Behavior of Plasmons in an Amorphous Silicon-Carbon Alloy System Studied by X-Ray Photoelectron Spectroscopy

Valence-electron plasmons in an amorphous silicon-carbon alloy system $a-{\mathrm{Si}}_x{\mathrm{C}}_{1-x} :\mathrm{H}$ ($0<~x<~1.0$) are observed as the satellites of core-electron levels in the x-ray photoemission spectra. The atomic density of $a-{\mathrm{Si}}_x{\mathrm{C}}_{1-x} :\mathrm{H}$ as a function of $x$ is determined from the valence-electron density $n_v$ obtained from observed plasmon energy $\hslash {\omega }_p$ with use of $\hslash {\omega }_p=\hslash {\left[\right(\frac{4\pi e^2}{m}\left)n_v\right]}^{\frac{1}{2}}$ and the results of thermal effusion experiments. The results are discussed in relation to the coordination of carbon atoms in $a-{\mathrm{Si}}_x{\mathrm{C}}_{1-x} :\mathrm{H}$.