Si K-emission bands of hydrogenated SiOx alloys

Abstract

X-ray Si K-emission bands of amorphous SiOx: H alloy films (0 ⩽ x ⩽ 1.7) are presented. The samples were prepared by rf glow discharge decomposition of SiH4-CO2-H2 gas mixtures in a capacitive reactor system. For x < 0.5 the Si K-emission bands are very similar in shape and peak position to that of a-Si: H, for 0.5 < x < 1.7, however, a dramatic reshaping of the Si K-emission bands occurs. For x = 1.7 the spectra resemble that of crystalline SiO2 (β-crystobalite). The resulting Si K-emission bands are compared with UPS/XPS spectra of a-SiOx in which, contrary to XES spectra, no impressive changes of spectral features are observed. Our measurements demonstrate that the Si K-emission bands of the system a-SiOx: H are more sensitive to sample composition than UPS/XPS spectra. The results delineate the nontrivial behaviour of Si p-like electrons evolving from covalent Si-Si to rather ionic Si-O bonds.