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Applied Surface Science (v.257, #11)

Novel heat-resistance UV curable waterborne polyurethane coatings modified by melamine by Z.H. Fang; H.Y. Duan; Z.H. Zhang; J. Wang; D.Q. Li; Y.X. Huang; J.J. Shang; Z.Y. Liu (pp. 4765-4768).

▶ In our work, the novel heat-resistance UV curable waterborne polyurethane coating was prepared via introducing the rigid triazine ring moiety into the main chain of polyurethane by melamine. ▶ Comparing with the unmodified UVWPU film, the heat-resistance, resistance to water and mechanical properties of the modified UVWPU film have great improvements.Novel UV curable waterborne polyurethane coatings (UVWPU) modified by melamine was prepared using isophorone diisocyanate (IPDI), polyethylene glycol (PEG), α,α-dimethylol propionic acid (DMPA), hydroxyethyl acrylate (HEA) as main materials. Copolymer structure was verified using Fourier transform infrared spectroscopy (FT-IR). Performance of the coatings was evaluated by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA), and mechanical tests such as pencil hardness and resistance to water. The results showed that the modified UVWPU film had the good thermal resistance, water resistance and mechanical properties. The optimum melamine dosage was 4.70wt.%, the glass transition temperature ( T_g) of the modified film increased by 20.4°C and 5% weight-loss temperature (253°C) increased by 105°C. No change color, crinkle, desquamate, dehisce and frothy were found after the modified film dried at 130°C for 2h.

Keywords: Coatings; Waterborne polyurethane; Melamine; Heat-resistance

Composite Ni–Co–fly ash coatings on 5083 aluminium alloy by C.N. Panagopoulos; E.P. Georgiou; A. Tsopani; L. Piperi (pp. 4769-4773).

▶ This research investigation focuses on a study of the surface technological properties of an electrodeposited Ni–Co–fly ash composite coating on zincate treated 5083 aluminium alloy substrate. Up to date, very few research articles have been reported on the correlation between microstructure and corrosion behaviour of complex metal matrix composite coatings on engineering alloys. Finally, this research study aims in expanding the technological application of massive fly ash produced in power stations on the important field of coatings technology. It is believed that in several cases fly ash might possibly replace other expensive commercial oxides.Ni–Co–fly ash coatings were deposited on zincate treated 5083 wrought aluminium alloy substrates with the aid of the electrodeposition technique. Structural and chemical characterization of the produced composite coatings was performed with the aid of X-ray diffraction (XRD), scanning electron microscopy (SEM) and electron dispersive X-ray analysis (EDS) techniques. The Ni–Co–fly ash coatings were found to consist of a crystalline Ni–Co solid solution with dispersed fly ash particles. In addition, chemical analysis of the Ni–Co matrix showed that it consisted of 80wt.% Ni and 20wt.% Co. The co-deposition of fly ash particles leads to a significant increase of the microhardness of the coating. The corrosion behaviour of the Ni–Co–fly ash/zincate coated aluminium alloy, in a 0.3M NaCl solution (pH=3.5), was studied by means of potentiodynamic corrosion experiments.

Keywords: Metal matrix composites (MMC); Coating; Aluminium alloys; Corrosion

Superhydrophilic porous TiO₂ film prepared by phase separation through two stabilizers by Weixin Huang; Wei Deng; Ming Lei; Hong Huang (pp. 4774-4780).

▶ This manuscript presented the novel fabrication of porous TiO₂ thin film with only two stabilizers without any templates. ▶ The appearance of interconnected or isolated pores for the films was discussed in relation to the phase separation in the sol–gel process with the presence of Acac and DEA. ▶ The TiO₂ films with interconnected or relatively isolated pores exhibit superhydrophilic characteristic. Deducing from the Wenzel–Cassie regimes’ transition criterion, we can find out that the existence of Cassie impregnating wetting regime can be used to explain the decrease of water contact angles upon these porosity-driven superhydrophilic surfaces.A novel method was developed to produce a TiO₂ film with circular pores on its surface. The pores aroused from the precursor solution using both acetylacetone (AcAc) and diethanolamine (DEA) as stabilizers. The appearance of interconnected or isolated pores for the films was discussed in relation to the phase separation in the sol–gel process with the presence of Acac and DEA. Macropore size, together with connectivity of pores and gel skeleton, can be controlled by selecting an appropriate composition for preparation at DEA amount or regulating a time scale of the sol–gel transition. Finally, wetting behavior of the resulting films was characterized by using contact angle measurements. The TiO₂ films with interconnected or relatively isolated pores exhibit superhydrophilic characteristic, although it is not exposed to ultraviolet irradiation. Deducing from the Wenzel–Cassie regimes’ transition criterion, the existence of Cassie impregnating wetting regime rather than Wenzel one upon these porosity-driven superhydrophilic surfaces can be obtained.

Keywords: Porous film; Acetylacetone; Diethanolamine; Sol–gel; Complexing agent

A novel approach to characterizing the surface topography of niobium superconducting radio frequency (SRF) accelerator cavities by Hui Tian; Guilhem Ribeill; Chen Xu; Charles E. Reece; Michael J. Kelley (pp. 4781-4786).

▶ Nb for SRF accelerator cavities etched by buffered chemical polish or electropolish. ▶ Topography measured by atomic force microscopy and stylus profilometry. ▶ Data analyzed by power spectral density methods used in optics, a first. ▶ Changes in the PSD reveal details of surface smoothening during polishing.As superconducting niobium radio-frequency (SRF) cavities approach fundamental material limits, there is increased interest in understanding the details of topographical influences on realized performance limitations. Micro- and nano-roughness are implicated in both direct geometrical field enhancements as well as complications of the composition of the 50nm surface layer in which the super-currents typically flow. Interior surface chemical treatments such as buffered chemical polishing (BCP) and electropolishing (EP) used to remove mechanical damage leave surface topography, including pits and protrusions of varying sharpness. These may promote RF magnetic field entry, locally quenching superconductivity, so as to degrade cavity performance. A more incisive analysis of surface topography than the widely used average roughness is needed. In this study, a power spectral density (PSD) approach based on Fourier analysis of surface topography data acquired by both stylus profilometry and atomic force microscopy (AFM) is introduced to distinguish the scale-dependent smoothing effects, resulting in a novel qualitative and quantitative description of Nb surface topography. The topographical evolution of the Nb surface as a function of different steps of well-controlled EP is discussed. This study will greatly help to identify optimum EP parameter sets for controlled and reproducible surface levelling of Nb for cavity production.

Keywords: Niobium; SRF cavities; Surface topography; Power spectral density

Adsorption and dissociation of O₂ on the Cu₂O(111) surface: Thermochemistry, reaction barrier by Riguang Zhang; Hongyan Liu; Huayan Zheng; Lixia Ling; Zhong Li; Baojun Wang (pp. 4787-4794).

Display Omitted▶ Dissociative adsorption is the main dissociation path of O₂ on the deficient surface. ▶ The oxygen species adsorbed show the characteristic of the peroxo form (O₂²⁻). ▶ The oxygen vacancy exhibits strong catalytic activity for O₂ dissociation. ▶ Cu_CUS is the advantageous site for O₂ adsorbed molecularly on the perfect surface.The adsorption and dissociation of O₂ on the perfect and oxygen-deficient Cu₂O(111) surface have been systematically studied using periodic density functional calculations. Different kinds of possible modes of atomic O and molecular O₂ adsorbed on the Cu₂O(111) surface are identified: atomic O is found to prefer threefold 3Cu site on the perfect surface and O_vacancy site on the deficient surface, respectively. Cu_CUS is the most advantageous site with molecularly adsorbed O₂ lying flatly over singly coordinate Cu_CUS–Cu_CSA bridge on the perfect surface. O₂ adsorbed dissociatively on the deficient surface, which is the main dissociation pathway of O₂, and a small quantity of molecularly adsorbed O₂ has been obtained. Further, possible dissociation pathways of molecularly adsorbed O₂ on the Cu₂O(111) surface are explored, the reaction energies and relevant barriers show that a small quantity of molecularly adsorbed O₂ dissociation into two O atoms on the deficient surface is favorable both thermodynamically and kinetically in comparison with the dissociation of O₂ on the perfect surface. The calculated results suggest that the presence of oxygen vacancy exhibits a strong chemical reactivity towards the dissociation of O₂ and can obviously improve the catalytic activity of Cu₂O, which is in agreement with the experimental observation.

Keywords: Oxygen; Cu; ₂; O(1; 1; 1); Adsorption; Dissociation; Density functional theory

Studies of structural evolution and sensing properties of ZnO nanocrystalline films by X.Y. Peng; M. Sajjad; J.Chu; B.Q. Yang; P.X. Feng (pp. 4795-4800).

Display Omitted▶ The average grain sizes of thin films remains nearly unchanged with deposition time when is prepared by D.C magnetron sputtering technology; ▶ Structural evolution can be observed due to the structure disorder with an increase of film thickness; ▶ The response time and recover time to methane of the ZnO-based gas sensor are less than 1s and 10s.ZnO nanocrystalline films have been prepared on Si(100) substrate using direct current (D.C) magnetron sputtering technique at room temperature. The thickness of nanocrystalline films almost linearly increased with deposition duration and the sizes of crystalline grains almost kept unchanged. After deposition, thermal annealing was performed at 800°C in atmosphere for 2h in order to improve the qualities of ZnO thin films. Scanning electron microscope (SEM) images showed the surface roughness of the films less than 45nm. X-ray diffraction (XRD) patterns revealed the slight evolution of the crystal structures. Raman scattering spectra confirmed the data obtained from X-ray diffraction measurements.With these ZnO nanocrystalline films, prototypic gas sensors were fabricated. Both sensitivity and response of the sensors to different gases (H₂ and CH₄) were investigated. A quick response of time, less than 1 second to CH₄ gas sensor has been achieved.

Keywords: ZnO; Annealing; Gas sensor; D.C. sputtering

Fabrication of superhydrophobic surfaces on zinc substrates by Wenguo Xu; Tao Ning; Xiaochan Yang; Shixiang Lu (pp. 4801-4806).

Display Omitted▶ The effects of reaction conditions on the surface morphology and hydrophobicity of prepared surfaces were carefully studied. ▶ The best stable superhydrophobic surface depends largely on the reactant concentration. ▶ The best superhydrophobic surface with the optimal surface structure (hierarchical micro-nanostructures, flower-like porous structures, great surface roughness) and the maximal CA value (161.43°) was prepared. ▶ Using octadecyl mercaptan as the modified material instead of common fluoride can reduce the toxicity and protect the environment.Stable superhydrophobic surfaces were fabricated on the zinc substrates through simple silver replacement deposition process with the modification of octadecyl mercaptan. The effects of reaction conditions on the surface morphology and wettability of the prepared surfaces were carefully studied. The results show that the fabrication of a best superhydrophobic surface depends largely on the moderate reactant concentration. When the concentration of AgNO₃ solution was 2mmol/L, the zinc substrate was covered by a dendritic outline structure. Aggregated silver nanoparticles were formed on the substrate in accordance with some certain laws, exhibiting great surface roughness. The typical hierarchical micro-nanostructures, flower-like structures and porous structures also could be found from the SEM images. The maximal water contact angle (CA) value of about 161±2°, and the minimal sliding angle (SA) of about 2° were obtained under the same reaction condition.

Keywords: Superhydrophobic; Surface morphology; Water contact angle

Enhanced electrical stability of flexible indium tin oxide films prepared on stripe SiO₂ buffer layer-coated polymer substrates by magnetron sputtering by Zhi-nong Yu; Jian-jian Zhao; Fan Xia; Ze-jiang Lin; Dong-pu Zhang; Jian Leng; Wei Xue (pp. 4807-4810).

► Stripe SiO₂ film is used as buffer layer for the deposition of flexible ITO film. ► The stripe SiO₂ buffer layer enhances the electrical stability of flexible ITO film. ► The electrical stability of ITO depends on mismatch factor, film adhesion and stress.The electrical stability of flexible indium tin oxide (ITO) films fabricated on stripe SiO₂ buffer layer-coated polyethylene terephthalate (PET) substrates by magnetron sputtering was investigated by the bending test. The ITO thin films with stripe SiO₂ buffer layer under bending have better electrical stability than those with flat SiO₂ buffer layer and without buffer layer. Especially in inward bending text, the ITO thin films with stripe SiO₂ buffer layer only have a slight resistance change when the bending radius r is not less than 8mm, while the resistances of the films with flat SiO₂ buffer layer and without buffer layer increase significantly at r=16mm with decreasing bending radius. This improvement of electrical stability in bending test is due to the small mismatch factor α in ITO–SiO₂, the enhanced interface adhesion and the balance of residual stress. These results indicate that the stripe SiO₂ buffer layer is suited to enhance the electrical stability of flexible ITO film under bending.

Keywords: Indium tin oxide (ITO); Buffer layer; Electrical properties; Magnetron sputtering

Effect of electrodeposition modes on surface characteristics and corrosion properties of fluorine-doped hydroxyapatite coatings on Mg–Zn–Ca alloy by E.C. Meng; S.K. Guan; H.X. Wang; L.G. Wang; S.J. Zhu; J.H. Hu; C.X. Ren; J.H. Gao; Y.S. Feng (pp. 4811-4816).

▶ Fluorine-doped hydroxyapatite coating was successfully prepared by pulse electrodeposition on Mg–Zn–Ca alloy. ▶ Nano rod-like fluorine-doped hydroxyapatite was synthetized by pulse electrodeposition. ▶ The pulse electrodeposition coating was dense and uniform, and showed high corrosion resistance and bioactivity.The microstructure, morphology and composition highly determine the corrosion resistance and bioactivity of coating. In traditional cathodic electrodeposition process, because of the unfavorable effects of the polarization of concentration difference and H₂ evolution, fluorine-doped hydroxyapatite coating was loose and porous. This coating could not ensure the long-term stability of the Mg alloy implants. In order to improve the corrosion resistance and bioactivity of coating, pulse electrodeposition and H₂O₂ were introduced into the electrodeposition to deposit fluorine-doped hydroxyapatite coating. As a comparative study, microstructure, corrosion resistance properties and bioactivity of traditional cathodic electrodeposition coating and pulse electrodeposition coating were investigated, respectively. The results revealed that nano fluorine-doped hydroxyapatite coating could be prepared by pulse electrodeposition, and the coating was dense and uniform. The potentiodynamic polarization experiment indicated that the dense and uniform coating could effectively protect Mg alloy substrate from corrosion. Immersion testing was performed in simulated body fluid. It was found that pulse electrodeposition coating could more effectively induce the precipitation of Mg²⁺, Ca²⁺ and PO₄³⁻ in comparison with traditional cathodic electrodeposition coating, because the nano phase had comparatively high specific surface area. Thus magnesium alloy coated with fluorine-doped nano-hydroxyapatite coating may be a promising candidate as biodegradable bone implants, and was worthwhile to further investigate the in vivo degradation behavior.

Keywords: Magnesium alloy; FHA coating; Pulse electrodeposition; Corrosion resistance; Bioactivity

Atomic structural variations of [0001]-tilt grain boundaries during ZnO grain growth occurred by thermal treatments by J.M. Yuk; J.Y. Lee; Zonghoon Lee; Y.S. No; T.W. Kim; J.Y. Kim; W.K. Choi (pp. 4817-4820).

▶ Plane-view zero-loss energy filtered transmission electron microscopy images showed that the [0001]-tilt grain boundary of as-grown ZnO thin films changed from the zigzag facet planes into the symmetric tilt grain boundary through the asymmetric tilt grain boundary with periodic{011¯0}/{358¯0} flat planes. Such an atomic structural variations of grain boundary changes from curved grain boundaries to flat shape was due to decrease of total boundary energy during grain growth.ZnO thin films were deposited on n-Si substrates by using plasma-assisted molecular beam epitaxy. Plane-view zero-loss energy filtered transmission electron microscopy (TEM) images showed that the grain boundaries between large and small grains changed from the curve to the straight shape during ZnO grain growth. The [0001]-tilt grain boundary of as-grown ZnO thin films changed from the zigzag facet planes into the symmetric tilt grain boundary through the asymmetric tilt grain boundary with periodic{011¯0}/{358¯0} flat planes. Such an atomic structural variation of grain boundary changes from curved grain boundaries to flat shape was due to decrease of total boundary energy during grain growth. The atomic structural variations of the [0001]-tilt grain boundaries during ZnO grain growth occurred by thermal treatments are described on the basis of the TEM images.

Keywords: PACS; 68.37.Lp; 68.56.HpZnO; Si; Atomic structure; Grain boundary

Facile fabrication of superhydrophobic polytetrafluoroethylene surface by cold pressing and sintering by Cheng Jiang; Weixin Hou; Qihua Wang; Tingmei Wang (pp. 4821-4825).

▶ The PTFE superhydrophobic surface was prepared by cold pressing and sintering. ▶ The wetting behavior of PTFE surface was greatly depended on sintering temperature. ▶ The superhydrophobic PTFE surface showed excellent stability under UV illumination.A series of superhydrophobic polytetrafluoroethylene (PTFE) surfaces were prepared by a facile cold pressing and sintering method, and their microstructures and wetting behaviors could be artificially tailored by altering sintering temperature and using different masks. Specifically, the microstructures mainly depended on the sintering temperature, whereas the wetting behaviors, water contact angle (WCA) and sliding angle (SA), greatly hinged on both the sintering temperature and mask. Then a preferable superhydrophobic surface with WCA of 162±2° and SA of 7° could be obtained when the sintering temperature was 360°C and the 1000grit abrasive paper was used as a mask. In addition, it was worth noting that the as-prepared surfaces exhibited excellent stability under UV illumination, which was the most key factor for them toward practical applications.

Keywords: Polytetrafluoroethylene; Superhydrophobic surface; Cold pressing; Sintering; Mask

Formation of strontium template on Si(100) by atomic layer deposition by C.B. Zhang; L. Wielunski; B.G. Willis (pp. 4826-4830).

▶ Epitaxial template layers for crystalline oxide heteroepitaxy on silicon have been grown by ALD. ▶ Ordered reconstructions of Sr/Si monolayers have been achieved by ALD with oxide desorption. ▶ Carbonate free SrO growth was achieved by ALD with cyclopentadienyl Sr precursor and water reactants. ▶ Silicate layers are proposed as intermediates for the formation of the epitaxial Sr layers. ▶ The present results demonstrate that ALD is a potential alternative to molecular beam epitaxy methods for the fabrication of epitaxial oxides on semiconductor substrates.The formation of ordered Sr overlayers on Si(100) by Atomic Layer Deposition (ALD) from bis(triisopropylcyclopentadienyl) Strontium (Sr(C₅ⁱPr₃H₂)₂) and H₂O has been investigated. SrO overlayers were deposited on a 1–2nm SiO₂/Si(100) substrate, followed by a deoxidation process to remove the SiO₂ layer at high temperatures. Auger electron spectroscopy, Rutherford backscattering spectrometry, spectroscopic ellipsometry, and low-energy electron diffraction were used to investigate the progress of both ALD and deoxidation processes. Results show that an ordered Sr/Si(100) surface with 2×1 pattern can be obtained after depositing several monolayers of SrO on Si using ALD followed by an anneal at 800–850°C. The (2×1) ordered Sr/Si(100) surface is known to be an excellent template for the epitaxial growth of SrTiO₃ (STO) oxide. The present results demonstrate that ALD is a potential alternative to molecular beam epitaxy methods for the fabrication of epitaxial oxides on semiconductor substrates.

Keywords: Silicon; Atomic layer deposition; Catalyzed deoxidation process; Strontium; High-; k; oxides

Lysine adsorption on the silanized SiO₂-surface for immobilization of the estrogen receptor hER_α by C. Cherkouk; L. Rebohle; W. Skorupa (pp. 4831-4835).

▶ The adsorption of lysine to SiO₂ as a function of the pH value was investigated. ▶ The infrared spectroscopy is not suitable to investigate the system. ▶ XPS was used to measure the binding energies C1s and N1s as function of the pH value. ▶ Optimal adsorption conditions at pH= 7.5 of the lysine to the SiO₂ were obtained.We investigated the adsorption of thel-lysine (200mmol) molecule to a silanized SiO₂ surface as a function of the pH value. The SSC (Spraying Spin Coating) method [Cherkouk et al., J. Colloid Interf. Sci. 337 (2009) 375–380] was applied to functionalize the SiO₂ surface by using the (3-aminopropyl)trimethoxysilane (APMS) as coupling agent with a NH₂ functional group. We adsorbed lysine molecules to the silane film for pH-values of 2.5, 7.5, 8.7, 9.5 and 13, which correspond to the di-cationic, cationic, zwitterinonic (pH 8.7 and 9.5) and the anionic charge state of lysine, respectively. The infrared spectroscopy is not suitable to investigate the system because the NH³⁺ signal at 1600cm⁻¹ originating from the silane film overlaps with the infrared signal of the deprotonated carboxyl group of the lysine molecule. X-ray photoelectron spectroscopy (XPS) was used to measure the binding energies C 1s and N 1s as function of the pH value. This pH change affects the charge state which was fitted in the XPS spectra to obtain the optimal adsorption conditions at pH 7.5 of the lysine to the functionalized SiO₂ surface.

Keywords: Lysine; Adsorption; SiO; ₂; Immobilization; pH value; Silanization; XPS; FTIR

Synthesis and characterization of nanostructured Ag on porous titania by Ming Wen; Yanqiong Li; Junmin Zhang; Weiming Guan; Yuncang Li; Cui’e Wen; Peter Hodgson (pp. 4836-4843).

▶ Ag/TiO₂ composites could be produce by chemical oxidation, ion beam sputtering, and annealing treatment. ▶ The fluctuation of metallic Ag concentration can be attribute the formation and decomposition of Ag oxide. ▶ The relatively high thermal stability of Ag in composites can be partly attributed to inhibiting diffusion of Ag by the porous titania.In this work, porous titania was prepared on bulk Ti by chemical oxidation, and then nanostructured silver (Ag) was deposited on titania surface by ion beam sputtering. After annealing treatment, Ag/TiO₂ composites were characterized using X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Results indicated that a nano-porous titania layer with mean pore size of 150nm and thickness of 1μm was formed by chemical oxidation at 80°C for 45min. There were three Ag species (Ag (0), Ag (1+), and Ag (2+)) on composites surface after annealing treatment, and metallic Ag content achieved maximum value with annealing temperature of 500°C in air. Ag showed high thermal stability being partly attributed to the inhibiting the diffusion of Ag by the underlying porous titania.

Keywords: PACS; 61.46Df; 68.47JnPorous titania; Nanostructured Ag; Oxidation; Thermal stability

Magnetically separable photocatalytic composite γ-Fe₂O₃@TiO₂ synthesized by heterogeneous precipitation by V. Tyrpekl; J. Poltierová Vejpravová; A.G. Roca; N. Murafa; L. Szatmary; D. Nižňanský (pp. 4844-4848).

Synthesis of magnetically separable photocatalytic active composite γ-Fe₂O₃@TiO₂ is the main objective of this work. In the first step, maghemite nanoparticles were prepared by a precipitation method and consequently covered by the citric acid in order to adjust the zeta-potential of the particle surface (A). The magnetic carrier was enfolded by TiO₂ via heterogeneous precipitation of TiOSO₄ using urea as a precipitation agent. The procedure was designed to minimize the production costs in order to be easily transferred into the industry scale conserving the high quality of the photoactive product (B). Nontoxic element oxides were used because of the ecological acceptance. Various methods were employed to characterize and study the intermediate (magnetic nanoparticles) and final materials (TiO₂-maghemite composite), respectively. Moreover, the influence of the subsequent annealing on the structure, phase composition and properties of the products is discussed.Display Omitted▶ We used surface modification of oxide nanoparticles in industrial scale method. ▶ We adjust industrial precipitation method for fine crystal morphology production. ▶ Ecologically acceptable photocatalytic nanocomposite was prepared. ▶ This composite was characterized by commonly used solid state methods.Synthesis of magnetically separable photocatalytic active composite γ-Fe₂O₃@TiO₂ is the main objective of this work. In the first step, maghemite nanoparticles were prepared by a precipitation method and consequently covered by the citric acid in order to adjust the zeta-potential of the particle surface. The magnetic carrier was enfolded by TiO₂ via heterogeneous precipitation of TiOSO₄ using urea as a precipitation agent. The procedure was designed to minimize the production costs in order to be easily transferred into the industry scale conserving the high quality of the photoactive product. Nontoxic element oxides were used because of the ecological acceptance. Various methods were employed to characterize and study the intermediate (magnetic nanoparticles) and final materials (TiO₂-maghemite composite), respectively. Moreover, the influence of the subsequent annealing on the structure, phase composition and properties of the products is discussed.

Keywords: Nano composite; Oxides; Magnetic properties; Transmission electron microscopy; X-ray powder diffraction

The in vitro biomineralization and cytocompatibility of polydopamine coated carbon nanotubes by Penghua Yan; Jinqing Wang; Lin Wang; Bin Liu; Ziqiang Lei; Shengrong Yang (pp. 4849-4855).

▶ A thin polydopamine (Pdop) layer has been coated on carbon nanotubles (CNTs). ▶ The Pdop coated CNTs (Pdop–CNTs) exhibits the good wettability and dispersibility. ▶ The bioactivity and cytocompatibilty of Pdop–CNTs are also improved. ▶ The CNTs–Pdop can find potential applications in biomedical fields.In this work, polydopamine coated carbon nanotubes were firstly prepared by a simple and feasible route. Then, for comparison, the in vitro bioactivity and cytocompatibility of the carbon nanotubes and the polydopamine coated carbon nanotubes were assessed by immersion study in simulated body fluids and 3-(4,5-dimethyldiazol-2-yl)-2,5-diphenyl tetrazolium bromide test using osteoblast cells (MC3T3-E1), respectively. As a result, it has been demonstrated that the introduction of polydopamine coating can greatly enhance the bioactivity and promote cell proliferation of the carbon nanotubes. The improvement of bioactive behavior is attributed to the good combination of catecholamines structure of the polydopamine and the structural advantages of carbon nanotubes as a framework material. It is anticipated that the polydopamine coated carbon nanotubes would find potential applications in bone tissue engineering and other biomedical areas.

Keywords: Nanocomposite material; Carbon nanotubes; Biomineralization; Apatite; Cytocompatibility

Dual N/Pb ion-implanted Si: Temperature dependence of the novel shift of the Pb peak under electron beam annealing by Andreas Markwitz; Fang Fang; Peter B. Johnson (pp. 4856-4862).

▶ Novel movement of lead under electron beam annealing of silicon shallowly dual implanted with nitrogen and lead has been discovered. ▶ The results are in stark contrast to those expected from conventional diffusion. ▶ The lead atoms, retaining a narrow profile, are swept into the depth via stress interactions.(100) Si was dual ion-implanted with 24keV N and 7keV Pb to peak concentrations ∼10at.%. Implanted samples were then electron beam annealed (EBA) at a peak temperature T for 30s with T ranging from 100°C to 900°C and for 15s at 1000°C. Pb profiles were measured using RBS and surfaces characterised by AFM. For T up to 500°C there was no shift in the profile from the implanted depth ∼10nm. For higher values of T a striking feature was the large movement of the Pb profile away from the surface without a significant change in width or Pb content. The profile depths were: ∼40nm for 600°C, ∼68nm for 700–900°C and ∼80nm for 1000°C. The response to EBA was found to be strongly dependent on both ion implantation order and Si starting structure. For (100) Si nanowhiskers formed on the treated surfaces for T=900°C and 1000°C. A model is developed based on the restructuring of the amorphous implanted layer under EBA. It is proposed that a compaction starting at the surface sweeps the Pb before it via a stress interaction as it advances into the Si.

Keywords: Silicon; Dual low-energy ion implantation; N implantation; Pb implantation; Electron beam annealing; Pb diffusion; Si nanowhisker formation

The characterization of Cr secondary oxide phases in ZnO films studied by X-ray spectroscopy and photoemission spectroscopy by J.W. Chiou; S.Y. Chang; W.H. Huang; Y.T. Chen; C.W. Hsu; Y.M. Hu; J.M. Chen; C.-H. Chen; K. Kumar; J.-H. Guo (pp. 4863-4866).

▶ O 2 p–Cr 3 d hybridization increases with Cr concentration. ▶ The possible formation of the ZnCr₂O₄ structure is only at high Cr concentrations. ▶ Cr is present as Cr³⁺ in (Zn, Cr)O films. The non-ferromagnetic behavior of (Zn, Cr)O films can be attributed to the dominant presence of SOPs of Cr₂O₃ in the films. ▶ Cr SOPs results them the most stable TM-doped ZnO material against etching.X-ray absorption near-edge structure (XANES), X-ray emission spectroscopy (XES), and X-ray photoemission spectroscopy (XPS) were used to characterize the Cr secondary oxide phases in ZnO films that had been prepared using a co-sputtering method. Analysis of the Cr L_3,2-edge XANES spectra reveals that the intensity of white-line features decreases subtly as the sputtering power increases, indicating that the occupation of Cr 3 d orbitals increases with Cr concentration in (Zn, Cr)O films. The O K-edge spectra show that the intensity of XANES features of (Zn, Cr)O films is lower than those of ZnO film, suggesting enhanced occupation of O 2 p-derived states through O 2 p–Cr 3 d hybridization. The XES and XPS spectra indicate that the line shapes in the valence band of (Zn, Cr)O films are quite different from those of ZnO and that the Cr₂O₃ phase dominates the spinel structure of (Zn, Cr)O films increasingly as the Cr sputtering power is increased. Over all results suggest that the non-ferromagnetic behavior of (Zn, Cr)O films can be attributed to the dominant presence of Cr₂O₃, whereas the bulk comprise phase segregations of Cr₂O₃ and/or ZnCr₂O₄, which results them the most stable TM-doped ZnO material against etching.

Keywords: Secondary oxide phases; X-ray absorption spectroscopy; X-ray emission spectroscopy; X-ray photoemission spectroscopy; Spinel structure

Simplified method to prepare atomically-ordered TiO₂(110)-(1×1) surfaces with steps and terraces by Ryota Shimizu; Katsuya Iwaya; Takeo Ohsawa; Tetsuya Hasegawa; Tomihiro Hashizume; Taro Hitosugi (pp. 4867-4869).

▶ TiO₂(110)-(1×1) step/terrace surfaces can be prepared without sputtering process. ▶ HF etching and UHV-annealing provide clean TiO₂(110)-(1×1) step/terrace surfaces. ▶ No air-annealing process is necessary. ▶ Sputtering free process can be applied from oxide electronics to surface science.An effective way to prepare atomically-ordered rutile TiO₂(110) surfaces that have distinct step and terrace structures suitable for oxide thin film deposition is demonstrated. Only a two-step procedure, consisting of 20% HF etching and UHV-annealing at 1100°C, was required to yield a clean (1×1) structure with step and terrace structures. Investigation of the surface using scanning tunneling microscopy, low-energy electron diffraction, and Auger electron spectroscopy reveals that carbon contamination is removed at around 800°C, and straight steps with clear terraces appear at around 1000°C.

Keywords: Oxide electronics; Surface science; Scanning probe microscopy; TiO; ₂; (1; 1; 0)

Improving separation capability of regenerated cellulose ultrafiltration membrane by surface modification by S.S. Madaeni; F. Heidary (pp. 4870-4876).

▶ Functional groups were introduced to ultrafiltration membrane by oxidation. ▶ Rejection and flux were improved up to a certain oxidization time. ▶ Longer oxidation time resulted in membrane degradation leading to lower rejection. ▶ The removal of Pb²⁺ was improved with pH increment. ▶ The removal capability was maintained even after four cycles.In this study we introduced dialdehyde groups to a commercial regenerated cellulose (RC) ultrafiltration membrane by periodate oxidation. They were further converted to nitrogen-containing derivatives by Schiff base reaction with diethylenetriamine (DETA). The modified membrane was challenged with aqueous solution containing Pb(II) metal ions. The different variables affecting the rejection of lead ion by membrane including oxidization time, concentration of DETA, initial metal ion concentration and pH of the solution were elucidated. The membranes were characterized by FTIR–ATR, SEM, EDAX and elemental analyses. The process efficiency was enhanced by improving the oxidization time up to a certain period. In our case this was diminished after 9h due to deterioration in the membrane integrity. The Pb²⁺ removal was facilitated by increasing feed pH and DETA concentration. This was diminished for more concentrated metal ion in the feed. Membrane regeneration was successfully utilized using 0.1M HNO₃ solution. The removal capability of the regenerated membranes was maintained even after four cycles.

Keywords: Membrane; Ultrafiltration; Regenerated cellulose; Schiff base reaction; Diethylenetriamine; Regeneration

Wetting process and interfacial characteristic of Sn–3.0Ag–0.5Cu on different substrates at temperatures ranging from 503K to 673K by Likun Zang; Zhangfu Yuan; Hongyan Xu; Bingsheng Xu (pp. 4877-4884).

Wetting process and interfacial characteristic of Sn–3.0Ag–0.5Cu have been investigated at temperatures ranging from 503K to 673K on Cu, Ni, stainless steel and quartz, respectively. The reactive wetting behavior of Sn–3.0Ag–0.5Cu melt alloy on Cu and Ni substrates were investigated. Contact angles decrease as exponential decay and equilibrium contact angles decrease between the solder and Cu, Ni substrates monotonously with the temperature increasing. The configuration of the triple line of Sn–3.0Ag–0.5Cu/Cu is discussed by the description of equilibrium. The calculated results based on experimental values of tension balances along each of the three interfaces at this final state show good agreement with theoretical analysis. Intermetallics of the Sn–3.0Ag–0.5Cu/Ni interface are identified as (Cu, Ni)₆Sn₅ adjacent to the solder and Ni₃Sn₄ adjacent to the Ni substrate, respectively. The contact angles between Sn–3.0Ag–0.5Cu and quartz, stainless steel substrates were measured to be greater than 90°, which means non-wetting, in the temperature range from 503K to 673K. Liquid–solid interfacial energy between the solder and different substrates are obtained based on the surface tension of molten solder and equilibrium contact angles at different temperatures. These results are of practical interest for composite lead-free solders preparations and joining of Sn–3.0Ag–0.5Cu to various substrates.

Keywords: Pb-free solder; Sessile drop method; Contact angle; Electronic materials

Solvothermal synthesis, characterization and optical properties of ZnO, ZnO–MgO and ZnO–NiO, mixed oxide nanoparticles by Alireza Aslani; Mohammad Reza Arefi; Aziz Babapoor; Asghar Amiri; Khalil Beyki-Shuraki (pp. 4885-4889).

► Simple low-temperature hydro/solvothermal method to synthesize of ZnO, ZnO–MgO and ZnO–NiO mixed oxide nanoparticles without any stabilizer or additive studied. ► The crystal quality of the nanoparticles could further be improved through reduction of strain and deep-level defects by annealing them in air. ► Particles size ZnO, ZnO–MgO and ZnO–NiO were controlled by varying the temperature and aging time of the reaction in solvothermal reactor. ► PL spectra results for the ZnO, ZnO–MgO and ZnO–NiO nanoparticles showed significant defects in their morphology due to their large surfaces, while the green emission peak in the nanoparticles was due to a decrease in the amount of excitations. ► The optical properties of these nanoparticles showed a blue-shift of the UV peak for the samples that were placed in the low temperature zone, which occurred due to the effect of Mg and Ni on the band-gap of the ZnO nanostructures.ZnO–MgO and ZnO–NiO mixed oxides nanoparticles were produced from a solution containing Zinc acetate, Mg and Ni nitrate by Solvothermal method. The calcination process of the ZnO–MgO and ZnO–NiO composites nanoparticles brought forth polycrystalline two-phase ZnO–MgO and ZnO–NiO nanoparticles of 40–80nm in diameters. ZnO, MgO and NiO were crystallized into würtzite and rock salt structures, respectively. The optical properties of ZnO–MgO and ZnO–NiO nanoparticles were obtained by solid state UV and solid state florescent. The XRD, SEM and Raman spectroscopies of these nanoparticles were analyzed.

Keywords: Solvothermal; X-ray diffraction; Mixed oxide; Electron microscopy

Structural, optical and electrical properties of ZnO/Zn₂GeO₄ porous-like thin film and wires by Mohd Muzafa Jumidali; Kamal Mahir Sulieman; Md Roslan Hashim (pp. 4890-4895).

▶ Zinc oxide/Zinc germanium oxide porous-like thin film wires were successfully fabricated using simple thermal evaporation method and the growth mechanisms have been proposed. ▶ The structures revealed strong spontaneous emission in the UV and weak emission in blue and green regions. ▶ The structures showed a good response as a MSM photodetector in the UV region.Zinc oxide/zinc germanium oxide (ZnO/Zn₂GeO₄) porous-like thin film and wires has been fabricated by simple thermal evaporation method at temperature about 1120°C for 2.5h. The structural and optical properties of the porous-like-thin film and wires have been investigated by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and photoluminescence (PL) spectroscopy. Metal semiconductor metal (MSM) photodetector structure was used to evaluate the electrical characteristics by using current–voltage ( I– V) measurements. Room temperature photoluminescence spectrum of the sample shows one prominent ultraviolet peak at 378nm and a shoulder at 370nm. In addition, broad visible blue emission peak at wavelength 480nm and green emission peak at 500nm are also observed. Strong photoelectric properties of the MSM in the UV demonstrated that the porous-like-thin film and wires contribute to its photosensitivity and therefore making ZnO/Zn₂GeO₄ wires potential photodetector in the shorter wavelength applications.

Keywords: ZnO/Zn; ₂; GeO; ₄; Porous-like structure; Structural properties; Optical properties; Electrical properties; MSM photodetector

X-ray photoelectron spectroscopy of Sm³⁺-doped CaO–MgO–Al₂O₃–SiO₂ glasses and glass ceramics by Peijing Tian; Jinshu Cheng; Gaoke Zhang (pp. 4896-4900).

▶ The Sm³⁺-doped CaO–MgO–Al₂O₃–SiO₂ glass and glass ceramics were investigated. ▶ Diopside crystal precipitated in the amorphous phase after heat treatment. ▶ Oxidation state of the Sm in samples was 3+. ▶ Sm₂O₃ behave as a glass modifier introducing NBO in glass. ▶ Sm³⁺ existed in diopside phase as the substitution for Ca²⁺ after heat treatment.Sm³⁺ doped CaO–MgO–Al₂O₃–SiO₂ glass and glass ceramics have been prepared. The diopside crystal (CaMgSi₂O₆) was identified in the glass ceramics by X-ray diffraction analysis. X-ray photoelectron spectra of the glass and glass ceramics were measured by a monochromatised Al-Kα XPS instrument. Sm 3d core level spectra for the Sm doped samples showed that Sm ions are predominantly in the Sm (III) state in glass and glass ceramics. The O 1s core spectra could be fitted by summing the contributions from bridging oxygen (BO) and non bridging oxygen (NBO) for samarium undoped glass, BO, NBO and Si–O–Sm for the doped glass. The O 1s XPS spectrum of undoped glass ceramics was curve fitted with BO and NBO in glass phase, as well as SiOSi, SiOMg and SiOCa in diopside. In addition to the five components above mentioned, SiOSm in diopside also appeared in O 1s XPS spectra of samarium doped glass ceramics. According to the fitting results, we demonstrate that the Sm₂O₃ exist in glass network as a glass modifier. After heat treatment, nearly all the Sm³⁺ existed in diopside phase as the substitution for Ca²⁺.

Keywords: XPS; Glass; Glass ceramics; Sm 3d; O 1s

Preparation and properties of SnS film grown by two-stage process by Feng Jiang; Honglie Shen; Chao Gao; Bing Liu; Long Lin; Zhou Shen (pp. 4901-4905).

▶ SnS film without any other phases was successfully prepared by two-stage sulfurization method. ▶ The effect of sulfurization time on the SnS film's property was systematically studied. ▶ The prepared SnS film shows obvious photoresponse effect ▶ Persistent photoconductivity of SnS film was detected in this work.SnS films have been prepared by a novel two-stage process. It involved sputtering of Sn film on glass substrate and sulfurization of the thin metallic tin precursor layers in a vacuum furnace. The X-ray diffraction results showed that the SnS layers had orthorhombic structure and (040) preferential growth is more and more obvious with the increase of sulfurization time. The SnS film obtained by this work shows high optical absorption efficiency, and the film has a direct optical band gap of about 1.3eV. The films show p-type conductivity and the resistivity of SnS film decreased obviously under illumination.

Keywords: SnS films; Tin precursor layer; Sulfurization; Photoconductivity

Effects of post-annealing on structural, optical and electrical properties of Al-doped ZnO thin films by Hao Tong; Zhonghua Deng; Zhuguang Liu; Changgang Huang; Jiquan Huang; Hai Lan; Chong Wang; Yongge Cao (pp. 4906-4911).

▶ The work involves a comparatively study by annealing in different atmospheres to explain the changes of the electrical conductivity for the AZO films. ▶ The work gives a simple explanation to the damage of electrical property for the AZO films when the annealing temperature was too high.Aluminum-doped zinc oxide (AZO) films were deposited at 400°C by radio-frequency magnetron sputtering using a compound AZO target. The effects of annealing atmospheres as well as hydrogen annealing temperatures on the structural, optical and electrical properties of the AZO films were investigated. It was found that the electrical resistivity varied depending on the atmospheres while annealing in air, nitrogen and hydrogen at 300°C, respectively. Comparing with that for the un-annealed films, the resistivity of the films annealed in hydrogen decreased from 9.8×10⁻⁴Ωcm to 3.5×10⁻⁴Ωcm, while that of the films annealed in air and nitrogen increased. The variations in electrical properties are ascribed to both the changes in the concentration of oxygen vacancies and adsorbed oxygen at the grain boundaries. These results were clarified by the comparatively XPS analyzing about the states of oxygen on the surface of the AZO films. There was great increase in electrical resistivity due to the damage of the surfaces, when AZO films were annealed in hydrogen with a temperature higher than 500°C, but high average optical transmittance of 80–90% in the range of 390–1100nm were still obtained.

Keywords: AZO films; Annealing; Electrical resistivity

A novel method for preparation of 8-hydroxyquinoline functionalized mesoporous silica: Aluminum complexes and photoluminescence studies by Alireza Badiei; Hassan Goldooz; Ghodsi Mohammadi Ziarani (pp. 4912-4918).

► Design a new method for grafting 8-HQ ligand to the surface of SBA-15 via a stable sulfonamide bond. ► Synthesis of 8-HQ aluminum complex containing of this new 8-HQ functionalized SBA-15 material. ► Different fluorescence behaviors of grafted 8-HQ ligand in comparison with 8-HQ molecules in a aqueous solution. ► Tuning the emission of grafted 8-HQ aluminum complexes through the ligand exchange reaction using appropriate substitution on coordinated 8-HQ.8-Hydroxyquinoline (8-HQ) was attached to mesoporous silica by sulfonamide bond formation between 8-hydroxyquinoline-5-sulfonyl chloride (8-HQ-SO₂Cl) and aminopropyl functionalized SBA-15 (designated as SBA-SPS-Q) and then aluminum complexes of 8-HQ was covalently bonded to SBA-SPS-Q using coordinating ability of grafted 8-HQ.The prepared materials were characterized by powder X-ray diffraction (XRD), nitrogen adsorption–desorption, Fourier transform infrared (FT-IR), thermal analysis (TGA–DTA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), elemental analysis and fluorescence spectra. The environmental effects on the emission spectra of grafted 8-HQ and its complexes were studied and discussed in details.

Keywords: Mesoporous silica; SBA-15; Tris(8-hydroxyquinoline)aluminum; Sulfonamide; Emission spectra

AFM analysis of piezoelectric nanogenerator based on n⁺-diamond/n-ZnO heterojunction by Zhengzheng Shao; Liaoyong Wen; Dongmin Wu; Xueao Zhang; Shengli Chang; Shiqiao Qin (pp. 4919-4922).

► We have demonstrated a high performance piezoelectric nanogenerator by contact-scanning a diamond-coated conductive tip on ZnO nanorod arrays in an AFM system. ► About 95% ZnO nanorods scanned by the tip generate piezoelectric current. ► Rectifying n⁺–n heterojunction is formed when the diamond tip contacted with a ZnO nanorod. ► The heterojunction plays a role in accumulating and releasing charges for nanogenerator. ► The conductive diamond film is an ideal electrode for the piezoelectric nanogenerator.We have demonstrated a high performance piezoelectric nanogenerator by scanning a diamond-coated conductive tip on ZnO nanorod arrays in an AFM system with contact-mode. About 95% ZnO nanorods generate piezoelectric current due to the excellent mechanical and electrical properties of the tip. The tip's nitrogen-doped diamond coating is the key factor to maintain effective physical contact and electrical contact to ZnO nanorods, leading to efficient piezoelectric generation. Rectifying n⁺–n heterojunction is formed when the nitrogen-doped diamond tip contacted with a ZnO nanorod, which plays an important role in accumulating and releasing piezoelectric charges of the piezoelectric nanogenerator. Our research indicates that conductive diamond film is an ideal electrode for this type of piezoelectric nanogenerator.

Keywords: ZnO nanorod; Piezoelectric nanogenerator; Nitrogen-doped diamond; Heterojunction; AFM

Diffusion barrier performance of TiVCr alloy film in Cu metallization by Du-Cheng Tsai; Yen-Lin Huang; Sheng-Ru Lin; De-Ru Jung; Shou-Yi Chang; Fuh-Sheng Shieu (pp. 4923-4927).

▶ 15nm-thick TiVCr alloy thin film is developed as diffusion barrier layers. ▶ No interdiffusion between Cu and Si in film after annealing at 700°C. ▶ The severely distorted lattices and dense structure provide a high diffusion resistance.In this study, 15nm-thick sputter-deposited TiVCr alloy thin films were developed as diffusion barrier layers for Cu interconnects. The TiVCr alloy film tends to form a solid solution and a simple crystal structure from the constituted elements. Under TEM, the 15nm-thick as-deposited TiVCr alloy film was observed to have a dense semi-amorphous or nanocrystalline structure. In conjunction with X-ray diffraction, transmission electron microscopy, and energy-dispersive spectroscopy analyses, the Si/TiVCr/Cu film stack remained stable at a high temperature of 700°C for 30min. The electrical resistance of Si/TiVCr/Cu film stack remained as low as the as-deposited value. These indicated that the mixed TiVCr refractory elements’ alloy barrier layer is very beneficial to prevent Cu diffusion.

Keywords: Nitrides; Sputtering; Electron microscopy; Thermal properties

Effect of added homopolymer on structures of thin films of PS- b-PDMS/PS mixture under solvent vapor annealing by Jinghui Yang; Qi Wang; Weiwei Yao; Feng Chen; Qiang Fu (pp. 4928-4934).

▶ The long-ordering of inorganic silica result from self assembly of PS-b-PDMS/PS blends followed by UV/O₃ treatment. ▶ Addition of homo-PS leads to phase transitions. ▶ Molecular weight and volumer fracture of blended homo-PS tune the spacing of inorganic silica.Self assembly of poly(styrene- b-dimethylsiloxane) (PS- b-PDMS) followed by reactive ion etching technique is a promising method for fabricating periodical silica nanopatterns and can be applicable for device fabrication on nanoscale. We demonstrated a technologically useful way to control the inorganic silica nanostructures in thin films by directly mixing asymmetric (PS- b-PDMS) diblock copolymer with homopolymers of majority component, polystyrene (PS) under solvent vapor annealing followed by UV/O₃ treatment. The effects of molecular weight and volume fraction of added homopolymer (PS) on morphology and size of the nanostructure of blends have been carefully investigated by atomic force microscopy. Different morphology transitions observed on the ordering film surface by atomic force microscopy (AFM) are associated with kinetics of phase evolution with respect to homo-PS with different molecular weight. The periodic spacings and dimensions of the microdomains were readily tuned at the same time, just by adjusting the molecular weight and volume fraction of the blended homopolymer.

Keywords: PS-; b; -PDMS; Thin film; Solvent annealing; Microphase separation

Facile synthesis of SERS active Ag nanoparticles in the presence of tri-n-octylphosphine sulfide by Xiaomiao Hou; Xiaoling Zhang; Shutang Chen; Yan Fang; Jilin Yan; Na Li; Pengxu Qi (pp. 4935-4940).

▶ Hydrophobic Ag nanoparticles were synthesized by using AgNO₃, tri-n-octylphosphine and sulfur powder in process. ▶ Tri-n-octylphosphine was used as solvent, reducing agent and stabilizer in the synthetic process. S could chelate with excessive tri-n-octylphosphine to form trioctylphosphine sulfide, which could adjust Ag nanoparticles’ growth due to its strong capping ability and served as second capping agent. ▶ Through surface exchange with 3-mercaptopropanoic acid, the hydrophobic Ag nanoparticles could be transformed into hydrophilic ones. ▶ The synthetic strategy was simple and the as-synthesized Ag nanoparticles could be used as substrates for SERS detection.A facile and novel way was reported here for the synthesis of hydrophobic Ag nanoparticles (NPs), using AgNO₃, tri-n-octylphosphine (TOP) and sulfur (S) powder in process. TOP was used as solvent, reducing agent and stabilizer. S could chelate with excessive TOP to form trioctylphosphine sulfide (TOPS), which served as second capping agent. The hydrophobic Ag NPs could be transformed into hydrophilic state through ligand exchange. Furthermore, surface-enhanced Raman scattering (SERS) spectra of 4-aminothiophenol (4-ATP) were obtained on the hydrophobic and hydrophilic Ag NPs modified substrates, indicating that the as-synthesized Ag NPs had great potential for high sensitive optical detection applications.

Keywords: Ag; NPs; Surfactant; SERS

Formation of GaAs1−_xN_x nanofilm on GaAs by low energy N₂⁺ implantation by V.M. Mikoushkin (pp. 4941-4944).

Nitridation of GaAs (100) by N₂⁺ ions with energy E_i=2500eV has been studied by Auger- and Electron Energy Loss Spectroscopy under experimental conditions, when electrons ejected only by nitrated layer, without contribution of GaAs substrate, were collected. Diagnostics for quantitative chemical analysis of the nitrated layers has been developed using the values of NKVV Auger energies in GaN and GaAsN chemical phases measured in one experiment, with the accuracy being sufficient for separating their contributions into the experimental spectrum. The conducted analysis has shown that nanofilm with the thickness of about 4nm was fabricated, consisting mainly of dilute alloy GaAs1−_xN_x with high concentration of nitrogen x∼0.09, although the major part of the implanted nitrogen atoms are contained in GaN inclusions. It was assumed that secondary ion cascades generated by implanted ions play an important role in forming nitrogen-rich alloy.

Keywords: PACS; 61.72.Vv; 68.55.Nq; 82.80.PvGaN; GaAsN; Nitridation; Implantation; Electron spectroscopy; AES; EELS; Chemical composition

Super-hydrophobicity and oleophobicity of silicone rubber modified by CF₄ radio frequency plasma by Song-Hua Gao; Li-Hua Gao; Ke-Sheng Zhou (pp. 4945-4950).

▶ Surface treatment of silicone rubber insulator by CF₄ low-temperature plasma. ▶ Nonpolar fluoric functional groups were introduced onto the sample's surface. ▶ Surface micro-topography was changed to form nano-scale concave–convex structure. ▶ The two factors dramatically improve the surface hydrophobicity and oleophobicity.Owing to excellent electric properties, silicone rubber (SIR) has been widely employed in outdoor insulator. For further improving its hydrophobicity and service life, the SIR samples are treated by CF₄ radio frequency (RF) capacitively coupled plasma. The hydrophobic and oleophobic properties are characterized by static contact angle method. The surface morphology of modified SIR is observed by atom force microscope (AFM). X-ray photoelectron spectroscopy (XPS) is used to test the variation of the functional groups on the SIR surface due to the treatment by CF₄ plasma. The results indicate that the static contact angle of SIR surface is improved from 100.7° to 150.2° via the CF₄ plasma modification, and the super-hydrophobic surface of modified SIR, which the corresponding static contact angle is 150.2°, appears at RF power of 200W for a 5min treatment time. It is found that the super-hydrophobic surface ascribes to the coaction of the increase of roughness created by the ablation action and the formation of [–SiF_x(CH₃)2−_x–O–]_n ( x=1, 2) structure produced by F atoms replacement methyl groups reaction, more importantly, the formation of [–SiF₂–O–]_n structure is the major factor for super-hydrophobic surface, and it is different from the previous studies, which proposed the fluorocarbon species such as C–F, C–F₂, C–F₃, CF–CF_n, and C–CF_n, were largely introduced to the polymer surface and responsible for the formation of low surface energy.

Keywords: Super-hydrophobicity and oleophobicity; CF; ₄; radio frequency plasma; Silicone rubber; Surface morphology; XPS

Influence of ammonia on the morphologies and enhanced photocatalytic activity of TiO₂ micro/nanospheres by Li Cong-Ju; Xu Guo-Rong (pp. 4951-4955).

Addition of ammonia during the hydrolysis of titanium tetra-n-butyl resulted in the formation of TiO₂ micro/nanospheres. In addition, it was found that with different pH values of the hydrolysis solutions, TiO₂ micro/nanospheres with different crystallinities (anatase/rutile composition) and different photocatalytic activities were obtained. (a) The obtained TiO₂ micro/nanospheres and (b) different photocatalytic activities of TiO₂ micro/nanospheres with tuned pH values of hydrolysis solutions.Display Omitted▶ Addition of ammonia in precursor results in the formation of TiO₂ micro/nanospheres. ▶ Ammonia has a crucial effect on the crystallinity of obtained TiO₂ samples. ▶ Ammonia has a crucial effect on the photocatalytic activity of TiO₂ samples.TiO₂ micro/nanospheres were synthesized by a combination process contains hydrolysis of titanium tetra-n-butyl in mixed solution of anhydrous ethanol/ammonia and the subsequent calcination under 550°C for 7h. The pH values of the mixed solution were tuned to be 10.4, 11.0 and 11.6, respectively, by adding different amounts of ammonia. Scanning electron microscope (SEM) and transmission electron microscope (TEM) were used to characterize the morphologies and the crystallinity. X-ray diffraction (XRD) patterns indicated that pH value of the precursors has an important effect on the crystal phase composition. UV–vis diffuse reflectance spectrum was applied to characterize the optical properties of samples. Degradation of methylene blue under the irradiation of 300W Hg lamp confirmed the enhanced photocatalytic activity of TiO₂ micro/nanospheres. In addition, the formation mechanism was proposed.

Keywords: Titanium dioxide; Spheres; Photocatalytic; Ammonia

Research on the icephobic properties of fluoropolymer-based materials by Shuqing Yang; Qiang Xia; Lin Zhu; Jian Xue; Qingjun Wang; Qing-min Chen (pp. 4956-4962).

▶ Fluoropolymer materials with a smooth surface can significantly reduce ice adhesion strength. ▶ Fluoropolymers with sub-micron surface structures can improve the hydrophobicity at normal temperature. It leads to an efficient reduction in the ice accretion on the surface at −8°C. ▶ Ice adhesion strength of fluoropolymers is highly correlated to CA reduction observed when the temperature was changed from 20°C to −8°C. ▶ Potential applications in anti-icing in many industrial fields.Fluoropolymer, because of the extremely low surface energy, could be non-stick to water and thus could be a good candidate as anti-icing materials. In this paper, the icephobic properties of a series of fluoropolymer materials including pristine PTFE plates (P-PTFE), sandblasted PTFE plates (SB-PTFE), two PTFE coatings (SNF-1 and SNF-CO1), a fluorinated room-temperature vulcanized silicone rubber coating (F-RTV) and a fluorinated polyurethane coating (F-PU) have been investigated by using SEM, XPS, ice adhesion strength (tensile and shear) tests, and static and dynamic water contact angle analysis. Results show that the fluoropolymer material with a smooth surface can significantly reduce ice adhesion strength but do not show obvious effect in reducing ice accretion at −8°C. Fluoropolymers with sub-micron surface structures can improve the hydrophobicity at normal temperature. It leads to an efficient reduction in the ice accretion on the surface at −8°C, due to the superhydrophobicity of the materials. But the hydrophobicity of this surface descends at a low temperature with high humidity. Consequently, once ice layer formed on the surface, the ice adhesion strength enhanced rapidly due to the existence of the sub-micron structures. Ice adhesion strength of fluoropolymers is highly correlated to CA reduction observed when the temperature was changed from 20°C to −8°C. This property is associated with the submicron structure on the surface, which allows water condensed in the interspace between the sub-micron protrudes at a low temperature, and leads to a reduced contact angle, as well as a significantly increased ice adhesion strength.

Keywords: Icephobic property; Fluoropolymer; Hydrophobicity; Ice adhesion; Ice accretion

Composited BCN/carbon fibers prepared by hot-filament chemical vapor deposition by Jiannan Lü; Hongdong Li; Pinwen Zhu; Xianyi Lü; Yingai Li (pp. 4963-4967).

▶ It is the first time to report BCN-C composite fibers prepared by HF-CVD. ▶ The fibers with porous configuration have the strong capacity to adsorb oxygen. ▶ The surface morphology and diameter of the fibers are affected by the gas source. ▶ The maximal breakdown volt varying with the configuration for BCN layer is 15V.The combined BCN/carbon fibers with porous configuration have been successfully prepared by hot-filament chemical vapor deposition (HF-CVD). The composited materials consist of carbon fiber inside covered by the cylindrical BCN films. The differences in the surface morphology and the diameter of the composite fibers are related to the different reactant gases. It is demonstrated that the elements of B, C, and N are chemically bonded with atomic-level BCN hybrid in the composite fibers. The resistance of the composite fibers is about 300Ω which is 10 times higher than that of the isolated carbon fibers (27.5Ω). When the applying voltage increases up to 8–15V, the BCN films have been broken down and the resistance of composite fibers decreases to the typical value of the carbon fibers. The composite fibers with porous configuration have the strongly capacity to adsorb oxygen. The findings suggest that the combined BCN/carbon fibers are favorable for achieving high performance nano-optoelectronic and sensor devices.

Keywords: BCN; Carbon fibers; FTIR spectrum; Composite

Structure and photoluminescence of β-Ga₂O₃:Eu³⁺ nanofibers prepared by electrospinning by Jianguo Zhao; Weiying Zhang; Erqing Xie; Ziwei Ma; Ake Zhao; Zhaojun Liu (pp. 4968-4972).

▶ The electrospinning preparation has not been reported. ▶ The concentration quench effect and energy transfer mechanism in β-Ga₂O₃:Eu³⁺ were also discussed.Eu³⁺-doped β-Ga₂O₃ nanofibers were fabricated by electrospinning. The influence of Eu³⁺ concentration on the photoluminescence properties of the obtained nanofibers was investigated. The morphology and structure of β-Ga₂O₃:Eu³⁺ were characterized by field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD) and Raman spectra. The diameter of the Eu³⁺-doped β-Ga₂O₃ nanofibers was in the range of 180–300nm. When the β-Ga₂O₃:Eu³⁺ nanofibers were excited by 325nm wavelength, the main emission peak of the samples was 620nm (⁵D₀→⁷F₂), which corresponded to a typical red emission (⁵D₀→⁷F_j ( j=1, 2, 3, 4) intra-4f transitions of Eu³⁺ ions). In addition, the concentration quench effect and energy transfer mechanism in β-Ga₂O₃:Eu³⁺ were also discussed.

Keywords: β-Ga; ₂; O; ₃; Electrospinning; Energy transfer; Photoluminescence

Growth, modulation and photoresponse characteristics of vertically aligned ZnO nanowires by J.P. Kar; S.N. Das; J.H. Choi; T.I. Lee; J. Seo; T. Lee; J.M. Myoung (pp. 4973-4977).

▶ Vertically aligned ZnO nanowires were grown on Si substrate by MOCVD. ▶ Aspect ratio and density of the nanowires were varied with an intermediate layer and the microcavity. ▶ Photoresponse characteristics were significantly varied with the aspect ratio and the density of NWs. ▶ UV detectors inside the microcavity have shown the higher on-off current ratio and fast photoresponse characteristics.Vertically aligned, c-axis oriented zinc oxide (ZnO) nanowires were grown on Si substrate by metal organic chemical vapor deposition (MOCVD) technique, where sputtered aluminum nitride (AlN) film was used as an intermediate layer and thermally evaporated barium fluoride (BaF₂) film as a sacrificial layer. The aspect ratio and density of the nanowires were also varied using only Si microcavity without any interfacial or sacrificial layer. The UV detectors inside the microcavity have shown the higher on–off current ratio and fast photoresponse characteristics. The photoresponse characteristics were significantly varied with the aspect ratio and the density of nanowires.

Keywords: PACS; 81.05.Dz; 81.07.−b; 81.15.Gh; 78.67.−n; 85.60.GzZnO nanowires; Metal organic chemical vapor deposition; Thin film; Etching; Microcavity; Photoresponse

Highly crystallized sputtered silicon with textured morphology for thin-film solar cells by Qiang Hu; Jian Wang; Yong Zhao; Dejie Li (pp. 4978-4981).

▶ A new type light-trapping structure base on evaporating Al is fabricated with a simple process, without any pre- or post-treatment. ▶ Sputtered amorphous silicon film is 100% crystallized by Cu induced crystallization. ▶ Average reflectivity as low as 10% can be obtained with only 840nm thick silicon film based on this structure.A light-trapping structure with textured morphology for thin-film solar cell is demonstrated in this paper. It is fabricated through Al evaporation, and has a root-mean-roughness (Rms) of about 120nm and lateral width of about 1μm for single bulge. A Mo layer is introduced to be a barrier layer. Subsequently sputtered amorphous silicon film is 100% crystallized by Cu induced crystallization. Reflectivity of samples with different silicon thickness is studied to reveal the light-trapping efficiency and the reflectivity as low as 10% is obtained with only 840nm thick silicon film. This is a low-cost structure promising for future thin-film solar cells with high efficiency.

Keywords: Light trapping; Copper-induced crystallization; Magnetron sputtering; Thin-film solar cells

Multilayer films of cationic graphene-polyelectrolytes and anionic graphene-polyelectrolytes fabricated using layer-by-layer self-assembly by Adila Rani; Kyoung Ah Oh; Hyeyoung Koo; Hyung jung Lee; Min Park (pp. 4982-4989).

Display Omitted▶ Successful multilayer thin films are created using layer-by-layer (LBL) assembly of PAH-G and PSS-G. ▶ The average thickness of the graphene oxide, PAH-G and PSS-G film is ∼1nm, ∼7nm and ∼4nm respectively. ▶ The electrical conductivity of multilayer film PDDA–(PSS-G/PAH-G)6 composites measured by the four-point probe method is 0.2Scm⁻¹. ▶ The thickness of the multilayer film is found to be ∼65nm with 82% transmittance at 550nm.Extremely thin sheets of carbon atoms called graphene have been predicted to possess excellent thermal properties, electrical conductivity, and mechanical stiffness. To harness such properties in composite materials for multifunctional applications, one would require the incorporation of graphene. In this study, new thin film composites were created using layer-by-layer (LBL) assembly of polymer-coated graphitic nanoplatelets. The positive and negative polyelectrolytes used to cover graphene sheets were poly allylamine hydrochloride (PAH) and poly sodium 4-styrenesulfonate (PSS). The synthesized poly allylamine hydrochloride-graphene (PAH-G) and poly sodium 4-styrenesulfonate-gaphene (PSS-G) were characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and thermo gravimetric analysis (TGA). The multilayer films created by spontaneous sequential adsorption of PAH-G and PSS-G were characterized by ultra violet spectroscopy (UV–vis), scanning electron microscopy (SEM), and AFM. The electrical conductivity of the graphene/polyelectrolyte multilayer film composites measured by the four-point probe method was 0.2Scm⁻¹, which was sufficient for the construction of advanced electro-optical devices and sensors.

Keywords: PAH-G; PSS-G; Layer-by-layer multilayer films; Electrical conductivity

Influences of space charge and electrode on the electrical transport through (Ba,Sr)TiO₃ thin film capacitors by J. Sun; X.J. Zheng; W. Yin; M.H. Tang; W. Li (pp. 4990-4993).

▶ We derive a combined model of thermionic emission and carrier drift-diffusion. ▶ The field-dependent permittivity is described by the derivative of the polarization. ▶ The space charges at the cathode interface have significant influence on the currents. ▶ The higher of barrier height is, the smaller of current densities are.The combined model of thermionic emission and carrier drift-diffusion is derived to simulate the electrical transport through BST thin film capacitors. In the model the field-dependent permittivity is obtained from the derivative of the polarization distinguished with the traditional characterization. The simulated currents show the hysteresis. The influences of space charges and electrode materials on the current density-applied voltage characteristics have been studied. The simulation results suggest that the current densities can be greatly influenced by the space charges at the cathode interface and the barrier height at the electrode/BST interface. It is expected that this work can provide some useful guidelines to the design and performance improvement of BST thin film capacitors and other BST thin film devices.

Keywords: Electrical transport; Field-dependent permittivity; Space charge; Electrode material; (Ba,Sr)TiO; ₃; thin film capacitors

Study on the interface between the organic and inorganic semiconductors by Dan Jin; Wei Wang; Ateeq Rahman; Jiang Lizhen; Hanjie Zhang; Haiyang Li; Pimo He; Shining Bao (pp. 4994-4999).

▶ Perylene molecule adsorbs uprightly with its long axis cross the dimer at the coverage of 0.5 mono layer. ▶ Molecule adsorbs uprightly with its short axis cross the dimer at the coverage of 1.0 monolayer. ▶ Organic molecules adsorb forming a zigzag structure at the coverage of multi layers. ▶ Work function first decreases, then increases and finally stays constant with the minimum value at the coverage of 1ML. ▶ The dipole, formed on the surface, contributes to the change in work function.The adsorption of perylene on Si (001) surface has been studied by UPS measurement and DFT calculation. With 0.5 monolayer, the perylene molecule adsorbs uprightly with its long axis cross the dimer. At the coverage of 1.0 monolayer, the perylene molecule adsorbs uprightly with its short axis cross the dimer. To increase the separation between the molecules, the molecules adsorb forming a zigzag structure. With coverage increasing, the work function decreases. When the coverage is 1ML, the work function is the minimum. The dipole, formed on the surface, contributes to the change in work function.

Keywords: Ultraviolet photoemission spectroscopy; Perylene; Si (0; 0; 1); DFT

Preparation and microwave absorption properties of Fe-phthalocyanine oligomer/Fe₃O₄ hybrid microspheres by Fanbin Meng; Rui Zhao; Yingqing Zhan; Yajie Lei; Jiachun Zhong; Xiaobo Liu (pp. 5000-5006).

▶ Fe-phthalocyanine oligomer/Fe₃O₄ hybrid microspheres were synthesized through a simple solvent-thermal route. ▶ The morphology and size of hybrids can be adjusted. ▶ A new magnetic loss peak of the hybrid microspheres appeared at high frequency. ▶ A maximum reflection loss of −31.1dB was obtained at 8.6GHz with 1g bis-phthalonitrile when the matching thickness was 3.0mm.The novel nano-scale Fe-phthalocyanine oligomer/Fe₃O₄ hybrid microspheres were synthesized from bis-phthalonitrile and FeCl₃·6H₂O through a simple solvent-thermal route. The morphology and structure of the hybrid microspheres were characterized by FTIR, XRD, SEM and TEM. These results showed that the hybrids were monodispersed solid microspheres and the morphology can be adjusted by controlling the addition of bis-phthalonitrile. On the basis of these results, the formation process was discussed. Magnetization measurement indicated that saturation magnetizations decreased linearly with increasing the addition of bis-phthalonitrile, while coercivities increased. The microwave absorption properties were measured by a vector network analyzer. The dielectric loss of the hybrid microspheres was larger and a new magnetic loss peak appeared at high frequency. The microwave absorbing properties enhanced with increasing the addition of bis-phthalonitrile and a maximum reflection loss of −31.1dB was obtained at 8.6GHz with 1g bis-phthalonitrile when the matching thickness was 3.0mm. The novel hybrid materials are believed to have potential applications in the microwave absorbing performances.

Keywords: Bis-phthalonitrile; Magnetite; Monodispersed hybrid microspheres; Magnetic properties; Microwave absorption properties

Growth and characterization of polycrystalline Ge1−_xC_x by reactive pulsed laser deposition by M.P. Hernández; M.H. Farías; F.F. Castillón; Jesús A. Díaz; M. Avalos; L. Ulloa; J.A. Gallegos; H. Yee-Madeiros (pp. 5007-5011).

▶ Polycrystalline thin films of Ge–C were grown on Si (111) substrates by means of reactive pulsed laser deposition with methane pressure of 100mTorr. ▶ The C content varied with the substrate temperature. ▶ The maximum value of C incorporation to substitutional sites was 0.032. ▶ The remaining C atoms are incorporated to interstitial sites.Polycrystalline thin films of Ge–C were grown on Si (111) substrates by means of reactive pulsed laser deposition with methane pressure of 100mTorr. Effect substrate temperature, T_s, on C incorporation to substitutional sites ( x) in Ge1−_xC_x was investigated systematically by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyzes. The substrate temperatures were ranging from 250 to 400°C. The substitutional C composition x in the films by XRD were estimated using the Vegard's linear law. The maximum value of x calculated by XRD was 0.032 for T_s of 350°C. The position of the C 1s peak at 283.4eV in the XPS spectrum confirmed the germanium–carbon alloys. XRD measurements indicated that x increased with T_s from 250°C to 350°C. At T_s=400°C, the estimation of x was lowered. However, the C content calculated by XPS analyzes increased with T_s being more these values than substitutional C composition x. XPS and XRD analyzes demonstrate that the remaining C atoms are incorporated to interstitial sites. The use of the T_s plays important roles in the incorporation of substitutional C and in restraining C-cluster formation in the reactive pulsed laser deposition growth of Ge–C/Si.

Keywords: Pulsed laser deposition; Ge–C films; XPS analysis; X-ray diffraction

Influence of the temperature and duration of the annealing on the lattice structure and growth of the Mg–Al spinel layer by Hailiang Zhang; Mingfu Zhang; Jiecai Han; Guobing Ying; Huaixin Guo; Chenghai Xu; Haitao Shen; Ningning Song (pp. 5012-5016).

▶ We have studied the effects of temperature and duration on the formation mechanism and kinetics of Mg–Al spinel layer. ▶ A combined investigation on the difference of the growth of the spinel layer between the polycrystalline and monocrystalline alumina substrates also have been investigated. ▶ The growth of formed Mg–Al spinel layer under 1300°C and 1600°C is discussed, as well as the thickness and orientation of the formed Mg–Al spinel.In this paper, MgO film is successfully grown on polycrystalline and monocrystalline alumina substrates using sol–gel method, and polycrystalline and monocrystalline Mg–Al spinels are fabricated by solid state reaction, respectively. The influence of annealing temperature and time on the lattice structure and growth of the formed Mg–Al spinel layer has been investigated. It is indicated that the annealing temperature and time on the as-synthesized polycrystalline Mg–Al spinel has more significant influence than that of single crystal Mg–Al spinel. The thickness of the Mg–Al spinel layer increases with the annealing temperature, both for polycrystalline and for monocrystalline alumina substrates. And the significantly intercrystalline diffusion of Mg²⁺ ions and Al³⁺ ions results in a quicker growth velocity of the Mg–Al spinel layer than that of intracrystalline diffusion.

Keywords: Alumina; Mg–Al spinel; Diffusion; Solid state reaction

Zn-catalyzed growth processes and ferromagnetism of Mn-doped ZnO nanorods on Si substrate by H.L. Yan; J.B. Wang; X.L. Zhong (pp. 5017-5020).

► Vertically ZnO nanorods are fabricated on the substrate. ► Zn catalyst is used to induce the growth of ZnO nanorods. ► The FM originates from the Mn²⁺-Mn²⁺ ferromagnetic coupling. ► The growth of nanorods follows a VLS and self-catalyzed model.Well-aligned ZnO nanorods and Mn-doped ZnO nanorods are fabricated on Si (100) substrate according to the contribution of Zn metal catalysts. Scanning electron microscopy and high-resolution transmission electron microscopy images indicate that the influence of Zn catalyst on the properties of ZnO can be excluded and the growth of ZnO nanorods follows a vapor–liquid–solid and self-catalyzed model. Mn-doped ZnO nanorods show a typical room temperature ferromagnetic characteristic with a saturation magnetization ( M_S) of 0.273 μ_B/Mn. Cathodoluminescence suggests that the ferromagnetism of Mn-doped ZnO nanorods originates from the Mn²⁺–Mn²⁺ ferromagnetic coupling mediated by oxygen vacancies. This technique provides exciting prospect for the integration of next generation Si-technology-based ZnO spintronic devices.

Keywords: Well-aligned Mn-doped ZnO nanorods; Zn catalyst; Room-temperature ferromagnetism; Cathodoluminescence

Epitaxial growth of fully relaxed Si_0.75Ge_0.25 on SOI substrate by Zhongying Xue; Xing Wei; Bo Zhang; Aimin Wu; Miao Zhang; Xi Wang (pp. 5021-5024).

▶ High crystal quality Si_0.75Ge_0.25 film has been grown directly on SOI substrate with no graded buffer, whose density of surface defects is lower than 10⁴cm⁻². ▶ For SiGe grown on SOI with low Ge content, the strain is redistributed between SiGe and the top Si of SOI substrate, and the strain residing in SiGe layer can be fully relaxed by the formation and expansion of dislocation half-loops near the SiGe/Si interface. ▶ For SiGe layer grown on SOI substrate with high Ge fraction, the lattice constant differences between Si and SiGe cannot be accommodated efficiently due to the restriction of buried oxide.A fully relaxed Si_0.75Ge_0.25 film with low dislocation densities is fabricated by epitaxial growth on SOI substrate without depositing graded buffers. The relaxation mechanism of the SiGe layer directly grown on SOI substrate is also analyzed. For SiGe grown on SOI with low Ge content, the strain is redistributed between SiGe and the top Si of SOI substrate, and the strain residing in SiGe layer can be fully relaxed by the formation and expansion of dislocation half-loops near the SiGe/Si interface. The surface morphology and crystal quality of all samples are analyzed by optical microscopy and transmission electron microscopy (TEM), respectively. Compared to the Si_0.75Ge_0.25 layer epitaxially grown on graded buffer, the Si_0.75Ge_0.25 directly grown on SOI substrate appears good surface morphology and perfect crystal quality.

Keywords: SiGe; Epitaxial growth; Relaxation; SOI substrate

Effects of (NH₄)₂SO₄ on the characteristics of the deposits and properties of an electroless Ni–P plating solution by Zhihui Xie; Gang Yu; Bonian Hu; Xiping Lei; Tingjing Li; Jun Zhang (pp. 5025-5031).

▶ Ammonium sulfate (AS) can be used as a rate controller on Mg AZ91 alloy in EN plating. ▶ The hypophosphite efficiency first decreases and then increases with an increase in AS concentration. ▶ A low accumulation of AS improves the corrosion resistance of the coating. ▶ A high sulfate buildup decreases the adhesion of the coating.The effects of ammonium sulfate (AS) in bath on the deposition rate, hypophosphite efficiency, bath stability, and characteristics of electroless nickel–phosphorous (EN) deposits were studied. The deposition rate of EN deposits was estimated by the gravimetric method. The results showed that the deposition rate of EN can be improved by the addition of AS when its concentration is lower than 12gdm⁻³. Bath stability test was used to determine the stabilization effect of AS. The stability of the EN bath can be significantly decreased by a low concentration of AS, whereas a minimal influence on bath stability was observed with an increased concentration of AS. The variation in the efficiency of hypophosphite was also examined by traditional methods of chemical analysis. Characterization of the deposits was carried out by potentiodynamic polarization experiments, scanning electron microscopy, and energy dispersive X-ray, which can analyze the Ni and P content. The results indicated that a low accumulation of AS (lower than 12gdm⁻³) in the plating process did not adversely affect the characteristics of the deposits. An optimum concentration of AS can decrease grain size, refine microstructure, and improve corrosion resistance. However, a very concentrated AS plating bath may result in an increase in stress of the coating, hence creating a cracked cross-section morphology.

Keywords: Electroless deposition; Ammonium sulfate; Bath stability; Efficiency of hypophosphite

Fabrication of Cu–SiC surface composite under ball collisions by S. Romankov; Y. Hayasaka; I.V. Shchetinin; J.-M. Yoon; S.V. Komarov (pp. 5032-5036).

▶ Cu–SiC surface composite was fabricated by ball collisions at room temperature after 15min treatment. ▶ Composite formation was the result of mechanical mixing of the plasticized Cu and the SiC particles. ▶ Ball collisions refined the grains near the surface to the nanometer scale. ▶ Initial rolling texture of the Cu plate was completely destroyed by 15min of ball collisions. ▶ Surface hardness of the composite layer was almost twice that of the initial Cu plate.A nano-grained Cu–SiC surface composite was fabricated on a Cu plate precoated with SiC particles at room temperature after 15min treatment using ball collisions. The composite formation was the result of mechanical mixing of the plasticized Cu and the SiC particles. Ball collisions refined the grains near the surface to the nanometer scale and destroyed the initial rolling texture of the Cu plate. The surface hardness of the composite layer was almost twice that of the initial Cu plate.

Keywords: Surface composites; Grain refinement; Nanocrystalline materials; Ball impacts; Copper

Collagen immobilization on 316L stainless steel surface with cathodic deposition of calcium phosphate by Agata Roguska; Sachiko Hiromoto; Akiko Yamamoto; Michał Jerzy Woźniak; Marcin Pisarek; Małgorzata Lewandowska (pp. 5037-5045).

► Collagen/calcium salts composite coatings are electrochemically formed on 316L stainless steel. ► Calcium salts consist of calcium phosphate and carbonate. ► The composite coatings slightly improve the ALP activity of osteoblast cells.Collagen fibril/(calcium phosphate and carbonate) composite coatings on 316L stainless steel were developed with a cathodic deposition technique. The response of SaOS-2 osteoblast-like cells to the collagen/calcium salt-coated 316L steel was investigated. The collagen fibrils were self-assembled on the 316L steel surface and immobilized by their partial incorporation into a calcium salt layer electrodeposited cathodically in Hanks’ solution. The amount of calcium salt depended on the applied cathodic potential. The mineralization of collagen fibrils was observed. The collagen coverage localized and the composition of calcium salts varied on the same specimen. Such non-uniform surfaces affected the cell response. The observed outlines of cell bodies and nuclei on the thin collagen coating were clearer than those on the thick collagen coating in most cases. The collagen coating did not significantly influence the mean viability of cells on the whole specimen surface. Interestingly, the alkaline phosphatase activity per cell on the collagen/calcium salt-coated specimens was higher than that on the as-received specimen. It was revealed that cathodic deposition is an effective technique to immobilize collagen fibrils on a 316L steel surface.

Keywords: 316L stainless steel; Electrochemical treatment; Collagen; Calcium phosphate; Calcium carbonate; SaOS-2 osteoblast-like cells

Low temperature synthesis of iodine-doped TiO₂ nanocrystallites with enhanced visible-induced photocatalytic activity by Yi Ma; Ji-Wen Fu; Xia Tao; Xin Li; Jian-Feng Chen (pp. 5046-5051).

A simple low-temperature method has been developed for the preparation of I-TNCs with anatase crystalline matrix, mesoporous structure framework and enhanced visible-induced photocatalytic activity.Display Omitted▶ Synthesis visible-activated I-TNCs at temperature as low as 120°C. ▶ I doping, crystallization and mesoporous structure achieved simultaneously. ▶ I-TNCs promote photocatalytic activity under visible light irradiation. ▶ I-TNCs were efficiently recycled without significant loss in activity.Iodine-doped TiO₂ nanocrystallites (denoted as I-TNCs) were prepared via a newly developed triblock copolymer-mediated sol–gel method at a temperature of 393K. I-doping, crystallization and the formation of porous structure have been simultaneously achieved. The obtained particles were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and UV–vis spectrophotometer. The results indicated that the as-prepared I-TNCs possessed a diameter of ca. 5nm with anatase crystalline structure and a specific surface area of over 200m²g⁻¹. The presence of iodine expanded the photoresponse in visible light range, and led to enrich in surface hydroxyl group on the TiO₂ surface. Compared with the commercial photocatalyst P25, the I-TNCs significantly enhanced the photocatalytic efficiency in the degradation of rhodamine B and 2,4-dichlorophenol, and the I-TNCs with 2.5mol% doping ratio exhibited the best photocatalytic activity.

Keywords: Low temperature; TiO; ₂; Iodine doping; Mesoporous structure; Photocatalyst

Deposition and characterization of low temperature silicon nitride films deposited by inductively coupled plasma CVD by Abhijeet Kshirsagar; Pradeep Nyaupane; Dhananjay Bodas; S.P. Duttagupta; S.A. Gangal (pp. 5052-5058).

▶ Silicon nitride thin films deposited at low substrate temperature of 70°C by ICP-CVD were found to be of β-phase having pinhole free film. ▶ The deposition rate was 13nm/min which is more than other reported techniques. ▶ AFM showed grain size in the range 3–8nm² equivalent to that obtained from XRD and film RMS roughness 0.1–0.6nm. ▶ These properties make the film a better choice for MEMS application, where low temperature, high deposition rate, low stress and better reliability structural layer is required.Silicon nitride films have been deposited at a low temperature (70°C) by inductively coupled plasma chemical vapor deposition (ICP-CVD) technique and their physical and chemical properties were studied. For a deposited SiN sample, β-phase was observed and refractive index of 2.1 at 13.18nm/min deposition rate was obtained. The attained stress of 0.08GPa is lower as compared to the reported value of 1.1GPa for SiN thin films. To study the deposited film, characterization was performed using X-ray photoelectron spectra (XPS), X-ray diffraction (XRD), micro Raman spectroscopy, Fourier transfer infrared spectroscopy (FTIR), cross-section scanning electron microscopy (SEM) and atomic force microscopy (AFM).

Keywords: Silicon nitride; Inductively coupled plasma; Low temperature

TiO₂ Wedgy Nanotubes Array Flims for Photovoltaic Enhancement by Hao Pan; Jieshu Qian; Ang Yu; Meigui Xu; Luo Tu; Qingli Chai; Xingfu Zhou (pp. 5059-5063).

In this study, TiO₂ wedgy nanotubes with rectangular cross-sections were fabricated on transparent conductive substrates by using TiO₂ nanorods as the precursor via the anisotropic etching route. TiO2 nanotubes with V-shaped hollow structure and the special crystal plane exposed on the tube wall possess nature of high surface area for more dye molecules absorption, and the strong light scattering effects and dual-channel for effective electron transport of the TiO₂ V-shaped nanotubes based dye-sensitized solar cell exhibit a remarkable photovoltaic enhancement compared with the TiO₂ nanorods. The photoanode based on our V-shaped TiO₂ nanotubes with a length of 1.5μm show a 123% increase of the dye loading and a 182% improvement in the overall conversion efficiency when compared with 4μm rutile TiO₂ nanorods photoanode.

Keywords: TiO; ₂; wedgy nanotubes; Dye-sensitized solar cell; Light-scattering

The preparation and evaluation of graded multilayer ta-C films deposited by FCVA method by Gui-Gen Wang; Hua-Yu Zhang; Wen-Yan Li; Fang-Xu Yang; Lin Cui; Hong-Bo Zuo; Jie-Cai Han (pp. 5064-5069).

▶ The graded multilayer tetrahedral amorphous carbon film has low internal stress. ▶ The film has more sp³ bonds when applying a larger negative substrate bias voltage. ▶ The sp³ fraction of ta-C film is increasing with larger thickness of outer sublayer. ▶ However, its internal stress also increases with thicker outer sublayer. ▶ The optimal sublayer thickness ratio is 1:1:1:1 for four-sublayer graded ta-C film.In this study, a series of graded multilayer ta-C films were investigated by varying their sublayer thickness ratios, in which each film sublayer was prepared at different substrate bias by filtered cathode vacuum arc (FCVA) method. The experimental results show that the graded multilayer film structure can effectively decrease the internal stress level of deposited ta-C film, and meanwhile the graded multilayer ta-C films still have high sp³ fractions. The applied substrate bias voltage and sublayer thickness ratio can apparently influence the microstructure characteristics and internal stress of the graded multilayer ta-C films. The graded multilayer ta-C film has larger sp³ fraction when applying a larger negative substrate bias voltage and having a thicker outer sublayer during the film deposition process. However, the internal stress in the as-deposited film also increases with larger thickness of the outer sublayer, and the optimal ratio of sublayer thicknesses is 1:1:1:1 for graded ta-C film with four sublayers.

Keywords: Graded multilayer ta-C films; Layer structure; Internal stress; Hardness; Filtered cathode vacuum arc

Destabilization of artificial biomembrane induced by the penetration of tryptophan by Liuhua Chen; Lihua Gan; Mingxian Liu; Rong Fan; Zijie Xu; Zhixian Hao; Longwu Chen (pp. 5070-5076).

▶ The penetration of tryptophan can destabilize artificial biological membranes. ▶ The penetration of tryptophan is beneficial for liposome fusion. ▶ Tryptophan can penetrate into lipid monolayer and reduce its stability. ▶ The existence of tryptophan leads to the formation of some defects in s-BLM.The effect of tryptophan on the membrane stability was studied by using three artificial biological membranes including liposome, Langmuir monolayer and solid supported bilayer lipid membrane (s-BLM) as models. All the results indicate that the penetration of tryptophan can destabilize different artificial biological membranes. The diameter of liposome and the leakage of calcein from liposome increased with the increase of tryptophan concentration because the penetration of tryptophan was beneficial for dehydrating the polar head groups of lipids and the formation of fusion intermediates. π-A isotherms of lecithin on the subphase of tryptophan solution further confirm that tryptophan can penetrate into lipid monolayer and reduce the stability of lipid monolayer. When the concentration of tryptophan increased from 0 to 2×10⁻³molL⁻¹, the limiting molecular area of lecithin increased from 110.5 to 138.5Å², but the collapse pressure of the monolayer decreased from 47.6 to 42.3mNm⁻¹, indicating the destabilization of lipid monolayer caused by the penetration of tryptophan. The resistance spectra of s-BLM demonstrate that the existence of tryptophan leads to the formation of some defects in s-BLM and the destabilization of s-BLM. The values of electron-transfer resistance and double layer capacitance respectively decreased from 5.765×10⁶Ω and 3.573×10⁻⁸F to 1.391×10⁶Ω and 3.340×10⁻⁸F when the concentration of tryptophan increased from 0 to 2×10⁻³molL⁻¹. Correspondingly, the breakdown voltage of s-BLM decreased from 2.51 to 1.72V.

Keywords: Destabilization; Artificial biomembrane; Tryptophan; Penetration; Lecithin

Estimation of the transient interfacial heat flux between substrate/melt at the initiation of magnesium solidification on aluminum substrates using the lumped capacitance method by E. Hajjari; M. Divandari; S.H. Razavi; S.M. Emami; S. Kamado (pp. 5077-5082).

▶ IHF for solid pure aluminum/magnesium melt and solid 413 aluminum alloy/magnesium melt couples is a function of surface roughness. ▶ For both solid pure aluminum/magnesium melt and solid 413 aluminum alloy/magnesium melt couples, by increasing the surface roughness, the maximum IHF increases at first and after reaching a maximum value, starts to decrease. ▶ Almost for all ranges of surface roughness, the maximum IHFs for solid 413 aluminum alloy/magnesium melt couples are higher than those for solid pure aluminum/magnesium melt couples.Interfacial heat flux (IHF) between solid pure aluminum/magnesium melt and solid 413 aluminum alloy/magnesium melt couples was evaluated using lumped capacitance method, and the interface microstructures were assessed by scanning electronic microscope. The variation of maximum IHF with surface roughness for these two couples also was evaluated. The results showed that, for both solid aluminum/magnesium melt couples, with increasing the surface roughness, the maximum IHF increases at first and then starts to decrease after reaching a maximum value. In addition the measured maximum IHF for solid 413 aluminum alloy/magnesium melt couples was found to be higher than those measured for solid pure aluminum/magnesium melt couples. That seems to be because of the better wettability of 413 aluminum alloy than pure aluminum, by magnesium melt.

Keywords: Interfacial heat flux; Surface roughness; Aluminum; Magnesium

Synthesis and optical properties of flower-like ZnO nanorods by thermal evaporation method by J.H. Zheng; Q. Jiang; J.S. Lian (pp. 5083-5087).

▶ In this article, we synthesized flower-like ZnO nanorods on substrates by a simple thermal evaporation process without any catalysts or templates. ▶ The PL spectrum showed that a sharp and strong UV emission band located at 386nm together with a weak and suppressed yellow–green emission band. ▶ The high intensity ratio of the UV peak to the defect emissions indicates fairly good crystallization of flower-like ZnO nanorods. ▶ The Zn liquid droplets function as catalyst plays an important role in the self-catalytic VLS growth process of flower-like ZnO nanorods at low temperature deposition region. ▶ The possible growth mechanism of these structures is investigated.Flower-like ZnO nanorods have been synthesized by heating a mixture of ZnO/graphite powders using the thermal evaporation and vapor transport on Si (100) substrates without any catalyst. The structures, morphologies and optical properties of the products were characterized in detail by using X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) and Raman spectroscopy. The synthesized products consisted of large quantities of flower-like ZnO nanostructures in the form of uniform nanorods. The flower-like ZnO nanorods had high purity and well crystallized wurtzite structure, whose high crystalline quality was proved by Raman spectroscopy. The as-synthesized flower-like ZnO nanorods showed a strong ultraviolet emission at 386nm and a weak and broad yellow–green emission in visible spectrum in its room temperature photoluminescence (PL) spectrum. In addition, the growth mechanism of the flower-like ZnO nanorods was discussed based on the reaction conditions.

Keywords: ZnO nanostructures; Thermal carbon reduction; Optical properties

Morphological and compositional analysis of passive film on austenitic stainless steel in nitric acid medium by N. Padhy; Ranita Paul; U. Kamachi Mudali; Baldev Raj (pp. 5088-5097).

▶ Passive film stability of 304L SS decreases with increase in nitric acid strength. ▶ In situ passive film study of 304L SS showed growth of platelet like structures. ▶ Passive film composition varies depending upon nitric acid concentration.Passive film properties of type 304L stainless steel in nitric acid medium are investigated in both ex situ and in situ conditions. Ex situ results revealed that variation in passive film morphology occurs depending upon the concentration and time of immersion. In situ surface morphological investigation showed formation of platelet like structures at lower concentrations (0.1M, 0.5M), and towards higher concentration (0.6M, 1M) the platelet like structures got agglomerated, homogenized and started depleting from the surface leading to opening up of oxide boundaries. Compositional analysis of the passive film revealed duplex nature at lower concentration consisting of hydroxide and oxide layer, and with increasing concentration oxide layer predominates over the surface.

Keywords: Stainless steel; AFM; Polarization; Passive film; Transpassivity

Effects of Ta on microstructure and microhardness of Ni based laser clad coating by Ting Yu; Qilin Deng; Gang Dong; Jianguo Yang (pp. 5098-5103).

▶ Ta refines coarse carbides in laser clad Ni-based alloy. ▶ Ta reduces crack susceptibility of laser clad Ni-based alloy. ▶ Ta improves microhardness of laser clad Ni-based alloy.Through addition of Tantalum, fine TaC particles were in situ synthesized in a NiCrBSi alloy laser clad composite coating. Microstructure, microhardness and abrasive wear resistance of the composite coating were investigated. The result showed that TaC particles were dispersed in Ni based alloy composite coating, refining the microstructure of the coating after laser cladding. Amount of coarse primary carbides such as M7C3 and eutectic of γ-Ni+M23C6 substantially decreased because the formation of TaC particles suppressed the formation of M7C3 and M23C6. On the one hand, fine TaC particles acted as hard phase, which improved the microhardness of the composite coating; on the other hand, a decrease in amount of the coarse M7C3 and eutectic of γ-Ni+M23C6 reduced the crack susceptibility of the Ni based composite coating. Also, Ta element improved the abrasive wear resistance of the Ni based coating.

Keywords: Laser cladding; NiCrBSi alloy; In situ synthesis; Crack; TaC; Microhardness

Synthesis and characterisation of Gd³⁺-doped mesoporous TiO₂ materials by Caixia Lv; Yi Zhou; Hong Li; Mingming Dang; Changchun Guo; Yancong Ou; Bin Xiao (pp. 5104-5108).

▶ The multi-walled carbon nano-tubes (MWNTs) are used as temple. ▶ M-TiO₂ with high surface area is formed, which favours the photo-catalytic activity of M-TiO₂. ▶ The substitution or interstitial incorporation of the Gd³⁺ ion into the TiO₂ lattice produces impurity energy levels in band gap and expands its visible-light response. ▶ The growth of Gd³⁺ in the crystal lattice of TiO₂ produces lattice distortion, damages the crystal sites of TiO₂ and avoids the probability of recombination of the electron–hole pair.Using multi-walled carbon nano-tubes (MWNTs) as the template, Gd³⁺-doped mesoporous TiO₂ (M-TiO₂) material was prepared by the homogeneous precipitation-assisted template method. The as-prepared photo-catalysts were characterised using X-ray diffraction, scanning electron microscopy, nitrogen adsorption/desorption and ultraviolet–visible (UV–vis) diffuse-reflection spectroscopy analyses. The photo-catalytic properties of Gd³⁺-doped M-TiO₂ were primarily investigated by the photo-degradation of methyl orange under Xe-lamp irradiation and compared with those of pure M-TiO₂ and the commercial photo-catalyst Degussa P25. The results showed that the as-synthesised samples were of anatase crystalline phase and had red shifts in their UV–vis patterns with different Gd³⁺-doping concentrations. Gd³⁺-adding at 0.12mol% could significantly enhance the photo-catalytic properties of the M-TiO₂ material and the rate of photo-degradation of methyl orange reached 97.3% under Xe-lamp irradiation for 150min.

Keywords: Gd; ³⁺; -doping; MWNTs; Mesoporous TiO; ₂; (M-TiO; ₂; ); Photo-catalytic properties

Surface characterization and reactivity of vanadium–tin oxide nanoparticles by Chien-Tsung Wang; Miao-Ting Chen; De-Lun Lai (pp. 5109-5114).

► Surface state and reactivity of vanadium-doped tin oxide. ► Vanadia dispersion and catalysts for methanol oxidation. ► Vanadium promotes catalytic conversion of methanol to formaldehyde. ► High oxidation state of vanadia and vanadium–tin interaction enhance redox activity.Surface state and reactivity of vanadium–tin mixed oxide nanoparticles (V/Sn ratios 0.05–0.2) were characterized by spectroscopic techniques and catalytic measurements. Analyses by X-ray photoelectron spectroscopy (XPS) and diffuse reflectance spectroscopy (DRS) revealed that the oxidation state and surface structure of vanadium oxide species and the electronic interaction between Sn and V atoms are dependent upon the vanadium content. These oxides were evaluated as catalysts for methanol oxidation in a fixed-bed reactor. Both reaction rate and formaldehyde selectivity increased with increasing the vanadium amount in catalyst. Results demonstrate that the V⁵⁺ site in the bridging V–O–Sn structure exhibits a high redox activity to facilitate the transformation of adsorbed methoxy to formaldehyde and that the vanadium dispersion plays a crucial role in the surface reactivity. A mechanism that elucidates the catalytic redox process is proposed.

Keywords: Nanoparticles; Tin oxide; Vanadium; XPS; Methanol oxidation

Investigation of oxidation inhibition properties of vaporized self-assembled multilayers on copper nanopowders by Jinhyeong Kwon; Shinyoung Park; Tae Hun Lee; Jun-Mo Yang; Caroline Sunyong Lee (pp. 5115-5120).

► Stability against oxidation was investigated for VSAM on nano-sized Cu powders. ► The amount of oxygen increased after 35 days, indicating sign of partial oxidation. ► The octanethiol film was consistently 10nm thick, for up to 35 days. ► This study achieves a great milestone toward inkjet printing technology.Stability against oxidation was investigated for vaporized self-assembled multilayers on nano-sized Cu powders. 100nm-sized copper powders were coated with 1-octanethiol to make a passivation layer against oxidation.As a result, the surface resistivity of the coated and uncoated nano-sized copper powders differed by two orders of magnitude. XPS analysis was used to monitor changes in the amount of sulfur and oxygen on the surface of octanethiol-coated Cu nano powders over a period of time. While sulfur was detected for up to 75 days, the amount of oxygen increased dramatically after 35 days, indicating sign of partial oxidation. Furthermore, HR-TEM images showed that the octanethiol film was consistently 10nm thick, for up to 35 days. After 35 days exposure to the air, the octanethiol film was partially damaged and its diffraction pattern detected the presence of Cu₂O. Based on these findings, vaporized octanethiol coating protected the copper nano powders from oxidation for up to 35 days. Therefore this oxidation inhibition property of VSAMs coating method on Cu powders achieves a great milestone toward inkjet printing technology.

Keywords: Cu; Nanopowder; Nanoparticle; 1-octanethiol; VSAM; XPS; HR-TEM

Effect of different annealing temperature on Sb-doped ZnO thin films prepared by pulsed laser deposition on sapphire substrates by Ziwen Zhao; Lizhong Hu; Heqiu Zhang; Jingchang Sun; Jiming Bian; Jianze Zhao (pp. 5121-5124).

► We obtained the p-type Sb-doped ZnO thin film by changing annealing temperature. ► We researched the effect of the Sb-related acceptors concentration to the crystallinity of the Sb-doped ZnO thin films. ► The measurements of low-temperature photoluminescence (PL) spectra indicate that the p-type Sb-doped ZnO showed strong acceptor-bound exciton (A⁰X) emission, and we proved that the A⁰X emission related to Sb-doping.Influence of annealing temperature on the properties of Sb-doped ZnO thin films were studied. Hall measurement results indicated that the Sb-doped ZnO annealed at 950°C was p-type conductivity. X-ray diffraction (XRD) results indicated that the Sb-doped ZnO thin films prepared at the experiments are high c-axis oriented. It was worth noting that p-type sample had the worst crystallinity. The measurements of low-temperature photoluminescence (PL) spectra indicate that the sample annealed at the temperatures of 950°C showed strong acceptor-bound exciton (A⁰X) emission, and confirmed that it is related to Sb-doping by comparing with the undoped ZnO low-temperature PL spectrum.

Keywords: Sb-doped ZnO; Pulsed laser deposition; Hall-effect-measurement; X-ray diffraction; Scan electronic microscopy; Photoluminescence spectra

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Applied Surface Science (v.257, #11)

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Applied Surface Science (v.257, #11)