Baoxing Zhao

Microstructure and optical properties of TiO2 thin films deposited at different oxygen flow rates

To research the influence of oxygen flow rate on the structural and optical properties of TiO2 thin film, TiO2 films on glass were deposited by reactive magnetron sputtering. The microstructure and optical properties were measured by X-ray diffractometry, AFM and UV-VIS transmittance spectroscopy, respectively. The results show that the films deposited at oxygen flow rate of 10 mL/min has the lowest roughness and the highest transmittance. The absorption angle shifts to longer wavelengths as oxygen flow rates increase from 5 to 10 mL/min, then to shorter ones as the oxygen flow rate increase from 10 to 30 mL/min. The band gap is 3.38 eV, which is nearly constant in the experiment. For the TiO2 thin films deposited at 10 mL/min of oxyge flow rate, there are nano-crystalline structures, which are suitable for anti-reflection (AR) coating in the solar cells structure system.

STRUCTURE AND PHOTOLUMINESCENCE PROPERTIES OF SILICON OXYCARBIDE THIN FILMS DEPOSITED BY THE RF REACTIVE SPUTTERING

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.

ELECTRICAL AND OPTICAL PROPERTIES OF ZnO THIN FILMS PREPARED BY R.F. MAGNETRON SPUTTERING

High transparency and conductivity of transparent conducting oxide thin film are very important for improving the efficiency of solar cells. ZnO thin film is a better candidate for transparent conductive layer of solar cell. N-type ZnO thin films were prepared by radio-frequency magnetron sputtering on glass substrates. ZnO thin films underwent annealing treatment after deposition. The influence of the sputtering power on the surface morphology, the electrical and optical properties were studied by AFM, XRD, UV2450 and HMS-3000. The experimental results indicate that the crystal quality of ZnO thin film is improved and all films show higher c-axis orientation with increasing sputtering power from 50 to 125 W. The average transparency of ZnO thin films is higher than 90% in the range of 400–900 nm between the sputtering power of 50–100 W. After the rapid thermal annealing at 550°C for 300 s under N2 ambient, the minimum resistivity reach to 10-2Ω⋅cm.

STRUCTURE AND PHOTOLUMINESCENT PROPERTIES OF SiCO THIN-FILMS DOPED WITH Al PREPARED BY DUAL MAGNETRON SPUTTERING

SiCO thin-films doped with aluminum (Al) prepared by alternate deposition of SiC and Al thin layers using Ar and O2 as sputtering gas were deposited on n-Si substrates. The as-deposited thin-films were annealed under 600°C in nitrogen ambient. The thin-films have been characterized by atomic force microscopy, energy dispersive spectrometer, X-ray diffraction, fourier transform infrared spectroscopy, and photoluminescence spectra. The results showed that the introduction of Al promotes the formation of Si—C bonds, but hinders amorphous SiC to further transform to crystalline SiC. The doped Al would react with SiOx in the thin-films to form more Si particles which strongly affect the optical properties. After Al doped, there presented a seven times of enhancement emission band centered around 412 nm, which is ascribed to nanostructure Si-related defect centers embedded in the SiCO thin-films. The obtained results are expected to have important applications in modern optoelectronic devices.