Direct evidence ofp-typeSrTiO3by high-resolution x-ray absorption spectroscopy

Abstract

We study x-ray absorption spectra below the O $1s$ threshold in Sc-doped stoichiometric strontium titanate $\left({\mathrm{SrTiO}}_3\right).\mathrm{}$ We find hole states at the top of the valence band and acceptor-induced levels just above the Fermi level. The x-ray absorption spectra features and their temperature dependence are in good agreement with electrical-conductivity studies on the same samples. It is concluded that Sc-doped ${\mathrm{SrTiO}}_3$ is a p-type semiconductor with deep acceptor levels lying in the middle of the band gap.