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 K-alpha 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. (C) 1998 Elsevier Science B.V. All rights reserved.