Ge1-xCx films deposited by using a medium frequency magnetron sputtering technique (MFMST) were analyzed with X-ray photoelectron and Raman spectroscopy. The deposited Ge1-xCx films consist of C, Ge, GeC and GeOy The GeC content in the Ge1-xCx films linearly decreases, and the C content linearly increases with increasing deposition temperature from 150 to 350 degrees C. The GeC content decreases from 11.6% at a substrate bias of 250 V to a lowest value of 9.6% at 350 V, then increases again to 10.4% at 450 V. While the C content increases from 49.0% at the bias of 250 V to a largest value of 58.0% at 350 V and then maintains this level at 450 V. It is found that selecting a bias parameter seems more effective than deposition temperature if we want to obtain a higher content of GeC in the deposited films. In addition, a new method is presented in this paper to estimate the changes of GeC content in the Ge1-xCx films by observing the shifts of Ge-Ge LO phonon peak in Raman spectra for the Ge1-xCx films. The related mechanism is also discussed in this paper. (c) 2007 Elsevier B.V. All rights reserved.