Effect of oxygen flow rate on microstructure properties of SiO2 thin films prepared by ion beam sputtering

Optical constants and micro-structure characteristics of SiO2 films deposited by ion beam sputtering were studied. The samples were prepared on substrates of silicon and silica with different oxygen flow rates ranged from 0 sccm to 40 sccm with a step of 10 sccm. Refractive index of the samples were obtained by spectra inversion technique. It's suggested that the value of refractive index presents first decrease and then increase as the oxygen flow rate larger, and the turning point is about 30 sccm both at 0.633 μm and 10.6 μm. And the SiO2 thin films were confirmed all amorphous structure by the XRD measurement. The proportion of hydroxyl in SiO2 thin film were determined by XPS, which is beneficial to analyze the film defects. Also the Si-O-Si angle and vibration frequency in TO mode and LO mode were researched by FTIR spectra.