Chemisorption and decomposition of tris(dimethylamino) phosphine on GaAs(100)

Abstract

The chemisorption and decomposition of tris(dimethylamino) phosphine (DMAP) on GaAs(100) are investigated with temperature-programmed reaction spectroscopy (TPR) and D atom coadsorption experiments. Below monolayer coverage, the majority of DMAP molecules adsorbed at 120 K dissociates at elevated temperatures. At higher surface coverages, DMAP desorbs molecularly with a desorption peak temperature decreasing from 350 to 170 K with increasing coverages. The dimethylamino groups desorb from the surface above 350 K via two reaction channels: radical ejection as dimethylamino radical or β-hydrogen elimination as N-methylmethyleneimine. Coadsorption of D atoms has identified the ejection of radicals rather than stable dimethylamine. The branching ratio of the two channels is affected by the surface coverage and sites available, specifically the relative amounts of Ga, As and P exposed on the surface. Pure phosphorus deposited on the surface desorbs as P 2 or P 4 above 700 K.