Electronic Structure of CdO Studied by Soft X-ray Spectroscopy

We present X-ray absorption spectroscopy (XAS) and resonance inelastic X-ray scattering (RIXS) measurements of CdO thin film. The observed differences between bulk and surface XAS signals suggest the presence of a surface electron accumulation layer in CdO film. The native defects (oxygen vacancies) strongly influence on the electronic structure of CdO resulting in the absorption threshold position/onset and spectral profile changes. To interpret the obtained data ab initio theoretical calculations, using the FEFF code, were performed and compared to the experimental results. The calculated angular-momentum-projected local density of states (PDOS) describes well the experimental data. The direct and indirect gaps of CdO were estimated to be ∼2.4 eV and ∼0.9 eV, respectively, by overlapping the XAS spectrum with RIXS. These results are consistent with our optical absorption measurements as well as theoretical and experimental band gap values of CdO reported in the literature