BONDING STRUCTURE AND DEFECTS IN WIDE-BAND GAP A-SI1-XCX-H FILMS DEPOSITED IN H-2 DILUTED SIH4+CH4 GAS-MIXTURES

Amorphous silicon-carbon thin films have been deposited by a newly designed ultra-high vacuum plasma enhanced chemical vapour deposition system starting from SiH4 + CH4 gas mixtures at different Y(CH4)=CH4/(SiH4 + CH4) ratios with deposition conditions optimized to grow high-quality material, having energy gaps in the range 1.9-3.5 eV. The effect of the addition of hydrogen to the plasma with Z(H-2)=H-2/(SiH4 + CH4 + H-2) ranging from 0 to 0.95 has been investigated. A detailed analysis of elemental composition, obtained by Rutherford backscattering and elastic recoil detection analysis, and of structural properties, obtained by infrared and Raman spectroscopies, has been carried out. The results have been correlated to the plasma conditions, the disorder and the optoelectronic properties of the a-Si1-xCx:H films.