Adsorption of trimethoxysilane and of 3-mercaptopropyltrimethoxysilane on silica and on silicon wafers from vapor phase: an IR study.

The interaction of trimethoxysilane (TMS) and of 3-mercaptopropyltrimethoxysilane (MPTMS) with silica and silicon wafers has been studied by the mean of transmission FTIR spectroscopy. TMS vapor adsorption on silica's silanols results in the formation of Si-O-Si bonds at room temperature, mainly through the elimination of one methanol molecule per TMS molecule. Similarly, MPTMS vapor reacts with the surface through "hydroxolysis" of one of Si-O-CH3 bonds, and most of the molecules have their SH group free. The same species is formed over the silicon wafer surface. On the other side, deposition of liquid MPTMS over silicon surface leads to the detection of spectral features characterizing a condensed layer.