Fe valence determination in doped SrTiO3 epitaxial films

Atomic Force Microscopy (AFM) measurements have been performed for Fe doped SrTiO
₃
thin films with an Fe concentration of 2 and 5 at%. Thin films with a thickness of about 20 nm were grown by pulsed laser deposition on single crystalline SrTi
_0.99
Nb
_0.01
O
₃
substrates. Low-energy electron diffraction examination showed that the films are single crystalline. The regions treated with the AFM tip (applied dc voltage up to 6V) showed inhomogeneity of the electrical conductivity.