First-principles Investigation of Cs Adsorption Behavior at Various Locations on Oxygen-containing GaAs Surfaces

Abstract

First-principles calculations were utilized to analyze O atoms binding at various locations on the GaAs(100)-β2(2 × 4) surface and its impact on Cs adsorption mechanisms. Computational models included oxygen-containing, Cs-adsorbed, and Cs adsorbed oxygen-containing surfaces. The results indicate that deep As-O-As and shallow As-O-Ga structures exhibit the highest adsorption stability based on adsorption energy calculations. Furthermore, the Cs adsorption energy in oxygen-containing models is observed to be marginally higher than that of clean-surface models, suggesting that the presence of O atoms enhances Cs adsorption stability. The deep As-O-As demonstrates the most significant impact on the work function, while the shallow As-O-As yields the lowest work function. This observation implies that the depth of the As-O-As strongly influences its effect on the work function. Notably, for the Ga-O-Ga structure, the difference in work function between Cs adsorbed oxygen-containing surfaces and Cs adsorbed clean surfaces is negligible, indicating that this oxygen-containing configuration has limited impacts on subsequent Cs adsorption. This study discloses that the presence of O atoms promotes charge transfer from Cs atoms and concurrently reduces charge transfer from Cs to the GaAs surface.