porosity of zinc phosphates, and of nickel and manganese modified zinc phosphates on electrogalvanized steel. The porosity of the phosphate layers ranges from 0.1% for the manganese-modified hopeite to 8% for hopeite, using the linear polarization and the electrochemical impedance spectroscopy techniques. The porosity values measured using the two techniques were in agreement. All impedance spectra of coated samples showed two steps, with two capacitive arcs and an inductive looping.

Keywords: Phosphate conversion coatings; Electrochemical impedance spectroscopy; Porosity; Linear polarization

Surface analysis of plasma grafted carbon fiber by Xuezhong Zhang; Yudong Huang; Tianyu Wang (pp. 2885-2892).

The surface characteristics of carbon fibers were studied by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and wetting measurements. The surface of carbon fiber was modified by means of plasma graft silsesquioxane. The oxygen/carbon and silicon/carbon ratio increased rapidly after treatments. Fitting the C 1s, O 1s, and Si 2p spectra demonstrated that new photopeaks were emerged, which were indicated C–Si, Si–O groups, respectively. The degree of surface roughness and the wettability of carbon fiber surface were both increased by plasma graft silsesquioxane. The results may shed some light on the design of the appropriate surface structure, which could react with resin, and the manufacture of the carbon fiber reinforced composites.

Keywords: Carbon fiber; Surface treatment; Plasma; XPS; AFM

Selective CO oxidation in hydrogen-rich gas over CuO/CeO₂ catalysts by Hanbo Zou; Xinfa Dong; Weiming Lin (pp. 2893-2898).

A series of CuO/CeO₂ catalysts with different Cu–Ce compositions were synthesized by co-precipitation method and characterized by X-ray diffraction, H₂-TPR, CO-TPD, SEM and X-ray photoelectron spectroscopy (XPS) techniques. The effects of Cu–Ce composition and water vapor on the catalytic properties for the selective CO oxidation in the hydrogen-rich gas were investigated. The results indicated that CuO (10%)/CeO₂ catalyst remained the maximum CO conversion and selectivity at 140 and 160°C, while the performance of CuO/CeO₂ catalysts deteriorated with the CuO molar ratio further increased. The interfacial CuO and CeO₂ interaction and synergistic effect enhanced the redox properties of CuO/CeO₂ catalyst and the highly dispersed copper species were proposed as the active sites for the selective CO oxidation. The blockage of catalytic active sites by absorbed water and the formation of CO–H₂O surface complexes reduced the activity of CuO (10%)/CeO₂ catalyst. The decreasing of surface lattice oxygen and absorbed oxygen species and the agglomeration of copper particles were the plausible interpretations for the deactivation of CuO (10%)/CeO₂ catalyst.

Keywords: Hydrogen-rich gas; CuO/CeO; ₂; catalyst; Selective carbon monoxide oxidation

DRIFTS study of surface reactivity to NO₂ by zinc nanoparticle aggregates and zinc hollow nanofibers by Stefano di Stasio; Vladimiro Dal Santo (pp. 2899-2910).

Zinc nanostructures synthesized with different morphologies from the same evaporation/condensation technique are studied with concern to surface reactivity to NO₂ by Diffuse Reflectance Infrared Fourier Transformed Spectroscopy (DRIFTS). Synthesis of nanopowders is obtained, according to previous work, by gas flow thermal evaporation at 540°C of bulk Zn grains. Two types of Zn powders are obtained and studied in experiments. The first one is collected on the cold walls of the reactor as a deposit produced by thermophoretic effect. It is constituted by grains (∼10μm) originated by the stratification of smaller aggregates (∼200nm) and isolated primary particles (∼50nm) born in the gas flow. The second type of powder is grown from the condensation of Zn chemical vapors within the expansion orifice of the quartz reactor after relatively long time (∼1h) deposition process. It is constituted mainly by hollow Zn nanofibers with external and internal diameter about 100 and 60nm. Preliminary characterization of the two types of powders is made by SEM, TEM, XRD. Thereafter, the two types of samples are studied by DRIFTS at variable temperature (VT). Comparison is made between the home-synthesized nanopowders with respect to commercial Zn standard dust. The Zn hollow nanofibers when exposed to NO₂ are found to exhibit dramatic reactivity, which is not observed at all either in the case of clustered aggregate zinc or of commercial Zn dust powders. Results indicate that, at increasing temperature from RT to 300°C, the hollow nanofibers surface reacts distinctively with adsorbant gas NO₂, with contemporary formation of a progressively growing narrow absorption band at 2500cm⁻¹ and contemporary depression of a doublet (∼1600–1628cm⁻¹) band. In order to justify this striking spectral feature, we propose the occurring of a possible polymerization process at nanofibers surface where most probably as a consequence of pre-treatment and exposure to gas NO₂ a very thin film of ZnO is formed. The possible role of huge specific surface of hollow nanofibers as inferred by preliminary SEM, TEM, XRD studies is discussed.

Keywords: PACS; 81.07.−b; 81.20.Rg; 68.43.−h; 78.67.ChZn; Nanoparticles; Nanofibers; TEM; SEM; XRD; DRIFTS

Effect of substrate temperature on structure and electrical resistivity of laser-ablated IrO₂ thin films by Chuanbin Wang; Yansheng Gong; Qiang Shen; Lianmeng Zhang (pp. 2911-2914).

IrO₂ thin films were prepared on Si(100) substrates by laser ablation. The effect of substrate temperature ( T_sub) on the structure (crystal orientation and surface morphology) and property (electrical resistivity) of the laser-ablated IrO₂ thin films was investigated. Well crystallized and single-phase IrO₂ thin films were obtained at T_sub=573–773K in an oxygen partial pressure of 20Pa. The preferred orientation of the laser-ablated IrO₂ thin films changed from (200) to (110) and (101) depending on T_sub. With the increasing of T_sub, both the surface roughness and crystallite size increased. The room-temperature electrical resistivity of IrO₂ thin films decreased with increasing T_sub, showing a low value of (42±6)×10⁻⁸Ωm at T_sub=773K.

Keywords: PACS; 81.15.Fg; 73.50.−hIrO; ₂; thin films; Laser ablation; Substrate temperature; Structure; Electrical resistivity

Temperature and N⁺ energy dependence on nano-structural modifications and characteristics of Mo surface by H. Savaloni; M. Motmaen-Dadgar; M. Ghoranneviss; M.R. Hantehzadeh (pp. 2915-2923).

The surface modifications of Mo massive samples (0.5mm foils) made by nitrogen ion implantation are studied by SEM, XRD, AFM, and SIMS. Nitrogen ions in the energy range of 16–30keV with a fluence of 1×10¹⁸N⁺cm⁻² were implanted in molybdenum samples for 1600s at different temperatures. XRD patterns clearly showed MoN (031) (hcp) very close to Mo (200) line. Crystallite sizes (coherently diffracting domains) obtained from MoN (031) line, showed an increase with substrate temperature. AFM images showed the formation of grains on Mo samples, which grew in size with temperature. Similar morphological changes to that has been observed for thin films by increasing substrate temperature (i.e., structure zone model (SZM)), is obtained. The density of implanted nitrogen ions and the depth of nitrogen ion implantation in Mo studied by SIMS showed a minimum for N⁺ density as well as a minimum for penetration depth of N⁺ ions in Mo at certain temperatures, which are both consistent with XRD results (i.e., IMo (20₀₎/ IMo (21₁₎) for Mo (bcc). Hence, showing a correlation between XRD and SIMS results. This phenomenon is explained on the basis of residual gas, substrate temperature, dissociation of water in the chamber and the ion energy.

Keywords: SEM; AFM; XRD; SIMS; Ion implantation; Depth profile; Molybdenum

Electrochemical properties of electrosynthesized TiO₂ thin films by S. Karuppuchamy; M. Iwasaki; H. Minoura (pp. 2924-2929).

Titanium dioxide (TiO₂) thin films prepared by cathodic electrodeposition on indium–tin-oxide coated glass substrates from simple aqueous peroxo-titanium complex solutions have been studied as a function of sintering temperature (25–500°C). The films crystallized in to anatase phase at relatively low temperature (300°C). Electrochemical properties of amorphous and anatase films were investigated by cyclic voltammogram (CV) in lithium ion containing organic electrolyte. All the films were found to show reversible electrochemical properties upon Li⁺ ion intercalation. The effects of sintering temperature on the crystallinity and consequently on the electrochemical properties of TiO₂ has been discussed.

Keywords: PACS; 47.54.Jk; 61.46.DfTitanium dioxide; Nanocrystalline; Electrodeposition; Electrochromism; Li; ⁺; intercalation

ITON Schottky contacts for GaN based UV photodetectors by N. Vanhove; J. John; A. Lorenz; K. Cheng; G. Borghs; J.E.M. Haverkort (pp. 2930-2932).

Lateral Schottky ultraviolet detectors were fabricated in GaN using indium-tin-oxynitride (ITON) as a contact metal. The GaN semiconductor material was grown on 2in. sapphire substrate by metal–organic chemical vapor deposition (MOCVD). The Schottky contact has been realized using ITON that has been deposited using sputter techniques. I– V characteristics have been measured with and without UV illumination. The device shows photo-to-dark current ratios of 10³ at −1V bias. The spectral responsivity of the UV detectors has been determined. The high spectral responsivity of more than 30 A/W at 240nm is explained by a high internal gain caused by generation–recombination centers at the ITON/GaN interface. Persistent photocurrent effect has been observed in UV light (on–off) switching operation, time constant and electron capture coefficient of the transition has been determined.

Keywords: ITON; Schottky contact; GaN; UV photodetector

Attachment of gold nanoparticles onto indium tin oxide surfaces controlled by adding citrate ions in a seed-mediated growth method by Akrajas Ali Umar; Munetaka Oyama (pp. 2933-2940).

A simple approach to control the attachment of gold nanoparticles (AuNPs) onto the indium tin oxide (ITO) surfaces is reported. Adjusting the concentration of trisodium citrate in the Au colloid solution for the seeding process from 1 to 50mM in the seed-mediated growth method, the dramatic changes in the SEM images and actual color were observed indicating the changes in nanostructures of AuNPs formed on the ITO surfaces. Whereas the attachment of smaller AuNPs with higher density were observed when 25mM citrate ions were added in the seed solution, larger AuNPs were observed to attach at 50mM. On the basis of this difference and the surface SEM images observed just after seeding, the roles of citrate ions were discussed. Consequently, it was inferred that the citrate ions affected the growth process as well as the seeding process. The repulsive power expected from the increased negative charges of citrate ions were not significant, but rather the dense attachment was promoted as the peculiar effect of citrate ions. Such control of the AuNPs attachment on ITO would be practically effective because the dense attachment can be performed by just changing the composition of the seed solution.

Keywords: Gold nanoparticles; Controlled attachment; Seed-mediated growth; Citrate ions; Surface modification; Indium tin oxides

XPS study of the deposited Ti layer in a magnetron-type sputter ion pump by Alenka Vesel; Miran Mozetic; Janez Kovac; Anton Zalar (pp. 2941-2946).

X-ray photoelectron spectroscopy (XPS) was used to study the surface chemical composition of the anode deposits in a miniature magnetron ion pump. The pump was mounted on an UHV system with the ultimate pressure of 1×10⁻⁹mbar. A stable discharge was established in the nitrogen atmosphere with some traces of CO at about 10⁻⁷mbar. The cathode was made of pure titanium. The sputtered titanium atoms deposited on the anode, where they reacted with gases to form a film of titanium compounds. The thickness of the deposited titanium layer on the anode was about 100nm. The results from XPS investigations indicate that active gases such as O₂ and N₂ react with Ti forming TiO₂ and TiN. While carbon containing molecules just adsorb on the surface and do not form carbide. In the bulk of the deposited layer almost pure TiN was found with some traces of oxygen and carbon. The part of carbon was bonded to TiC, which can be caused by ion sputtering during the depth profiling.

Keywords: PACS; 81.65; 52.80.Sm; 52.80.Vp; 79.60; 82.80EXPS; Thin films; Titanium nitride; Titanium oxide; Titanium carbide; Sputter ion pump; Discharge cell; Magnetron cell; Sputtering; Deposition

Characteristic of ceramic coatings on aluminum by plasma electrolytic oxidation in silicate and phosphate electrolyte by Guohua Lv; Weichao Gu; Huan Chen; Wenran Feng; M. Latif Khosa; Li Li; Erwu Niu; Guling Zhang; Si-Ze Yang (pp. 2947-2952).

In the present work, four processes were carried out to produce ceramic coatings on aluminum substrate in two kinds of electrolytes (silicate and phosphate solution systems) using plasma electrolytic oxidation (PEO) technology. The voltage–time responses were recorded during different PEO processes. SEM/EDX and XRD were adopted to investigate the microstructure, elements distribution and phase composition of the coatings prepared in the two electrolyte systems. It is found that coatings produced in the silicate electrolyte have a more homogeneous morphology than those produced in the phosphate system. EDX analysis shows that silicon element tends to present primarily in the outer region of the coatings while phosphorus distributes uniformly throughout the coating thickness. According to the conventional anodic oxidation mechanism, a model is set up to explain the different characteristics of ceramic coatings fabricated in different electrolytes which is helpful to understand the growth mechanism of PEO coatings.

Keywords: PACS; 77.22.JP; 82.45.HK; 68.55.JK; 68.47.GhPlasma electrolytic oxidation; Aluminum; Element distribution

Structure transition of single-texture CoSi₂ nanolayer grown by refractory-interlayer-mediated epitaxy method by O. Akhavan; A.Z. Moshfegh (pp. 2953-2957).

In this investigation, the crystalline structure of a nanometric CoSi₂ layer, formed in heat treated Co/W_xTa(1− x₎/Si(100) systems, has been studied by XRD analysis. Careful measurements of the diffraction intensities revealed that temporary formation of a metastable diamond cubic structure of CoSi₂ phase, rather than its usual CaF₂ structure, was occurred. It has been shown that formation of this metastable structure depends on the kind of the applied interlayer in addition to the annealing temperature. Among the studied systems with x=0, 0.25, 0.5, 0.75 and 1, the second and the last systems resulted in growing a (100) single-texture CoSi₂ layer with the preferred usual CaF₂ structure, a strained lattice parameter, and the best thermal stability (900–1000°C).

Keywords: PACS; 68.55.Jk; 65.40.−b; 61.10.NzSilicide; CoSi; ₂; Interlayer; XRD

Numerical study on surface acoustic wave method for determining Young's modulus of low- k films involved in multi-layered structures by Xia Xiao; Xueyi You (pp. 2958-2963).

The surface acoustic waves (SAWs) technique is becoming an attractive tool for accurately and nondestructively characterizing the mechanical property of the brittle low dielectric constant (low- k) thin film. The theoretical equations for describing SAWs propagating on the multi-layered structure are derived in this study. The dispersion features of SAWs propagating on different structures of low- k/SiO₂/Si substrate, SiO₂/low- k/Si substrate, low- k/Si substrate, and low- k/Cu/Si substrate are investigated to instruct an accurate and facile fitting process for determining Young's modulus of low- k films. The dependence of dispersion relation on the film thickness, elastic modulus of low- k materials as well as frequency are provided and discussed in detail. The study shows an obvious influence of layered structure on the dispersion relation of SAWs. For a fixed structure, the dispersion curvature increases with the decrease of Young's modulus of low- k films.

Keywords: Low-; k; ULSI interconnection; Multi-layer; SAW; Young's modulus

Modulation of the magnetic properties of CoNi coatings by electrodeposition in the presence of a redox cationic surfactant by S. Pané; E. Gómez; J. Garcia-Amorós; D. Velasco; E. Vallés (pp. 2964-2968).

Magnetic properties of CoNi films have been drastically modified by alloy electrodeposition from solutions containing a redox cationic surfactant (4-butylazobenzene-4′-(oxyethyl)trimethylammonium iodide-AZTMAI). Electrodeposition in presence of AZTMAI allows preparing CoNi coatings evolving to hard-magnetic behaviour. A gradual increase of CoNi films coercivity accompanied by a decrease of remanence and susceptibility was observed by increasing AZTMAI concentration. CoNi electrodeposition process has been modified by the presence of AZTMAI in the bath. The redox behaviour of the cationic surfactant synthesised in our laboratory was studied in the CoNi electrolytic bath revealing that additive reduces during cobalt–nickel electrodeposition. Cobalt-rich CoNi deposits obtained in the presence of AZTMAI were uniform and compact, showing acicular morphology and hcp structure with [10.0]+[11.0] orientation. The changes in crystalline structure of deposits were the responsible of magnetic properties modification.

Keywords: Electrodeposition; Magnetic alloys; Cobalt–nickel alloy; Cationic surfactant

Processing parameters and transport properties of vacuum evaporated CdSe thin films by S.A. Mahmoud; A. Ashour; E.A. Badawi (pp. 2969-2972).

Semiconducting thin films of cadmium selenide have been grown by conventional thermal evaporation technique on glass substrate. Films evaporated at substrate temperature equal 523K are stoichiometric and homogeneous. Effect of various growth parameters like rate of deposition and substrate temperature on the electrical properties has been studied in details. Also, the annealed at 673K under vacuum for 1h films have been analyzed for resistivity and Hall effect.

Keywords: CdSe thin film; Thermal evaporation; Hall effect; Electrical properties

Characterization of surface deformation around Vickers indentations in InGaAsP epilayers on InP substrate by R. Navamathavan; V. Ganesan; D. Arivuoli; G. Attolini; C. Pelosi; Chi Kyu Choi (pp. 2973-2977).

The deformation surrounding Vickers indentations on InGaAsP/InP epilayers have been studied in detail. The surface topography was characterized by using atomic force microscopy (AFM). The material pile-up and sink-in regions around the indentation impression was observed for the quaternary InGaAsP/InP epilayers. The sectional analysis mode of the AFM shows the depth profile at the indented region. Microindentation studies were carried out for different atomic fraction of the quaternary InGaAsP/InP compound semiconductor alloys. The microhardness values of InGaAsP/InP epilayers were found to be in the range of 5.08 and 5.73GPa. These results show that the hardness value of the quaternary alloy drastically increases as the composition of As was increased by 0.01 atomic fraction and when the phosphorous concentration decreases from 0.4 to 0.38. The reason may be that the increase in As concentration hardens the lattice when phosphorous concentration was less and hardness decreases when phosphorous was increased.

Keywords: PACS; 71.55.Eq; 68.37.Ps; 62.20.Fe; 46.55.+d; 62.20.-xMicroindentation; InGaAsP/InP epilayer; Deformation; AFM; Pile-up; Sink-in

Microphase separation behavior on the surfaces of PEG–MDI–PDMS multiblock copolymer coatings by Hongxia Fang; Shuxue Zhou; Limin Wu (pp. 2978-2983).

A series of poly(ethylene glycol)(PEG)–4,4′-diphenylmethanediisocyanate(MDI)–poly(dimethylsiloxane) (PDMS) multiblock copolymers were synthesized by employing two-step growth polymerization technique. Atomic force microscopy (AFM) observed nanoscopically well-organized phase-separated surfaces consisting of hydrophilic domain from PEG and MDI segments and hydrophobic domain from PDMS segments even with 50wt.% PDMS in the copolymer, and the multiblock copolymer coatings presented a surface free energy of as low as 6–8mNm⁻¹.

Keywords: Atomic force microscopy; Microphase separation; Multiblock copolymer; PEG–MDI–PDMS; Surface free energy

Oxidation and reduction of rough and flat Au surfaces by Dong Chan Lim; Young Dok Kim (pp. 2984-2987).

Very recently, we have shown that the oxidation pattern of very small (<0.7nm in particle height) and larger Au nanoparticles are dissimilar, i.e. lager particles form Au(III) species upon atomic oxygen exposures, whereas this was not found for the smaller Au nanoparticles. In the present work, we found that the oxidation pattern of a flat Au surface is analogous to those of the larger Au nanoparticles, whereas a rough surface shows a similar oxidation pattern as those of the smaller particles. This result confirms that an increase of the number of undercoordinated atoms of smaller nanoparticles should be responsible for different oxidation patterns. The oxygen species formed on flat Au surfaces can readily react with CO to CO₂, whereas the oxygen species of the rough Au surface is mostly inert to the CO-oxidation, also in agreement with the results for supported Au nanoparticles.

Keywords: X-ray photoelectron spectroscopy; Au; Oxidation; Heterogeneous catalysis; CO-oxidation

A novel process of electroless Ni-P plating with plasma electrolytic oxidation pretreatment by Zhenmin Liu; Wei Gao (pp. 2988-2991).

A novel Ni based coating – plasma electrolytic oxidation (PEO) pre-treatment followed by electroless nickel (EN) plating – has been developed to produce pore free Ni coatings on AZ91 magnesium alloy. The application of the PEO film between the nickel coating and the substrate acts as an effective barrier and catalytic layer for the subsequent nickel plating. The potentiodynamic tests indicated that the corrosion current density of the PEO+EN plating on AZ91 decreased by almost two orders of magnitudes compared to the traditional EN coating. Salt fog spray testing further proved this improvement. More importantly, the new technique does not use Cr⁺⁶ and HF in its pretreatment, therefore is a much environmentally friendlier process.

Keywords: PACS; 81.15.Pq; 81.65.Kn; 68.55.AcPlasma electrolytic oxidation; Magnesium; Electroless Ni-P plating; Corrosion; Catalytic

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Applied Surface Science (v.253, #5)

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Applied Surface Science (v.253, #5)