THERMAL-DECOMPOSITION OF TETRAETHOXYSILANE (TEOS) ON SI(111)-(7X7)

We report results of a combined scanning tunneling microscopy and X-ra y photoelectron spectroscopy study on the thermal decomposition of tet raethoxysilane (TEOS), a precursor for SiO2 formation by chemical vapo r deposition, on Si(111)-(7 x 7). Annealing after predominantly dissoc iative adsorption at room temperature, where triethoxysiloxane and eth yl groups are the main adsorbate species, leads to further decompositi on with various products evolving, including diethoxysiloxane and furt her ethyl groups. This goes along with structural changes on the (7 x 7) reconstructed surface. A characteristic new structural element, wit h a maximum on interstitial sites,is interpreted as the very beginning of surface oxide formation.