First-principles molecular dynamics of the initial oxidation of Si{001} by ozone

Ozone has recently received considerable attention as an alternative oxidant in the low-temperature oxidation of silicon. Here, we use density-functional theory to elucidate the initial oxidation stages of O-3 on Si{001}. Ozone favors a barrierless dissociation with two surface reaction centers involving either the up (Si-u) or the down (Si-d) dimer atom of the buckled Si dimer. The Si-u site exhibits a strong steering effect which leads typically to partial dissociation, whereas Si-d initially interacts only weakly with the molecule, resulting sometimes in complete dissociation. We discuss the underlying electronic structure of the reaction, with particular emphasis on the spin evolution.