Pathways for thermal phosphorus desorption from the silicon (001) surface

Abstract

We use density-functional theory and transition-state search methods to characterize the thermal desorption of P2 molecules from the phosphorus-doped silicon 001 surface. We compare two desorption pathways, one proceeding via an in-surface P-P homodimer, the other via an on-surface P-P addimer. While intuitive, the homodimer pathway has an overly large reaction barrier which is not consistent with experimental measurements in the literature. Instead, P2 desorption proceeds by the alternative addimer pathway which requires the presence of silicon adatoms. We present a simple chemical-potential model which explains the appearance of these adatoms at high temperatures.