SILICON EPOXIDE - UNEXPECTED INTERMEDIATE DURING SILICON-OXIDE FORMATION

Infrared absorption spectroscopy and density functional cluster calcul ations are used to identify the intermediate oxide structures formed b y high temperature annealing of the water-exposed Si(100)-(2 x 1) surf ace. We find that initially there is a strong tendency for oxygen to a gglomerate on single dimer units at T similar to 800 K. Upon dehydroge nation, a remarkable structural transition is observed, wherein the da ngling bonds recombine to form silicon epoxides (three-membered Si-O-S i rings). We demonstrate that these epoxides are the thermodynamically favored product in such constrained systems and, consequently, should be preferentially formed at silica interfaces. [S0031-9007(98)07445-6 ].