Effects of Sputtering Pressure and Substrate Temperature on Structure and Optical Absorption Properties of Si_1-xGe_x Thin Films

Si1-xGex thin film was deposited by radio frequency magnetron sputtering method. The effects of sputtering pressure and substrate temperature on the structure, thickness, surface morphology, composition and optical absorption properties of the films were studied. The results show that phase composition of the film was microcrystalline structure, and it would not change with change of the sputtering pressure and substrate temperature. Crystal properties lowered with increase of the pressure, and improved with increase of the temperature. Thin film thickness first increases and then decreases with increase the pressure or temperature, and reached the maximum at 1.0 Pa or 400 ℃. Cluster disappeared and the thin film surface became smooth with increase of the temperature, but the surface had holes and channel when the pressure was 8.0 Pa. Ge content in thin film decreased with increase of pressure, and optical absorption intensities decreased, while the optical bandgap increased; the substrate temperature had little effect on the optical bandgap of film.