Thermal dissociation and desorption ofPH3on Si(001): A reinterpretation of spectroscopic data

Abstract

It was recently shown that low-coverage $\mathrm{P}{\mathrm{H}}_3$ dosing of the Si(001) surface is fully dissociative at room temperature with $\mathrm{P}{\mathrm{H}}_2+\mathrm{H}$, $\mathrm{P}\mathrm{H}+2\mathrm{H}$, and $\mathrm{P}+3\mathrm{H}$ as intermediate species. Here, we consider high-coverage $\mathrm{P}{\mathrm{H}}_3$ dosing and show that the increased density of adsorbates leads to qualitatively different behavior due to competition between thermal dissociation and desorption. Using a combination of existing temperature-programmed desorption data and density functional theory simulations, we present a detailed mechanistic understanding of phosphine adsorption, dissociation, and desorption on the surface. This understanding provides a consistent interpretation of existing infrared and x-ray spectroscopic data, as well as an explanation of the dependence of the phosphorus saturation coverage on dosing conditions.