First-principles investigation of structural, electronic and optical properties of cubic K2CsSb with different surface orientations

Abstract

The bi-alkali antimonide photocathodes have been widely applied in the fields of fast-speed photodetection and high-energy physics. To guide the preparation of high-sensitive K2CsSb photocathode, by first-principles calculations based on density functional theory, the electronic and optical properties of cubic K2CsSb surface models with different surface orientations and atomic terminations are investigated. More specifically, the properties including surface geometry structures, electronic structure, optical properties, work function and surface energies of the (100) K-terminated, (100) Cs Sb-terminated, (111) Cs-terminated and (111) K-terminated and (110) surfaces are analyzed to determine the surface with superior photoemission performance. It is found that the (111) Cs-terminated surface exhibits the highest conductivity and the lowest work function, indicating its best emission ability, meanwhile, the lowest surface energy and Gibss free energy show its best structural stability and thermodynamic stability. Moreover, the (111) Cs-terminated surface with the advisable optical properties in the photon energy range of 3.1–3.2 eV, is conducive to the improvement of quantum efficiency, which makes it favorable for radiation detection from scintillators.