Direct evidence of p-type SrTiO3 by high-resolution x-ray absorption spectroscopy -: art. no. 033201

We study x-ray absorption spectra below the O 1s threshold in Sc-doped stoichiometric strontium titanate (SrTiO3), 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 SrTiO3 is a p-type semiconductor with deep acceptor levels lying in the middle of the band gap.