Surface chemistry of phosphorus-containing molecules: I. Interaction of PH3 with Rh(100) and the effect of preadsorbed phosphorus

Abstract

The interaction of PH3 with Rh(100) has been investigated using temperature-programmed desorption spectroscopy, Auger electron spectroscopy, low-energy electron diffraction, and work function change measurements. A mobile precursor state is involved in the adsorption kinetics at 100 K. The overlayer is saturated after an exposure of 3 L, at which point the work function has decreased by 1.2 eV, indicating adsorption through the phosphorus atoms. Heating the crystal above 100 K desorbs molecular PH3 and H2, and leaves adsorbed phosphorus atoms on the surface. The PH3 thermal desorption spectra show a coverage-dependent adsorption energy associated with repulsive lateral interactions between the adsorbed molecules. There are two thermal desorption states of hydrogen, one of which is characteristic of hydrogen on clean Rh(100). Preadsorbed phosphorus atoms partially passivate the surface, preventing PH3 decomposition until higher temperatures are reached. Preadsorbed phosphorus also reduces the capacity of the surface for H2 adsorption, but does not alter the activation energy for H2 desorption.