Wang Demiao

Modelling and Optimization for Deposition of SiOxNy Films by Radio-Frequency Reactive Sputtering

SiOxNy films are deposited by reactive sputtering from a Si target in Ar/O2/N2 atmospheres. In order to achieve the control of film composition and to keep a high deposition rate at the same time, a new sputtering model based on Bergs work is provided for the condition of double reactive gases. Analysis based on this model shows that the deposition process can easily enter the target-poisoning mode when the preset gas flow (N2 in this work) is too high, and the film composition will change from nitrogen-rich to SiO2-like with the increase of oxygen supply while keeping the N2 supply constant. The modelling results are confirmed in the deposition process of SiOxNy. Target self-bias voltages during sputtering are measured to characterize the different sputtering modes. FTIR-spectra and dielectric measurements are used to testify the model prediction of composition. Finally, an optimized sputtering condition is selected with the O2/N2 flow ratio varying from 0 to 1 and N2 supply fixed at 1 sccm. Average deposition rate of 17 nm/min is obtained under this selected condition, which has suggested the model validity and potential for industry applications.

A new low-emissivity films Prepared by Magnetron Sputtering

Low-emissivity (Low-E) films, which have low transparence in near infrared region, are prepared by RF magnetron reactive sputtering and DC sputtering in turn as the structure of air/TiO2/Ti/Ag/TiO2/ on the glass. Titanium layer protection Ag layer from being oxidized is observed. The transmittance of low-E films was measured by spectrophotometer. The Low-E films can get a best transmittance, while the thickness of titanium layer is about 1 nanometer. In the visible region (380 nm - 780 nm), the highest transmittance is up to 82.4%, and the average transmittance is 75%. In the near infrared region (780 nm - 2500 nm), the average transmittance is 16.2%.

Design of dielectrically-loaded printed quadrifilar helical antenna for GPS applications

A quadrifilar antenna for GPS applications is designed by HFSS. This quadrifilar antenna has four helical arms wound around a dielectric cylinder which has high permittivity and low loss. The four arms are fed with equal amplitudes with 0deg, 90deg, 180deg, 270deg phase by integrated feeding network. Through precisely control of phase and design of high permittivity ceramic, quadrifilar antenna obtains proper resonant frequency and good radiation pattern. The effects including resonant frequency, axial ratio, radial pattern, impedance, gain, efficiency are simulated.