Heterogeneous Oxygen-Containing Species Formed via Oxygen or Water Dissociative Adsorption onto a Gallium Phosphide Surface

Interactions of O-2 or H2O with a GaP(111) surface were investigated over wide ranges of pressure and temperature using near-ambient pressure X-ray photoelectron spectroscopy. We demonstrated the formation of several oxygen-containing species from the dissociative adsorption of gas-phase molecules onto GaP(111). Chemical evolutions were determined at the gas/semiconductor interfaces based on changes in the high-resolution photoelectron spectra, which allowed us to identify the final products formed either directly or through intermediate species. We then used the Ga 2p(3/2) spectra to create maps of the relative abundances of surface oxides and hydroxyl groups present under various experimental conditions. In the case of the O-2/GaP(111) interface, we detected Ga-P bonds, and various oxygen-containing species, i.e., Ga2O, Ga2O3, and GaPOm. In the case of the H2O/GaP(111) interface, in addition to the detection of Ga-P bonds, species were formed with a different extent of oxidation and hydroxylation, O-n-Ga-(OH)(3-n), via a Ga2O-like intermediate species. In both cases, the co-existence of multiple species represented as (GaPO)(A) or (GaPOH)(B), was displayed under specific conditions.