J. Vilcarromero et Fc. Marques, XPS study of the chemical bonding in hydrogenated amorphous germanium-carbon alloys, APPL PHYS A, 70(5), 2000, pp. 581-585
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.