Electronic and chemical structure of the H2O/GaN(0001) interface under ambient conditions

We employed ambient pressure X-ray photoelectron spectroscopy to investigate the electronic and chemical properties of the H(2)O/GaN(0001) interface under elevated pressures and/or temperatures. A pristine GaN(0001) surface exhibited upward band bending, which was partially flattened when exposed to H(2)O at room temperature. However, the GaN surface work function was slightly reduced due to the adsorption of molecular H(2)O and its dissociation products. At elevated temperatures, a negative charge generated on the surface by a vigorous H(2)O/GaN interfacial chemistry induced an increase in both the surface work function and upward band bending. We tracked the dissociative adsorption of H(2)O onto the GaN(0001) surface by recording the core-level photoemission spectra and obtained the electronic and chemical properties at the H(2)O/GaN interface under operando conditions. Our results suggest a strong correlation between the electronic and chemical properties of the material surface, and we expect that their evolutions lead to significantly different properties at the electrolyte/electrode interface in a photoelectrochemical solar cell