Atomic structures and electronic properties of molecular oxygen adsorption on In0.19Ga0.81As(100) surface: Ab-initio study combined with XPS/UPS analysis

Abstract

Due to the surface oxidation issues, the performances of InGaAs photocathodes are hindered in practical applications, so it is necessary to carry out the corresponding research from theory to experiment. Through ab-initio study based on density functional theory, molecular oxygen adsorption at different sites on the nonpolar In0.19Ga0.81As(100) β2(2 × 4) surface is investigated from the perspectives of atomic and electronic properties. By chemical absorption, molecular oxygen easily dissociates into atomic oxygen when combining with two surface atoms of the same type. The calculation results show that As oxides have the largest destructive effect, followed by Ga oxides, while the In oxides are the least destructive. In addition, the most stable adsorption is the bonding of O atom with Ga atoms, while the bonding of O atom with As atoms is relatively unstable. Combined with the surface analysis method of photoelectron spectroscopy, it is found that the unstable As oxides are the easiest to remove, followed by the In oxides, while the Ga oxides are the most difficult to remove. It is concluded that the work function of the InGaAs surface decreases with the reduction of these oxides, which is conducive to the subsequent preparation of negative-electron-affinity InGaAs photocathodes.