Narrow Results

A set of AlN thin films was prepared by reactive magnetron sputtering at room temperature. The effect of oxygen impurities on the structural and optical properties of AlN films is discussed. The structural and optical properties were characterized using X-ray diffraction (XRD) and spectroscopic ellipsometry, respectively. Depending on the deposition conditions, films can grow hexagonal (würzite, P6₃m3) or cubic (zinc-blende, Fm3m) in microstructure. From the optical measurements, the ellipsometric parameters (ψ, Δ) and the real refractive index as a function of energy were obtained. From the ellipsometric measurements, a model of Lorentz single-oscillator was employed to estimate the optical band gap, E_g. In the theoretical part, a calculation of density of states (DOS) and band structure was performed to be compared with the experimental results.

Silicon oxycarbide (SiCO) thin films were prepared by the RF reactive sputtering technique on n-type silicon substrates with the target of sintered silicon carbide (SiC), and high purity oxygen was used as the reactant gas. The as-deposited films were annealed at temperatures of 600^°C, 800^°C, and 1000^°C under nitrogen ambient, respectively. The films were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction and photoluminescence (PL) spectrophotometer. The results show that annealing temperature plays an important role in the structure and photoluminescence of the films. The temperature 600^°C is the most favorable annealing temperature for SiO₂ crystallization and the formation of 6H-SiC crystal phase in the SiCO films. The intense PL peaks located at 375 nm and 470 nm are observed at room temperature. The origin of the PL was discussed.

We have fabricated photoconductors of indium nitride (InN) grown by radio frequency (RF) sputtering. The InN thin films were deposited on Si(100), Si(110) and Si(111) substrates at room temperature. The Ag/Al contact has been deposited by thermal evaporation in vacuum (10^-5Torr) and then annealed under the flowing of the nitrogen gas environment in order to relieve stress and also induce any favorable reactions between metals and the semiconductor. Current–voltage (I–V) measurements after heat treatment at 400°C were carried out for samples in dark and illumination conditions. It was found that Ag/Al formed a good ohmic contact on top of InN. In addition, the characteristics of the contacts were significantly affected by the orientation of substrates.

Titanium oxide thin films were prepared by sputtering technique onto glass substrates at room temperature (RT). The structure of the films was confirmed using X-ray diffraction (XRD) and revealed the stoichiometry with an O and Ti ratio of 2. The deposited films at RT were found to be amorphous and the films annealed at 300 and 400°C for 2 h were crystalline with orthorhombic structure. The lattice constants and grain size of the film are calculated. The electrical resistivity was found to depend on the film thickness and decreased with increasing the film thicknesses. The optical constants of the films such as the refractive index, extinction coefficient, and absorption coefficient were also determined using the optical transmittance measurements, and the results were discussed. The optical band gap varies from 3.2 to 3.5 eV as a function of oxygen/argon ratios.

Hydrogenated silicon carbonitride (SiCN:H) thin films were deposited by sputtering of silicon carbide target in hydrogen-doped argon and nitrogen atmospheres. The properties of the SiCN:H films were analyzed by scanning electron microscopy with energy dispersive spectrometer, atomic force microscope, Fourier transform infrared spectroscopy, X-ray diffraction and fluorescence spectrophotometer. No distinct crystal was formed in the SiCN:H films as-deposited and annealed at 600^∘C and 800^∘C. The SiCN:H films were mainly composed of Si–N, Si–C, Si–O, C–C, C–N, C$\equiv$N, N–H_n bonds and SiC_xN_y network structure. The strong blue photoluminescence observed from the SiCN:H film annealed at 600^∘C was attributed to SiC_xN_y network structure.

PtO_x films were deposited by direct current (DC) reactive magnetron sputtering in Ar/O₂ mixture atmosphere at substrate temperatures ranging from 200^∘C to 400^∘C. The influence of substrate temperature on the structure, morphology, composition, electrical resistivity and infrared emissivity of PtO_x films was studied. The X-ray photoelectron spectroscopy (XPS) and grazing incidence X-ray diffraction (GIXRD) results revealed that the as-deposited amorphous PtO_x films were mainly composed of PtO and PtO₂ phases. It was found that with the increase in the substrate temperature, the proportion of PtO phase in the films increased, while the electrical resistivity and infrared emissivity of the films decreased with the increasing substrate temperature.