Advanced Materials Research Vols. 652-654

Abstract: Thallium-doped cesium iodide CsI(Tl) scintillation film has been manufactured by radio frequency (RF) magnetron sputter method onto the quartz glass substrates. The X-ray diffraction (XRD) pattern of the film shows preferable growth of the crystalline film in the (200) orientation. The optical and scintillation properties of CsI(Tl) film were investigated, including photoluminescence excitation (PLE), photoluminescence (PL), X-ray excited luminescence (XEL) spectra and decay curve. The main emission peak at about 2.28 eV is related to the radiative relaxation from the strong-off configuration of localized excitons around Tl+ ions. Under UV excitation, the 2.28 eV emission of CsI(Tl) film presents a single exponential decay with 545 ns.

Abstract: In this work, Y₃Al₅O₁₂:Eu³⁺ phosphors were coated with Bi₂O₃ by the coprecipitation method. The crystal structure and surface morphology were characterized by XRD, Zeta potential and IR, respectively. The results showed that the surface of Y₃Al₅O₁₂:Eu³⁺ phosphors were evenly coated with Bi₂O₃ by the electrostatic attraction, i.e. after surface treatment, the crystal structure of Y₃Al₅O₁₂:Eu³⁺ phosphors remained the same as that of the uncoated samples. The results demonstrated that the luminous intensity of coated Y₃Al₅O₁₂:Eu³⁺ phosphors with 5wt% Bi₂O₃ attained the maximun value, increasing to 1.17 times that of uncoated Y₃Al₅O₁₂:Eu³⁺ phosphors.

Abstract: The exposure schedule model of uniform diffraction efficiency in single monomer photopolymer is extended to that in dual monomers with partially-overlapping multiplexing methods. The proposed model can be thought of solving an optimization problem. The exposure schedule for 51 holograms are calculated and verified by the numerical simulation. The result shows that the exposure schedule is effective to produce the uniform diffraction efficiency for the multiplexing holographic storage.

Abstract: The fabrication procedure of silicon nanowire thermoelectric device has been developed based on the electroless etching method. Under a fixed etching solution concentration ratio and the etching reaction temperature, silicon nanowire arrays of different lengths manufactured at different etching time were investigated. The longer etching time results in the longer nanowire length. The silicon nanowire arrays were utilized to produce a silicon nanowire thermoelectric device. The I-V characteristics of the present SiNWs thermoelectric device were recorded under different heating temperatures, and the power outputs of silicon nanowire thermoelectric devices were calculated. The longer the silicon nanowire thermoelectric device lines, the greater the power output of thermoelectric device is. The SiNWs TED power output in the present study ranges from 1.62 to 7.2 nano-Watt with the chip size 2×2 cm² while the applied temperature at 150 °C.

Abstract: CdS nanocrystals were synthesized by a solvent-thermal method in ethylenediamine at different temperature and time. The samples were investigated by XRD, TEM, Uv-vis absorption and PL spectroscopy. The solvent-thermal temperature at 200 °C is an optimal reaction temperature for preparing CdS nanorods with high crystallinity. The PL spectra exhibited two typical emissions: near band edge emission (centered at ~520nm) and defect emission (a broad peak in the range of 550-750nm). The defect emission decreased gradually and disappeared finally with the reaction time increasing from 1 to 12h, but the near band edge emission increased. This revealed that the quality of the CdS samples improved by degrees as the reaction time increased. The growth of single-crystalline CdS nanorods followed three steps; (a) CdS nuclei formed by reacting Cadmium chloride dihydrate and thiourea in ethylenediamine at 200 °C, (b) CdS nuclei grew into thin nanowhiskers after 1h reaction, (c) the growth of CdS nanorods based on nanowhiskers via a Ostwald ripening process.

Abstract: Silicon nanowires with fine tip curvature and high aspect ratio are the promising alternative as the electron emitter to promote field electron emission characteristics. The fabrication of silicon nanowires based on the vapor-liquid-solid (VLS) mechanism was performed in the low pressure chemical vapor deposition chamber in the present work. The gold has its lower eutectic point than other materials and deposited on silicon wafer as the catalyst for silicon nanowire synthesis. The structural properties of the nanowires, including number density, size, aspect ratio and tapering geometry, were optimized by various experimental recipes. The results showed that the low turn-on filed of the nanowire was comparable with the published materials. The 1.2 V/μm low turn-on field was detected from the silicon nanowires which have high aspect ratio and tapered tip emitter when the silicon nanowires were synthesized under the reaction conditions at 620 °C grown for 60 minutes with silane and nitrogen flow rates at 100 SCCM.

Abstract: This paper presets a process of fabrication and measurements of Au/TiO₂/Au resistive switching memory. The device was fabricated using crosspoint structure, and the electrode width and TiO₂ film of which are 1 µm and 50 nm. According to our experimental result, resistive switching cells exhibit good stability and reliability with bipolar resistive switching behavior.

Abstract: Eu³⁺ doped CdWO₄ nanorods, with nearly uniform nanoscale was synthesized via a novel simple hydrothermal method easy for commercial run at 160 °C, of which the average dimensions are about 250, 50 and 20 nm in length, width and height respectively from the result of transmission electron microscopy (TEM). Powder X-ray diffraction (PXRD) pattern shows the product is pure wolframite structure. Different from undoped products showed brilliant blue-green irradiation and block crystals with multi-emission bands in red light range, the Eu doped nanorods give preferred strong ⁵D₀→⁷F₂ transition and are excellent red phosphor with high color purity supported by the photoluminescent (PL) measurements and ultraviolet visible diffuse reflectance spectroscopy (UV-Vis DRS). This suggests that a combination of the Eu³⁺ doped and undoped products are potential to realize the white lighting LED with blue, green and red components.

Abstract: Nanocrystalline Y₂O₂S: Eu ³⁺ , Mg ²⁺ , Ti ⁴⁺ red long-lasting phosphor was synthesized successfully by combustion method using thiourea and citric acid as fuel. The structure, morphology and luminescent properties of these phosphors were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence spectroscopy (PL). The experimental results revealed that the phosphor was composed of sheet-shaped Y₂O₂S with hexagonal crystal structure. They exhibited strong red emission at 617 nm and 626nm. In addition, the dosage of citric acid has great effect on the phosphor. When molar ratio of citric acid to Y ³⁺ is 1.3, the resulted phosphor gives the highest emission intensity.

Abstract: Bilayer-type ZTO thin films were prepared by MOCVD, metal organic chemical vapor deposition. As the films were investigated with UV spectrophotometer, XRD, SEM and other modern research methods, the optics and crystal properties of the ZTO thin films were researched. From the analysis of testing results, visible light transmittance of ZnO/SnO2-type film was superior to SnO2/ZnO-type film, and ternary compound, Zn2SnO4, was found in the two kinds of bilayer-type films. The priority of nucleation should emerged between the (100) crystal plane of ZnO and the (110) crystal plane of SnO2.