X-ray photoelectron spectroscopy and Raman spectroscopy investigations of amorphous Si xC 1x(H) coatings obtained by chemical vapour deposition from thermally labile organosilicon compounds

Abstract

Thermal decomposition of organosilicon molecules was carried out in order to obtain amorphous coatings with variable silicon and carbon contents. We selected four molecules: two cyclic molecules, sila-5-spiro[4.4] nona-2,7-diene (I A) and dimethyl-2,7-sila-5-spiro[4.4]nona-2,7-diene (I B), and two non-cyclic molecules, tetrapropargylsilane (II A) and tetraethynylsilane (II B). Classical chemical vapour deposition (CVD) apparatus was used and the nature of various influences was studied. The coatings were investigated by X-ray photoelectron spectroscopy and micro Raman spectrometer analysis. The coatings have the general formula Si x C 1− x (H), where x varies from 0.24 to 0.82 (depending on the molecule and the decomposition temperature). The binding energies of the core electrons in the Si 2s and C 1s levels ( E b(Si 2s) ≈ 152.4 eV; E b(C 1s) ≈ 284.2 eV) are shifted relative to those for an SiC standard sample ( E b(Si 2s) = 151.6 eV; E b(C 1s) = 283.7 eV). Nevertheless, the Raman spectra display two peaks (800 and 960 cm −1) corresponding to SiC after annealing of the deposits. The correlations between the properties of the solid phase (coating) and the gas phase (decomposition byproducts) in the CVD reaction permit an understanding of the decomposition. The coating composition is related to the structure of the starting molecule.