XPS study of the chemical bonding in hydrogenated amorphous germanium-carbon alloys

A systematic study of the chemical bonding in hydrogenated amorphous german ium-carbon (a-Ge1-xCx:H) alloys using X-ray photoelectron spectroscopy (XPS ) is presented. The films, with carbon content ranging from 0 at. % to 100 at. %, were prepared by the rf co-sputtering technique. Raman spectroscopy was used to investigate the carbon hybridization. Rutherford backscattering spectroscopy (RBS) and XPS were used to determine the film stoichiometry. The Ge 3d and C 1s con levels were used for investigating the bonding prope rties of germanium and carbon atoms, respectively. The relative concentrati ons of C-Ge, C-C, and C-H bonds were calculated using the intensities of th e chemically shifted C 1s components. It was observed that the carbon atoms enter the germanium network with different hybridization, which depends on the carbon concentration. For concentrations lower than 20 at. %, the carb on atoms are preferentially sp(3) hybridized, and approximately randomly di stributed. As the carbon content increases the concentration of sp(2) sites also increases and the films are more graphitic-like.