Elucidating Raman Auger Behavior in Cu, Cu2O and CuO by Resonant Auger Electron Spectroscopy to Interpret X-ray Absorption Spectroscopy.

Abstract

The understanding and modulation of electronic structures on copper and copper oxides are of great value in the fields of material science and condensed matter physics. Due to the full or nearly full 3d electrons, the band structures of Cu and its oxides have not been clearly investigated in terms of experiments and calculations. Here mapping of resonant Auger electron spectroscopy (mRAS) is utilized to understand the non-radiative decay process of core hole around the absorption threshold. The mRAS can be used for X-ray absorption spectroscopy (XAS) in high energy resolution electron detection mode (HERED), which can help interpret the Cu L_3,2-edge XAS. Additionally, the mRAS results clearly distinguish the band-structure and exitonic contribution in XAS spectra. Together with the spectral calculations, the origin of asymmetrical main absorption peak in Cu L₃-edge XAS of Cu₂O can be explained. Moreover, the non-linear Raman profile around absorption threshold is also found in the mRAS of Cu₂O and CuO, which correlated with the core-hole intermediate state in the XAS process. This work demonstrates the progressiveness of mRAS method for traditional absorption spectrum, which can enhance the capability to study the complex core-hole state in the copper and related systems.