Phosphine Adsorption and Dissociation on the Si(001) Surface: An Ab Initio Survey of Structures

We report a comprehensive ab initio survey of possible dissociation intermediates of phosphine $({\mathrm{PH}}_{3})$ on the Si(001) surface. We assign three scanning tunneling microscopy (STM) features, commonly observed in room-temperature dosing experiments, to ${\mathrm{PH}}_{2}+\mathrm{H}$, $\mathrm{PH}+2\mathrm{H}$, and $\mathrm{P}+3\mathrm{H}$ species, respectively, on the basis of calculated energetics and STM simulation. These assignments and a time series of STM images which shows these three STM features converting into another, allow us to outline a mechanism for the complete dissociation of phosphine on the Si(001) surface. This mechanism closes an important gap in the understanding of the doping process of semiconductor devices.