X-ray photoelectron spectra of crystalline LiNbO3:(Er,Yb)

Core-level XPS spectra of single crystalline LiNbO3:Er,Yb (0.4 at% each) are reported for the first time. They were acquired in the Al Kα monochromatized mode with use of an electron flood gun. In the stable conditions of surface charge neutralization the Nb 3d spectrum indicated a pure +5 valence of Nb without any contribution of lower valences. Despite low concentration of Er and Yb (almost at the XPS detectability limit), their 4d core-level spectra were recorded in a prolonged acquisition time. They were found indicative of the +3 valence state of both dopants.