Bonding properties of rf-co-sputtering amorphous Ge-C films studied by X-ray photoelectron and Raman spectroscopies

The bonding properties of hydrogenated amorphous germanium-carbon (a-Ge1-xCx:H) alloy films, deposited by the rf-co-sputtering technique, were measured by Fourier transform infrared, micro-Raman and X-ray photoelectron spectroscopies. Films with carbon content in the 0 to 100 at.% range were prepared under the same deposition conditions used to prepare a-Ge:H films. The infrared spectra revealed that the carbon is bonded in both sp(3) and sp(2) configurations. XPS measurements show a chemical shift of the binding energy of the Ge 3d core electrons toward larger energies as the carbon content increases, while the line-width remains almost constant. On the other hand, the peak associated with the C 1s orbital displays a doubler related to the C-Ge and C-C bonds. The Raman spectroscopy data are analyzed over a wide frequency range of the Stokes scattering for different alloy compositions. (C) 1998 Elsevier Science B.V. All rights reserved.