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

Interactions of O₂ 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 O₂/GaP(111) interface, we detected Ga-P bonds, and various oxygen-containing species, i.e., Ga₂O, Ga₂O₃, and GaPO_m. 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.