THE CHEMISTRY OF ORGANOSILANE METAL-OXIDE INTERFACES - REACTION OF TRIMETHOXYSILANE ON MGO AND SIO2 SURFACES

The adsorption and reaction of trimethoxysilane (TMS) on MgO(100) and amorphous SiO2 thin films were studied using temperature-programmed desorption, X-ray photoelectron spectroscopy and Auger electron spectroscopy. TMS dissociated on MgO(100) at temperatures below 200 K to form primarily adsorbed HSi(OCH3)2 and methoxy groups. For submonolayer coverages of TMS on MgO(100), the primary reaction pathway was recombination to produce gaseous TMS at 310 K. Small amounts of methanol, tetramethoxysilane and methane were also produced at 280, 380, and 540 K, respectively. For multilayer coverages on MgO(100), TMS formed a siloxane polymer upon adsorption. This polymeric species decomposed at 390 K producing gaseous organosilanes and amorphous silica. TMS was also found to adsorb dissociatively on amorphous SiO2 thin films. Heating the TMS-dosed SiO2 surface resulted in the formation of methanol at 180 K, dimethylether at 200 K, and trimethoxysilane at 290 K. Polymerization of TMS did not occur on the SiO2 surface.