The Effects of Substrate Temperature on the Composition and IR Transmission Properties of Germanium Carbon Films Deposited by Reactive RF Magnetron Sputtering

Abstract

Germanium carbon films were prepared on ZnS substrates by reactive RF magnetron sput- tering of a Ge target in Ar and CH4 mixtures for IR antireflective and protective purposes. IR transmit- ttance spectra of the specimens were measured, with which H content in the films was investigated. The C and Ge contents and the atomic binding state were studied by X-ray photoelectron spectroscopy. The results show that H involved in the films combine mainly with C at low substrate temperatures. IR absorption peaks caused by the C-H bonds decrease with increasing temperature, indicating the drop of the C-H bonds content in the film. At relatively low temperature the film is high in C content and low in refractive index; at high temperature the film is low in C content and high in refractive index. Both C-Ge and C-C bonds exist in the film and O impurity combines mainly with Ge.