Advanced Materials Research Vols. 602-604

Abstract: The influence of deposition time on the properties of SnS films grown using the thermal evaporation was reported. The deposition time was varied between 0.7 – 3 min, keeping other deposition variables constant. The layers showed single phase with orthorhombic crystal structure, exhibiting a strong (040) reflection. With an increase of deposition time, the Sn/S atomic ratio and grain size and the number of crystallites in the layers increased while the dislocation density and bulk resistivity decreased. The increase of crystallinity of the layers was confirmed by the change of strain from tensile to compressive with increasing deposition time. The transmittance of the films were > 70% for deposition time ≤ 1min and decreased drastically otherwise. The energy band gap varied in the range 1.80 - 1.30 eV with the lower values obtained at longer deposition times.

Abstract: The TiO2 films with hierarchical structure consisting of porous structure and spinodal phase separation structure have been synthesized by sol-gel method. The influence of the different photomonomers, different coating times and different heat treatment temperatures on the structure and photocatalytic activity of TiO2 film has been investigated and the possible mechanism was proposed. The performances of as-prepared TiO2 films were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD). The photocatalytic activities of the as-prepared TiO2 films have been carried out by the degradation of methylene blue (MB) dye under the UV irradiation. The results indicated that the as-prepared TiO2 film with hierarchical structure exhibited significant photocatalytic activity, which might be due to its high specific surface area and high-speed electron migration that enhanced the subsequent photocatalytic reactions and led to a positive synergistic effect.

Abstract: In this paper, propagation of flexural vibration in phononic crystal thin plates with a point defect are explored using finite element method. The plate is composed of an array of circular crystalline Al₂O₃ cylinders embedded periodically in the epoxy matrix with a square lattice. The point defect is introduced by changing one of the cylinders’ radii. Comparing the results of finite element method with that of improved plane wave expansion method, complete and accurate band structures and transmission response curves are obtained using the former method to identify the point defect eigenmodes and band gaps. The results show that the finite element method is efficient and suitable for the exploring of point defect states of phononic crystal thin plates.

Abstract: Nickel-doped ZnO thin films with different Ni contents (0 - 15%) were deposited on glass substrate at 350°C by a spray pyrolysis technique. 0.1 M solutions of zinc acetate and nickel sulphate were used as the precursors with air as the carrier gas. The effect of Ni-doping on the structural and optical properties of the layers was evaluated using appropriate techniques. The X-ray diffraction studies revealed that nickel atoms were successively incorporated into ZnO host matrix without forming any detectable secondary phase. All the grown films were polycrystalline with the (002) plane as the preferred orientation and the peak position shifted towards higher diffraction angle with the increase of doping content in the films. The films had hexagonal shaped grains and the evaluated grain size varied in the range of 20 - 48 nm. The optical studies revealed a decrease of transmittance with the increase of Ni-doping content in the films and the evaluated energy band gap was found to be direct that decreased from 3.32 eV to 3.05 eV.

Abstract: The thermal transportation caused by absorbing inclusions in optical films under the radiation of laser pulse is unsteady heat conduction. The temperature distribution in films is ununiform and time-dependent. Considering the small size of inclusions, the absorbing inclusions were treaded as dot-heat sources. Based on this assumption, the unsteady heat conduction model was brought out and the temperature distribution in films was figured out and discussed, the mechanism that the catastrophic damage may avoid with micro-damage or micro-deformation in films through the release of stress concentration is presented. By comparing the thermal effects caused respectively by single inclusion and assembling ones, the effect of inclusion size on thermal damage in films was discussed.

Abstract: In this paper we report the preparation and characterization of the NbxSi1−x films which would be used as Josephson junction barrier layer. The compositional dependence of dc magnetron co-sputtered NbxSi1−x films on sputtering power is analyzed using Energy Dispersive Spectrometer (EDS) and X-ray Photoelectron Spectrometer (XPS) respectively. The corresponding resistivity measurements of NbxSi1−x films indicate that the film resistivity could be controlled from 0.28 to about 1.29 mΩ·cm which is useful for resistance adjustment of Josephson junction barrier layer. The surface morphology of the NbxSi1−x films is studied by atomic force microscope (AFM) and scanning electron microscope (SEM).

Abstract: With the development of high power laser systems, laser protection of optical components becomes more and more important. In order to enhance the laser-induced damage capability of optical films components, besides advanced methods and processes, post-treatment has significant influence on the laser-induced damage threshold (LIDT) of thin films. Q switch Nd:YAG laser of the working wave length at 1064nm, was used to post process on ZnSe single layer films with thickness of /2 (=1064nm) deposited by thermal evaporation, and the laser-induced damage and optical properties were investigated. By changing the energy density and pulse number under the spot size remained a fixed value, their effects on thin films damage threshold were studied respectively, the optimal processing parameters were obtained: energy density is 3.0 J/cm2 and pulse number is 1.The LIDT of post processed ZnSe films was improved from 5.0J/cm2 to 8.2J/cm2.

Abstract: According to the formation mechanism and characteristics of ELID oxidation film, based on the LabVIEW development platform, the oxidation film thickness was measured by using the laser displacement sensor and eddy current displacement sensor. And the experiments show that it is a feasible method to use laser and eddy current sensor to measure the thickness of oxidation film, the static and dynamic measuring deviation is 6 μm.

Abstract: In this experiment, we use the opaque mirror stainless steel as the substrate to investigate decorative color variations after insertion of the Na+ ion in the film and prescribe the combination coating film with reversible and excellent coating characteristics. In manufacturing of the coating film, reactive gas pass through the metal tungsten target and form the amorphous tungsten oxide thin film on stainless steel and the various colors, such as green and pink color, on the mirror stainless by adjusting the process parameters. The coating film device then immerse in sodium bicarbonate aqueous solution and induce cyclic potential of -2V～+2V. Base color of stainless steel produce the color change reaction by inserting Na+ in the film. Experimental observations show that the green base color will transform to pink then blue and the pink base color transform to green then blue.

Abstract: The temperature dependence Raman scattering from m-plane GaN thin films grown on m-plane sapphire substrate by Molecular Beam Epitaxy (MBE) has been investigated. Three pieces of m-plane GaN films grown with different Ⅲ/Ⅴ ratios were studied by confocal micro-Raman spectrometer from -180 °C to 240 °C. Raman shift and the full width at half maximum (FWHM) were fitted by lorentzian line shape, which reveal the quality and compressive stress of sample. It’s obvious that the Raman shift and FWHM exhibit a quadratic dependence on temperature, and that the redshift of Raman peak position with increasing temperature should be due to anharmonic coupling to phonons of other branches, volume expansion or lattice dilation. Comparing the experiment data and calculated results, the three-phonons processes are dominant in the redshift of E₁(LO) and E₂(high).