Competition between initial- and final-state effects in valence- and core-level x-ray photoemission of Sb-doped SnO2

High resolution valence- and core-level photoemission spectra of undoped an d 3% Sb-doped SnO2 are presented. Conduction-band occupation due to Sb dopi ng in SnO2 leads to a shift of valence-band features to high binding energy . However, the shift is less than the width of the occupied part of the con duction band. This is attributed to a shrinkage of the bulk band gap with d oping, arising from an attractive dopant electron interaction and screening of the Coulomb repulsion between valence and conduction electrons. Core-le vel spectra provide evidence for strong screening by the conduction electro n gas in 3% Sb-doped SnO2, giving rise to "screened" and "unscreened" final -state peaks in photoemission. The dominant screening response involves exc itation of conduction electron plasmons. [S0163-1829(99)04803-1].