Surface diffusion of phosphorus on Si(100) after PBr3 adsorption

Abstract

Phosphorus diffusion on a Si(100) surface was studied using scanning tunneling microscopy (STM) at temperatures of 77 and 300 K. The phosphorus source utilized was the PBr$_3$ molecule, which fully dissociates on the surface at 77 K. We observed diffusion of P atoms both along and across the rows of Si dimers. To support the observation of different diffusion pathways of phosphorus, activation energy calculations were performed using density functional theory. At 77 K, phosphorus diffusion started and (or) finished mostly in bridge positions. At 300 K, phosphorus diffuses predominantly between end-bridge positions, accompanied by bromine diffusion. The presence of Br near phosphorus significantly restricts its mobility. Additionally, phosphorus was found to diffuse to an oxygen atom that appeared on the surface as a result of water adsorption. This diffusion occurs because the P site near the oxidized dimer is more stable compared to that on the clean surface. The obtained results complement the knowledge about the interaction of phosphorus with the silicon surface, specifically the phosphorus diffusion pathways on the Si(100) surface.