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Applied Surface Science (v.257, #14)

Effects of rapid thermal annealing on the structural and electrical properties of Na-doped ZnMgO ﬁlms by Ya Xue; Haiping He; Yizheng Jin; Zhizhen Ye (pp. 5927-5930).

► It has been reported that the Na-doped ZnMgO films show p-type conductivity. However, the effect of annealing temperature on the p-type ZnMgO conductivity is not well understood. In this study, we demonstrate that the electrical properties of the p-type ZnMgO are strongly dependent on annealing temperature. ► The crystallinities of the Na doped ZnMgO ﬁlms were improved with RTA at 400–700°C, the crystal size get larger as the annealing temperature growed. The as-deposited and annealed Na-doped ZnMgO ﬁlms showed great optical efficiency from the PL measurements. The hole concentration increased while the resistivity and the Hall mobility decreased after annealed at 400–700°C. The carrier type converted from p to n at an annealing temperature higher than 800°C. ► From our experiments, we can find a wide temperature window for achieving reasonable p-type by RTA, which is important because RTA is generally needed to get p-type Ohmic contact when fabricating LED.Rapid thermal annealing (RTA) is a general approach to improve the crystallinity of thin solid films. In this study, we investigated the effects of RTA on the structural and electrical properties of Na-doped ZnMgO ﬁlms grown by pulsed laser deposition. X-ray diffraction (XRD) results showed that the crystallinity of the Na-doped ZnMgO ﬁlms was improved with RTA at 400–700°C, and the grain size became larger as the annealing temperature increased. Moreover, room-temperature photoluminescence (PL) measurements demonstrated decent optical quality of the as-deposited and annealed Na-doped ZnMgO ﬁlms. Hall-effect measurements showed that the hole concentration increased from 4.9×10¹⁴ to 6.6×10¹⁵cm⁻³ to 1.9×10¹⁷ to 8.3×10¹⁷cm⁻³ while the resistivity and the Hall mobility decreased after the RTA treatments. The conduction type of the films converted from p to n when the annealing temperature is higher than 800°C. Therefore a wide temperature window to obtain reasonable p-type Na-doped ZnMgO films by RTA is achieved. It is important because RTA is generally needed to obtain p-type Ohmic contact in the fabrication processes of light-emitting diodes (LEDs).

Keywords: Rapid thermal annealing; Pulsed laser deposition; Na-doped ZnMgO

Reactor scale modeling of multi-walled carbon nanotube growth by Jeffrey J. Lombardo; Wilson K.S. Chiu (pp. 5931-5937).

► Simulation of tube flow chemical vapor deposition reactor for growth of single- and multi-walled carbon nanotubes. ► Limiting reaction processes for multi-walled carbon nanotubes change at different temperatures than the single walled carbon nanotubes. ► Optimum conditions for CNT growth governed by critical inlet methane concentration that results in hydrogen abstraction limited versus hydrocarbon adsorption limited reaction kinetic regime ► Activation energy of reaction for a given reactor temperature and inlet methane concentration also affects optimal CNT growth conditions.As the mechanisms of carbon nanotube (CNT) growth becomes known, it becomes important to understand how to implement this knowledge into reactor scale models to optimize CNT growth. In past work, we have reported fundamental mechanisms and competing deposition regimes that dictate single wall carbon nanotube growth. In this study, we will further explore the growth of carbon nanotubes with multiple walls. A tube flow chemical vapor deposition reactor is simulated using the commercial software package COMSOL, and considered the growth of single- and multi-walled carbon nanotubes. It was found that the limiting reaction processes for multi-walled carbon nanotubes change at different temperatures than the single walled carbon nanotubes and it was shown that the reactions directly governing CNT growth are a limiting process over certain parameters. This work shows that the optimum conditions for CNT growth are dependent on temperature, chemical concentration, and the number of nanotube walls. Optimal reactor conditions have been identified as defined by (1) a critical inlet methane concentration that results in hydrogen abstraction limited versus hydrocarbon adsorption limited reaction kinetic regime, and (2) activation energy of reaction for a given reactor temperature and inlet methane concentration. Successful optimization of a CNT growth processes requires taking all of those variables into account.

Keywords: Multi-walled carbon nanotube; COMSOL; Reactor scale; Simulation

Substrate–target distance dependence of structural and optical properties in case of Pb(Zr,Ti)O₃ films obtained by pulsed laser deposition by A.C. Galca; V. Stancu; M.A. Husanu; C. Dragoi; N.G. Gheorghe; L. Trupina; M. Enculescu; E. Vasile (pp. 5938-5943).

► The balance between nucleation rate and grains growth depends on the target–substrate distance. ► Parasitic phases can be diminished by increasing the target to substrate distance. ► Optical inspection gives qualitative information about stoichiometry and/or porosity.The paper presents the influence of pulsed laser deposition (PLD) parameters on the structural and optical properties of PZT thin films grown on platinum substrate. X-ray diffraction (XRD), spectroscopic ellipsometry (SE) and X-ray photoelectron spectroscopy (XPS) are used to determine the thin film properties. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) are employed to get additional information. By changing the distance between target and substrate, different crystalline orientations of PZT are obtained. The thin film thickness and its roughness, as well as the refractive index are also influenced by the chosen distance.

Keywords: PACS; 77.55.fg; 61.05.cj; 81.15.Fg; 78.66.BzPZT; Thin films; XRD; XPS; Ellipsometry

Micro arc oxidized HAp–TiO₂ nanostructured hybrid layers-part I: Effect of voltage and growth time by S. Abbasi; M.R. Bayati; F. Golestani-Fard; H.R. Rezaei; H.R. Zargar; F. Samanipour; V. Shoaei-Rad (pp. 5944-5949).

► HA–TiO₂ nanostructured porous layers were derived by micro arc oxidation method. ► Effect of the growth time on properties of the layers was studied. ► A correlation between the voltage and the properties of the layers was proposed.Micro arc oxidation was employed to grow hydroxyapatite–TiO₂ nanostructured porous composite layers. The layers were synthesized on the titanium substrates in the electrolytes consisting of calcium acetate and sodium β-glycerophosphate salts under different applied voltages for various times. SEM and AFM investigations revealed a porous structure and rough surface where the pores size and the surface roughness were respectively determined as 70–650nm and 9.8–12.7nm depending on the voltage and time. Chemical composition and phase structure of the layers were evaluated using EDX, XPS, and XRD methods. The layers consisted of the hydroxyapatite, anatase, α-TCP, and calcium titanatephases with a varying fraction depending on the growth conditions. The hydroxyapatite crystalline size was also determined as ∼42nm. The sample fabricated under the voltage of 350V for 3 min exhibited the most appropriate Ca/P ratio (∼1.60) as well as the highest amount of the hydroxyapatite phase. This sample had a fine surface morphology and a high pores density.

Keywords: Micro arc oxidation; Hydroxyapatite; Composite; Titania; Voltage; Time

Differences between Zn-porphyrin-coupled titanate nanotubes with various anchoring modes: Thermostability, spectroscopic, photocatalytic and photoelectronic properties by Xiangqing Li; Lifang Liu; Shi-Zhao Kang; Jin Mu; Guodong Li (pp. 5950-5956).

► The 5-(4-hydroxyphenyl)10,15,20-triphenylporphyrin zinc (ZnMOHPP) molecules were bonded on the outer surfaces of the titanate nanotubes (TNTs) through hydrogen bonds, while the 5,10,15,20-tetraphenylporphyrin zinc (ZnTPP) molecules were physically adsorbed into the pore channels of the TNTs via a capillary process. ► The influence of anchoring mode on the properties of the ZnP sensitized TNTs were explored. ► The different anchoring modes of ZnP on the TNTs as well as the special morphology of TNTs resulted in the remarkable distinctions in the thermal stability, photocatalytic and photoelectrochemical properties.In order to study the effects of anchoring modes on the properties of porphyrin zinc (ZnP) coupled titanate nanotubes (TNTs), the TNTs coupled with 5,10,15,20-tetraphenylporphyrin zinc (ZnTPP) and 5-(4-hydroxyphenyl)10,15,20-triphenylporphyrin zinc (ZnMOHPP), which were denoted as TNTs–ZnTPP and TNTs–ZnMOHPP, were prepared using a simple refluxing method, respectively. Based on the different experimental phenomena observed during the synthesis process as well as the results of the spectral characterization, thermogravimetric analysis, photocatalysis test and photoelectrochemistry measurement, it was demonstrated that the ZnMOHPP molecules were bonded mainly on the outer surfaces of the TNTs through hydrogen bonds, while the ZnTPP molecules were physically adsorbed into the pore channels of the TNTs via a capillary process. The different anchoring modes of ZnP on the TNTs as well as the special morphology of TNTs resulted in the remarkable distinctions in the thermal stability, photocatalytic and photoelectrochemical properties.

Keywords: Titanate nanotube; Porphyrin; Anchoring mode; Sensitization; Property

Observation of ultra-long lifetime UV-induced infrared absorption in undoped and magnesium-doped congruent lithium niobate crystals by Atif Mossad Ali; Y.C. Huang (pp. 5957-5960).

► Observation of ultra-long lifetime UV-induced IR absorption in LiNbO₃ and LiNbO₃:Mg was reported. ► The saturated absorption coefficient change in undoped CLN was higher than that in CLN:Mg. ► UV-illuminated LiNbO₃:Mg was fully recovered before undoped LiNbO₃ in the dark after 2 days. ► UV-induced absorption was due to creation of hole-trapped intermediate states O⁻ near Li vacancies.We report experimental observation of ultra-long lifetime UV-induced absorption in undoped and 5mol.% Mg-doped congruent lithium niobate crystals between 400nm and 2500nm wavelength range. The saturated absorption coefficient change in undoped congruent lithium niobate was about 3 to 7 times that in Mg-doped congruent lithium niobate in the mid-infrared spectrum. The UV-illuminated LiNbO₃:Mg was fully recovered in the dark after 2 days, whereas the undoped congruent LiNbO₃ still exhibited nontrivial infrared absorption. We attribute the cause of the UV-induced absorption to the creation of hole-trapped intermediate states O⁻ near lithium vacancies.

Keywords: Doping; Holographic storage; Two-color recording; Lithium niobate; Photorefractive materials

Microchemical surface analysis of two Numidian coins by Hénia Mousser; Redha Amri; Abdelghani Madani; André Darchen; Abdelhamid Mousser (pp. 5961-5965).

Display Omitted► Microchemical surface of two Numidian coins were studied. ► Photographs, scanning electron microscopy coupled with the energy dispersive spectrometry, the energy dispersive X-ray fluorescence spectrometry and X-ray diffraction were used. ► Three basic metals Cu, Sb and Pb were detected and analyzed. ► The corrosion products litharge (PbO), hydrocerussite (Pb₃(CO₃)₂(OH)₂), bindheimite (Pb₂Sb₂O₇) and bystromite (MgSb₂O₆) were identified on the coin's surfaces.This work is a contribution to the microchemical surface analysis of two Numidian coins. Numidia was an ancient kingdom of northern Algeria during 2nd and 1st century BC. Investigations were performed with scanning electron microscopy (SEM) coupled with energy dispersive spectrometry (EDS), energy dispersive X-ray fluorescence spectrometry (EDXRF) and X-ray diffraction (XRD). The identification of the coins was done thanks to the name initials and effigy of King Massinissa. SEM observations of coins showed heterogeneous surfaces. SEM and EDXRF analyses showed an alloy structure with copper (65%), antimony (19%) and lead (16%). The XRD identified a metal structure and corrosion products which were on the coin surfaces: Litharge (PbO), Hydrocerussite (Pb₃(CO₃)₂(OH)₂), Bindheimite (Pb₂Sb₂O₇) and Bystromite (MgSb₂O₆).

Keywords: Microchemical analysis; Numidian coin; Litharge; Hydrocerussite; Bindheimite; Bystromite

Transparent conductive and near-infrared reflective Cu-based Al-doped ZnO multilayer films grown by magnetron sputtering at room temperature by Y.P. Wang; J.G. Lu; X. Bie; Z.Z. Ye; X. Li; D. Song; X.Y. Zhao; W.Y. Ye (pp. 5966-5971).

► We prepared three kinds of multilayer films for property comparison. ► Both the AZO and Cu layers are prepared using DC magnetron sputtering. ► The multilayer is prepared using a procedure without vacuum break. ► AZO/Cu bilayer films show better photoelectrical properties than the other two.Cu-based Al-doped ZnO multilayer films were deposited on glass substrates by DC magnetron sputtering at room temperature. Three kinds of multilayer structures (AZO/Cu, AZO/Cu/AZO, and Cu/AZO) were designed for comparison, and the effects of the Cu layer thickness on photoelectrical properties of the multilayer films were investigated. The results revealed that the transparent-conductive property and near-infrared reflectance of the films are closely correlated with the Cu layer thickness, and among the three structures, AZO/Cu bi-layer films exhibited preferable photoelectrical properties. The AZO/Cu bi-layer film with a Cu layer thickness of 7nm displayed the highest figure of merit of 4.82×10⁻³Ω⁻¹, with a low sheet resistance of 21.7Ω/sq and an acceptable visible transmittance of 80%. The near infrared reflectance above 50% can be simultaneously obtained. The good performance of the coatings indicates that they are promising for coated glasses, thin film solar cells and heat-reflectors.

Keywords: Al-doped ZnO; Cu; Multilayer; Transparent conductive films; Near-infrared reflection

Effect of vacuum heat treatment on tensile strength and fracture performance of cold-sprayed Cu-4Cr-2Nb coatings by Min Yu; Wen-Ya Li; Chao Zhang; Hanlin Liao (pp. 5972-5976).

► We examine the effect of post-spray heat treatment on the microstructure and microhardness of the cold-sprayed Cu-4Cr-2Nb coatings. ► Heat treatment had a great contribution to the healing-up of the incompleteness of the interfaces between the deposited particles. ► The tensile strength of the coatings was significantly increased to approximately 299MPa compared to that of 45MPa for the as-sprayed ones.The previous study indicated that dense thick Cu-4Cr-2Nb coatings could be formed by cold spraying, and the post-spray heat treatment could significantly influence the microstructure and microhardness of the as-sprayed Cu-4Cr-2Nb coatings. In this study, the tensile strength and fracture performance of the Cu-4Cr-2Nb coatings after annealing were investigated. The vacuum heat treatment was conducted under 10⁻²Pa at 850°C for 4h. Results showed that the heat treatment had a great contribution to the healing-up of the incompleteness of the interfaces between the deposited particles. In addition, the coating microhardness decreased from 156.8±4.6Hv_0.2 for the as-sprayed coatings to 101.7±4.5Hv_0.2 for the annealed ones. The mean tensile strength of the annealed coatings was approximately 294.1±36.1MPa compared to that of 45.0±10.5MPa for the as-sprayed ones, which results from the partially metallurgically bonded zones between the deposited particles inducing by the heat treatment process.

Keywords: Cold spraying; Cu-4Cr-2Nb coatings; Vacuum heat treatment; Tensile strength; Fracture performance

A comparative study of the microstructural and magnetic properties of110 textured thin polycrystalline Fe100−_xGa_x (10≤ x≤35) films by A. Javed; N.A. Morley; T. Szumiata; M.R.J. Gibbs (pp. 5977-5983).

► In this work we examined the microstructure and magnetic properties of thin polycrystalline Fe100−_xGa_x (10≤ x≤35) films. ► It was found that all films had 〈110〉 texture normal to the film plane. ► No peaks corresponding to the D0₃ or L1₂ phases were observed from XRD. ► It was found that the effective saturation magnetostriction constant λ_eff (for the films grown without forming field H_f) were 40–50% higher compared to the films grown with H_f. ► In this study we concluded that the H_f reduced saturation field H_s but also reduced effective saturation magnetostriction constant λ_eff in the films.In this work, we present a detailed analysis of the microstructure and magnetic properties of 50±2nm thick polycrystalline Fe100−_xGa_x (10≤ x≤35) films. Two sets of Fe100−_xGa_x films were fabricated on Si100 substrates with and without a forming field H_f present. Microstructural properties were studied using X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS) and conversion electron Mössbauer spectroscopy (CEMS). Magnetic properties were studied using the magneto optical Kerr effect (MOKE) magnetometer. For all films, the110 texture normal to the film plane was observed from XRD. No peaks corresponding to the ordered D0₃ or L1₂ phases were observed from XRD. Using CEMS, the disordered A2 phase was confirmed in all films. It was found that the magnetostriction in Set-1 (forming field H_f=0) films was ∼40–50% higher compared to the Set-2 ( H_f≠0) films over the whole Ga composition range studied. Both film sets have a strong dependence of saturation field H_s on Ga composition. Set-1 films were magnetically isotropic but a weak uniaxial anisotropy was observed in Set-2 films. The saturation field H_s in Set-2 films was significantly lower compared to the Set-1 films. It was concluded that the H_f reduced H_s but also reduced effective saturation magnetostriction constant λ_eff in the films.

Keywords: Fe–Ga alloys; Thin films; Texture; Magnetic properties

Synthesis and properties of boron doped ZnO nanorods on silicon substrate by low-temperature hydrothermal reaction by Qi Yu; Liuan Li; Hongdong Li; Shiyong Gao; Dandan Sang; Jujun Yuan; Pinwen Zhu (pp. 5984-5988).

► The boron doped ZnO nanorods on silicon are synthesized by hydrothermal technique. ► The variations of growth and properties of the products are related to boron doping level. ► The incorporation of boron in the ZnO lattice is to occupy the octahedral interstice site. ► The proper boron doping level improves the intensity ratio of UV to visible emissions of ZnO nanorods.Boron doped ZnO nanorods were fabricated by hydrothermal technique on silicon substrate covered with a ZnO seed layer. It is found that the concentration of boric acid in the reaction solution plays a key role in varying the morphology and properties of the products. The growth rate along the [0001] orientation (average size in diameter) of the doped ZnO nanorods decreased (increased) with the increase of boric acid concentration. Based on the results of XRD, EDX and XPS, it is demonstrated that the boron dopants tend to occupy the octahedral interstice sites. The photoluminescence of the ZnO nanorods related to boron doping are investigated.

Keywords: ZnO nanorods; Boron doping; Hydrothermal; Photoluminescence properties

Study of the recast layer of a surface machined by sinking electrical discharge machining using water-in-oil emulsion as dielectric by Yanzhen Zhang; Yonghong Liu; Renjie Ji; Baoping Cai (pp. 5989-5997).

► The properties of the recast layer formed in the sinking electrical discharge machining process using water-in-oil emulsion as dielectric were characterized and compared with that formed using kerosene and de-ionized water as dielectric. ► The composition and phases presented in the recast layer were identified. ► The formation of micro-crack and micro-void was discussed. ► Micro hardness of the recast layer was determined.Electrical discharge machining (EDM) caused a recast layer to form at the machined surface of the workpiece. The characteristics of the recast layer have a great relationship with the type of dielectric. The research work in this paper aims to acquire a profound knowledge of the recast layers of a surface machined by sinking EDM using water-in-oil (W/O) emulsion as dielectric. Scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive spectrograph (EDS) and micro hardness analysis were performed. The characteristics of the recast layer formed in W/O emulsion were investigated by comparing them with those of the recast layer formed in kerosene and de-ionized water dielectric. It was found that the recast layer formed in W/O emulsion exhibited larger surface roughness, thickness and micro hardness compared with that formed in kerosene and de-ionized water. Both carbide and oxide were detected in the recast layer formed in W/O emulsion whereas only carbide was detected in the recast layer formed in kerosene. Due to the higher supersaturation of gases in the melted material, the recast layer formed in W/O emulsion was found to possess more micro-voids than that formed in kerosene and de-ionized water.

Keywords: Electrical discharge machining (EDM); Recast layer; Water-in-oil; Emulsion

Influence of sputter-etching of substrate on the microstructural and optical properties of ZnO films deposited by RF magnetron sputtering by C.P. Li; B.H. Yang; X.C. Wang; F. Wang; M.J. Li; L. Su; X.W. Li (pp. 5998-6003).

► ZnO films were prepared with increasing sputter-etching time of substrate. ► The grain size decreases and the film surface becomes smoother. ► The crystallinity and c-axis orientation are improved. ► The E₁(TO) phonon mode blue-shifts while A₁(TO) mode red-shifts.► The optical band gap increases from 3.10eV to 3.23eV.ZnO films were prepared using radio frequency magnetron sputtering on Si(111) substrates that were sputter-etched for different times ranging from 10 to 30min. As the sputter-etching time of the substrate increases, both the size of ZnO grains and the root-mean-square (RMS) roughness decrease while the thickness of the ZnO films shows no obvious change. Meanwhile, the crystallinity and c-axis orientation are improved by increasing the sputter-etching time of the substrate. The major peaks at 99 and 438cm⁻¹ are observed in Raman spectra of all prepared films and are identified as E₂(low) and E₂(high) modes, respectively. The Raman peak at 583cm⁻¹ appears only in the films whose substrates were sputter-etched for 20min and is assigned to E₁(LO) mode. Typical ZnO infrared vibration peak located at 410cm⁻¹ is found in all FTIR spectra and is attributed to E₁(TO) phonon mode. The shoulder at about 382cm⁻¹ appearing in the films whose substrates were sputter-etched for shorter time (10–20min) originates from A₁(TO) phonon mode. The results of photoluminescence (PL) spectra reveal that the optical band gap (Eg) of the ZnO films increases from 3.10eV to 3.23eV with the increase of the sputter-etching time of the substrate.

Keywords: ZnO films; Microstructure; Sputter-etching; Optical properties

Functionalized SBA-15 materials for bilirubin adsorption by Tao Tang; Yanling Zhao; Yao Xu; Dong Wu; Jun Xu; Feng Deng (pp. 6004-6009).

► NH₂, CH₃-functionalized SBA-15 mesoporous material as bilirubin adsorbent. ► The driving force investigation for bilirubin adsorption on mesoporous materials. ► The electrostatic force dominantly drives bilirubin adsorption. ► The hydrophobic interaction promotes bilirubin adsorption. ► Higher bilirubin adsorption capacity on this bifunctionalized material.To investigate the driving force for bilirubin adsorption on mesoporous materials, a comparative study was carried out between pure siliceous SBA-15 and three functionalized SBA-15 mesoporous materials: CH₃-SBA-15 (MS), NH₂-SBA-15 (AS), and CH₃/NH₂-SBA-15 (AMS) that were synthesized by one-pot method. The obtained materials exhibited large surface areas (553–810m²/g) and pore size (6.6–7.1nm) demonstrated by XRD and N₂-ad/desorption analysis. The SEM images showed that the materials had similar fiberlike morphology. The functionalization extent was calculated according to²⁹Si MAS NMR spectra and it was close to the designed value (10%). The synthesized mesoporous materials were used as bilirubin adsorbents and showed higher bilirubin adsorption capacities than the commercial active carbon. The adsorption capacities of amine functionalized samples AMS and AS were larger than those of pure siliceous SBA-15 and MS, indicating that electrostatic interaction was the dominant driving force for bilirubin adsorption on mesoporous materials. Increasing the ionic strength of bilirubin solution by adding NaCl would decrease the bilirubin adsorption capacity of mesoporous material, which further demonstrated that the electrostatic interaction was the dominant driving force for bilirubin adsorption. In addition, the hydrophobic interaction provided by methyl groups could promote the bilirubin adsorption.

Keywords: Mesoporous materials; Bilirubin; Adsorption

Fabrication of silver nanoparticles deposited on boehmite sol for surface enhanced Raman scattering by Atsuya Towata; Judy Lee; Kyuichi Yasui; Toru Tuziuti; Teruyuki Kozuka; Yasuo Iida (pp. 6010-6015).

► The relationship between the SERS of composite and its surface morphology was examined. ► The addition of boehmite only became effective when the concentration of Ag is increased. ► The addition of moderate amount of boehmite sol promoted the contact between the Ag nanoparticles. ► Structure comprises of networks and is responsible for SERS improvement compared to no boehmite.The composite consisting of silver nanoparticles deposited on boehmite hybrid was synthesized by NaBH₄ reduction technique. The morphology of the composite was studied by TEM, UV/Vis spectrophotometer and particle sizer. The size of the silver nanoparticles deposited on the surface of the boehmite ranged from 10nm to 100nm. The contact of silver nanoparticles increased by means of deposition of silver nanoparticles on the boehmite sol and the aggregation of the composites. This leads to the appearance of a shoulder at 450nm in the UV–Vis absorption spectra with the addition of 0.15mg and 1.5mg boehmite. It was found that the intensity of the SERS in the case of the composite was higher than for silver colloids consisting of a concentration of silver greater than 3.2mM.

Keywords: SERS; Silver; Composite; Boehmite

Structural stability and electronic structure of iron adsorption on the GaN(0001) surface by Rafael González-Hernández; William López Pérez; Jairo Arbey Rodríguez M. (pp. 6016-6020).

► The most stable positions of a Fe adatom on GaN(0001) surface are the H3 sites and T4 sites, for low and high Fe coverage respectively. ► The Fe–H3 surface reconstruction exhibits a half-metallic behavior with a spin band gap and stable ferromagnetism ordering. ► The iron monolayers on the GaN(0001) surface present a ferromagnetic order and a large thermal stability. ► The iron monolayer stability may be due to the Fe–Ga covalent bond formation on the GaN(0001) surface.In this work, we have investigated by means of first-principles spin-polarized calculations, the electronic and magnetic properties of iron (Fe) adsorption and diffusion on the GaN(0001) surface using density functional theory (DFT) within a plane-wave pseudopotential scheme. In the surface adsorption study, results show that the most stable positions of a Fe adatom on GaN(0001) surface are the H3 sites and T4 sites, for low and high Fe coverage respectively. We found that the Fe–H3 2×2 surface reconstruction exhibits a half-metallic behavior with a spin band gap and stable ferromagnetism ordering, which is a desirable property for high-efficiency magnetoelectronic devices. In addition, confirming previous experimental results, we found that the iron monolayers present a ferromagnetic order and a large thermal stability. This is interesting from a theoretical point of view and for its technological applications.

Keywords: Density functional calculations; Gallium nitride; Chemisorption; Surface diffusion

Angle dependent laser nanopatterning of poly(ethylene terephthalate) surfaces by P. Slepička; A. Chaloupka; P. Sajdl; J. Heitz; V. Hnatowicz; V. Švorčík (pp. 6021-6025).

► F₂ irradiation of PET induces the formation of angle dependent ripples. ► F₂ angle irradiated PET has lower amount of oxygen than pristine and KrF irradiated. ► PET surface chemistry affects the Au sputtered layer growth. ► Au sputtering on KrF irradiated PET causes nano-wire formation. ► Au sputtering on F₂ angle irradiated PET causes continuous pattern with nano-hills.Interference effects can lead to the formation of ripple structures at laser-irradiated poly(ethylene terephthalate) surfaces. Poly(ethylene terephthalate) surface was irradiated with linearly polarized light of a pulsed 157nm laser. In a certain range of irradiation parameters, the irradiation resulted in the formation of coherent ripples patterns. The dimension of the pattern depends on the angle of the laser beam incidence. The surface morphology of the nano-patterned poly(ethylene terephthalate) was analyzed by atomic force microscopy and focused ion beam-scanning electron microscopy. Oxygen concentration in the modified polymer surface was studied by angular resolved X-ray induced photo-electron spectroscopy. Gold nano-layers were consecutively sputtered onto the laser irradiated poly(ethylene terephthalate) surfaces. The morphology of the sputtered gold nano-layers was investigated with atomic force microscopy too. We found that the morphology of the gold nano-layers changes and depends on the surface pattern of the laser irradiated poly(ethylene terephthalate). Formation of gold “nano-hills” is observed at the ridges of the ripple structures. The amount of oxygen together with the morphology of prepared polymer pattern may be the dominant factors controlling the gold layer growth. The present results are compared with those obtained earlier on PET irradiated with krypton fluoride laser.

Keywords: Polyethyleneterephtalate; Excimer laser; Ripples; Gold; Sputtering; Morphology

A template-free sol–gel technique for controlled growth of ZnO nanorod arrays by N. Huang; M.W. Zhu; L.J. Gao; J. Gong; C. Sun; X. Jiang (pp. 6026-6033).

► The oriented ZnO nanorod arrays were fabricated by template-free sol–gel technique. ► The orientation of ZnO nanorods can be controlled by adjusting the heating temperatures and withdrawal speed. ► The room temperature PL spectrum of aligned ZnO arrays exhibits a strong UV emission with a weak green emission and a blue double-peak emission. ► The different in alignment of the nanorods is ascribed to different orientation of the film between the substrate and nanorods dependent on the experimental parameters.The growth of ZnO nanorod arrays via a template-free sol–gel process was investigated. The nanorod is single-crystalline wurtzite structure with [0001] growth direction determined by the transmission electron microscope. The aligned ZnO arrays were obtained directly on the glass substrates by adjusting the temperatures and the withdrawal speeds, without seed-layer or template assistant. A thicker oriented ZnO nanorod arrays was obtained at proper experimental conditions by adding dip-coating layers. Room temperature photoluminescence spectrum exhibits an intensive UV emission with a weak broad green emission as well as a blue double-peak emission located at 451 and 468nm, respectively. Further investigation results show that the difference in the alignment of nanorods ascribes to the different orientations of the nanoparticles-packed film formed prior to nanorods on the substrate. Well ordered ZnO nanorods are formed from this film with good c-axis orientation. Our study is expected to pave a way for direct growth of oriented nanorods by low-cost solution approaches.

Keywords: Nanostructure; Sol–gel technique; Morphology; Zinc oxide

Designing N-halamine based antibacterial surface on polymers: Fabrication, characterization, and biocidal functions by Yong Chen; Qiuxia Han (pp. 6034-6039).

► Polymers of arbitrary chemistry can be functionalized by spin coating a layer of functional block copolymers. ► Density of introduced functional groups is controlled by concentration of block copolymer solutions.► Reactivity of surface bound functional groups is confirmed using conjugation reaction.► Stability and biofuntion of the functionalized surface are studied.We demonstrate a valuable method to generate reactive groups on inert polymer surfaces and bond antibacterial agents for biocidal ability. Polystyrene (PS) surfaces were functionalized by spin coating of sub-monolayer and monolayer films of poly(styrene- b- tert-butyl acrylate) (PS-P tBA) block copolymer from solutions in toluene. PS-P tBA self-assembled to a bilayer structure on PS that contains a surface layer of the P tBA blocks ordering at the air–polymer interface and a bottom layer of the PS blocks entangling with the PS substrate. The thickness of P tBA layer could be linearly controlled by the concentration of the spin coating solution and a 2.5nm saturated monolayer coverage of P tBA was achieved at 0.35% (w/w). Carboxyl groups were generated by exposing the tert-butyl ester groups of P tBA on saturated surface to trifluoroacetic acid (TFA) to bond tert-butylamine via amide bonds that were further chlorinated to N-halamine with NaOCl solution. The density of N-halamine on the chlorinated surface was calculated to be 1.05×10⁻⁵mol/m² by iodimetric/thiosulfate titration. Presented data showed the N-halamine surface provided powerful antibacterial activities against Staphylococcus aureus and Escherichia coli. Over 50% of the chlorine lost after UVA irradiation could be regained upon rechlorination. This design concept can be virtually applied to any inert polymer by choosing appropriate block copolymers and antibacterial agents to attain desirable biocidal activity.

Keywords: Surface functionalization; Antibacterial polymer surfaces; N-halamine; Spin coating

Digital image correlation approach to cracking and decohesion in a brittle coating/ductile substrate system by D.J. Wu; W.G. Mao; Y.C. Zhou; C. Lu (pp. 6040-6043).

► We monitored strain evolutions of thermal barrier coatings by DIC technique. ► The results clarified several controversial assumptions applied in other models. ► We have estimated mechanical properties of thermal barrier coatings by this method.By using a digital image correlation technique, the full/local field strain in a brittle coating/ductile substrate system during tension has been successfully monitored. One of the most important experimental results indicates that the distribution of interfacial shear stress in the segmented coating is antisymmetric about the center, which clarifies several controversial assumptions introduced in theoretical models. Two key mechanical properties of thermal barrier coatings, fracture strength in coating and interfacial adhesion strength, were determined as 35.0±4.6 and 14.1±3.2MPa, respectively, which are consistent with available experimental data.

Keywords: Digital image correlation; Tensile fracture strength; Interfacial shear strength; Thermal barrier coating

Fabrication and characterization of a cotton candy like surface with superhydrophobicity by You Hu; Chengya Huang; Dong Su; Qiangwei Jiang; Yunfeng Zhu (pp. 6044-6048).

► In this study, the in situ polymerization compositions of D₅/SiO₂ used to prepare superhydrophobic films are novel and first time. ► The fabrication of the superhydrophobic film can be achieved by one step and it has a thermal stability up to 450°C. This provides a sample and inexpensive method to fabricate superhydrophobic surface with high temperature resistance. ► We introduced a sample 2-D model to simulate and analyses the wetting behavior, air trapping and capillary force on superhydrophobic behavior were evaluated.Superhydrophobic thin films were prepared on glass by air-brushing the in situ polymerization compositions of D₅/SiO₂. The wettability and morphology were investigated by contact angle measurement and scanning electron microscopy. The most superhydrophobic samples prepared had a static water contact angle of 157° for a 5μl droplet and a sliding angle of ∼1° for 10μl droplet. Thermal stability analysis showed that the surface maintained superhydrophobic at temperature up to 450°C. Air trapping and capillary force on superhydrophobic behavior were evaluated.

Keywords: Superhydrophobic; D; ₅; Cotton candy; Capillary force

Adsorption of SO₂ on Li atoms deposited on MgO (100) surface: DFT calculations by Kh.M. Eid; H.Y. Ammar (pp. 6049-6058).

► The SO₂ molecule in both cases (S-atom down) or (O-atom down) preferably adsorbed on MgO( F_s) than on regular MgO(O⁻²) sites for the MgO substrate surfaces. ► The strong adsorption (chemisorption) of SO₂ molecule on F_s site may be referred to the high basicity of the MgO substrate surfaces containing F_s. ► The F_s-site substrate surfaces lead to form a stable surface sulfite. ► The SO₂ molecule is strongly adsorbed when O-atom down toward Li/MgO(O⁻²) systems than S-atom down toward Li/MgO(O⁻²) systems. ► The Li atom supported by MgO(O⁻²) substrate surfaces convert the adsorption processes of SO₂ on Li/MgO(O⁻²) systems from physisorption into chemisorption, therefore, the Li atom supported by MgO(O⁻²) substrate surfaces have a catalytic activity. ► The spin density (SD) distributions between Li atom and SO₂ molecules in the SO₂/Li/MgO(O⁻²) systems play a rule for the change of the adsorption processes from physisorption into chemisorption.The adsorption of sulfur dioxide molecule (SO₂) on Li atom deposited on the surfaces of metal oxide MgO (100) on both anionic and defect ( F_s-center) sites located on various geometrical defects (terrace, edge and corner) has been studied using density functional theory (DFT) in combination with embedded cluster model. The adsorption energy ( E_ads) of SO₂ molecule (S-atom down as well as O-atom down) in different positions on both of O⁻² and F_s sites is considered. The spin density (SD) distribution due to the presence of Li atom is discussed. The geometrical optimizations have been done for the additive materials and MgO substrate surfaces (terrace, edge and corner). The oxygen vacancy formation energies have been evaluated for MgO substrate surfaces. The ionization potential (IP) for defect free and defect containing of the MgO surfaces has been calculated. The adsorption properties of SO₂ are analyzed in terms of the E_ads, the electron donation (basicity), the elongation of S–O bond length and the atomic charges on adsorbed materials. The presence of the Li atom increases the catalytic effect of the anionic O⁻² site of MgO substrate surfaces (converted from physisorption to chemisorption). On the other hand, the presence of the Li atom decreases the catalytic effect of the F_s-site of MgO substrate surfaces. Generally, the SO₂ molecule is strongly adsorbed (chemisorption) on the MgO substrate surfaces containing F_s-center.

Keywords: Adsorption of SO; ₂; Chemisorption; MgO surfaces; Density-functional theory; F; _s; -Center

An easy and novel approach for the decoration of graphene oxide by Fe₃O₄ nanoparticles by Ying Li; Jia Chu; Jingyao Qi; Xin Li (pp. 6059-6062).

A simple and tunable approach for the decoration of graphene oxide by magnetite nanoparticles is reported.Display Omitted► A new and relatively general route was developed to fabricate graphene oxide (GO)–Fe₃O₄ hybrid. ► The highly water-soluble magnetite colloidal nanocrystals coated GO by reacting with the GO functionalized with COCl groups. ► The as-synthesized GO–Fe₃O₄ hybrid was investigated in detail using various techniques.A new and relatively general route was developed to fabricate graphene oxide (GO)–Fe₃O₄ hybrid. X-ray diffraction, transmission electron morphology, X-ray photoelectron spectroscopy (XPS) and energy-dispersive spectrum were used to demonstrate the successful attachment of iron oxide nanoparticles to GO sheets. Transmission electron microscopy observation indicates that the size of the Fe₃O₄ nanoparticles was about 2.7nm with narrow size distribution. Moreover, this hybrid shows superparamagnetic property and allows the rapid separation under an external-magnetic field. In addition, the method could be extended to further development of graphene-based nanoelectronics.

Keywords: Graphene oxide; Fe; ₃; O; ₄; nanoparticles; Decoration; Hybrid

Studies on distribution of element contents in transient layer at interface between boron-doped diamond film electrode and tantalum substrate by Jiachang Liang; Chengyao Gao; Liping Zhang; Lihui Jiang; Zhengquan Yang; Zhiping Wang; Chaohui Ji; Xiaoyun Le; Cuihua Rong; Jian Zhang (pp. 6063-6067).

► Continuous transient layer was grown at interface between film and substrate. ► Mismatch of thermal expansion coefficients at interface was eliminated. ► Stress-corrosion delamination of film disappeared. ► Corrosion stability and working lifetime of boron-doped diamond film increased.The boron-doped diamond film (BDD) grown on tantalum (Ta) substrate as an electrode (BDD/Ta) was prepared by hot filament chemical vapor deposition method. The experimental results demonstrated that our BDD/Ta had high current efficiency, strong ability to degrade wastewater, good corrosion stability and long lifetime. These excellent characteristics of BDD/Ta have been explained in terms of Rutherford backscattering (RBS) experiments. RBS investigation revealed that the continuous transient layer at the interface between boron-doped diamond film and Ta-substrate was formed and the microstructure of the continuous transient layer given by the continuous distribution of all element contents at the interface was obtained. The thicknesses of boron-doped diamond film and the continuous transient layer were about equal to 8000×10¹⁵atoms/cm² and 5800×10¹⁵atoms/cm², respectively. The formation of the continuous transient layer at the interface can eliminate the mismatch of thermal expansion coefficients (TEC) at the interface and only lead to the slow change of TEC because of the continuous distribution of element contents of the film and substrate in the transient layer at the interface. Thus, there is no residual stress to concentrate on the interface and the stress-corrosion delamination of the film disappears. Therefore, the corrosion stability and lifetime of BDD/Ta increase and last well, that have been verified by X-ray diffraction (XRD) experiments.

Keywords: PACS; 68.35.Fx; 68.55.Ln; 61.82.BgMicrostructure of continuous transient layer; Boron-doped diamond film; Rutherford backscattering

Modification of surface properties of polyamide 6 films with atmospheric pressure plasma by Zhiqiang Gao (pp. 6068-6072).

► We treated polyamide 6 films using pure helium (He), He/O₂ and He/CF₄, respectively. ► We investigated the effect of the different plasma gases treatment on the surface modification of atmospheric pressure plasma. ► The addition of O₂ or CF₄ to He plasma had different effectiveness on the polymer surface modification.To investigate the effect of the different plasma gases treatment on the surface modification of atmospheric pressure plasma, polyamide 6 films were treated using pure helium (He), He/O₂ and He/CF₄, respectively. Atomic force microscopy (AFM) showed rougher surface, while X-ray photoelectron spectroscopy (XPS) revealed increased oxygen and fluorine contents after the plasma treatments. The plasma treated samples had lower water contact angles and higher T-peel strength than that of the control. The addition of small amount of O₂ or CF₄ to He plasma increases the effectiveness of the plasma treatment in polymer surface modification in terms of surface roughness, surface hydrophilic groups, etching rate, water contact angle and bonding strength.

Keywords: Atmospheric pressure plasma; Polyamide 6; Etching rate; AFM; XPS; T-peel strength

Structure and optoelectronic properties of multi-element oxide thin film by Ruei-Sung Yu; Chueh-Jung Huang; Rong-Hsin Huang; Chung-Hsing Sun; Fuh-Sheng Shieu (pp. 6073-6078).

► The (ZnSnCuTiNb)1−_xO_x films are all of amorphous without any multi-phase structure. ► By controlling the oxygen content which changes electron binding energy of the cations, we can alter the electrical and optical properties of the films. ► The (ZnSnCuTiNb)1−_xO_x films possess the characteristics of optoelectronic semiconductor whose oxygen content are 51.6 and 56atom%. ► These films have carrier concentrations of 2.62×10²⁰ and 1.37×10¹⁷cm⁻³, and conductivities ( σ) of 57.2 and 9.45×10⁻³(Ωcm)⁻¹, and indirect band gaps of 1.69 and 2.26eV, respectively.This paper focuses on analyzing structural and optoelectronic properties of (ZnSnCuTiNb)1−_xO_x films. The results of XRD and HRTEM indicate that the (ZnSnCuTiNb)1−_xO_x films are all of amorphous without any multi-phase structure. XPS analysis confirms that the increase of the oxygen content makes the cations electron binding energy higher, suggesting the removal of valence electrons or the extent of oxidation can change the optoelectronic properties of the films. The (ZnSnCuTiNb)1−_xO_x films possess the characteristics of optoelectronic semiconductor whose oxygen content are 51.6 and 56atom%. These films have carrier concentrations of 2.62×10²⁰ and 1.37×10¹⁷cm⁻³, and conductivities ( σ) of 57.2 and 9.45×10⁻³(Ωcm)⁻¹, and indirect band gaps of 1.69 and 2.26eV, respectively. They are n-type oxide semiconductors.

Keywords: Structure; Optoelectronic properties; Semiconductor; Transparent conducting oxide; Multi-element oxide

Annealing effect on microstructure and mechanical properties of amorphous Al–C–N films by Q.H. Luo; Y.H. Lu; Y.Z. Lou (pp. 6079-6084).

► This study revealed that the microstructure of annealed Al–C–N films strongly depended on not only annealing temperature but also Al content. ► At a low temperature below 700°C, Al–C–N shows its high thermal stability. ► When temperature was increased to 1000°C and above, Al–C–N thin films with different Al contents exhibited different annealing responses. ► For the thin films at low Al content, film delamination rather than crystallization occurred. ► Otherwise, annealing treatment led to the formation of nanocomposites of AlN embedded into amorphous matrices.Al–C–N thin films with different Al contents were deposited on Si (100) substrates by closed-field unbalanced reactive magnetron sputtering in the mixture of argon and nitrogen gases. These films were subsequently vacuum-annealed at 700°C and 1000°C, respectively. The microstructures of as-deposited and annealed films were characterized by X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM); while the hardness and elastic modulus values were measured by nano-indention method. The results indicated that the microstructure of both as-deposited and annealed Al–C–N films strongly depended on Al content. For thin films at low Al content, film delamination rather than crystallization occurred after the sample was annealed at 1000°C. For thin films at high Al content, annealing led to the formation of AlN nanocrystallites, which produced nanocomposites of AlN embedded into amorphous matrices. Both the density and size of AlN nanocrystallites were found to decrease with increasing depth from the film surface. With increasing of annealing temperature, both hardness and elastic modulus values were decreased; this trend was decreased at high Al content. Annealing did not change elastic recovery property of Al–C–N thin films.

Keywords: Al–C–N films; Annealing; Microstructure; Mechanical properties

The influence of Mn content on luminescence properties in Mn-doped ZnO films deposited by ultrasonic spray assisted chemical vapor deposition by D. Shuang; X.X. Zhu; J.B. Wang; X.L. Zhong; G.J. Huang; C. He (pp. 6085-6088).

Mn-doped ZnO (Zn1−_xMn_xO, 0≤ x≤0.1) films are prepared by an ultrasonic spray assisted chemical vapor deposition method. X-ray diffraction and Raman scattering show that all the Zn1−_xMn_xO films are good wurtzite structures without any impurity phases. Cathodoluminescence spectra show that ultraviolet emission and green luminescence can be observed. The intensity of ultraviolet emission decreases with the increment of x, while the intensity of green luminescence increases with the increment of x when x≤0.02. However, when x ( x>0.02) is further increased, the intensity of green luminescence decreases gradually, and the green luminescence disappears when x is above 0.075. We consider that the change of the luminescence is related to the competition between the radiative recombination and the non-radiative recombination.

Keywords: PACS; 78.20.−e; 81.15.−z; 81.05.DzSpray assisted chemical vapor deposition; Cathodoluminescence

The use of a perylenediimide derivative as a dopant in hole transport layer of an organic light emitting device by Ilker Oner; Canan Varlikli; Siddik Icli (pp. 6089-6094).

► A PDI derivative, was used as a dopant in the hole transport layer of green OLED. ► PDI doping increased the luminous and power efficiencies by a factor of 15. ► PDI acts as a trap for holes leading to a better charge balance. ► Surface roughness is an important parameter on OLED performance. ► PDI presence reduced the surface roughness from 1.5nm to 0.75–0.85nm.A perylene diimide (PDI) derivative was used as a dopant in the hole transport layer (HTL) of an organic light emitting device. The HTL examined was poly (N-vinylcarbazole) (PVK) and the PDI used was N,N′-di-dodecylperylene-3,4,9,10-bis-(dicarboximide), (N-DODEPER). The structure of the device was ITO/PEDOT:PSS (70nm)/PVK:N-DODEPER(0, 0.2, 0.4, 0.8wt.%) (65nm)/Alq₃ (35nm)/LiF (1.3nm)/Al (100nm). 0.8wt.% N-DODEPER presence exhibited a luminous efficiency of 7.87cd/A and an external quantum efficiency of 0.78% at 21mA/cm² and a power efficiency of 3lm/W at 12mA/cm². The luminous and power efficiency values were significantly enhanced by a factor of 15 with respect to that of undoped device.

Keywords: Organic electroluminescence; Solution processed; Perylenediimide; n-Type semiconductor

Study on the deterioration process of bipolar coating using electrochemical impedance spectroscopy by Xiaomei Su; Qiong Zhou; Qingyi Zhang; Yu Zhang; Hong Zhang (pp. 6095-6101).

► Anticorrosion mechanism of bipolar coating using EIS. ► Impedance module of bipolar coating keeps steady during the immersion period. ► p–n junction formed in the bipolar coating. ► p–n junction acted as ion barrier prevents the further corrosion of metal substrate.A bipolar coating, which is composed of inner layer epoxy with nano SiO₂ modified by cetyltrimethylammonium bromide (CTAB) (containing positive fixed charge) and outer layer epoxy with nano SiO₂ modified by sodium dodecylbenzenesulfonate (SDBS) (containing negative charge), was prepared in this paper. Its deterioration process after exposure to 5% KCl solution was also studied by EIS measurement and SEM observation. The results indicate that the impedance module of the bipolar coating is about 1E+9ohm after a longer time immersion period. The bipolar coating has a better anti-corrosion capacity than that of epoxy coating. The cation-selective outer layer in bipolar coating inhibits the aggressive anion, such as Cl⁻ ion, passing through the outer coating. Similarly, the anion-selective inner layer inhibits the metal cation passing through the inner coating. Thus the bipolar coating can protect the metal substrate from corrosion effectively. The p–n junction of bipolar coating, which has great charge storage ability, is the key factor in the anti-corrosion capacity of bipolar coating.

Keywords: Bipolar coating; p–n junction; EIS; Ion-selective; Anticorrosion

The kinetic process of non-smooth substrate thin film growth via parallel Monte Carlo method by Zi-Yi Chen; Yuan Zhu; Shu-Han Chen; Zhi-Ren Qiu; Shao-Ji Jiang (pp. 6102-6106).

► We evaluated a Monte Carlo simulation model of thin film growth based on parallel algorithm. ► Non-smooth substrate with special defect mode is introduced in such a model. ► We applied a new substrate dividing method in order to carry on parallel algorithm more efficient. ► Results show that surface defect mode contributes to crystal nucleation. ► We find that density defect points, substrate temperature and the number of processors contribute decisively to the parallel efficiency and speedup.A Monte Carlo simulation model of thin film growth based on parallel algorithm is presented. Non-smooth substrate with special defect mode is introduced in such a model. The method of regionalizing is used to divide the substrate into sub-regions. This method is supposed to be modulated according to the defect mode. The effects of surface defect mode and substrate temperature, such as the nucleation ratio and the average island size, are studied through parallel Monte Carlo method. The kinetic process of thin film growth in the defect mode is also discussed. Results show that surface defect mode contributes to crystal nucleation. Analyzing parallel simulation results we find that density defect points, substrate temperature and the number of processors contribute decisively to the parallel efficiency and speedup. According to defect mode we can obtain large grain size more feasibly and the parallel algorithm of this model can guide the non-smooth substrate simulation work.

Keywords: Thin film growth; Simulation; Monte Carlo method; Parallel algorithm

Effect of NH₄OH concentration on p-type doped ZnO film by solution based process by Ian Y.Y. Bu (pp. 6107-6111).

► Highly c-axis oriented crystalline nitrogen/aluminium co doped zinc oxide film can be obtained through earth abundant aqua ammonia and aluminium chloride. ► Excessive aqua ammonia resulted in increasing precipitation and rough surface. ► Good quality p-type ZnO films can be synthesized through sol–gel process.Highly oriented and large scale p-type ZnO:Al:N films have been successfully synthesized by a simple, solution-based approach. In this approach, p-type doping of zinc oxide was achieved using combination of aqueous ammonia, zinc acetate and aluminium chloride. X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), photoluminescence and Hall measurements indicate that the structure of the ZnO:Al:N films were highly influenced by aqueous ammonia concentration. Excessive aqueous ammonia results in randomly oriented film with excessive precipitation.

Keywords: Zinc oxide; Sol–gel; Highly oriented; Aqueous ammonia; p-Type

New optical features to enhance solar cell performance based on porous silicon surfaces by Asmiet Ramizy; Z. Hassan; Khalid Omar; Y. Al-Douri; M.A. Mahdi (pp. 6112-6117).

► Porous silicon formed on both sides. ► Investigate the effect of PS on performance of Si solar cells and enhance the efficiency by manipulating reflected mirrors. ► Solar cell efficiency is increased to 15.4% with PS formed on both sides. ► New features of refractive index and optical dielectric constant of PS.Electrochemical etching is used to fabricate porous silicon (PS) surfaces for both sides of the Si wafer. The effect of PS on performance of Si solar cells is investigated and the reflected mirrors are manipulated to enhance solar cell efficiency. The process is promising for solar cell manufacturing due to its simplicity, lower cost and suitability for mass production. The PS surface has discrete pores and short-branched pores on the polished wafer side. In contrast, the etched backside of the wafer has smaller pore size, with random pores. PS formed on both sides has lower reflectivity value compared with results in other works. Solar cell efficiency is increased to 15.4% with PS formed on both sides compared with the unetched sample and other results. Using empirical models, the optical properties of the refractive index and the optical dielectric constant are investigated. The porous surface texturing properties could enhance and increase the conversion efficiency of porous Si solar cells. The obtained results are in agreement with experimental and other data.

Keywords: PACS; 61.43.Gt; 88.40.H−; 72.80.Jc; 78.20.CiPorous silicon; Solar cell; Crystalline silicon; Refractive index

Physical characterization of a new composition of oxidized zirconium–2.5wt% niobium produced using a two step process for biomedical applications by V. Pawar; C. Weaver; S. Jani (pp. 6118-6124).

► Depth of hardening depends on oxide thickness and diffusion hardened zone. ► Oxide thickness and diffusion hardened zone cannot be independently controlled in standard oxidation processes for Zr2.5Nb. ► A post oxidation vacuum process dissolves portion of the oxide and forms a thicker diffusion hardened zone and thus a greater depth of hardening. ► Oxide hardness is similar but a secondary phase is observed in the oxide. ► Critical load required to crack the oxide is more due to increase depth of hardening.Zirconium and particularly Zr–2.5wt%Nb (Zr2.5Nb) alloy are useful for engineering bearing applications because they can be oxidized in air to form a hard surface ceramic. Oxidized zirconium (OxZr) due to its abrasion resistant ceramic surface and biocompatible substrate alloy has been used as a bearing surface in total joint arthroplasty for several years. OxZr is characterized by hard zirconium oxide (oxide) formed on Zr2.5Nb using one step thermal oxidation carried out in air. Because the oxide is only at the surface, the bulk material behaves like a metal, with high toughness. The oxide, furthermore, exhibits high adhesion to the substrate because of an oxygen-rich diffusion hardened zone (DHZ) interposing between the oxide and the substrate.In this study, we demonstrate a two step process that forms a thicker DHZ and thus increased depth of hardening than that can be obtained using a one step oxidation process. The first step is thermal oxidation in air and the second step is a heat treatment in vacuum. The second step drives oxygen from the oxide formed in the first step deeper into the substrate to form a thicker DHZ. During the process only a portion of the oxide is dissolved. This new composition (DHOxZr) has approximately 4–6μm oxide similar to that of OxZr. The nano-hardness of the oxide is similar but the DHZ is approximately 10 times thicker. The stoichiometry of the oxide is similar and a secondary phase rich in oxygen is present through the entire thickness. Due to the increased depth of hardening, the critical load required for the onset of oxide cracking is approximately 1.6 times more than that of the oxide of OxZr. This new composition has a potential to be used as a bearing surface in applications where greater depth of hardening is required.

Keywords: Zirconium; Oxidation; Diffusion zone; Nano-hardness; Micro-scratch; Secondary phase

Optimization of parameters for deposition of Ga-doped ZnO films by DC reactive magnetron sputtering using Taguchi method by Xun Bie; Jianguo Lu; Yuping Wang; Li Gong; Quanbao Ma; Zhizhen Ye (pp. 6125-6128).

► ZnO:Ga thin films are prepared by DC reactive magnetron sputtering. ► The Taguchi method is applied to find the optimal growth conditions. ► ZnO:Ga films have acceptable structural, electrical, and optical properties.Ga-doped ZnO (ZnO:Ga) transparent conductive films were deposited on glass substrates by DC reactive magnetron sputtering. Taguchi method was used to find the optimal deposition parameters including oxygen partial pressure, argon partial pressure, substrate temperature, and sputtering power. By employing the analysis of variance, we found that the oxygen and argon partial pressures were the most influencing parameters on the electrical properties of ZnO:Ga films. Under the optimized deposition conditions, the ZnO:Ga films showed acceptable crystal quality, lowest electrical resistivity of 2.61×10⁻⁴Ωcm, and high transmittance of 90% in the visible region.

Keywords: ZnO:Ga; Transparent conductive films; Magnetron sputtering; Taguchi method

Growth and characterization of Mg(OH)₂ film on magnesium alloy AZ31 by Yanying Zhu; Guangming Wu; Yun-Hong Zhang; Qing Zhao (pp. 6129-6137).

► The magnesium hydroxide film was successfully grown on the substrate of AZ31 magnesium alloy by a new and simple way, hydrothermal method. ► The corrosion resistance of the magnesium alloy with films grown on is effectively improved in comparison with the control sample. ► The magnesium hydroxide film on the Mg alloy substrate can provide a potential material for appropriate orthopedic surgery.Magnesium-based biomaterials have been proposed as potential candidates for biodegradable implant materials, such as bone screws, bone plates, intraluminal stents and so on. However, the poor corrosion resistance inhibits their applications in surgery. They collapse before the injured tissues are healed. In this paper, Mg(OH)₂ nonstructural film was synthesized on the substrate of AZ31 magnesium alloy by hydrothermal method with NaOH solution as mineralizer to reduce the corrosion rate of magnesium-based materials. The obtained films were characterized by XRD, SEM, and XPS. The results showed that a Mg(OH)₂ film with nanostructure surface can be synthesized by hydrothermal method. It was observed that the thickness of film increased with the holding time. Corrosion rates of the films were studied by immersing the samples in Hank's solution (37°C). Surface deposits of samples with films soaked in Hank's solution for 31 days were investigated by XRD, SEM, EDS, XPS, and FTIR. It verified that the corrosion rate of the magnesium alloy with grown film was slowed down in the Hank's solution and the behavior of corrosion was inhibited effectively. Amorphous calcium apatite precursor was observed to deposit on the surface of the film during corrosion experiments in Hank's solution. And the tape test revealed a strong adhesion between the film and the substrate.

Keywords: Magnesium alloy; Hydrothermal; Magnesium hydroxide; Corrosion; Biomaterial

Dopant passivation and work function tuning through attachment of heterogeneous organic monolayers on silicon in ultrahigh vacuum by Ashley J. Cooper; Kian Keyvanfar; Albert Deberardinis; Lin Pu; John C. Bean (pp. 6138-6144).

► Heterogeneous organic monolayers on silicon surfaces. ► Ultra-high vacuum hydrosilylation under ultraviolet illumination. ► Band bending and contact potential track monolayer dipole and density. ► Hydrogen passivation of boron dopant atoms.Electronic structures of silicon–organic interfaces were studied by the scanning Kelvin probe technique. These surfaces were fabricated by covalent bonding of a range of phenylacetylene-based molecules ( p-X–C₆H₄CCH, where X=CF₃, OCH₃, and H) onto a hydrogen-terminated silicon surface. Organic molecules were bound to the surface under high vacuum conditions by ultraviolet light-induced hydrosilylation. Changes in the electronic structure due to electron-donating ability and dipole moment were analyzed under dark and illuminated conditions. The origin of the silicon band bending was tested to separate the effects of molecular monolayers and unintended dopant passivation. In addition, heterogeneous monolayers were grown by controllably diluting the incoming vapor stream with acetylene during growth. The measured work functions follow a trend linked to dipole moment that can be further tuned by molecular dilution. These results suggest a way to use heterogeneous organic monolayers to tune the electron affinity of silicon and directly alter channel modulation in small semiconductor devices.

Keywords: Hydrosilylation; Silicon; UHV; Ultraviolet; Surface

Study on phase separation in a-SiO_x for Si nanocrystal formation through the correlation of photoluminescence with structural and optical properties by Jie Gan; Qian Li; Zhigao Hu; Wenlei Yu; Kun Gao; Jian Sun; Ning Xu; Jiada Wu (pp. 6145-6151).

► We study the phase separation in a-SiO_x for the formation of Si nanocrystals. ► The phase separation includes two separate processes that should be distinguished. ► The precipitated Si atoms exist first as amorphous Si clusters and then crystallize. ► The structural and optical properties and the PL features depend on annealing process.The phase separation in amorphous silicon suboxide (a-SiO_x) films upon thermal annealing for the formation of light emitting silicon nanocrystals (Si-NCs) was studied through the correlation of photoluminescence (PL) and photoluminescence excitation (PLE) with structural and optical properties. The PL and PLE features and the structural and optical properties show a strong dependence on the annealing process and reveal that the precipitation of the excess Si in a-SiO_x and the formation of Si-NCs from the precipitated Si are two separate processes which should be distinguished in the phase separation in a-SiO_x. They proceed at different temperatures and the formation of Si-NCs is a slow process compared with the precipitation of the excess Si. The nanocrystal size and size distribution evolve with annealing time at the initial stages and are mainly dependent on annealing temperature for a certain O content in the initial a-SiO_x with the density of the formed Si-NCs increasing with longer annealing duration.

Keywords: Silicon nanocrystal; Light emission; Phase separation; Precipitation; Crystallization; Thermal annealing

Grafting of bifunctional phosphonic and carboxylic acids on Phynox: Impact of induction heating by S. Devillers; L. Lanners; J. Delhalle; Z. Mekhalif (pp. 6152-6162).

► Both carboxylic and phosphonic acid functions are able to bind Phynox surface. ► Phosphonic acid function has a greater affinity for the Phynox substrate. ► Induction heating is unfavorable to carboxylic acid binding. ► Induction heating can lead to a more selective adsorption of bifunctional molecules. ► Alcohols can be grafted on the formed monolayers via an esterification reaction.Phynox, a cobalt–chromium alloy, exhibits interesting mechanical properties making it a valuable material for a number of applications. However, its applications (especially biomedical ones) often require specific surface properties that can be imparted via suitable surface functionalizations. Based on Faraday's law of induction, induction heating is a widely used method to heat metallic substrates directly and contactless. The aim of this work is to compare the influence of induction heating and a conventional heating method on the functionalization of Phynox surfaces with bifunctional (6-phosphonohexanoic and 11-phosphoundecanoic acids) monolayers in order to create a platform for a large variety of post-grafting chemical reactions, e.g. with alcohols and amines, to modify and control the surface properties. In a first part, we assess the influence of the heating method on the interaction between the two terminal moieties of the 6-phosphonohexanoic and 11-phosphoundecanoic acids and the Phynox surface by studying the grafting of n-dodecylphosphonic acid and n-dodecanoic acid separately. The suitability of such bifunctional molecules for post-grafting chemical reactions has then been assessed by studying the post-grafting of a fluorinated alcohol by the Steglich esterification reaction between the carboxylic end of the grafted bifunctional molecules and the alcohol function of the post-grafted molecule. It has been shown that induction heating can lead to a much more selective adsorption of bifunctional molecules on the surface of Phynox, leaving a higher amount of free carboxylic acid functions to react during the second modification step.

Keywords: Induction heating; Surface modification; Phynox; Phosphonic acid; Carboxylic acid

Static dissolution rate of tungsten film versus chemical adjustments of a reused slurry for chemical mechanical polishing by C.M. Coetsier; F. Testa; E. Carretier; M. Ennahali; B. Laborie; C. Mouton-arnaud; O. Fluchere; P. Moulin (pp. 6163-6170).

► Ultrafiltration process allows the regeneration of slurry physical properties. ► Recycled slurry adjusted with H₂O₂ alone is unstable and not efficient for reuse. ► Iron addition decreases the static etch rate to the reference value. ► Oxalic acid addition increases the static etch rate and decrease H₂O₂ decomposition. ► Reused slurry is obtained after ultrafiltration and appropriate chemical adjustment.Tungsten is widely used as deposited layer for the multi-level interconnection structures of wafers. The chemical composition of abrasive slurry plays an important role in chemical mechanical polishing (CMP) process. Removal of tungsten is driven by complex oxidation mechanisms between slurry components. The slurry for tungsten CMP generally contains oxidizer, iron catalyst, complexing agents and stabilizers in a pH adjusted solution of abrasive particles. Interaction between iron complex and H₂O₂ in the slurry is the main factor governing the chemical mode of material removal, oxidation potencies and kinetics.In this study, we investigate the effects of chemical additives in silica (SiO₂)-based slurry on the removal rate of the tungsten film. Experiments were carried out in static batch as a preliminary study to understand and optimize chemical mechanisms in CMP–Tungsten process. Experiment designs were conducted to understand the influence of the chemical additives on the main performances of W–CMP. Used slurry, concentrated and retreated with chemical adjustments, is compared to the original slurry as a reference.

Keywords: Abbreviations; A; wafer surface (cm; ²; ); Å; Angström; aq; aqueous; C; concentration; C; ₀; initial concentration; CMP; chemical and mechanical polishing; Cu; copper; CUFS; post-filtrated and concentrated after use slurry; CUS; concentrated after use slurry; Δ; w; tungsten weight loss; Eq; equivalent; Fe; iron ferric nitrate; F; _obs; observed ratio of the error variances under Fischer–Snedecor's test; F; _x,y,α; F; from Fischer–Snedecor's table with; x; and; y; degrees of freedom and with a confidence interval; α; h; hour; K; rate constant for H; ₂; O; ₂; decomposition; L; p0; initial permeability; min; minute; MSR; mean square of the regression; MWCO; molecular weight cut-off; N; number of experiments; NTU; nephelometric turbidity unit; Ox. Ac.; oxalic acid; p; number of coefficients of the model; Pat.; patent; POU; slurry at point of use reference; ρ; tungsten thin deposit layer density; RR; static etch rate removal rate; σ; ²; variance of the experimental error; S; surface; s; ²; pure error variance; SDS; sodium dodecyl sulfate; t; time (min); T; time (h); TMP; trans membrane pressure; US; used slurry; W; tungstenTungsten film; CMP; Material removal; Reused slurry; Chemical additives

Sepiolite nanofluids with liquid-like behavior by Ya Ping Zheng; Jiao Xia Zhang; Lan Lan; Pei Ying Yu (pp. 6171-6174).

► Sepiolite nanofluids is synthesized via tertiary amine and sulfonate anions. ► The sepiolite nanofluids behaves liquid-like without solvent at room temperature. ► The content of sepiolite is 25wt.%.We report the synthesis of sepiolite nanofluids via tertiary amine and sulfonate anions. After modified, the sepiolite behaves liquid-like without solvent at room temperature. The content of sepiolite is 25wt.%. The unique properties of the sepiolite nanofluids and its dispersion have made this promising in the applications as multiphase systems like in common liquids.

Keywords: Sepiolite; Nanofluids; Liquid-like behavior

Influence of photo-induced superhydrophilicity of titanium dioxide nanoparticles on the anti-fouling performance of ultrafiltration membranes by S.S. Madaeni; N. Ghaemi; A. Alizadeh; M. Joshaghani (pp. 6175-6180).

► TiO₂ nanoparticles were deposited on the surface of composite ultrafiltration membrane and irradiated by ultraviolet light. ► The modified membrane leads to creation of photocatalytic property with an increasing hydrophilicity. ► The deposition of nanoparticles was carried out through coordinance bonds with OH functional groups of the membrane polymer. ► The flux of the modified membrane was increased to a large extent.Fouling is one of the most present prominent problems in almost all membrane processes. An increase in the membrane hydrophilicity is one of the effective ways to improve the membrane resistance to fouling. In this research, TiO₂ nanoparticles were deposited on the surface of composite ultrafiltration (UF) membrane, and then irradiated by ultraviolet (UV) light. The coating of the membrane surface with TiO₂ nanoparticles and radiation with (UV) light led to the considerable increase of hydrophilicity on the membrane surface. The deposition of TiO₂ nanoparticles was carried out through coordinance bonds with OH functional groups of the polymer on the membrane surface. The flux through a coated and (UV) light radiated membrane was increased to a large extent compared to a virgin membrane. In this research, the effect of different concentrations of TiO₂ nanoparticles in the presence and absence of (UV) irradiation was investigated, and the role of increasing of hydrophilicity on the anti-fouling property of membranes was studied. In order to characterize the membranes FTIR, XRD, SEM, water contact angle and cross-flow filtration were employed. This procedure is a useful technique for improvement of hydrophilicity to decrease (increase) fouling (anti-fouling performance) and enhance the permeation of membranes.

Keywords: Titanium dioxide nanoparticles; Superhydrophilicity; Anti-fouling; Ultraviolet irradiation; Ultrafiltration

TiAlN coatings deposited by triode magnetron sputtering varying the bias voltage by D.M. Devia; E. Restrepo-Parra; P.J. Arango; A.P. Tschiptschin; J.M. Velez (pp. 6181-6185).

► TiAlN coatings composition is strongly influenced by the Ar/N2 ratio in a sputtering system. ► An increase in the bias voltage could not produce an increase in the TiAlN film thickness. ► The bias voltage has strong influence on the coefficient of crystallographic texture.TiAlN films were deposited on AISI O1 tool steel using a triode magnetron sputtering system. The bias voltage effect on the composition, thickness, crystallography, microstructure, hardness and adhesion strength was investigated. The coatings thickness and elemental composition analyses were carried out using scanning electron microscopy (SEM) together with energy dispersive X-ray (EDS). The re-sputtering effect due to the high-energy ions bombardment on the film surface influenced the coatings thickness. The films crystallography was investigated using X-ray diffraction characterization. The X-ray diffraction (XRD) data show that TiAlN coatings were crystallized in the cubic NaCl B1 structure, with orientations in the {111}, {200} {220} and {311} crystallographic planes. The surface morphology (roughness and grain size) of TiAlN coatings was investigated by atomic force microscopy (AFM). By increasing the substrate bias voltage from −40 to −150V, hardness decreased from 32GPa to 19GPa. Scratch tester was used for measuring the critical loads and for measuring the adhesion.

Keywords: Titanium aluminum nitride; Crystallography; Microstructure; Hardness; Adhesion

ArF laser surface modification of polyethersulfone film: Effect of laser fluence in improving surface biocompatibility by H. Pazokian; S. Jelvani; M. Mollabashi; J. Barzin; G. Azizabadi Farahani (pp. 6186-6190).

► Platelet adhesion on PES decreases with ArF laser treatment at a fluence below the ablation threshold. ► Platelet adhesion on PES increases with ArF laser treatment at a fluence above the ablation threshold. ► The change in platelet adhesion is attributed to change in surface chemistry and surface roughness.ArF laser treatment of polyethersulfone (PES) films was performed to improve biocompatibility of surfaces. For this purpose, the threshold fluence for laser ablation of PES was obtained from experimental measurements and then samples were irradiated at 2 separate ranges of fluences, i.e. below and above the ablation threshold. In order to investigate the physico-chemical changes, the modified surfaces were characterized by attenuated total reflectance (ATR) infrared spectroscopy and contact-angle measurements. The biocompatibility of the treated samples in comparison to those untreated was examined in vitro using a platelet adhesion test. The number of adhered platelets was obtained using the lactate dehydrogenase (LDH) method. For surfaces irradiated below the ablation threshold, a high reduction in the number of the adhered platelets was observed; while this number increased in samples treated at the fluence above the ablation threshold. The change in platelet adhesion was attributed to the change in chemistry and roughness of the irradiated surfaces.

Keywords: ArF laser; Polyethersulfone film; Biocompatibility

ZnO epitaxy on SiC(0001¯) substrate: Comparison with ZnO/SiC(0001) heterostructure by Almamun Ashrafi; Mohammod Aminuzzaman (pp. 6191-6196).

► Six-fold crystal symmetry in ZnO/6H–SiC(000±1) heterostructures is observed with an epitaxial relationship of (0002)_ZnO||(0006)_SiC and [112¯0]_ZnO||[112¯0]_SiC. ► The valence band offsets of ZnO/6H–SiC(0001) and ZnO/6H–SiC(0001¯) heterostructures are 1.12eV and 1.09eV, leading to the conduction band offset values of 0.75eV and 0.72eV, respectively. ► From this experimental comparison, ZnO/6H–SiC(0001) heterostructure is found to be superior in structural and optical properties than ZnO/6H–SiC(000-1) heteroepitaxy.ZnO thin layers deposited on 6H–SiC substrates showed six-fold crystal symmetry with an epitaxial relationship of (0002)_ZnO||(0006)_SiC and [112¯0]_ZnO||[112¯0]_SiC. Despite the different 6H–SiC substrate surface orientations for the ZnO epitaxy, the orientation relationship of ZnO/6H–SiC heterostructures is identical, as confirmed by X-ray diffraction studies. In these ZnO/6H–SiC(0001) and ZnO/6H–SiC(0001¯) heterostructures, the valence band offsets are measured to be 1.12eV and 1.09eV, leading to the conduction band offset values of 0.75eV and 0.72eV, respectively. These slightly different band-offset values in ZnO/6H–SiC heterojunctions are attributed to the variation of valence band maximums and the different interface charge compensation mechanisms.

Keywords: PACS; 73.61.Ga; 81.05.Dz; 61.05.js; 73.20.AtZnO heteroepitaxy; Crystal symmetry; Local atomic relaxation; Local interface chemistry

Effect of different electrolytes on porous GaN using photo-electrochemical etching by K. Al-Heuseen; M.R. Hashim; N.K. Ali (pp. 6197-6201).

► We report the properties and the behavior of GaN during the photoelectrochemical etching process using four different electrolytes. ► The measurements show that the porosity strongly depends on the electrolyte and highly affects the surface morphology of etched samples. ► Peak intensity of the photoluminescence (PL) spectra of the porous GaN samples was observed to be enhanced and strongly depend on the electrolytes. ► There was a red shift in E₂ (high) in all samples, indicating a relaxation of stress in the porous GaN surface with respect to the underlying single crystalline epitaxial GaN. ► H₂SO₄:H₂O₂ is the best solution for etching GaN.This article reports the properties and the behavior of GaN during the photoelectrochemical etching process using four different electrolytes. The measurements show that the porosity strongly depends on the electrolyte and highly affects the surface morphology of etched samples, which has been revealed by scanning electron microscopy (SEM) images. Peak intensity of the photoluminescence (PL) spectra of the porous GaN samples was observed to be enhanced and strongly depend on the electrolytes. Among the samples, there is a little difference in the peak position indicating that the change of porosity has little influence on the PL peak shift, while it highly affecting the peak intensity. Raman spectra of porous GaN under four different solution exhibit phonon mode E₂ (high), A₁ (LO), A₁ (TO) and E₂ (low). There was a red shift in E₂ (high) in all samples, indicating a relaxation of stress in the porous GaN surface with respect to the underlying single crystalline epitaxial GaN. Raman and PL intensities were high for samples etched in H₂SO₄:H₂O₂ and KOH followed by the samples etched in HF:HNO₃ and in HF:C₂H₅OH.

Keywords: Electrolyte; Gan; Photo-electrochemical etching; Porosity

Surface study of cerium oxide based coatings obtained by cathodic electrodeposition on zinc by L. Martínez; E. Román; J.L. de Segovia; S. Poupard; J. Creus; F. Pedraza (pp. 6202-6207).

► Ce oxide based coatings composition. ► Ce (III) and Ce (IV) oxides with hydroxides, carbonates, nitrates and water. ► Upon sputtering and XPS less reactive and more hydrophobic surface. ► H⁺ is the only detected ion desorbed from Ce–O–H and Ce–H species.A surface study of electrodeposited cerium oxide based coatings is presented. Different surface analytical techniques were used in order to obtain complementary information to fully characterize such complex systems. X-ray Photoelectron Spectroscopy was used as the main technique to determine the surface composition of the coating. The analysis of the core level peaks of the elements provides additional information about the functional groups present on the surface. A mixture of Ce (III) and Ce (IV) was found in the coating and their proportion was calculated at different depths. The analysis of the O 1s core level peak revealed a triple structure whose origin will be discussed. To support the results obtained, electron stimulated desorption was performed. The study was completed with Auger electron spectroscopy and Raman spectroscopy, both techniques having different surface sensitivities. From all these results, it is derived that incomplete electrochemical reactions occurred during the growth of the coatings. This led to rather complex compositions, in which defective cerium oxides are the major species. In addition, hydroxides, carbonates and nitrates are also present, together with adsorbed water.

Keywords: Cerium oxides; XPS; ESD; AES

First experimental evidence by SIMS of different surface binding energies for uranium according to its oxidation state by L. Desgranges; B. Pasquet; I. Roure (pp. 6208-6211).

► Evidence of two peaks in the energy spectrum of U sputtered from UO₂. ► Change of their relative intensity with surface oxygenation measured by O18 method. ► Attribution of the two peaks to at least two different oxidation states of uranium. ► Interpretation of the energy spectrum as a function of uranium surface oxidation.The existence of two peaks in the energy spectrum of uranium was evidenced for the first time with SIMS during the sputtering of a UO₂ sample as a function of the oxidation state of the surface. The surface oxidation state was quantitatively determined using the O18 method. These two peaks were attributed to two different surface binding energies of uranium. Since their relative intensities change as a function the surface oxidation state, the two surface binding energies must be associated with two different oxidation states of uranium.

Keywords: SIMS; Uranium oxide; Ionisation

In situ polyphenyl derivatisation and the effect of thermal decomposition of adsorbed and chemisorbed polyphenyls on the structure of multi-wall carbon nanotubes by András Gergely; Kálmán Újszászy; Csaba Peltz; Péter Király; Gábor Tárkányi; Judith Mihály; Erika Kálmán (pp. 6212-6219).

► Polyphenyl grafting of MWCNTs is performed by consecutive diazonium coupling. ► Chemical derivatisation of MWCNTs with polyphenyl moieties was evidenced by MS. ► Surface modification scales linearly with the applied excess of activated reagent. ► Pyrolysis results in structure degradation of MWCNTs with chemisorbed polyphenyls. ►²H NMR and MS results suggest recognition of endohedral modification of the MWCNTs.This study presents the exploitation of an alternative reaction route of deamination of arylamines to perform in situ derivatisation of multi-walled carbon nanotubes (MWCNTs) with polyphenyl (PPh) species of various masses. As a result of consecutive derivatisation, high conversion of PPh grafting of the MWCNTs was realised with the collateral outgrowth of physical modification with adsorbed additional PPhs. Applied derivatisation process exceeds the monolayer coverage related superficial saturation limitations in the overall grafting yield of the nanotubes. Thus, a linear relationship was recognized between the overall quantities of chemisorbed PPhs composed of D₅-phenylene oligomers and the applied excess of diazonium activated reagents, corresponding to²H MAS NMR spectroscopy results. According to mass spectrometry (MS) investigations, uniform thermal decomposition of the chemisorbed PPhs modified MWCNTs was found besides the more intense and altered decomposition characteristic-featured adsorbate-chemisorbate PPhs contained MWCNTs during sequential pyrolysis under inert atmosphere. This is attributed to the pyrolysis provoked isomerisation, decomposition and the formation of adsorbed and chemisorbed PPh moieties. As a result, a mediated and an even more pronounced degradation in the order of graphitic lattice of the MWCNTs were evidenced in the adsorbate-chemisorbate and the chemisorbate PPhs contained samples by FT-Raman spectroscopy and transmission electron microscopy (TEM), respectively.²H MAS NMR supplied results of relevant amount of deuterium in the chemisorbate PPh contained sample without traces of aromatic related MS detected volatile products, these allow us to conclude about a thermally stable derivatisation that is interpreted as an endohedral modification of the nanotubes.

Keywords: MWCNTs; Sequential derivatisation; Polyphenyls; Thermal decomposition

Influence of ionic liquids on the surface properties of poplar veneers by Catalin Croitoru; Silvia Patachia; Nicolae Cretu; Attila Boer; Christian Friedrich (pp. 6220-6225).

► Treating poplar wood veneers with four types of alkylimidazolium-based ionic liquids. ► Wood wettabillity is increased by ionic liquid treatment. ► Electrical conductivities of treated wood were in the 0.5–1mS/cm range. ► Decreasing the crystallinity and improving the flexibility of the cellulose matrix. ► The surface roughness decreases in comparison with the untreated samples.In this paper, the influence of four types of imidazolium-based ionic liquids (ILs) on the surface properties of common aspen ( Populus tremula) veneers has been studied by using contact angle, electrical conductivity and Fourier transform infrared spectroscopy analysis. The measurements showed that wood wettabillity is increased by IL treatment. The electrical conductivities of treated wood were in the 0.5–1mS/cm range, higher than the ones reported in the reference literature. It has been determined that the ILs decrease the crystallinity and improve the flexibility of the cellulose matrix. It has been determined by photographic image analysis that the surface roughness of the IL treated veneers decreases in comparison with the untreated samples.

Keywords: Wood veneers; Ionic liquids; Surface energy; Anti-electrostatic materials; FTIR spectroscopy

Temperature-dependent growth mode of W-doped ZnO nanostructures by B.D. Ngom; M. Chaker; N. Manyala; B. Lo; M. Maaza; A.C. Beye (pp. 6226-6232).

► We report on the effects of glass substrate temperature on the crystal structure and morphology of tungsten (W)-doped ZnO nanostructures synthesized by pulsed-laser deposition. ► X-ray diffraction analysis data shows that the W-doped ZnO thin films exhibit a strongly preferred orientation along a c-axis (000 L) plane. ► Well-aligned W-doped ZnO nanorods with unique shape were directly and successfully synthesized at substrate temperature of 550°C and 600°C without any underlying catalyst or template. ► Possible growth mechanism of these nanorods is suggested and discussed.We report on the effects of glass substrate temperature on the crystal structure and morphology of tungsten (W)-doped ZnO nanostructures synthesized by pulsed-laser deposition. X-ray diffraction analysis data shows that the W-doped ZnO thin films exhibit a strongly preferred orientation along a c-axis (000 L) plane, while scanning electron and atomic force microscopes reveal that well-aligned W-doped ZnO nanorods with unique shape were directly and successfully synthesized at substrate temperature of 550°C and 600°C without any underlying catalyst or template. Possible growth mechanism of these nanorods is suggested and discussed.

Keywords: PACS; 61.10.−I; 68.35.D; 85.40.R; 74.25.Gz; 81.15.ZLaser ablation; Nucleation; Nanostructures; ZnO nanomaterials

Surface modification of hydroxyapatite with poly(methyl methacrylate) via surface-initiated ATRP by Yan Wang; Xi Zhang; Jinliang Yan; Yan Xiao; Meidong Lang (pp. 6233-6238).

► Hydroxyapatite (HAP) was firstly surface grafted with poly(methyl methacrylate) (PMMA) via atom transfer radical polymerization. ► The surface-grafted HAP nanocomposites had 48.7% grafting PMMA amount in a relatively short reaction time. ► A polymer layer coated HAP particles and dramatically increased the hydrophobicity of the surface. ► The surface-grafted HAP nanocomposites showed excellent dispersibility in both aqueous solution and organic solvent.This article describes the fabrication of hydroxyapatite (HAP) nanocomposites grafted with poly(methyl methacrylate) (PMMA). Surface-initiated atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) was carried out from hydroxyapatite particles derivatized with ATRP initiators. The structure and properties of the nanocomposites were investigated by thermogravimetric analysis (TGA), transmission electron microscopy (TEM), differential scanning calorimeter (DSC) measurements, and contact angle analyses. TGA was used to estimate the grafting density of ATRP initiators (0.49 initiator/nm²) and the amount of grafted PMMA on the HAP surface. The contact angle analyses indicated that grafting PMMA onto the HAP surface dramatically increased the hydrophobicity of the surface. Moreover, the HAP nanocomposites showed excellent dispersibility in both aqueous solution and organic solvent.

Keywords: ATRP; Nanocomposites; Hydroxyapatite; Poly(methyl methacrylate)

A chemical lithography route to Bi₂S₃ nanotubes by Junjun Zhang; Weixin Zhang; Zeheng Yang (pp. 6239-6242).

Display Omitted► The chemical lithography method can be successfully used to prepare Bi₂S₃ nanotubes. ► Feather-like and fiber-like nanotubes are prepared by lithography the precursor. ► The precursor comes from hydrolysis of Bi(NO₃)₃ hydrothermally with addition of PVP.Two different semiconducting bismuth sulfide (Bi₂S₃) nanostructures (feather-like Bi₂S₃ nanotubes and fiber-like Bi₂S₃ nanotubes) with diameters around 50–60nm and lengths about tens of micrometers were prepared successfully by a chemical lithography route. The results indicated that the employment of polyvinylpyrrolidone led to the precursor with feather-like morphology and the acid had ripening effect on and etching action to the ultimate formation of the fiber-like Bi₂S₃ nanotubes. The photoluminescence spectra of two different Bi₂S₃ nanostructures revealed that the relative position of emission peaks was influenced by the thin edges of the feather-like nanotubes due to the quantum-confinement effect.

Keywords: Bi; ₂; S; ₃; Nanotubes; Chemical lithography; Photoluminescence

Femtosecond laser ablation of polymeric substrates for the fabrication of microfluidic channels by Raffaella Suriano; Arseniy Kuznetsov; Shane M. Eaton; Roman Kiyan; Giulio Cerullo; Roberto Osellame; Boris N. Chichkov; Marinella Levi; Stefano Turri (pp. 6243-6250).

► Near-IR fs laser ablation on common thermoplastic polymers was investigated. ► The dimensions of femtosecond ablated microchannels are easily tunable. ► Surface quality of ablated microchannels is similar to that obtained by micromilling. ► Poly(methyl methacrylate)’s structure is the most stable during laser irradiation. ► Polystyrene and cyclic olefin polymer show darkening and oxidation.This manuscript presents a study of physical and chemical properties of microchannels fabricated by femtosecond laser processing technology in thermoplastic polymeric materials, including poly(methyl methacrylate) (PMMA), polystyrene (PS) and cyclic olefin polymer (COP). By surface electron microscopy and optical profilometry, the dimensions of microchannels in the polymers were found to be easily tunable, with surface roughness values comparable to those obtained by standard prototyping techniques such as micromilling. Through colorimetric analysis and optical microscopy, PMMA was found to remain nearly transparent after ablation while COP and PS darkened significantly. Using infrared spectroscopy, the darkening in PS and COP was attributed to significant oxidation and dehydrogenation during laser ablation, unlike PMMA, which was found to degrade by a thermal depolymerization process. The more stable molecular structure of PMMA makes it the most viable thermoplastic polymer for femtosecond laser fabrication of microfluidic channels.

Keywords: Femtosecond laser; Ablation; Polymer; Microfluidics

Reduction of interlayer thickness by low-temperature deposition of Mo/Si multilayer mirrors for X-ray reflection by V.I.T.A. de Rooij-Lohmann; A.E. Yakshin; E. Zoethout; J. Verhoeven; F. Bijkerk (pp. 6251-6255).

► We compared cryogenic deposition of Mo/Si multilayer structures with room temperature deposition. ► Cryogenic deposition leads to nearly 60% thinner MoSi₂ interlayers than room temperature deposition. ► The mechanisms contributing to the interlayer thickness reduction are discussed.Thin interlayers are essential for high-quality multilayer optics. We present the first investigation of reducing the interlayer thickness of Mo/Si multilayer structures by cooling the substrate with liquid nitrogen during the deposition. The structures were deposited by means of electron beam evaporation. Even after warming up to room temperature prior to analysis, the interlayers that formed upon cryogenic deposition were found to be approximately 60% thinner compared to room temperature deposition. The interlayer thickness reduction at low temperature and its preservation upon warming up are attributed to a lower mobility of adatoms, reduced surface segregation of Si during Mo-on-Si growth, and/or crystallization of Mo.

Keywords: Cryogenic deposition; Interlayer thickness; Mo/Si multilayers

Effect of calcination temperature on the structure and hydroxylation activity of Ni_0.5Cu_0.5Fe₂O₄ nanoparticles by Xiaoyan Tan; Ying Zhao; Guiying Li; Changwei Hu (pp. 6256-6263).

► The decomposition and ferritization occur simultaneously at 280–350°C. ► 800°C is required for the formation of homogeneous cubic spinel. ► High calcination temperature makes more Fe_B³⁺, Cu_A²⁺ and O_I on the surface. ► Cu_B²⁺ species on the spinel surface is active for the hydroxylation.Nanocrystalline Ni_0.5Cu_0.5Fe₂O₄ was synthesized by sol–gel method with varying calcination temperature over the range of 500–1000. The powders obtained were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). In addition, thermal analysis (TG–DTG–DTA) of the precursor was carried out. The study reveals the simultaneous decomposition and ferritization process at rather low temperature (280–350). For the crystalline structure investigated, single cubic spinel is gained when the precursor was decomposed at 800–1000, whereas separated crystal CuO formed when calcination temperature is below 800. The increase of calcination temperature favors the appearance of Fe_B³⁺, Cu_A²⁺ and O on the spinel surface. The hydroxylation activity is relative to the amount of Cu_B²⁺ species on the spinel surface. The lattice oxygen species on the spinel surface are favorable for the deep oxidation of phenol.

Keywords: Nanocrystalline Ni; _0.5; Cu; _0.5; Fe; ₂; O; ₄; Surface characteristics; Sol–gel method; XPS; Hydroxylation

Anti-icing performance of superhydrophobic surfaces by S. Farhadi; M. Farzaneh; S.A. Kulinich (pp. 6264-6269).

► A number of superhydrophobic samples were prepared. ► Their anti-icing performance was tested on “dry” and “wet” surfaces. ► Their anti-icing performance was tested as a function of icing/deicing cycles.This article studies the anti-ice performance of several micro/nano-rough hydrophobic coatings with different surface chemistry and topography. The coatings were prepared by spin-coating or dip coating and used organosilane, fluoropolymer or silicone rubber as a top layer. Artificially created glaze ice, similar to the naturally accreted one, was deposited on the nanostructured surfaces by spraying supercooled water microdroplets (average size ∼80μm) in a wind tunnel at subzero temperature (−10°C). The ice adhesion strength was evaluated by spinning the samples in a centrifuge at constantly increasing speed until ice delamination occurred. The results show that the anti-icing properties of the tested materials deteriorate, as their surface asperities seem to be gradually broken during icing/de-icing cycles. Therefore, the durability of anti-icing properties appears to be an important point for further research. It is also shown that the anti-icing efficiency of the tested superhydrophobic surfaces is significantly lower in a humid atmosphere, as water condensation both on top and between surface asperities takes place, leading to high values of ice adhesion strength. This implies that superhydrophobic surfaces may not always be ice-phobic in the presence of humidity, which can limit their wide use as anti-icing materials.

Keywords: PACS; 68.35.Md; 68.08.Bc; 82.45.MpIce adhesion; Ice repellency; Superhydrophobicity; Ice adhesion strength; Roughness; Water condensation; Durability

Effects of surface concentration on the porphine monolayers: Molecular simulations at the nanoscale water–gas interface by Sriprajak Krongsuk; Teerakiat Kerdcharoen (pp. 6270-6275).

The porphine monolayers at the water–gas interface investigated by using molecular dynamic simulations exhibit a cover full range of the monolayer phase formation including gaseous, expanded, condensed, and collapsed phases, respectively.Display Omitted► Molecular structure and film stability of the porphine (PH₂) monolayers are investigated using molecular dynamics simulation. ► The monolayer phase transfer corresponding to gaseous, expanded, condensed, and collapsed phases are observed with the increasing of the PH₂ surface concentrations. ► Increment of a number of the PH₂ molecules not only affects the significantly decreasing water density at the interface but also the monolayer surface tension.The effect of surface concentration on the structure and stability of porphine (PH₂) monolayers at the water–gas interface was studied by using molecular dynamics simulation. Five monolayer systems having different surface concentrations were investigated in order to cover a full range of the experimental π– A isotherm. The simulation results show that increment of a number of the PH₂ molecules not only affects the significantly decreasing water density at the interface but also the monolayer surface tensions. The calculated surface tensions of the five systems indicate that the monolayer phase transfer corresponding to gaseous, expanded, condensed, and collapsed phases are observed. The hydrogen bonding between water and the PH₂ molecules at the interface plays an important role on the monolayer film formation, especially at the lower surface concentrations. The PH₂ orientations for all surface concentrations, except the highest one, are favored to be the β-structure as observed in the copper porphyrazine (CuPz) monolayer.

Keywords: Porphine monolayer; Molecular dynamics; Surface concentration; Density profile; Surface tension; Phase transfer

Effect of Cr on the wetting in Cu/graphite system by Longlong Yang; Ping Shen; Qiaoli Lin; Feng Qiu; Qichuan Jiang (pp. 6276-6281).

► The wettability improves with increasing Cr content in the alloy as a result of phase transition from Cr₃C₂ to more wettable and metallic-like Cr₇C₃ developed at the interface of the Cu–Cr/graphite system. ► The spreading kinetics is controlled by the interfacial reaction in the early stage and the diffusion of Cr from the drop bulk to the triple junction in the later stage together with a transition in the intermediate stage. ► The different effects of Cr and Ti on the wetting in the Cu/graphite system are primarily attributed to their different activities in liquid Cu.The isotherm wetting and spreading behaviors of the molten Cu–Cr alloys with 0.5, 1.0 and 2.0at.% Cr on porous graphite substrates were investigated at 1373K in a flowing Ar atmosphere using a modified sessile drop method. The wettability improves with increasing Cr content in the alloy as a result of phase transition from Cr₃C₂ to more wettable and metallic-like Cr₇C₃ developed at the interface. The spreading kinetics are controlled by the interfacial reaction in the early stage and the diffusion of Cr from the drop bulk to the triple junction in the later stage together with a transition in the intermediate stage.

Keywords: Alloys; Carbides; Interfaces; Microstructure; Reactions

Surface modification of PVDF membrane via AGET ATRP directly from the membrane surface by Jian-Qiang Meng; Chun-Lin Chen; Li-Ping Huang; Qi-Yun Du; Yu-Feng Zhang (pp. 6282-6290).

► The surface-initiated ATRP leads to decreased surface roughness. ► The surface-initiated ATRP leads to enhanced hydrophilicity of the surface. ► The surface-initiated ATRP leads to decreased pore size distribution. ► The membrane permeability can be altered by the graft yields of the surface-initiated ATRP.This contribution demonstrates a method for PVDF microporous membrane modification via surface-initiated activators generated by electron transfer atom transfer radical polymerization (AGET ATRP) directly from the membrane surface. Three hydrophilic polymers, poly(2-(N,N-dimethylamino) ethyl methacrylate) (PDMAEMA), poly(2-oligo (ethylene glycol) monomethyl ether methacrylate) (POEGMA), and poly(2-hydroxyethyl methacrylate) (PHEMA), were grafted from the PVDF membrane surface in aqueous solution at room temperature. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) confirmed the successful covalent tethering of the polymer chains onto the PVDF membrane surface. The gravimetry results indicated an approximately linear increase of the graft yields, up to about 330μg/cm² for DMAEMA and 470μg/cm² for both HEMA and OEGMA, with the polymerization time. Block copolymer brushes were prepared by chain extension. Water contact angle decreased over 50% for high yields, indicating improved surface hydrophilicity. The effects of the graft polymerization on membrane surface morphology, pore structure and permeability were investigated. It was found that the surface roughness was decreased and the pore size distribution was narrowed. The membrane permeability increased at low graft yields due to the enhanced hydrophilicity and decreased at high graft yields due to the overall reduction of the pore diameters.

Keywords: PVDF membrane; AGET ATRP; Surface modification; Graft copolymerization

Hydrogenation of Pd-capped Mg thin films prepared by DC magnetron sputtering by Yogendra K. Gautam; Amit K. Chawla; Rajan Walia; R.D. Agrawal; Ramesh Chandra (pp. 6291-6295).

► Ex situ study of the hydrogenation/dehydrogenation of Pd-capped Mg thin films. ► Desorption kinetics in vacuum revealed the phase transformation α-MgH₂ to γ-MgH₂ at 250°C. ► Hydrogenated (H loaded) samples were observed partially transparent in comparison of as deposited. ► Thus switchable mirror properties were obtained in Pd-capped Mg film.Structural and optical properties of pure Mg thin film coated with Pd have been investigated. Pd-capped Mg thin films had been prepared by DC magnetron sputtering. This work presents an ex situ study on hydrogenation and dehydrogenation kinetics of Pd/Mg films at different conditions using XRD, AFM and optical spectrophotometer. We have succeeded to load thin films of Mg to MgH₂ at normal temperature and normal pressure of hydrogen gas. In hydrogenation, α-MgH₂ phase of magnesium hydride was observed in hydrogenated films at 200°C and γ-MgH₂ at 250°C respectively. The desorption kinetics in vacuum also revealed the phase transformation α-MgH₂ to γ-MgH₂. A reflectance change was observed in hydrogenated films in comparison of as deposited thin film. Hydrogenated (H loaded) samples were observed partially transparent in comparison of as deposited.

Keywords: Nano structured films; AFM; Metal hydride; Mg thin film; Optical reflectance

High thermal stability and low thermal conductivity in Ga₃₀Sb₇₀/Sb₈₀Te₂₀ nanocomposite multilayer films by Changzhou Wang; Jiwei Zhai; Suyuan Bai; Bo Shen (pp. 6296-6299).

► The crystallization temperature and activation energy can be modulated. ► The data retention of Ga₃₀Sb₇₀/Sb₈₀Te₂₀ multilayer films was higher than Ge₂Sb₂Te₅. ► The thermal conductivity of the multilayer films was lower than monolayer films.The reliability characteristics and thermal conductivity of Ga₃₀Sb₇₀/Sb₈₀Te₂₀ nanocomposite multilayer films were investigated by isothermal resistance and transient thermoreflectance (TTR) measurements, respectively. The crystallization temperature and activation energy for the crystallization can be modulated by varying the layer thickness of Ga₃₀Sb₇₀. A data retention time of ten years of the amorphous state [Ga₃₀Sb₇₀ (3nm)/Sb₈₀Te₂₀ (5nm)]₁₃, [Ga₃₀Sb₇₀ (5nm)/Sb₈₀Te₂₀ (5nm)]₁₀, and [Ga₃₀Sb₇₀ (10nm)/Sb₈₀Te₂₀ (5nm)]₇ was estimated when ambient temperature is 137, 163, and 178°C, respectively. Ga₃₀Sb₇₀/Sb₈₀Te₂₀ nanocomposite multilayer films were found to have lower thermal conductivity in both the amorphous and crystalline state compared to Ge₂Sb₂Te₅ film, which will promise lower programming power in the phase-change random access memory.

Keywords: PACS; 62.23.Pq; 68.65.Ac; 61.50.Ks; 68.60.Dv; 65.60+aNanocomposite; Multilayer films; Data retention; Phase-change random access memory; Thermal conductivity

Anchoring of alkylphosphonic derivatives molecules on copper oxide surfaces by Grégory Fonder; Isabelle Minet; Cédric Volcke; Sébastien Devillers; Joseph Delhalle; Zineb Mekhalif (pp. 6300-6307).

Display Omitted► A new approach for copper surface functionalization using phosphonic acid molecules and derivative. ► Results revealed the efficient grafting, the organization as well as the grafting mode of molecules on the copper surface. ► This opens a new range of applications in the area of oxide surface and interface science and technology.In this study, a new approach of copper surface modification, taking advantage of the oxide layer naturally present, is proposed using phosphonic acids derivatives. Phosphonic acids are a class of molecules particularly known for their spontaneous self-assembly on oxidized substrates. On this basis, copper substrates chemically oxidized using H₂O₂ (5%) were successfully modified with n-dodecylphosphonic acid and 1-pyrrolyl-10-decanephosphonic acids.The oxidation state of copper substrate, just after chemical oxidation, was probed by XPS and PM-IRRAS. Surface characterization was completed by contact angle and AFM measurements. Molecular integrity, alkyl chain ordering and wettability were evaluated for both elaborated coatings. The panel of characterization tools used demonstrates the efficient grafting of phosphonic acid compounds on oxidized copper surfaces. The grafting mode appears similar for both investigated molecules and is evaluated as a tridentate mode.

Keywords: Phosphonic acid; Copper; Oxide; Monolayer

Ni-doped TiO₂ nanotube arrays on shape memory alloy by R. Qin; D.Y. Ding; C.Q. Ning; H.G. Liu; B.S. Zhu; M. Li; D.L. Mao (pp. 6308-6313).

► Anodization of NiTi shape memory alloy. ► Growth of Ni-doped nanotubes on the surface. ► Moderate heat-treatment to keep nanotubular structures. ► The nanotubular oxide demonstrates a good hydrophilicity.Self-organized Ni–Ti–O nanotube arrays were fabricated through a direct anodization of NiTi shape memory alloy in glycerol-based electrolyte. The growth of Ni-doped TiO₂ nanotube arrays was mainly affected by anodization voltage and temperature. Higher anodization voltage facilitated the growth of uniform nanotube arrays. Large-area open-ended Ni–Ti–O nanotube arrays could form on the surface of the shape memory alloy under a higher anodization temperature. The oxide nanotubes had a gradually changed composition along the growth direction of the nanotube and presented a thermal stability up to 400°C. The nanotubular oxide demonstrated a much better hydrophilic behavior than that of the traditional oxide layer grown on NiTi substrate through air oxidization. The successful fabrication of Ni-doped TiO₂ nanotube arrays here makes it feasible to further explore excellent physical and chemical as well as biomedical properties of the nanotube-modified surfaces of the NiTi shape memory alloy.

Keywords: Shape memory alloy; Surface modification; Anodization; Nanotube arrays

Laser energy density, structure and properties of pulsed-laser deposited zinc oxide films by M.G. Tsoutsouva; C.N. Panagopoulos; M. Kompitsas (pp. 6314-6319).

► ZnO thin films were grown by pulsed laser deposition at 20Pa oxygen ambient and 300C. ► The focusing lens position was changed to select the laser energy density. ► The energy gap and the resistivity increased with the energy density. ► Film thickness and surface roughness decreased with increasing energy density. ► The average optical transmission was within the 80–90% for all energy density values.Zinc oxide thin films were deposited on soda lime glass substrates by pulsed laser deposition in an oxygen-reactive atmosphere at 20Pa and a constant substrate temperature at 300°C. A pulsed KrF excimer laser, operated at 248nm with pulse duration 10ns, was used to ablate the ceramic zinc oxide target. The structure, the optical and electrical properties of the as-deposited films were studied in dependence of the laser energy density in the 1.2–2.8J/cm² range, with the aid of X-ray Diffraction, Atomic Force Microscope, Transmission Spectroscopy techniques, and the Van der Pauw method, respectively. The results indicated that the structural and optical properties of the zinc oxide films were improved by increasing the laser energy density of the ablating laser. The surface roughness of the zinc oxide film increased with the decrease of laser energy density and both the optical bang gap and the electrical resistivity of the film were significantly affected by the laser energy density.

Keywords: ZnO films; Nanosecond pulsed laser deposition; Structural; Optical and electrical properties; Laser energy density dependence

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Applied Surface Science (v.257, #14)

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Applied Surface Science (v.257, #14)