Stability of Se passivation layers on Si(001) surfaces characterized by time-of-flight positron annihilation induced Auger electron spectroscopy

Abstract

The stability of the selenium passivation layer on the Si(001) surface was investigated using a nondestructive surface-sensitive technique: time-of-flight positron annihilation induced Auger electron spectroscopy. After 10days of exposure in the air, the Se passivation layer was observed to incorporate some oxygen but to remain largely intact. Part of the adsorbed oxygen was desorbed during annealing up to 400°C in the ultrahigh-vacuum environment. However, some oxygen remained on the surface until high-temperature annealing at 1030°C. We posit that the oxygen that remained after the low-temperature anneals was chemisorbed on the Si surface at defects in the Se passivation layer. The Se passivation layer was stable up to an annealing temperature of ∼800°C before desorbing from the surface. The stability of the Se-passivated Si(001) surface is attributed to the saturation of the Si dangling bonds on the surface and to the strong Se–Si bonds.