A first principle research on optical properties of GaN nanowire surface adsorbed with Cs/NF3

In order to study optical properties of GaN nanowire photocathode surface adsorbed with Cs/NF3, GaN nanowire surface models of adsorbing Cs/NF3, 2Cs/NF3, 3Cs/NF3 and 4Cs/NF3 were built respectively. And their band structure, dielectric function, complex refractive index, absorption coefficient, reflectivity and loss function were calculated based on first principle. The results show that band gap value of GaN nanowire surface adsorbed with 4Cs/NF3 is lower than that of nanowire surface adsorbed with Cs/NF3, 2Cs/NF3 and 3Cs/NF3. And with the number of adsorbing Cs atoms increases, conduction band and valence band both shift to low energy range. Absorption coefficient curves of GaN nanowire surface adsorbed with 3Cs/NF3 and 4Cs/NF3 appear new peaks, while maximum value of the absorption coefficient decreases. Moreover, in view of similarities and differences of GaN nanowire photocathodes and GaN thin film photocathodes after Cs/NF3 activation, we researched optical properties of Cs/NF3 adsorbed on GaN nanowire surface and GaN thin film surface. This work can further guide experiment of Cs/NF3 adsorption on GaN nanowire surface, and it is of great significance to improve photoemission performance of GaN nanowire devices.