X-ray photoelectron spectroscopy study of Sb-doped SrTiO3 transparent conducting thin films

Optically transparent Sb-doped SrTiO3 (SrTi1-xSbxO3) thin films with a transmittance higher than 90% in visible region have been grown on SrTiO3 (001) substrates by pulsed laser deposition method using an XeCl laser under oxygen partial pressure of 20 Pa. The thin film with Sb doping concentration of x = 0.05 shows metallic-like conductivity with a resistivity rho similar to 6.99 x 10(-3)Ohm(.)cm at room temperature. XPS and synchrotron radiation photoelectron spectroscopy (SR-PES) measurement from the SrTi0.95Sb0.05O3 thin film reveals that the shallow and deep impurity donor levels within the band gap of the parent compound SrTiO3 are induced by the Sb doping. The delocalized electrons within the shallow levels near the Fermi level can be excited to the conduction band as free carriers for electrical conduction by thermal ionization. The wide band gap, small transition probability and weak absorption due to the low density of states in the impurity levels result in the optical transparency of the film.