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Applied Surface Science (v.258, #4)

Obituary to Prof. dr. F.H.P.M (Frans) Habraken (pp. iii).

The structural properties of Al doped ZnO films depending on the thickness and their effect on the electrical properties by Kang Hyon Ri; Yunbo Wang; Wen Li Zhou; Jun Xiong Gao; Xiao Jing Wang; Jun Yu (pp. 1283-1289).

► We studied the structural and electrical properties of AZO films with different film thickness. ► Grain size increases and stress decreases with thickness increase, leading to enhanced crystallinity. ► Grain size dependence of stress follows the same tendency for all samples regardless of deposition temperature. ► Defects at grain boundary are reduced with increase of film thickness or deposition temperature. ► The mobility increase is accompanied by grain size increase and compressive stress reduction.In this study, the structural and electrical properties of AZO films with different film thickness deposited by r.f. magnetron sputtering were interpreted in relation with film growth process. The result shows that the grain size increases during film growth, which is accompanied by decrease of compressive stress, indicating the enhancement of crystallinity. The relationship between grain size and compressive stress follows the same tendency for the samples regardless of deposition temperature, which implies the strong dependencies between the grain size and the compressive stress. The XPS analysis shows that the defects such as chemisorbed oxygen and segregated Al₂O₃ cluster at grain boundary are reduced with increase of film thickness or deposition temperature, leading to increase of carrier concentration and mobility. The mobility increase is accompanied by grain size increase and compressive stress reduction, indicating the influences of grain boundary and crystallinity on the mobility.

Keywords: Al doped zinc oxide; Transparent conducting film; Film thickness

Effects of hydrogen on photoluminescence properties of a-SiN_x:H films prepared by VHF-PECVD by Chao Song; Rui Huang; Xiang Wang; Yanqing Guo; Jie Song; Yixiong Zhang; Zehao Zheng (pp. 1290-1293).

► PL intensity can be changed by controlling the hydrogen flow rates. ► The hydrogen passivation of nonradiative defect states related to N and Si enhances PL intensity. ► The PL intensity of the film is found to be four times higher than that of the film without hydrogen dilution.Luminescent hydrogenated amorphous silicon nitride films were prepared with different hydrogen flow rate in very high frequency plasma enhanced chemical vapor deposition system. Very bright orange–red light emissions can be clearly observed with the naked eye in a bright room for the films grown at the hydrogen flow rate of 30sccm. The photoluminescence intensity of the film grown at the hydrogen flow rate of 30sccm is found to be four times higher than that of the film without hydrogen dilution. However, with further increasing the hydrogen flow rate from 30 to 90sccm, the photoluminescence intensity of the film rapidly decreases. Fourier-transform infrared absorption spectra indicate that the introduction of hydrogen concentration bonded to silicon and nitrogen is of a key role to enhance the photoluminescence intensity of the films. Based on the measurements of structural and bonding configurations, the improved photoluminescence intensity is attributed to the well hydrogen passivation of nonradiative defect states related to N and Si at proper hydrogen flow rate.

Keywords: Photoluminescence; Silicon nitride; Hydrogen; Chemical vapor depositionPACS; 78.55.−m; 68.55aj; 67.80.fh; 68.55.Ln; 81.15.Gh

Mechanism of enhanced photocatalysis of TiO₂ by Fe³⁺ in suspensions by Junwei Zhang; Dafang Fu; Haiying Gao; Lin Deng (pp. 1294-1299).

► The degradation of SD can be promoted by the addition of Fe³⁺ in TiO₂ suspension, and Fe²⁺ is found not to give an obvious impact on the SD degradation. ► The hydroxyl radical generated by TiO₂/Fe³⁺ photocatalysis is in a higher yield, and adsorption amount of TiO₂ is greatly enhanced by the addition of Fe³⁺ in suspensions. ► The enhancement of photocatalytic activity of TiO₂ by Fe³⁺ can be attributed to the fact, which is both oxygen and Fe³⁺ as the electron acceptors to trap the electron in the conduction band of TiO₂.In this work, the mechanism of enhanced photocatalysis of TiO₂ with Fe³⁺ was studied using Sulfadiazine (SD) as the model compound. Results indicated that degradation rate of SD was enhanced by the addition of Fe³⁺ in TiO₂ suspension. The crystalline structure of TiO₂ particles was stable in suspensions. The hydroxyl radical generated by TiO₂/Fe³⁺ (both TiO₂ and Fe³⁺) photocatalysis was in a higher yield. Moreover, Fe²⁺ was found not to give an obvious impact on the SD degradation in TiO₂ suspension, whereas Fe³⁺ had a notable effect. The adsorption amount of TiO₂ was greatly enhanced by the addition of Fe³⁺ in suspensions. Finally, an interaction model of SD degradation in TiO₂ suspension containing Fe³⁺ was also proposed by investigating of surface behaviors of TiO₂ particles. It will be beneficial to use Fe³⁺ as the electron acceptors on the surface of TiO₂ particles, which helps to improve the yield of hydroxyl radical.

Keywords: TiO; ₂; Photocatalysis; Fe; ³⁺; Enhancement; Mechanism

STM studies of PTCDA supramolecular self-assembling on anisotropic surfaces of reconstructed InSb by Szymon Godlewski; Marek Szymonski (pp. 1300-1305).

► We apply room temperature STM to study the self-assembly of PTCDA molecules on InSb. ► We show a new approach comparing molecule behavior on different reconstructions. ► We use a new preparation procedure providing both reconstructions on the same sample. ► Molecules form well-ordered chains on the c(8×2) face and adsorb singly on the (1×3). ► The molecules form ordered structures on the c(8×2) surface and random on the (1×3).Self-assembly of 3,4,9,10-perylene-tetracarboxylic-dianhydride (PTCDA) molecules on a c(8×2) reconstructed InSb(001) surface as well as on an asymmetrical (1×3) InSb(001) is investigated by means of high resolution scanning tunneling microscopy. The formation of well-ordered one-dimensional molecular lines is observed at low coverage on a former face, whereas on the latter molecules are found as isolated entities. At room temperature spontaneous hopping between energetically similar sites is observed within the lines. At a monolayer coverage flat molecular surface is obtained for both reconstructions, on the c(8×2) the layer is composed of neighboring one-dimensional lines, on the (1×3) molecular structure does not reveal any long range order. Application of the special experimental procedure provides direct comparison of molecule behavior on both reconstructions of the same sample.

Keywords: STM; Organic molecules; Self-assembly; Semiconductors

The influence of pre-adsorbed water on adsorption of methane on fumed and nanoporous silicas by V.M. Gun’ko; V.V. Turov; V.M. Bogatyrev; A.Y. Petin; A.V. Turov; V.V. Trachevskyi; J.P. Blitz (pp. 1306-1316).

► Methane adsorption is maximal at 10% hydration of nanosilica. ► Methane adsorption leads to appearance of weakly associated water (WAW). ► Amounts of WAW correlate to concentration of adsorbed methane. ► Methane adsorption on micro/mesoporous silica 200DF decreases with hydration.Co-adsorption of water and methane onto fumed (A-300, A-380) and micro/mesoporous (Gasil 200DF) silicas was studied. FTIR and¹H NMR spectroscopy with layer-by-layer freezing-out of bound water were used at different levels of hydration ( h=0.005–1.0g of water per gram of silica). Methane adsorption was largest (1–2wt% at T<280K) for nanosilica A-300 ( S_BET=337m²/g) at hydration h=0.1g of water per gram of silica for a non-equilibrated system. This sample was characterised by a large amount of weakly associated water ( δ_H≈1ppm), and maximal clustering of all bound water. These conditions provide the increased microporosity necessary for enhanced methane adsorption. Heating and subsequent wetting, or long equilibration of nanosilica, decreased the adsorption of methane. The adsorption of methane on silica 200DF decreased with increasing amounts of pre-adsorbed water, characterised by significant associativity ( δ_H≈5ppm) at h≥0.005g/g.

Keywords: PACS; 61.43.Gt Powders porous materials; 68.08.-p Liquid–solid interfaces; 68.43.-h Chemisorption/physisorption: adsorbates on surfaces; 68.35.Md Surface thermodynamics surface energiesNanosilica; Nanoporous silica gel; Water adsorption; Methane–water co-adsorption; FTIR; ¹; H NMR

Facile synthesis of CuO hollow nanospheres assembled by nanoparticles and their electrochemical performance by Mei Kong; Weixin Zhang; Zeheng Yang; Shaoying Weng; Zhangxian Chen (pp. 1317-1321).

Display Omitted► CuO hollow nanospheres were prepared by thermal oxidation of Cu₂O solid nanospheres. ► The formation of CuO hollow nanospheres mainly results from the Kirkendall effect. ► CuO hollow nanospheres can be used as anode materials for lithium ion batteries. ► CuO hollow nanospheres show better electrochemical properties than nanoparticles.CuO hollow nanospheres with an average diameter of 400nm and shell thickness of 40nm have been successfully synthesized via a simple thermal oxidation strategy with Cu₂O solid nanospheres as the precursor. The products have been characterized by X-ray diffraction, transmission electron microscopy and field emission scanning electron microscopy. The formation of CuO hollow nanospheres mainly results from the Kirkendall effect on the basis of temperature-dependent experiments. Furthermore, the electrochemical performance of CuO hollow nanospheres as anode materials for lithium ion batteries has been evaluated by cyclic voltammetry and galvanostatic discharge-charge experiments. The as-prepared CuO hollow nanospheres assembled by nanoparticles exhibit higher initial discharge capacity and better cycle performance than the reported CuO nanoparticles. The hierarchical hollow nanospheres have been demonstrated to take the advantages of nanoparticles and hollow architectures, which could not only shorten the lithium ion transport distance and increase the kinetics of conversion reactions, but also provide suitable electrode/electrolyte contact area and accommodate the volume change associated with lithium ion insertion and extraction.

Keywords: CuO; Hollow nanospheres; Synthesis; Kirkendall effect; Lithium ion batteries

Three dimensional imaging using secondary ion mass spectrometry and atomic force microscopy by Yves Fleming; Tom Wirtz; Urs Gysin; Thilo Glatzel; Urs Wegmann; Ernst Meyer; Urs Maier; Jörg Rychen (pp. 1322-1327).

► We present a method for correcting the 3D secondary ion distribution using AFM. ► We compare traditional SIMS 3D imaging with AFM corrected SIMS 3D imaging. ► AFM-SIMS permits a more accurate determination of the sputter rate. ► AFM-SIMS allows the accurate localization secondary ion signal hotspots. ► AFM scanning of the sputter zone allows accurate determination of the ion fluence.With the breakthroughs in lateral resolution with regards to secondary ion mass spectroscopy in recent years, new areas of research with much promise have opened up to the scientific community. Even though the much improved lateral resolution of 50nm can effectively deliver more accurate 3D-images, the traditional 3D reconstructions, consisting of compiling previously acquired successive secondary ion mass spectrometry images into a 3D-stack, do not represent the real localized chemical distribution of the sputtered volume. Based on samples initially analyzed on the Cameca NanoSIMS 50 instrument, this paper portrays the advantages of combining the topographical information from atomic force microscopy and the chemical information from secondary ion mass spectrometry. Taking account of the roughness evolution within the analyzed zone, 3D reconstructions become a lot more accurate and allow an easier interpretation of results. On the basis of an Al/Cu sample, a comparison between traditional 3D imaging and corrected 3D reconstructions is given and the advantages of the newly developed 3D imaging method are explained.

Keywords: 3D imaging; Atomic force microscopy; Secondary ion mass spectrometry; AFM corrected SIMS imaging; Sputter rate; Ion fluence

The structure, surface topography and mechanical properties of Si–C–N films fabricated by RF and DC magnetron sputtering by Zhifeng Shi; Yingjun Wang; Chang Du; Nan Huang; Lin Wang; Chengyun Ning (pp. 1328-1336).

► The Si–N film coating on Co–Cr alloy as biomechanical coating was put forward. ► The Si–N film/UHMWPE sliding pair displays super-low friction coefficient, the friction curve shows the downtrend. ► Micro–scratch results showed that DLC and Si–N films possess the high–quality interfacial bonding in the film/substrate. ► The nano–indentation results that DLC and Si-N film enhances the hardness of the Co–Cr alloy to seven times and three times. ► DLC film indentation hardness values in the range of 60 GPa (super hard region).Silicon carbon nitride thin films were deposited on Co-Cr alloy under varying deposition conditions such as sputtering power and the partial pressure ratio of N₂ to Ar by radio frequency and direct current magnetron sputtering techniques. The chemical bonding configurations, surface topography and hardness were characterized by means of X-ray photoelectron spectroscopy, atomic force microscopy and nano-indentation technique. The sputtering power exhibited important influence on the film composition, chemical bonding configurations and surface topography, the electro-negativity had primary effects on chemical bonding configurations at low sputtering power. A progressive densification of the film microstructure occurring with the carbon fraction was increased. The films prepared by RF magnetron sputtering, the relative content of the Si–N bond in the films increased with the sputtering power increased, and Si–C and Si–Si were easily detachable, and C–O, N–N and N–O on the film volatile by ion bombardment which takes place very frequently during the film formation process. With the increase of sputtering power, the films became smoother and with finer particle growth. The hardness varied between 6GPa and 11.23GPa depending on the partial pressure ratio of N₂ to Ar. The tribological characterization of Co–Cr alloy with Si–C–N coating sliding against UHMWPE counter-surface in fetal bovine serum, shows that the wear resistance of the Si–C–N coated Co–Cr alloy/UHMWPE sliding pair show much favourable improvement over that of uncoated Co–Cr alloy/UHMWPE sliding pair. This study is important for the development of advanced coatings with tailored mechanical and tribological properties.

Keywords: Silicon carbon nitride; Magnetron sputtering; Chemical bonding configuration; Nano-indentation and tribological

Preparation, characterization and dye adsorption properties of γ-Fe₂O₃/SiO₂/chitosan composite by H.Y. Zhu; R. Jiang; Y.-Q. Fu; J.-H. Jiang; L. Xiao; G.-M. Zeng (pp. 1337-1344).

► γ-Fe₂O₃/SiO₂/chitosan composite was prepared by water-in-oil emulsification method. ► Adsorption process followed the pseudo-second-order kinetic model. ► The intraparticle diffusion was related to the adsorption but not as a sole rate-controlling step. ► The equilibrium adsorption data was well described by Freundlich isotherm model. ► The adsorption process was feasible, spontaneous and exothermic in nature.A γ-Fe₂O₃/SiO₂/chitosan composite was prepared by water-in-oil emulsification, and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM). Effects of various factors, including adsorbent dosage, initial dye concentration, solution pH, and competing anions, on the adsorption of methyl orange from aqueous solutions by the resulting composite were studied by batch adsorption experiments. The adsorption kinetics was found to follow the pseudo-second-order kinetic model, and intraparticle diffusion was related to the adsorption, but not as a sole rate-controlling step. The equilibrium adsorption data were well described by the Freundlich isotherm model. Evaluation of the thermodynamic parameters Δ G°, Δ H°, and Δ S° revealed that the adsorption process was naturally feasible, spontaneous, and exothermic. The composite was proven to be efficient, suitable and promising for the removal of methyl orange from aqueous solutions since it has a relatively higher adsorption capacity than other low-cost adsorbents.

Keywords: Adsorption; Methyl orange; γ-Fe; ₂; O; ₃; SiO; ₂; Chitosan

Nd-laser irradiations effects and AFM-investigations on structural and surface features of optimally lutetium thorium-co-doped-2212-BSCCO by Khaled M. Elsabawy; Mohamed H. El-Newehy (pp. 1345-1352).

Visualized XRD-profile of lutetium-thorium co-doped-2212-BSCCO and unit cell diagram shows CuO6-polyhedra units inside 2212-BSCCO structure.Display Omitted► Optimally co-doped Lu–Th-superconductor sample crystallized in tetragonal phase 2212-BSCCO. ► The fingerprint of both structures experimental and theoretical are nearly identical. ► The average grain size in different spots inside the sample found in between 0.35 and 1.45μm. ► After maximum Nd-laser irradiation dose the morphology of the surface is directed and oriented. ► The T_c-onsets of the optimally co-doped Lu–Th-sample increase as irradiation power and duration time increases.Lutetium–thorium optimally co-doped sample with general formula Bi2− x−_yLu_xTh_ySr₂Ca₁Cu₂O₈ where x= y=0.15mol was selected to be the target for three different doses of Nd-laser beam irradiations the 1st 15W/cm² for 60min, 2nd 30W/cm² for 120min and 3rd 45W/cm² for 240min, respectively. Nd-Laser irradiations doses were monitoring as function of micro-structure, superconducting and structural features of Lu–Th-optimally co-doped 2212-BSCCO. AFM and SE-microscopy were applied to investigate changes occurred in the surface's layers after each Nd-laser irradiation dose. Both of bulk superconductivity and surface resistivity were measured to establish the promotion occurred on the superconducting features due to Nd-laser irradiation doses.

Keywords: Doping; 2212-BSCCO; Laser-irradiations; Superconductors; Structure; AFM; SEM

Preparation and characterization of SnS nanocrystals by a triethanolamine-assisted diethylene glycol solution synthesis by Li Ren; Zhengguo Jin; Weidong Wang; Hui Liu; Junyun Lai; Jingxia Yang; Zhanglian Hong (pp. 1353-1358).

► We prepared SnS nanocrystals by ambient pressure solution chemical synthesis. ► ZB and OR phases of SnS can be controlled by varying TEA amounts in DEG solvent. ► Basic characterization data of ZB and OR SnS nanocrystals were described by XRD, FESEM, EDS, FETEM and UV–vis–NIR.Stoichiometric, phase-controllable SnS nanocrystals (NCs) were prepared by a solution chemical synthesis using triethanolamine-assisted diethylene glycol solvent, tin(II) chloride and thioacetamide as precursors at injection temperature of 180–220°C. The influences of triethanolamine adding amounts, injection temperature, refluxing time on crystal phase, growth morphology and optical property of the synthesized SnS NCs were investigated. The results showed that both orthorhombic (OR) and zinc-blende (ZB) phase of SnS NCs could be formed by altering triethanolamine amounts.

Keywords: SnS nanocrystals; Diethylene glycol solvent; Triethanolamine; Orthorhombic phase; Zinc-blende phase

Fabrication of superhydrophobic surfaces on zinc substrates and their application as effective corrosion barriers by Tao Ning; Wenguo Xu; Shixiang Lu (pp. 1359-1365).

The SEM image of the prepared superhydrophobic surface with the novel and interesting composite structure and the highest CA value, which can be used as an effective corrosion barrier.Display Omitted► Effective composite structures which were only responsible for the superhydrophobicity were successfully fabricated through one-step method. ► Different interesting composite structures were prepared by changing the reaction temperature. ► The optimal superhydrophobic surface could be used as an effective corrosion barrier on the zinc substrate.Stable superhydrophobic surfaces have been effectively fabricated on the zinc substrates through one-step platinum replacement deposition process without the further modification or any other post processing procedures. The effect of reaction temperatures on the surface morphology and wettability was studied by using SEM and water contact angle (CA) analysis. Under room temperature, the composite structure formed on the zinc substrate was consisted of microscale hexagonal cavities, densely packed nanoparticles layer and micro/nanoscale structures like the flowers. The structure has exhibited great surface roughness and porosity contributing to the superhydrophobicity where the contact angle could reach an ultra high value of around 170°. Under reaction temperature of 80°C, the composite structure, on the other hand, was hierarchical structure containing lots of nanoscale flowers and some large bushes and showed certain surface roughness (maximum CA value of about 150°). In addition, an optimal superhydrophobic platinum surface was able to provide an effective anticorrosive coating to the zinc substrate when it was immersed into an aqueous solution of sodium chloride (3% NaCl) for up to 20 days. The corrosion process was monitored through electrochemical means and the results are compared with those of unprotected zinc plates.

Keywords: Superhydrophobic surfaces; Composite structures; Wettability; Corrosion resistances

Selective growth, characterization, and field emission performance of single-walled and few-walled carbon nanotubes by plasma enhanced chemical vapor deposition by Mihnea Ioan Ionescu; Yong Zhang; Ruying Li; Xueliang Sun (pp. 1366-1372).

► Plasma enhanced CVD at relatively low synthesis temperature. ► Vertically aligned CNTs on semiconducting silicon wafer. ► CNT average length increases with plasma power and decreases with distance to plasma. ► Selective growth of few-walled and single-walled CNTs by tuning the catalyst thickness. ► Single-walled CNTs exhibit better field emission characteristics than the few-walled CNTs.Single-walled carbon nanotubes (SWCNTs) and few-walled carbon nanotubes (FWCNTs) have been selectively synthesized by plasma enhanced chemical vapor deposition at a relative low temperature (550°C) by tuning the thickness of iron catalyst. The parametric study and the optimization of the nanotube growth were undertaken by varying inductive power, temperature, catalyst thickness, and plasma to substrate distance. When an iron film of 3–5nm represented the catalyst thickness for growing FWCNT arrays, SWCNTs were synthesized by decreasing the catalyst thickness to 1nm. The nanotubes were characterized by field emission scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy. Electron field emission properties of the nanotubes indicate that the SWCNTs exhibit lower turn-on field compared to the FWCNTs, implying better field emission performance.

Keywords: Carbon nanotubes; Plasma enhanced chemical vapor deposition

Effect of non-magnetic doping on leakage and magnetic properties of BiFeO₃ thin films by Jie Wei; Desheng Xue (pp. 1373-1376).

► The leakage properties of BiFeO₃ (BFO) films are greatly improved by Zr-doping. ► The magnetic properties of Zr-BFO films are affected as a weak ferromagnetism. ► A model is proposed to explain the origin of ferromagnetism in Zr-BFO films.In this paper, we show that the leakage current properties of BiFeO₃ (BFO) thin films have been greatly improved by Zr-doping. In contrast, the magnetic properties of Zr-doped BFO films are affected as a weak ferromagnetism. Beyond the double-exchange interactions arising from the creation of Fe²⁺, we propose another simple model considering the replacement of the magnetically active Fe³⁺, time to time, by a non-active Zr⁴⁺, which is expected to induce a local ferromagnetic coupling rather than an antiferromagnetic one.

Keywords: Multiferroics; Thin films; Leakage current; Ferromagnetism; Double-exchange interaction

Correlation between microstructure and property of electroless deposited Pt counter electrodes on plastic substrate for dye-sensitized solar cells by Xue-Long He; Mei Liu; Guan-Jun Yang; Sheng-Qiang Fan; Chang-Jiu Li (pp. 1377-1384).

.Display Omitted► Pt CE with high electrocatalytic property was prepared by electroless deposition. ► The assembled DSCs show comparable efficiency to that with sputtered Pt CEs. ► Correlation between microstructure and property of Pt film was demonstrated. ► A model for the change of surface area of the Pt film was proposed.Flexible Pt counter electrodes (CEs) were prepared on indium-doped tin oxide coated polyethylene naphthalate (ITO-PEN) substrate by electroless deposition. The correlation between the microstructure and the property of the Pt CEs was investigated. Results showed that isolated Pt nanoparticles were uniformly distributed on the ITO surface at a short deposition duration, and then grew with the deposition duration, leading to the interconnection of adjacent Pt nanoparticles. The interconnection of Pt nanoparticles was beneficial to the electrical property of the Pt CEs, while it was unfavorable to the electrocatalytic property of the Pt CEs. A microstructure model was proposed to explain the correlation between the microstructure and the property of the Pt CEs. In addition, the Pt CEs showed low charge transfer resistance (1.66–0.58Ωcm²), which was comparable to that (1.16Ωcm²) of the conventional sputtered Pt CE. The high electrocatalytic property of the electroless deposited Pt CEs makes the assembled DSCs present comparable energy conversion efficiency of the DSCs using sputtered Pt CE.

Keywords: Dye-sensitized solar cells; Counter electrode; Electroless deposition; Microstructure; Pt loading; Electrocatalytic property

Electrospun cross linked rosin fibers by Woo-il Baek; R. Nirmala; Nasser A.M. Barakat; Mohamed H. El-Newehy; Salem S. Al-Deyab; Hak Yong Kim (pp. 1385-1389).

► Fiber formation of rosin via an electrospinnning technique by using various solvents and different polymer concentrations. ► We performed experiments to determine a suitable solvent for electrospinning of rosin fibers. ► We propose a likely mechanism for the formation of rosin fibers during the electrospinning process. ► Electrospinning of pure rosin in fiber form is first time reported.In this study, we describe the first reported preparation of rosin in fiber form through use of an electrospinning technique utilizing various solvent systems. The polymer concentration of the formed fiber was studied by using various solvents such as chloroform, ethanol, N-N dimethylformamide (DMF), tetrahydrofuran (THF), acetone, and methylene chloride (MC). An electrospray of the solution resulted in the beaded form of the rosin. By varying the polymer concentration with MC, we were then able to obtain uniform fibers. However, the fibers exhibited large diameter. We believe that it is possible to reduce the diameter of the rosin fibers through appropriate selection of electrospinning parameters. In addition, the morphological transitions from beads, to beaded fiber, to fiber were studied at different polymer concentrations. We propose a possible physical cross linking mechanism for the formation of rosin fibers during the electrospinning process. Our results demonstrate the feasibility of producing fiber nanostructures of rosin by using an electrospinning technique.

Keywords: Rosin; Solvents; Polymer; Electrospinning; Fibers

BiFeO₃/Zn1−_xMn_xO bilayered thin films by Jiagang Wu; John Wang; Dingquan Xiao; Jianguo Zhu (pp. 1390-1394).

► Bilayered BiFeO₃/Zn1−_xMn_xO ( x=0–0.08) thin films have highly (110) orientation. ► Diode-like and resistive hysteresis behavior is demonstrated for all bilayers. ► A large remanent polarizationof 2 P_r∼121.0–∼130.6μC/cm² for all bilayers. ► A highest M_s value of ∼15.2emu/cm³ for BiFeO₃/Zn1−_xMn_xO ( x=0.04).BiFeO₃/Zn1−_xMn_xO ( x=0–0.08) bilayered thin films were deposited on the SrRuO₃/Pt/TiO₂/SiO₂/Si(100) substrates by radio frequency sputtering. A highly (110) orientation was induced for BiFeO₃/Zn1−_xMn_xO. BiFeO₃/Zn1−_xMn_xO thin films demonstrate diode-like and resistive hysteresis behavior. A remanent polarization in the range of 2 P_r∼121.0–130.6μC/cm² was measured for BiFeO₃/Zn1−_xMn_xO. BiFeO₃/Zn1−_xMn_xO ( x=0.04) bilayer exhibits a highest M_s value of ∼15.2emu/cm³, owing to the presence of the magnetic Zn_0.96Mn_0.04O layer with an enhanced M_s value.

Keywords: BiFeO; ₃; /Zn; 1−; _x; Mn; _x; O; Bilayered thin films; Magnetron sputtering; Electrical properties

One-step electrodeposition process to fabricate cathodic superhydrophobic surface by Zhi Chen; Feng Li; Limei Hao; Anqi Chen; Youchao Kong (pp. 1395-1398).

► A superhydrophobic surface on the cathodic electrode had been fabricated by a one-step electrodeposition process. ► The prepared surface has a high water contact angle of 163° and a low rolling angle of less than 3°. ► The needed minimum electrolytic time is largely shortened to 1min, and have a promising future in industrial fields.In this work, a rapid one-step process is developed to fabricate superhydrophobic cathodic surface by electrodepositing copper plate in an electrolyte solution containing manganese chloride (MnCl₂·4H₂O), myristic acid (CH₃(CH₂)₁₂COOH) and ethanol. The superhydrophobic surfaces were characterized by means of scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The shortest electrolysis time for fabricating a superhydrophobic surface is about 1min, the measured maximum contact angle is 163° and rolling angle is less than 3°. Furthermore, this method can be easily extended to other conductive materials. The approach is time-saving and cheap, and it is supposed to have a promising future in industrial fields.

Keywords: Superhydrophobic; Contact angle; Myristic acid; Cathodic surface; Electrodeposition

Surface microstructures and antimicrobial properties of copper plasma alloyed stainless steel by Xiangyu Zhang; Xiaobo Huang; Li Jiang; Yong Ma; Ailan Fan; Bin Tang (pp. 1399-1404).

► Antibacterial steel surfaces with different copper content have been prepered. ► The antibacterial rate increased with increasing time of contacting the bacteria. ► The higher the amount of surface copper, the better is the antibacterial efficacy. ► Cu-ions were dissolved from the Cu-alloyed surface, killing the bacteria.Bacterial adhesion to stainless steel surfaces is one of the major reason causing the cross-contamination and infection in many practical applications. An approach to solve this problem is to enhance the antibacterial properties on the surface of stainless steel. In this paper, novel antibacterial stainless steel surfaces with different copper content have been prepared by a plasma surface alloying technique at various gas pressures. The microstructure of the alloyed surfaces was investigated using glow discharge optical emission spectroscopy (GDOES) and scanning electron microscopy (SEM). The viability of bacteria attached to the antibacterial surfaces was tested using the spread plate method. The antibacterial mechanism of the alloyed surfaces was studied by X-ray photoelectron spectroscopy (XPS). The results indicate that gas pressure has a great influence on the surface elements concentration and the depth of the alloyed layer. The maximum copper concentration in the alloyed surface obtained at the gas pressure of 60Pa is about 7.1wt.%. This alloyed surface exhibited very strong antibacterial ability, and an effective reduction of 98% of Escherichia coli ( E. coli) within 1h was achieved by contact with the alloyed surface. The maximum thickness of the copper alloyed layer obtained at 45Pa is about 6.5μm. Although the rate of reduction for E. coli of this alloyed surface was slower than that of the alloyed surface with the copper content about 7.1wt.% over the first 3h, few were able to survive more than 12h and the reduction reached over 99.9%. The XPS analysis results indicated that the copper ions were released when the copper alloyed stainless steel in contact with bacterial solution, which is an important factor for killing bacteria. Based on an overall consideration of bacterial killing rate and durability, the alloyed surface with the copper content of 2.5wt.% and the thickness of about 6.5μm obtained at the gas pressure of 45Pa is expected to be useful as antimicrobial materials that may have a promising future in antimicrobial applications.

Keywords: Stainless steel; Plasma alloying; Copper content; Antibacterial property

Hydrogen outgassing mechanism in titanium materials by Masatoshi Takeda; Hiroki Kurisu; Setsuo Yamamoto; Hamazo Nakagawa; Katsunobu Ishizawa (pp. 1405-1411).

► The titanium material has slow hydrogen atoms diffusion at the boundary region between the surface oxide layer and the bulk. ► The quick hydrogen atoms diffusion at the surface oxide layer and rapid desorption of adsorbed hydrogen atoms at the surface. ► These facts give very low hydrogen concentration at a surface layer playing the significant role for an extremely low outgassing property of vacuum materials.This paper addresses a hydrogen outgassing mechanism in titanium materials with extremely low outgassing property by investigating the distribution of hydrogen atoms concentration in depth below the surface, and the activation energy for desorption of dissolved hydrogen atoms into the boundary region between the surface oxide layer and the bulk titanium and that of adsorbed hydrogen atoms on the surface. The distribution of hydrogen atoms concentration in depth below the surface was analyzed by a time-of-flight secondary ion mass spectrometry (TOF-SIMS). The activation energy for desorption of dissolved hydrogen atoms was estimated by the thermal desorption spectroscopy (TDS) measurement with various heating rates. The activation energy for desorption of adsorbed hydrogen atoms was estimated by the temperature dependence of the outgassing rate in titanium material. In the titanium material, hydrogen atoms show maximum concentration at the boundary between the surface oxide layer and the bulk titanium. Concentration of hydrogen atoms decreases rapidly at the surface oxide layer, while it decreases slowly in the deep region below the surface layer–bulk boundary by the vacuum evacuation without/with the baking process. The activation energy for desorption of 1.02eV of dissolved hydrogen atoms into the surface layer–bulk boundary is about three times as large as that of 0.38eV of the adsorbed hydrogen atoms on the surface. These results suggest that the hydrogen outgassing mechanism in the titanium material is composed the follows processes, i.e. the slow hydrogen atoms diffusion at the surface layer–bulk boundary, quick hydrogen atoms diffusion at the surface oxide layer and rapid desorption of adsorbed hydrogen atoms on the surface. This outgassing mechanism gives very low hydrogen concentration near the surface, which results in the extremely low outgassing rate in titanium materials.

Keywords: Hydrogen outgassing; Titanium material; Distribution of hydrogen atoms concentration; Activation energy for desorption

Synthesis and properties control of fluorinated organic–inorganic hybrid films by Qingjie Yu; Jianming Xu; Yuanyuan Han (pp. 1412-1416).

. Three layered fluorinated organic–inorganic hybrid films have been studied in order to determine the effect of TMOS content on the microstructure and surface wettability.Display Omitted► Three layered fluorinated organic–inorganic hybrid films were synthesized. ► Surface wettability of the films was governed by fluorocarbon groups of the outermost layer. ► The most of tetramethoxysilane added were arranged to the bottom layer to improve the thickness. ► The increase in tetramethoxysilane content had a slight effect on surface wettability.Fluorinated organic–inorganic hybrid films were prepared by free-radical random copolymerization and sol–gel process through dodecafluoroheptyl methacrylate (DFMA), vinyltriethoxysilane (VTES), and tetramethoxysilane (TMOS). It was found that the prepared fluorinated organic–inorganic hybrid film was very hydrophobic and exhibits excellent water repellency. Hydrophobic fluorocarbon side chains were preferentially enriched to the outermost layer at the interface of coating film–air, and three layers probably exist in the coating films. The fluorinated hybrid films possessed fluorocarbon side chains orient toward the air originating from DFMA as the top layer, hydrocarbon backbone chain originating from vinyl polymerization as the middle layer, and silica network originating from the hydrolysis and condensation of siloxane as the bottom layer. It demonstrated that most of TMOS added might be arranged to the bottom layer of the fluorinated hybrid films, and had a slight impact on the enrichment of fluorocarbon side chains of the outermost layer. However, the useful properties of the fluorinated organic–inorganic hybrid films such as thickness and corrosion resistant can be significantly improved by the increase of TMOS content.

Keywords: Fluorinated hybrid films; Tetramethoxysilane; Water repellency

Surface chemistry and growth mechanisms studies of homo epitaxial (100) GaAs by laser molecular beam epitaxy by Dawei Yan; Weidong Wu; Hong Zhang; Xuemin Wang; Hongliang Zhang; Weibin Zhang; Zhengwei Xiong; Yuying Wang; Changle Shen; Liping Peng; Shangjun Han; Minjie Zhou (pp. 1417-1421).

► The deposition of GaAs epilayer using LMBE was achieved. ► Chemistry evolution of GaAs epilayer during deposition was investigated using in situ XPS. ► The growth process is heavily influenced by the surface chemistry and morphology of thermally desorbed GaAs substrate. ► It is found that a predominant step flow growth mode for the growth of GaAs by LMBE in this study. ► The incorporation of As species into GaAs epilayer is more efficient in LMBE than conventional MBE.In this paper, GaAs thin film has been deposited on thermally desorbed (100) GaAs substrate using laser molecular beam epitaxy. Scanning electron microscopy, in situ reflection high energy electron diffraction and in situ X-ray photoelectron spectroscopy are applied for evaluation of the surface morphology and chemistry during growth process. The results show that a high density of pits is formed on the surface of GaAs substrate after thermal treatment and the epitaxial thin film heals itself by a step flow growth, resulting in a smoother surface morphology. Moreover, it is found that the incorporation of As species into GaAs epilayer is more efficient in laser molecular beam epitaxy than conventional molecular beam epitaxy. We suggest the growth process is impacted by surface chemistry and morphology of GaAs substrate after thermal treatment and the growth mechanisms are discussed in details.

Keywords: GaAs; LMBE; Thermal treatment; XPS

Very low pressure plasma sprayed alumina and yttria-stabilized zirconia thin dense coatings using a modified transferred arc plasma torch by Lin Zhu; Nannan Zhang; Baicheng Zhang; Fu Sun; Rodolphe Bolot; Marie-Pierre Planche; Hanlin Liao; Christian Coddet (pp. 1422-1428).

► A transferred arc nozzle was designed and made to improve low-energy plasma spray torch under very low pressure condition. ► The Al₂O₃ and YSZ thin dense ceramic coatings were successfully deposited by such transferred arc nozzle. ► The transferred arc nozzle effects and the electron temperature on the plasma jet were evaluated. ► The transferred arc sprayed coatings exhibited better properties.As a novel thermal spray process, very low pressure plasma spray (VLPPS) process has been significantly used to deposit thin, dense and homogenous ceramic coating materials for special application needs in recent years. In this study, in order to enhance low-energy plasma jet under very low pressure ambience, a home-made transferred arc nozzle was made and mounted on a low-power F100 plasma torch to fully melt or evaporate powder feedstock. As a result, thin and dense alumina (Al₂O₃) and yttria-stabilized zirconia (YSZ) ceramic coatings with an average thickness of 30–40μm were successfully elaborated by the VLPPS process below 1mbar. An optical emission spectroscopy (OES) was used to analyze the plasma jet properties. The microstructures of the coatings were observed by means of a scanning electron microscopy (SEM). It was found that the YSZ coatings displayed a bimodal microstructure which was composed of splats formed by melted particles and a little amount of vapor condensation from evaporated particles. However, vapor condensation could not be observed in the Al₂O₃ coatings, and only lamellar splats were found. The mechanical properties of both coatings were also evaluated.

Keywords: Yttria-stabilized zirconia; Alumina; Very low pressure plasma spray; Optical emission spectroscopy; Electron temperature; Transferred arc

Theoretical investigation of CO adsorption on TM-doped (MgO)₁₂ (TM=Ni, Pd, Pt) nanotubes by Mingxia Yang; Yonghong Zhang; Shiping Huang; Hui Liu; Peng Wang; Huiping Tian (pp. 1429-1436).

► Adsorption behavior of CO on TM-doped (MgO)₁₂ nanotubes has investigated. ► CO is more strongly bound to the 3-fold transition metal atoms in TM-1 models. ► TM–C bonding can be described in 5σ forward-donation and 2π^* back-donation mode.CO adsorption on TM-doped magnesia nanotubes (TM=Ni, Pd and Pt) have been studied by using density functional theory. Our calculation results show that CO favors adsorption on TM-doped magnesia nanotubes in the form of C atom bonding with TM atom. Fukui indices analysis clearly exhibits that doping of impurity TM atom allows for a noticeably enhancement of nucleophilic reactivity ability of magnesia nanotube. The adsorption energies demonstrate that CO molecule is more strongly bound on the 3-fold TM atoms than the 4-fold TM atoms. This finding is well confirmed by TM–C bond length, charge transfer and C–O vibrational frequency. The high adsorption energy of 2.55eV is found when CO adsorbs on 3-fold Pt in Pt-doped magnesia nanotubes, implying the kind of the doping TM atom has a significant influence on the chemical reactivity.

Keywords: CO adsorption; TM-doped (MgO); ₁₂; nanotubes; Density functional theory; Chemisorption; Electronic properties; Vibrational frequencies

Photoactive thin films of polycaprolactam doped with europium (III) complex using phenylalanine as ligand by Irene Teresinha Santos Garcia; Patrícia Velleda Ribeiro; Diogo Silva Corrêa; Igor Michel Neto da Cunha; Neftali Lenin Villarreal Carreño; Eduardo Ceretta Moreira; Fabiano Severo Rodembusch (pp. 1437-1442).

Display Omitted► The present manuscript covers in detail our study related to the conditions for obtaining a phenylalanine complex and the effects on the polycaprolactam thin films. ► The synthesis and performance of an amino acid based europium complex to prepare photoactive thin films is presented, as well as the comparison with acetyl-β-acetonate europium complex. ► This paper is an important contribution in the area of production of thin photoluminescent surfaces.A photoactive complex based on europium(III) using the amino acid phenylalanine as ligand was prepared and characterized. The obtained europium(III)/phenylalanine complex presents an effective energy transfer from ligands to the rare earth center. The observed photoluminescent behavior for europium(III)/phenylalanine complex was similar to the well known europium(III)/ acetyl-β-acetonate hydrate. New photoactive polyamide thin films were prepared using polycaprolactam as host of these complexes. The structural characterizations of the films were studied through Rutherford backscattering (RBS), Fourier transform infrared (FTIR) and Raman spectroscopies. The polyamide films doped with the amino acid and acetyl-β-acetonate rare earth complexes maintain the original photoluminescent behavior, narrow emission bands corresponding to transitions⁵D₀→⁷F_0-4, which indicates that this polymer is an excellent host to these complexes.

Keywords: Photoactive films; Polyamide; Photoluminescence; Phenylalanine europium complex

Preparation of a novel Ni/Co-based alloy gradient coating on surface of the crystallizer copper alloy by laser by Suiyuan Chen; Jing Liang; Changsheng Liu; Kai Sun; Jyoti Mazumder (pp. 1443-1450).

► Laser cladding a Ni/Co-based alloy gradient coating with high wear-resistance on the Cu alloy surface. ► The gradient coating has three layers using elements gradient design. The hardness of the third Co-based alloy layer reaches 876HV. ► The gradient coating reveals good adhesive friction and wear properties. ► This novel technique may have good application to make an advanced coating on the surface of the Cu alloy crystallizer.A high wear-resistant gradient coating made of Ni/Co-based alloys on the surface of a Cu alloy substrate was synthesized using a YAG laser induced in situ reaction method. The coating consists of three layers: the first is a Ni-based alloy layer, the second and third are Co-based alloy layers. The microhardness increases gradually from 98HV in the Cu alloy substrate to the highest level of 876HV in the third layer. The main phase of the Co-based alloy layer is CoCr₂(Ni,O)₄, coexisting with the Fe₁₃Mo₂B₅, Cr(Co(Mo, and FeCr_0.29Ni_0.16C_0.06 phases. Wear tests indicate that the gradient coating has good bond strength and wear properties with a wear coefficient of 0.31 (0.50 for the Cu alloy substrate). Also, the wear loss of the coating is only 0.01g after it has been abraded for 60min, which is only one fifth of that of the Cu alloy of the crystallizer. Wear tests of the gradient coating reveal good adhesive friction and wear properties when sliding against steel under dry conditions. This novel technique may have good application to make an advanced coating on the surface of the Cu alloy crystallizer in a continuous casting process.

Keywords: Gradient coating; Laser cladding; Hard particle phase; Hardness; Wear properties

Quantifying adhesion energy of mechanical coatings at atomistic scale by Deqiang Yin; Xianghe Peng; Yi Qin; Jiling Feng; Zhongchang Wang (pp. 1451-1455).

► First-principles calculations are applied to quantify adhesion energy of TiN coating at atomistic scale. ► Adhesion energies for (111) and (001) surfaces are small under no residual stress, yet increase linearly once stressed. ► Adhesion strengthening is due to the stress-induced shrinkage of neighboring bonds and enhanced bond interactions. ► Finite elements simulation reproduces initial cracking process, validating the use of adhesion energy for coatings.Coatings of transition metal compounds find widespread technological applications where adhesion is known to influence or control functionality. Here, we, by first-principles calculations, propose a new way to assess adhesion in coatings and apply it to analyze the TiN coating. We find that the calculated adhesion energies of both the (111) and (001) orientations are small under no residual stress, yet increase linearly once the stress is imposed, suggesting that the residual stress is key to affecting adhesion. The strengthened adhesion is found to be attributed to the stress-induced shrinkage of neighbouring bonds, which results in stronger interactions between bonds in TiN coatings. Further finite elements simulation (FEM) based on calculated adhesion energy reproduces well the initial cracking process observed in nano-indentation experiments, thereby validating the application of this approach in quantifying adhesion energy of surface coating systems.

Keywords: Adhesion energy; First-principles calculation; Residual stress; TiN coatings

In situ atomic force microscopy observation of hydrogen absorption/desorption by Palladium thin film by Itoko Matsumoto; Kouji Sakaki; Yumiko Nakamura; Etsuo Akiba (pp. 1456-1459).

► The surface morphology of a Pd thin film during hydrogen absorption and desorption was observed using in situ AFM. ► Residual stress in the film was compressive for the as-sputtered film, but changed to tensile after a hydrogen absorption/desorption cycle. ► Hydrogen absorption of the film induced irreversible grain agglomeration. ► These results indicate that residual tensile stress after an absorption/desorption cycle develops because of irreversible grain agglomeration.Grain structure changes in Pd thin film during hydrogen absorption and desorption were observed by in situ atomic force microscopy. The as-sputtered film had a smooth flat surface with 20–30nm grains. Film that absorbed hydrogen showed buckling, caused by the compressive stress due to lattice expansion as Pd metal reacted with hydrogen to form the hydride. Grains on the buckles were agglomerated and deformed unlike those on flat areas beside the buckles. Film that absorbed and then desorbed hydrogen still showed some buckling; however, many buckles shrank and flattened when the compressive stress of lattice expansion was released during desorption. On both the remaining and the shrunken buckles, grain agglomeration was retained; whereas, the deformed grains reverted back to their original form. X-ray diffraction indicated compressive residual stress in the as-sputtered film and tensile residual stress in the film after hydrogen absorption/desorption. These results indicate that irreversible grain agglomeration is related to residual tensile stress in the film although agglomeration occurs only on the buckled areas.

Keywords: Atomic force microscopy; Film morphology; Palladium film; Pd–H system; In situ observation; Hydrogen storage materials

Study of Ti addition in channel layers for In–Zn–O thin film transistors by Yao Qijun; Li Shuxin; Zhang Qun (pp. 1460-1463).

► Thin film transistors with Ti added In–Zn–O as channel layer materials. ► Threshold voltage shows positive shift as Ti content increases. ► Positive shift is induced by suppression of oxygen vacancies in channel layer. ► Field effect mobility is not decreased as Ti content increases.Ti added In–Zn–O thin films and their application to thin film transistors were studied. The In–Zn–O films were deposited by pulsed plasma deposition using targets with various Ti contents added. High content of Ti in In–Zn–O films was found to induce a decrease in carrier concentration. The effect was attributed to suppression of oxygen vacancies by Ti incorporation. For thin film transistors with Ti added In–Zn–O as channel layer materials, threshold voltage showed positive shift as Ti content increases and field effect mobility was not decreased at the same time. Results of a bias stress experiment on device fabricated at room temperature are also given.

Keywords: Thin film transistors; Indium oxide; Zinc oxide; Pulsed plasma deposition

Engineering of hydrophilic and plasmonic properties of Ag thin film by atom beam irradiation by Udai B. Singh; D.C. Agarwal; S.A. Khan; Manish Kumar; A. Tripathi; R. Singhal; B.K. Panigrahi; D.K. Avasthi (pp. 1464-1469).

► Synthesis of plasmonic surface by atom beam sputtering. ► Tuning of size of nanostructures with fluence. ► Characterization using atomic force microscopy, UV Visible spectroscopy, contact angle measurement and Rutherford backscattering spectroscopy are reported.► Tailoring of contact angle of Ag nanostructures with surface roughness. ► Areal concentration of Ag is decreased with increase in fluence.Hydrophilic Ag nanostructures were synthesized by physical vapour deposition of 5nm Ag thin films followed by irradiation with 1.5keV Ar atoms. Optical absorbance measurements show a characteristic surface plasmon resonance absorption band in visible region. A blue-shift in absorbance from 532 to 450nm is observed with increasing fluence from 1×10¹⁶ to 3×10¹⁶atoms/cm². Atomic force microscopy was performed for the pristine and irradiated samples to study the surface morphology. The atom beam irradiation induced sputtering and surface diffusion lead to the formation of plasmonic surface. Rutherford backscattering spectroscopy of the pristine and irradiated film indicates that metal content in the film decreases with ion fluence, which is attributed to the sputtering of Ag by Ar atoms. The contact angle measurement demonstrates the possibility of engineering the hydrophilicity by atom beam irradiation.

Keywords: Hydrophilic property; Surface plasmon resonance; Power spectral density; Contact angle; Rutherford backscattering spectroscopy

Preparation of silica nanowires using porous silicon as Si source by Yi Liang; Bai Xue; Yang Yumeng; Nie Eryong; Liu Donglai; Sun Congli; Feng Huanhuan; Xu Jingjing; Chen Yu; Jin Yong; Jiao Zhifeng; Sun Xiaosong (pp. 1470-1473).

► Layered porous silicon has been prepared by electrochemical etching process. ► Without the assistant metal catalyst, abundance silica nanowires have been grown in the cracks. ► The mechanism has been discussed and the induced stress may play an important role in the growth of silica nanowires.This very paper is focusing on the preparation of silica nano-wires via annealing porous silicon wafer at 1200°C in H₂ atmosphere and without the assistant metal catalysts. X-ray diffraction, X-ray energy dispersion spectroscopy, scanning electron microscopy, high-resolution transmission electron microscopy and selected area diffraction technology have been employed for characterizing the structures, the morphology and the chemical components of the nano-wires prepared, respectively. It is found that the diameter and the length of the nano-wires were about 100nm and tens micron, respectively. Meanwhile, it is also necessary to be pointed out that silica NWs only formed in the cracks of porous wafers, where the stress induced both by the electro-chemical etching procedure for the porous silicon preparation and nanowires growth procedure is believed to be lower than that at the center of the island. Therefore, a stress-driven mechanism for the NWs growth model is proposed to explain these findings.

Keywords: Silica nanowires; Porous silicon; Catalyst-free; Stress-driven

Surface modification of porous poly(tetrafluoroethylene) film via cold plasma treatment by Tongna Shi; Meiling Shao; Hongrui Zhang; Qing Yang; Xinyuan Shen (pp. 1474-1479).

► The poly(tetrafluoroethylene) films were modified with air, acrylic acid and helium plasma and characterized by scanning electron microscopy(SEM), scanning probe microscope(SPM), X-ray photoelectron spectroscopy (XPS) and water contact angle measurements. ► According to SEM and SPM measurements, the surface roughness increased at different levels after plasma treatment. ► Compared to air and AAc plasma treatment, the He plasma treatment introduced large amounts of oxygen into the surface, as known from XPS results. ► Contact angle measurements revealed that the hydrophilicity of the PTFE film surface was greatly improved.In this study, cold plasma technology was applied for the surface modification of porous polytetrafluoroethylene (PTFE) film to improve the hydrophilicity. The surface properties of PTFE, modified by air, helium (He) or acrylic acid (AAc), were investigated with scanning electron microscopy (SEM), scanning probe microscope (SPM), in situ X-ray photoelectron spectroscopy (XPS) and water contact angle measurements. The changes of the surface property before and after plasma treatment were discussed. According to SEM and SPM measurements, the surface roughness increased at different levels after plasma treatment. Compared to air and AAc plasma treatment, the He plasma treatment introduced large amounts of oxygen into the surface, as known from XPS results. Contact angle measurements revealed that the hydrophilicity of the PTFE film surface was greatly improved due to the surface roughness and changes of chemical elements on the PTFE surface.

Keywords: Polytetrafluoroethylene; Surface modification; Plasma treatment; Scanning probe microscope; Contact angle

Surface oxidation of NiCo alloy: A comparative X-ray photoelectron spectroscopy study in a wide pressure range by Y.T. Law; T. Dintzer; S. Zafeiratos (pp. 1480-1487).

Display Omitted► NiCo alloy surface oxidation is studied in two pressure regimes (5×10⁻⁷mbar and 0.5bar). ► Segregation and preferential oxidation of cobalt onto NiCo alloy surface. ► Cobalt segregation reaches a maximum in 0.5bar O₂ upon complete oxidation of Co⁰ to Co²⁺. ► Formation of Co_xNi1−_xO spinel oxide is favoured only at atmospheric O₂ pressure oxidation.Oxidation of NiCo alloy has been studied under two pressure regimes, 5×10⁻¹⁰ and 5×10⁻¹bar, by X-ray photoelectron spectroscopy (XPS). The aim of this work is to investigate the synergetic effect between the two alloy components during the initial stages of oxidation. The results showed that at low oxygen pressure, segregation and preferential oxidation of cobalt takes place, while oxidation of nickel is largely suppressed. The species dominating the surface is CoO but small amount of metallic cobalt still remains even after prolonged oxidation at 670K. At 0.5bar O₂ pressure, alloy oxidation was found to be temperature depended. From 420K to 520K, cobalt is completely transformed to CoO and the Ni:Co atomic ratio at the surface approaches a minimum, similar to the observations at low pressure regime. However, at higher temperatures (from 520K to 720K), nickel is re-segregated on the surface, in the expense of cobalt, while CoO is further oxidized to Co₃O₄. At this temperature range formation of mixed Ni–Co–O spinel-like oxides is probable as supported by the characteristic modifications of the Ni 2p_3/2 photoelectron peak and the increase of the Ni:Co atomic ratio.

Keywords: Bimetallic catalysts; NiCo alloy; X-ray photoelectron spectroscopy; Pressure gap; Ethanol reforming

Surface morphology and crystalline structure of high-stable polycrystalline transparent conductive zinc oxide films by Takashi Kuchiyama; Kenji Yamamoto; Shigehiko Hasegawa; Hajime Asahi (pp. 1488-1490).

Surface morphology and crystalline structure of high-stable zinc oxide films were evaluated by atomic force microscopy, scanning electron microscopy and X-ray diffraction (XRD) measurements. AFM measurement revealed that the higher stable samples have smaller roughness (average roughness and root mean square) parameters than the lower stable samples. Furthermore, in-plane XRD measurement showed that the crystallite size of high stable samples is smaller than that of the low stable samples. These results indicate that the larger surface area and lower film density deteriorates the stability of zinc oxide films through the adsorption and reaction of water or oxygen molecules. They also suggest that we can prepare the high stable zinc oxide transparent electrode films by controlling the surface morphology.

Keywords: Zinc oxide; Damp heat exposure; Surface morphology; Crystalline structure

Controlled synthesis of oriented ZnO nanorod arrays by seed-layer-free electrochemical deposition by Yu Lin; Jiyuan Yang; Xiaoya Zhou (pp. 1491-1494).

Display Omitted► Oriented ZnO nanorod arrays were prepared by seed-layer-free electrodeposition. ► The effects of Zn(NO₃)₂ concentration, deposition time and current are investigated. ► The sizes of nanorods can be tuned by controlling the electrodeposition parameters.Oriented ZnO nanorod arrays were successfully prepared on transparent conductive substrates by seed-layer-free electrochemical deposition in solution of Zn(NO₃)₂ at a low temperature of 70°C without using any catalysts, additives, and additional seed crystals. The effects of the Zn(NO₃)₂ concentration, deposition time and applied current on the localized nanorod arrays are investigated. X-ray powder diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) were used to characterize the structures and the morphologies of ZnO nanorod arrays. The heights and diameters of ZnO nanorods can be tuned by controlling the electrodeposition parameters.

Keywords: ZnO nanorod arrays; Seed-layer-free; Electrodeposition

The influence of annealing temperature on the slip plane activity and optical properties of nanostructured ZnO films by V. Soleimanian; S.R. Aghdaee (pp. 1495-1504).

► ZnO thin films were prepared by sol–gel method. ► CMWP procedures were used to evaluate the microstructure of films at different annealing temperatures. ► The optical band gap of films was determined as a function of annealing temperature. ► The optical band gap increases with crystallite size but decreases with strain and dislocation density.The zinc oxide films were prepared by the sol–gel method on the ordinary glass substrates. The activity of slip systems were evaluated by X-ray diffraction line broadening analysis using convolution multiple whole profile (CMWP) fitting procedures. It was found that in all temperatures the 〈a〉 type dislocations is dominating and its fraction increases with the rise of annealing temperature in the range of 350–600°C. The investigation on the optical properties of films showed that the optical band gap energy increases linearly with the annealing temperature and crystallite size but decreases with the lattice strain.

Keywords: Keyword; Zinc oxide; Sol–gel; Optical band gap; X-ray diffraction; Slip systems

The preferential growth of pyrite films prepared by thermal sulfuration of Fe₂O₃ films by Z.J. Luan; L.Y. Huang; F. Wang; L. Meng (pp. 1505-1509).

► Effect of sulfurizing temperature on crystal orientations of pyrite films has been investigated. ► Both surface free energy and intrinsic strain decreased with increasing sulfurizing temperature. ► Surface free energy mainly controlled the film growth when sulfurizing temperature was low and films developed into (111) preferred orientation. ► Strain energy mainly controlled the films growth when sulfurizing temperature was high and films developed into (200) and (311) preferred orientations.Pyrite thin films were prepared by the sol–gel dip coating process and sulfuration treatment. The evolution of crystal orientation for the pyrite films was investigated as a function of sulfuration temperature. And the effect of crystal orientation on the electrical and optical properties was studied. It was found that films show (111) preferred orientation after sulfurized at low temperature. However, the (200) and (311) mixed preferred orientations were observed when pyrite films were sulfurized at higher temperature. Experimental results also indicate that the carrier concentration is high when the films show (111) preferred orientation. And the optical absorption coefficient is also large when the films grow with (111) preferred orientation. It is speculated that surface free energy could play a more important role in determination of preferred orientation when films were sulfurized at low temperature. However, the strain energy plays a more important role in determination of preferred orientation when films were sulfurized at higher temperature.

Keywords: Thin film; X-ray diffraction; Crystal structure; Preferred orientation

Microstructure and dielectric properties of (Ba_0.6Sr_0.4)TiO₃ thin films grown on super smooth glazed-Al₂O₃ ceramics substrate by Hongwei Chen; Chuanren Yang; Shanxue Zheng; Jihua Zhang; Qiaozhen Zhang; Guanhuan Lei; Feizhi Lou; Lijun Yang (pp. 1510-1513).

.Display Omitted► Modified Al₂O₃ ceramic substrate replaces single-crystal LaAlO₃ for BST films. ► The almost equivalent dielectric properties are observed on both substrates. ► Modified substrate is obtained by coating a layer of high temperature glaze. ► Glaze decreases the surface roughness to RMS <0.3nm.Modified substrates with nanometer scale smooth surface were obtained via coating a layer of CaO–Al₂O₃–SiO₂ (CaAlSi) high temperature glaze with proper additives on the rough-95% Al₂O₃ ceramics substrates. (Ba_0.6Sr_0.4)TiO₃ (BST) thin films were deposited on modified Al₂O₃ substrates by radio-frequency magnetron sputtering. The microstructure, dielectric, and insulating properties of BST thin films grown on glazed-Al₂O₃ substrates were investigated by X-ray diffraction (XRD), atomic force microscope (AFM), and dielectric properties measurement. These results showed that microstructure and dielectric properties of BST thin films grown on glazed-Al₂O₃ substrates were almost consistent with that of BST thin films grown on LaAlO₃ (100) single-crystal substrates. Thus, the expensive single-crystal substrates may be substituted by extremely cheap glazed-Al₂O₃ substrates.

Keywords: PACS; 77.55.−g; 77.55.−fe; 81.05.kfGlazed-Al; ₂; O; ₃; substrate; Barium strontium titanate; Ferroelectric thin film; Electrical property

Surface geometry of pure iridium oxidized at 1373K in air by Z.B. Bao; H. Murakami; Y. Yamabe-Mitarai (pp. 1514-1518).

► Distinct surface morphologies are formed on the grains with different crystal orientations. ► {111} face serves the habit plane. ► PBC vectors are important to affect the etching process and determine the ultimate surface geometry.The surface microstructure of a polished Ir sample during isothermal heat treatment at 1373K in air was characterized. Various surface morphologies including triangular pits and terraces, “pyramid”-like plateaus and striated edges were observed. Changes in surface geometry were highly dependent on the original grain orientation. Most grains were confirmed to possess or partly exhibit a geometric configuration of {111} faceting habit, while periodic bond chain (PBC) vectors played an important role in determining the ultimate surface morphology. The mechanism and process of how these distinct surface morphologies formed are discussed.

Keywords: Iridium; Surface structure; Faceting; Oxidation

Assembly of single-walled carbon nanotubes on patterns of Au nanoparticles by Saleem G. Rao; Ling Huang; Jennifer Murray (pp. 1519-1524).

► Assembly and alignment of single-walled carbon nanotubes (SWNTs) on micron scale patterns of Au nanoparticles (NPs). ► Extensive adhesion and strong affinity of SWNTs on the Au NPs and no SWNT on ODT was observed. ► Partial coverage of ODT with Au does not allow the CNTs to assemble until ODT is almost covered with Au particles/clusters. ► DCA measurements revealed a direct correlation between the surface wettability and the SWNTs assembly on a molecular template.We report on the assembly of single-walled carbon nanotubes (SWNTs) and gold nanoparticles (NPs) hybrid structure without any surface modification of SWNTs on patterns of Au nanoparticles (NPs). Microscale Au NP patterns were created on composite self-assembled monolayer (SAM) templates of octadecanethiol (ODT) and octanedithiol (OD) through self-assembly of Au NPs via the thiol-Au chemical bond onto the OD region. On such templates, we observed extensive adhesion and strong affinity of SWNTs on the Au NPs and no SWNT on ODT. We also examined systematically the adhesion of SWNTs on ODT with varying coverage of vapour-deposited Au. We observed little SWNT attachment even when there are high-density of Au clusters on the ODT SAM. Extensive adhesion of SWNTs is observed only when the coverage of ODT by Au is almost complete. Dynamic contact angle measurements of dichlorobenzene on the ODT/Au substrates revealed a direct correlation between the surface wettability and the SWNT assembly on a molecular template.

Keywords: Carbon nanotube; Gold nanoparticles; Patterned hybrid thin films; Metal deposition on SAMs

Sorption of Sb(III) on carbon steel surface in presence of molybdate and selenite in citric acid medium by Vinit K. Mittal; Santanu Bera; S.V. Narasimhan; S. Velmurugan (pp. 1525-1530).

This study describes the mechanism of Sb(III) adsorption on carbon steel (CS) surface at pH 2.8 in presence of MoO₄²⁻ and SeO₃²⁻ oxanions. The figure shows the X-ray photoelectron spectra of (A) Mo 3d_5/2 and (B) Se 3d at adsorbed surface complex layer and surface precipitate layer.Display Omitted► MoO₄²⁻ and SeO₃²⁻ in acid aqueous medium reduced Sb(III) pickup on carbon steel. ► MoO₄²⁻ with Sb(III) reduced the redox reaction at carbon steel surface. ► SeO₃²⁻ with Sb(III) prohibited the formation of surface complex of Sb(III).Sorption of Sb(III) on carbon steel surface in aqueous medium (pH 2.8) in presence of different oxyanions like molybdate and selenite has been studied. It is observed that the presence of molybdate or selenite in solution reduced Sb(III) adsorption and surface precipitation to a great extent. The solution at different stages of the adsorption experiment has been analyzed by inductively coupled plasma-atomic emission spectroscopy technique. X-ray diffraction and X-ray photoelectron spectroscopy (XPS) techniques have been used to characterize the precipitate layer and the adsorbed layer. A detailed analysis of the XPS data reveals the mechanism involved in the two cases.

Keywords: Antimony; Adsorption; Oxyanions; Surface complexes; X-ray photoelectron spectroscopy

Microstructure and mechanism of Al₂O₃–ZrO₂ eutectic coating prepared by combustion-assisted thermal explosion spraying by Yongting Zheng; Hongbo Li; Tao Zhou (pp. 1531-1534).

► Al₂O₃–ZrO₂ eutectic coating was produced by combustion-assisted thermal explosion spraying, which is a process-simplifying and energy-saving method. ► The cross-sectional microstructure of the coating shows successively amorphous, cellular and dendrite structure along the thickness direction. ► The formation mechanism and microstructure of the coating was analyzed and studied.Thin Al₂O₃–ZrO₂ eutectic coating was produced by combustion-assisted thermal explosion spraying using a mixture of Al and Zr(NO₃)₄ powders. The cross-sectional microstructure of the coating shows successively amorphous, cellular, and dendrite structure along the direction perpendicular to the Cu substrate. The formation mechanism of the coating structure was analyzed based on the experimental results, and the morphology of different crystal structure was observed by SEM and TEM.

Keywords: Microstructure; Al; ₂; O; ₃; –ZrO; ₂; coating; Thermal explosion spraying

Oxidation temperature dependent properties of MgO thin film on alumina by S. Patil; Vijaya Puri (pp. 1535-1540).

► Thickness and oxidation temperature has drastic effect on surface morphology of MgO thin film. ► Microwave transmittance of alumina increases due to Mgo thin film. ► Higher microwave dielectric constant and lower loss useful for MIC.The magnesium oxide thin films were prepared by thermal oxidation (in air) of vacuum evaporated magnesium thin film on alumina. It was found that oxidation temperature (623K, 675K and 723K) and thickness (103nm and 546nm) dependent effects were prominently manifested in the surface morphology. Electrical and microwave properties (8–12GHz) of the MgO thin films were also carried out. X-ray diffraction showed orientation along (200) and (220) directions. Flowerlike morphology was observed from SEM and flake like morphology for films of higher thickness oxidized at higher temperatures. The magnesium oxide thin film showed NTC behavior. Microwave transmittance was found to increase with increase in oxidation temperature but was lower than alumina. Frequency and oxidation temperature dependent microwave permittivity was obtained. The microwave dielectric constant varied in the range 8.3–15.3.

Keywords: Magnesium oxide thin film; Oxidation temperature; Morphology; Resistivity; Microwave transmittance; Permittivity

Electronic state of ruthenium deposited onto oxide supports: An XPS study taking into account the final state effects by Yurii V. Larichev; Boris L. Moroz; Valerii I. Bukhtiyarov (pp. 1541-1550).

► The chemical state of Ru in the Ru/oxide catalysts was examined by XPS. ► The experimental binding energies of supported Ru were corrected for the differential charging and relaxation effects. ► The initial state energies of Ru atoms in the Ru/oxide catalysts were found identical regardless of acid-base properties of the support. ► Metallic Ru deposited on MgO, γ-Al₂O₃ and SiO₂ is characterized by a deficit of electron density.The electronic state of ruthenium in the supported Ru/EO_x (EO_x=MgO, Al₂O₃ or SiO₂) catalysts prepared by with the use of Ru(OH)Cl₃ or Ru(acac)₃ (acac=acetylacetonate) and reduced with H₂ at 723K is characterized by X-ray photoelectron spectroscopy (XPS) in the Ru 3d, Cl 2p and O 1s regions. The influence of the final state effects (the differential charging and variation of the relaxation energy) on the binding energy (BE) of Ru 3d_5/2 core level measured for supported Ru nanoparticles is estimated by comparison of the Fermi levels and the modified Auger parameters determined for the Ru/EO_x samples with the corresponding characteristics of the bulk Ru metal. It is found that the negative shift of the Ru 3d_5/2 peak which is observed in the spectrum of ruthenium deposited onto MgO (BE=279.5–279.7eV) with respect to that of Ru black (BE=280.2eV) or ruthenium supported on γ-Al₂O₃ and SiO₂ (BE=280.4eV) is caused not by the transfer of electron density from basic sites of MgO, as considered earlier, but by the differential charging of the supported Ru particles compared with the support surface. Correction for the differential charging value reveals that the initial state energies of ruthenium in the Ru/EO_x systems are almost identical (BE=280.5±0.1eV) irrespectively of acid–base properties of the support, the mean size of supported Ru crystallites (within the range of 2–10nm) and the surface Cl content. The results obtained suggest that the difference in ammonia synthesis activity between the Ru catalysts supported on MgO and on the acidic supports is accounted for by not different electronic state of ruthenium on the surface of these oxides but by some other reasons.

Keywords: Ruthenium; Oxide supports; Electronic state; XPS; Differential charging

Surface modification of zinc oxide nanorods for potential applications in organic materials by Lei Zhang; Min Zhong; Hongliang Ge (pp. 1551-1554).

► A new modifier with special molecular structure was introduced for modification of ZnO nanrods. ► The modified ZnO nanorods changed from hydrophilicity to lipophilicity with simple modification condition. ► A thin layer capping on the surface of ZnO nanorods can be found from TEM pictures.A facile and simple modification method towards changing surface property of ZnO nanorods from a hydrophilic one to a hydrophobic one have been developed by refluxing precursor in three-necked flask. Comparing with the other modifiers discussed in the paper, NDZ-311w titanate coupling agent was selected as the best one not only because of the good lipophilic modification effect, but also for its multifunctional groups could play a crucial part in further composite with organic materials. Moreover, transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR), respectively, were used to evaluate the morphology, structure and combinative way before and after surface modification. The TEM result showed, after modifying process, there was a thin layer capping on the surface of ZnO nanorods which could be considered as NDZ-311w titanate coupling agent. Through the structure analysis by XRD, it was found that the surface modification had not substantially altered crystalline structure. Besides, the FT-IR test proved that NDZ-311w titanate coupling agent was rather covalently bonded to the surface of ZnO nanorods than physically capping. More practically speaking, the NDZ-311w titanate coupling agent modified ZnO nanorods have much more potential applications in organic materials than unmodified ones.

Keywords: ZnO nanorods; Surface modification; NDZ-311w titanate coupling agent

On the surface topography of ultrashort laser pulse treated steel surfaces by J. Vincenc Obona; V. Ocelík; J.Z.P. Skolski; V.S. Mitko; G.R.B.E. Römer; A.J. Huis in’t Veld; J.Th.M. De Hosson (pp. 1555-1560).

► Influence of ultrashort pulsed laser–matter interaction on formation of small and big ripples is discussed. ► Small ripples lying between big ones are formed as common walls of adjacent exploding bubbles. ► Electron–phonon coupling strength and electron thermal conductivity are key factors for explanation of the ripples formation.This paper concentrates on observations of the surface topography by scanning electron microscopy (SEM) on alloyed and stainless steels samples treated by ultrashort laser pulses with duration of 210fs and 6.7ps. Globular-like and jet-like objects were found depending on the various levels of the fluence applied. It is shown that these features appear due to solid–liquid and liquid–gas transitions within surface layer irradiated by intense laser light. The observations are confronted to the theory of short-pulsed laser light–matter interactions, including interference, excitation of electrons, electron–phonon coupling as well as subsequent ablation. It is shown that the orientation of small ripples does not always depend on the direction of the polarization of laser light.

Keywords: Ultrashort laser pulses; Ripples; Bubbles; Jets; Scanning electron microscopy; Ultra fast laser nano-machining

Study on selective adsorption of deuterium on boron nitride using photon-stimulated ion-desorption by Kaveenga Rasika Koswattage; Iwao Shimoyama; Yuji Baba; Tetsuhiro Sekiguchi; Kazumichi Nakagawa (pp. 1561-1564).

Adsorption behavior of atomic deuterium on a hexagonal boron nitride ( h-BN) thin film is studied by photon-stimulated ion desorption (PSID) of D⁺ and near edge X-ray absorption fine structure (NEXAFS) at the B and N K-edges. After the adsorption of atomic deuterium, D⁺ desorption yield η( hν) shows clear enhancement at the B K-edge and almost no enhancement at the N K-edge. NEXAFS spectra show a large change in the B K-edge and a small change in the N K-edge after the adsorption. We propose selective adsorption of atomic deuterium on the h-BN thin film based on the experimental results, and mention the effectiveness of applying the PSID method with X-ray to study hydrogen storage materials.

Keywords: Site-selective adsorption; Hexagonal boron nitride (; h; -BN); Deuterium; Photon-stimulated ion desorption (PSID); Near edge X-ray absorption fine structure (NEXAFS)

Effects of Cr buffer layer thickness on the microstructure and the properties of Ni thin films deposited on polyimide substrate by Jun Xu; Tianmin Shao (pp. 1565-1571).

► Cr buffer layers with different thickness were deposited between the Ni films and the soft material substrates like polyimide. ► Correlation between the Cr buffer layer thickness and the properties of Ni film is achieved. ► The optimal Cr buffer layer thickness was 11.8nm, which gave the lowest residual stress and resistivity, and the highest TCR value of Ni thin film. ► The effect of inter diffusion at Ni/Cr interface on the electrical properties of films was analyzed by the description of interface resistance.Ni thin films were prepared on pre-treated polyimide (PI) substrates by ion beam assisted deposition (IBAD). Cr buffer layers with the thickness varied from 0 to 78.7nm were deposited between the Ni films and the substrates. Effects of the Cr buffer layer thickness on the structural, mechanical and electrical properties of the Ni thin films were investigated. It was found that existence of Cr buffer layer obviously improved the quality of the Ni thin films. The optimum Cr buffer layer thickness was determined which gave the lowest surface roughness ( R_a) and the highest temperature coefficient of resistivity (TCR) of Ni thin film. Mechanical measurements indicated that the nanohardness of the Ni films increased with the thickness of Cr buffer layer, while the residual stress of the films decreased and then increased. The decrease of resistivity and the increase of TCR were contributed to the improvement of crystallization degree of Ni films caused by the Cr buffer layer. Interdiffusion effect on the electrical properties was also analyzed by the description of interface resistance.

Keywords: Cr buffer layer; Thickness; Microstructure; Resistivity; TCR

Thermal stable superhydrophobic polyphenylsilsesquioxane/nanosilica composite coatings by Haowei Yang; Yuanrong Cheng; Fei Xiao (pp. 1572-1580).

► Superhydrophobic PPSQ/nanosilica composite coatings obtained by spray coating. ► Superhydrophobicity of the composite coatings shows excellent thermal stability. ► Pure PPSQ coating by solvent–nonsolvent method lost superhydrophobicity at 200°C.The superhydrophobic polyphenylsilsesquioxane (PPSQ)/nanosilica composite coatings were prepared by spray coating method with nano fumed silica (NFS) particles embedded in PPSQ matrix. The water contact angle (WCA) increased from 92.9° to 152.5° and the sliding angle (SA) decreased from more than 60° to 3.9° as the NFS content increased. The superhydrophobicity retained up to 500°C, sustained by the hierarchical micro–nano structures and excellent thermal stability of PPSQ. A superhydrophobic PPSQ coating with WCA of 152.6° and SA of 7.8° was obtained by solvent–nonsolvent method for comparison as well. However, it gradually lost superhydrophobicity at 200°C because of the elimination of nanostructures by the thermal softening of PPSQ.

Keywords: Superhydrophobic; Polyphenylsilsesquioxane (PPSQ); Thermal stable; Spray coating; Nano silica

N-doped TiO₂ photo-catalyst for the degradation of 1,2-dichloroethane under fluorescent light by Yi-Hsing Lin; Tang-Chun Chiu; Hsin-Ta Hsueh; Hsin Chu (pp. 1581-1586).

► Nitrogen-doped TiO₂ shows superior photo-catalytic activity. ► The degradation depends on oxygen concentration and relative humidity. ► Oxygen molecule is the major factor to degrade 1,2-dichloroethane in gas phase. ► Some by-products were analyzed by FTIR.The photo-catalytic degradation of 1,2-dichloroethane (1, 2-DCE) using nitrogen-doped TiO₂ photo-catalysts under fluorescent light irradiation was investigated. Highly pure TiO₂ and nitrogen-doped TiO₂ were prepared by a sol–gel method and characterized by thermo-gravimetric/differential-thermal analysis (TG/DTA), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FTIR) spectroscopy. The results indicate that the photo-catalysts were mainly nano-size with an anatase-phase structure. The degradation reaction of 1,2-DCE was operated under visible-light irradiation, and the photo-catalytic oxidation was conducted in a batch photo-reactor with various nitrogen doping ratios (N/Ti=0–25mol%). The relative humidity (RH) was controlled at 0–20% and the oxygen concentration was controlled at 0–21%. The photo-degradation with nitrogen-doped TiO₂ showed superior photo-catalytic activity compared to that for pure TiO₂. TiO₂ doped with 15mol% nitrogen exhibited the best photo-catalytic efficiency under the tested conditions. The products from the 1,2-DCE photo-catalytic oxidation were CO₂ and water; the by-products included dichloromethane, methyl chloride, ethyl chloride, carbon monoxide, and hydrogen chloride. The reaction pathway of 1,2-DCE indicates that oxygen molecules are the major factor that causes the degradation of 1,2-DCE in the gas phase.

Keywords: Photo-degradation; Titanium dioxide; Nitrogen-doped TiO; ₂; Visible-light; 1,2-dichloroethane

Sol–gel preparation and enhanced photocatalytic performance of Cu-doped ZnO nanoparticles by Min Fu; Yalin Li; Siwei wu; Peng Lu; Jing Liu; Fan Dong (pp. 1587-1591).

► Cu-doped ZnO nanoparticles were prepared by a sol–gel method for the first time. ► Cu-doped ZnO nanoparticles exhibited enhanced photocatalytic performance. ► The enhanced charge carrier separation and increased surface hydroxyl groups contributed to the enhanced photocatalytic activity. ► This research could provide a feasible route for organic wastewater treatment.Cu-doped ZnO nanoparticles were prepared by a sol–gel method for the first time. XRD, XPS, UV–vis and FS techniques were used to characterize the Cu-doped ZnO samples. The photocatalytic activity was tested for methyl orange degradation under UV irradiation. The results show that the crystal sizes of ZnO and 0.5% Cu/ZnO nanoparticles with wurtzite phase are 32.0 and 28.5nm, indicating that Cu-doping hinder the growth of crystal grains. The doped Cu element existed as Cu²⁺. The optimal Cu doping concentration in ZnO is 0.5%. The optimal calcination condition is at 350°C for 3h. The MO degradation rate of 0.5% Cu/ZnO reaches 88.0% when initial concentration of MO is 20mg/L, exceeding that of undoped ZnO. The enhanced charge carrier separation and increased surface hydroxyl groups due to Cu-doping contributed to the enhanced photocatalytic activity of 0.5% Cu/ZnO.

Keywords: ZnO; Cu doping; Photocatalysis; Sol–gel; Methyl orange

Characterization of in situ synthesized TiB₂ reinforcements in iron-based composite coating by Panpan Zhang; Xibao Wang; Lijie Guo; Lijuan Cai; Hongling Sun (pp. 1592-1598).

► Acicular shaped and blocky formed TiB₂ phases could be synthesized in situ in iron-based composite coating. ► Gradient distributed TiB₂ phases appeared in both the vertical and horizontal direction of the coating's cross-section. ► With the increase of coating dilution, TiB₂ at the edge of the coating tends to be acicular or clubbed shaped.TiB₂ reinforced iron-based composite coatings can be fabricated on the mild steel substrate with a powder mixture of Ti and B₄C by plasma transferred arc (PTA) powder surfacing process. Characterizations of the TiB₂ reinforcements in the coated surface were investigated in this paper. The experimental work enables the following findings to be obtained: (i) acicular shaped and blocky formed TiB₂ phases could be synthesized in situ using PTA powder surfacing process in the iron-based composite coating. (ii) Gradient distributions of TiB₂ reinforcements appeared in the composite coating from both the vertical and horizontal direction of the coating's cross-section. Significant changes of the size, shape and volume fraction for TiB₂ particles appeared in different regions of the surface coating, due to the effects of the dilution rate and mass density. (iii) Values of coating dilution could have profound impacts on the characterization of TiB₂ reinforcements in the coated surfaces. With the increase of coating dilution, TiB₂ grain tends to be acicular shaped at the edge of the surface coating, while it remains to be granular formed in the center of the composite coating.

Keywords: TiB; ₂; reinforcement; Coating dilution; Gradient distribution

Improving wear resistance of pure copper by laser surface modification by Mingyu Li; Mingju Chao; Erjun Liang; Jumei Yu; Junji Zhang; Dechuan Li (pp. 1599-1604).

► Mechanical strength of copper was improved without deteriorating its conductivity. ► The wear resistance was enhanced by 4 times mainly due to precipitation hardening. ► The electrical conductivity is just weakly affected by laser surface modification.With the aim of improving surface strength on copper with the electrical conductivity of the integral bulk retained, laser surface modification on copper was carried out using powder preplacement. The microstructures, hardness, wear resistance and electrical conductivity of the sample was investigated. It was shown that the modified layer of sample had crack-free, fine and homogeneous microstructures. Compared with pure copper, the average hardness of the sample was enhanced by a factor of six (about HV_0.1650), and the wear mass loss was reduced by 4/5, but the electrical conductivity of the integral bulk was only slightly decreased. The improvement of hardness and wear resistance could be attributed to the precipitation hardening of boride and carbide, grain refinement and solid solution strengthening in the layer.

Keywords: Laser application; Laser surface modification; Copper; Wear resistance; Electrical conductivity

A spectroscopic study of water-soluble pyronin B and pyronin Y in Langmuir–Blodgett films mixed with stearic acid by Kadem Meral; H. Yıldırım Erbil; Yavuz Onganer (pp. 1605-1612).

The formation of Langmuir–Blodgett film of pyronin B and Y mixed with stearic acid on water subphase is checked by their surface pressure ( π)–area ( A) isotherms.Display Omitted► Langmuir–Blodgett (LB) films of pyronin dyes mixed with stearic acid were executed. ► The formation of mixed LB film was checked by using surface pressure–area ( π– A) isotherms. ► Photophysical properties of pyronin dyes were investigated by spectroscopic techniques. ► Morphological investigation of the LB film was performed with Atomic Force Microscopy.Mono and multilayer of water-soluble pyronin B (PyB) and pyronin Y (PyY) mixed with stearic acid (SA) have been incorporated in Langmuir–Blodgett (LB) films. The surface pressure–area ( π– A) isotherm studies pointed out that pure PyB and PyY are incapable of forming stable films at air–water interface and collapsed readily at low surface pressures. However, mixture of PyB or PyY with SA easily formed stable films at the air–water interface and they were easily transferred onto solid substrates. The average area per molecule of mixed films of PyB and PyY at the air–water interface was observed to decrease with increasing concentrations of PyB and PyY. The spectroscopic characteristics of PyB and PyY in chloroform, in SA containing chloroform and in LB films have also been investigated by using absorption and steady-state and time-resolved fluorescence spectroscopy techniques. The morphology of the LB film surfaces has been characterized by using atomic force microscopy (AFM).

Keywords: Thin film; Surface pressure–area (; π; –; A; ) isotherm; Molecular aggregation; Exciton theory; Atomic force microscopy (AFM)

Effects of substrate temperature on properties of NbN_x films grown on Nb by pulsed laser deposition by Ashraf Hassan Farha; Ali Oguz Er; Yüksel Ufuktepe; Ganapati Myneni; Hani E. Elsayed-Ali (pp. 1613-1618).

► Niobium nitride thin films were deposited on Nb using pulsed laser deposition at different substrate temperatures. ► Increasing temperature leads to change in the phase structure of the film. ► The structure changes from hexagonal to a mixed and then back to a hexagonal phase. ► Crystallite sizes of the hexagonal phase increased as the temperatures increased.NbN_x films were deposited on Nb substrate using pulsed laser deposition. The effects of substrate deposition temperature, from room temperature to 950°C, on the preferred orientation, phase, and surface properties of NbN_x films were studied by X-ray diffraction, atomic force microscopy, and electron probe micro analyzer. We find that the substrate temperature is a critical factor in determining the phase of the NbN_x films. For a substrate temperature up to 450°C the film showed poor crystalline quality. With temperature increase the film became textured and for a substrate temperature of 650−850°C, mix of cubic δ-NbN and hexagonal phases (β-Nb₂N+δ′-NbN) were formed. Films with a mainly β-Nb₂N hexagonal phase were obtained at deposition temperature above 850°C. The c/ a ratio of β-Nb₂N hexagonal shows an increase with increased nitrogen content. The surface roughness of the NbN_x films increased as the temperature was raised from 450 to 850°C.

Keywords: PACS; 74.70.Ad; 74.78.Db; 74.62.Bf; 79.20.Eb; 61.05.cp; 68.37.Ps; 68.55.-aNbN; _x; Pulsed laser deposition; Thin films; Surface morphology

In situ AFM and Raman spectroscopy study of the crystallization behavior of Ge₂Sb₂Te₅ films at different temperature by Yongkuan Wu; Kun Liu; Dawei Li; Yingnan Guo; Shi Pan (pp. 1619-1623).

► The structure and morphology of Ge₂Sb₂Te₅ film cooled to RT was different with that at high temperature. ► The structure of amorphous Ge₂Sb₂Te₅ films began to change at a temperature of as low as 100°C. ► The coverage of film surface with crystal and the morphology varied at different temperature. ► The crystallization process of Ge₂Sb₂Te₅ film at different temperature is illustrated.Using in situ atomic force microscope (AFM) and Raman spectroscopy, the real-time crystallization properties of Ge₂Sb₂Te₅ films at different temperature were characterized. The given AFM topograph and phase images revealed that the structure of amorphous Ge₂Sb₂Te₅ films began to change at a temperature of as low as 100°C. When the temperature reached 130°C, some crystal fragments had formed at the film surface. Heating up to 160°C, the size of the visible crystal fragments increased, but decreased at a higher temperature of 200°C. When the Ge₂Sb₂Te₅ film was cooled down to room temperature (RT) from 200°C, the crystal fragments divided into crystal grains due to the absence of heating energy. The Raman spectra at different temperature further verified the structure evolution of the Ge₂Sb₂Te₅ film with temperature. This work is of significance for the preparation of Ge₂Sb₂Te₅ films and the erasing of data.

Keywords: Ge; ₂; Sb; ₂; Te; ₅; Crystallization; AFM; Raman spectroscopy; Temperature control

The microstructure, mechanical and friction properties of protective diamond like carbon films on magnesium alloy by Y.S. Zou; Y.F. Wu; H. Yang; K. Cang; G.H. Song; Z.X. Li; K. Zhou (pp. 1624-1629).

► Well-adhered DLC films without observable cracks were deposited on AZ91 Mg alloy by arc ion plating. ► Negative pulse bias voltage has a significant effect on sp³ carbon content and mechanical properties of DLC films. ► Wear resistance and surface hardness of AZ91 Mg alloy are significantly improved by coating with DLC film. ► AZ91 Mg alloy coated with DLC film exhibits a low friction coefficient and a narrow, shallow wear track.Protective hard coatings deposited on magnesium alloys are believed to be effective for overcoming their poor wear properties. In this work, diamond-like carbon (DLC) films as hard protective films were deposited on AZ91 magnesium alloy by arc ion plating under negative pulse bias voltages ranging from 0 to −200V. The microstructure, composition and mechanical properties of the DLC films were analyzed by scanning electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy and nanoindentation. The tribological behavior of uncoated and coated AZ91 magnesium alloy was investigated using a ball-on-disk tribotester. The results show that the negative pulse bias voltage used for film deposition has a significant effect on the sp³ carbon content and mechanical properties of the deposited DLC films. A maximum sp³ content of 33.3% was obtained at −100V, resulting in a high hardness of 28.6GPa and elastic modulus of 300.0GPa. The DLC films showed very good adhesion to the AZ91 magnesium alloy with no observable cracks and delamination even during friction testing. Compared with the uncoated AZ91 magnesium alloy, the magnesium alloy coated with DLC films exhibits a low friction coefficient and a narrow, shallow wear track. The wear resistance and surface hardness of AZ91 magnesium alloy can be significantly improved by coating a layer of DLC protective film due to its high hardness and low friction coefficient.

Keywords: Diamond-like carbon; Magnesium alloy; Microstructure; Mechanical properties; Friction

Texture change through film thickness and off-axis accommodation of (002) planes by A.R. Shetty; A. Karimi (pp. 1630-1638).

► Contrary to the prediction of growth models, the (002) grains are not completely overlapped by (111) grains at higher thickness. ► The (002) grains still constitute the surface, but are tilted away to allow the (111) planes remain parallel to film surface. ► Intrinsic stress along (111) and (002) shows a strong dependence with preferred orientation. ► Results indicate that texture development is a complex interplay between thermodynamic and kinetic forces.We present our recent experimental results on the formation of off-axis texture and crystallographic tilting of crystallites that take place in thin film of transition metal nitrides. For this purpose, the microstructural development of TiAlN film was studied, specially the change in texture with film thickness. Fiber texture was measured using θ–2 θ and pole figure X-ray diffraction (XRD), while scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to observe the microstructure and changes in texture with thickness. The sin² ψ method was applied to determine the stresses on (111) and (002) plane. With deposition parameters chosen, the growth texture mechanism is discussed in three different stages of film growth. Surface energy minimization at low thickness leads to the development of (002) orientation. On the other hand, the competitive growth promotes the growth of (111) planes parallel to film surface at higher thickness. However, contrary to the prediction of growth models, the (002) grains are not completely overlapped by (111) grains at higher thickness. Rather the (002) grains still constitute the surface, but are tilted away from the substrate normal showing substantial in-plane alignment to allow the (111) planes remain parallel to film surface. Intrinsic stress along (111) and (002) shows a strong dependence with preferred orientation. The stress level in (002) grains which was compressive at low thickness changes to tensile at higher thickness. This change in the nature of stress allows the (002) planes to tilt away in order to promote the growth of 〈111〉 parallel to film normal and to minimize the overall energy of system due to high compressive stress stored in the (111) grains. The change in surface morphology with thickness was observed using SEM. An increase in surface roughness with film thickness was observed which indicates the development of (111) texture parallel to film surface. TEM observations support the XRD results regarding texture change. Film hardness was measured by nanoindentation and a correlation between (111) texture, stress and hardness is obtained. The results indicate that texture development is a complex interplay between thermodynamic and kinetic forces. An attempt is made to understand this phenomenon of off-axis accommodation of (002) at higher thicknesses, which is a new result not reported previously.

Keywords: Off-axis tilt; Texture accommodation; Competitive growth; (1; 1; 1) orientation; Surface roughness; Hardness; Intrinsic stress; Pole figure XRD

Corrigendum to “Numerical modeling of laser shock peening with femtosecond laser pulses and comparisons to experiments” [Appl. Surf. Sci. 256 (2010) 4376–4382] by Benxin Wu; Sha Tao; Shuting Lei (pp. 1639-1639).

Retraction notice to “Photovoltaic behavior and work function of zinc oxides as solar cells” [Appl. Surf. Sci. 257 (2010) 1141–1144] by Xun-qiong Tan; Zheng-qiu Wu; Wen Zhi (pp. 1640-1640).

Retraction notice to “Modification of magadiite surface by organofunctionalization for application in removing As(V) from aqueous media: Kinetic and thermodynamic” [Appl. Surf. Sci. 256 (2009) 702–709] by Denis L. Guerra; Alane A. Pinto; Rúbia R. Viana; Claudio Airoldi (pp. 1641-1641).

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Applied Surface Science (v.258, #4)

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Applied Surface Science (v.258, #4)