Materials Science Forum Vols. 663-665

Abstract: Soda-based glass samples were fabricated in a laboratory scale using quartz sands that was a by-product of feldspar floatation in Tak Province, northern Thailand, and 25-wt% commercial-grade Na2CO3 as the main compositions. Fe2O3 of 0.1 to 10.0 wt% concentrations was doped into the glass mixture. Well-mixed and dried powders were melted in a ceramic crucible for 6 h at 1250°C using an electric furnace. Transparent and bubble-free glass samples were obtained as results. It was found that Fe2O3 dopant turned the otherwise colorless glass to dark brown. Dielectric property and physical properties, such as, color, specific gravity, and refractive index of the glass samples were studied. The samples’ dielectric constant, specific gravity, and refractive index increased with increasing Fe2O3 doping concentration. UV-VIS-NIR and synchrotron-based X-ray absorption spectra were measured and discussed.

Abstract: A new diffraction optics element (DOE) which combines semiconductor laser and polymer-based DOE processing technology into a single optoelectronic polymer device is proposed. To directly combine the VCSEL (Vertical-Cavity Surface-Emitting Laser) with DOE, DOE surface profile can be integrated on the top of VCSEL utilizing polymer gratings by soft-lithography technique. Such a new kind of polymer-based DOE-VCSEL can control spatial distribution of emitting laser energy and output angle. Through the innovative development, it can be predicted that the optical loss and traveling distance in DOE system are decreased due to the shrinking the device volume by this new design.

Abstract: We have investigated the morphology and photoluminescence (PL) of Zinc Oxide (ZnO) and Zinc sulphide (ZnS) compound grown on porous silicon at room temperature. Under different excitation wavelengths (320 nm, 340nm, 370 nm), the photoluminescence (PL) spectra of PS-ZnS-ZnO composites were different, and at 550nm there is a strong photoluminescence peak. Energy dispersive spectroscopy (EDS) has been carried out to evaluate the existing of ZnO/ZnS compound. In addition, the scanning electron microscopy (SEM) observation shows that the morphology of the PS-ZnS-ZnO composites was well grown on porous silicon.

Abstract: The effect of an impurity as a donor or an acceptor in ZnO film is determined by its distribution in ZnO lattice. In this paper the distribution of Li is investigated by X-ray diffraction (XRD) and photoluminescence (PL). It is found that Li-doped ZnO films own different dependence on heat treatment temperature by contrast with pure ZnO films. For Li-doped ZnO films, although the crystallinity is promoted after heat treatment at 500oC, it is impeded effectively after heat treatment at 600oC. The abnormal phenomenon implies that Li preferential inhabits at Zn-sublattice to form a substitutional defect as an acceptor unless Li content exceeds its solubility in Zn-sublattice. The change of the PL spectra of pure ZnO films after heat treatment at different temperatures reveals that the PL peak at 650nm origins from interstitial defects. Moreover, with the increase of Li content, the intensity of the peak at 650nm decreases firstly and then increases again. This interesting changing trend further reveals that superfluous Li will enter into the octahedral interspaces as donors. As a conclusion it is proposed that it is difficult to obtain high conductive p-ZnO by monodoping of Li.

Abstract: TiO2 thin films were deposited from Ti2¬O3, TiO2 and Ti3O5 source materials by e-beam. The refractive index and extinction coefficient of the films in the visible and near infrared（IR） region were measured. The structural and chemical properties of the films were investigated by x-ray diffraction (XRD), atomic force microscopy (AFM) and x-ray photoelectron spectroscopy (XPS). XRD measurements revealed that all the deposited films were amorphous. XPS analysis showed the films were stoichiometric TiO2. The AFM investigation confirmed that the surface roughness of the films was dependent on the deposition conditions.

Abstract: The size of quantum dots (QDs), their shape, and ordered arrays have significant impact on electrical and optical properties of the QDs. We synthesized near-infrared-emitting PbSe QDs via an oil phase method in a noncoordinating solvent. Transmission electron microscopy (TEM) and photoluminescence (PL) spectroscopy were used to characterize the samples. Sizes of the QDs were accurately controlled from 4.2 nm to 10.2 nm through control of the reaction time as well as the growth temperature. The PL spectra showed strong size dependence, which is large red shift with increasing size of the QDs.

Abstract: Highly monodisperse ZnO nanorods were synthesized by simple solution chemical process. The produced ZnO nanorods have uniform diameters about 30 nm with average aspect ratios more than 40. Raman and photoluminescence measurements were used to examine their optical properties. Raman spectrum presents weak quantum confinement effects of the fine nanorods. Laser power-dependent photoluminescence spectra show the products have intense UV emissions with narrow full width at the half maximum (FWHM). All the performed experiments determine the good crystal and optical quality of synthesized nanorods.

Abstract: In this paper, thin HfO2 films were grown by using E-beam evaporation technique in vacuum and O2 ambient, respectively. Effects of O2 ambient on structural, optical and electrical properties of the HfO2 films were investigated by deploying x-ray photoelectron spectroscopy, ultraviolet visible spectroscopy, I-V and C-V characteristics. Results show that the O2 ambient deposited HfO2 films exhibited excellent structural, optical and electrical properties as compared with vacuum ambient HfO2 films, which especially performs a low content of metal Hf, a high transmittance, a low leakage current and a high dielectric constant.

Abstract: YVO4:Eu3+ phosphors were prepared by microwave hydrothermal method in this work. YVO4:Eu3+ phosphors were probed by photoluminescence (PL), X-ray powder diffraction (XRD) and scanning electron microscope (SEM). The effects of different preparation conditions on the photoluminescence, the structure and the morphology of YVO4:Eu3+ phosphors were studied. The experiment results show that the pH value and the Eu3+ doping amount have some important effect on the photoluminescence and the morphology of YVO4:Eu3+phosphors.

Abstract: A bolometer with stress equilibrium based on α-Si and metal films is proposed in this paper. The sensitive and support material α-Si films are prepared by plasma enhanced chemical vapor deposition（PECVD）, their stress and deposition rate are studied, and the technological parameter of the low stress and higher temperature coefficient of resistance (TCR) α-Si film are obtained. The result shows that the stress of the α-Si films can be adjusted between positive and negative. Pt films are deposited by electron-beam evaporating equipment. Their square resistance, TCR and stress are tested by four point resistivity test system and film-stress interferometer. The result shows this material is a good heat-sensitive material, and at the same time it can balance the stress of α-Si film. Finally it is found that Pt film is in compressive stress state in the selected technological parameters, and α-Si thin film is in tensile stress state, so the stress of micro-bridge structure can be balanced by this method. In the final, 160×120 infrared micro-bridge array on the wafer and read out integrated circuit (ROIC) chip are successfully fabricated.