Adsorption and decomposition of 1,3-disilabutane on Si (111)-7×7

The adsorption and decomposition of 1,3-disilabutane (DSB) was studied on Si (111)-7×7 in the temperature range 100-1200 K by Cs⁺ reactive ion scattering and X-ray photoelectron spectroscopy (XPS). By combining the results of these two techniques, adspecies in the intermediate states during the decomposition of DSB were qualitatively identified and an adsorption model was proposed. At 100-150 K, DSB was found to adsorb on the surface as the C₂H₈Si₂ species as well as CH₄Si and to condense molecularly on a monolayer of C₂H₈Si₂ adspecies. XPS indicates that the molecular species desorbs mostly at 200 K and completely at 300 K. Up to 600 K, the C₂H₈Si₂ adspecies are converted to CH₄Si with increasing temperature and then above this temperature the CH₄Si species decomposes to form the SiC film. The intensity variations of Si (2p) and total C (1s) peaks and the analysis by curve fitting of the C (1s) peaks suggest that one CH₄Si species leaves the system by cleavage of C-Si bonds in C₂H₈Si₂ adspecies rather than to form two CH₄Si adspecies, and the breakage probably occurs within the extremity ones in accordance with the double-bonded chemisorption character.