Residual gas adsorption studies on activated surfaces of AlGaN nanowire photocathode based on first principles

To investigate the effect of residual gas adsorption on activation surface of AlGaN nanowire photocathode surface, adsorption of H 2 O, CO 2 and CO on different activation surfaces of Al[Formula: see text]Ga[Formula: see text]N nanowire has been simulated by using the first principle software, and analyzed stability, charge transfer, changes of band structure, density of states, and optical properties after adsorption. Theoretical data show that H 2 O, CO 2 and CO in Al[Formula: see text]Ga[Formula: see text]N nanowires exhibit a high tendency to adsorb when confronted with Cs/NF 3 activated surfaces. Meanwhile, it is further observed that electronic structure of adsorbed gases shows a characteristic distribution: the s-orbital electrons form a deep energy level in valence band region, while the p-orbital electrons show a shallow energy level distribution. The CO adsorption had the greatest effect on reflectivity and absorption coefficient of Cs/NF 3 -activated surface. In addition, the work function of Cs/NF 3 -activated surface is 2.88[Formula: see text]eV, and the work functions after adsorption of residual gases are all higher than this value, which is unfavorable to the improvement of electron escape and quantum efficiency, and impairs the performance of photocathode.