Cs,O coadsorption on Al0.5Ga0.5N(0001) surface

First-principles density functional theory (DFT) simulations have been performed to investigate the adsorption of Cs and O atoms on the surface of (2 x 2) Al0.5Ga0.5N(0001). The adsorption energy, dipole moment, and bond population of atoms of the surface of (2 x 2) Al0.5Ga0.5N(0001) are analyzed. It is found that the adsorption energy of Cs, O coadsorption is less than that of Cs adsorption only for all the surfaces, Cs, O coadsorption leads to stability and improves the surface structure comparing with the adsorption of Cs only, especially when Cs coverage is 0.75 ML. At this coverage, we found that the H-3 is the most ideal adsorption site where 2Cs + O + Cs form the adsorption structure, responsible for ionic bonds between Cs-O and Cs-Cs. In the case of O adsorption, the absorption edge energy and intrinsic absorption peak value increase which consequently enhance the quantum efficiency. On the other hand, at 1 ML Cs coverage, it is inferred that only T-1 site is stable and the dipoles are less than that of 0.75 ML Cs coverage. Moreover, the dipoles of Cs surface at T-1 and BN sites are negative which prevents escaping of electrons, while plastic deformation is found in the BN and H-3 surfaces.