We show that by co-doping SrTiO3 (STO) epitaxial thin films with equal amounts of La and Cr it is possible to produce films with an optical band gap ~0.9 eV lower than that of undoped STO. Sr1-xLaxTi1-xCrxO3 thin films were deposited by molecular beam epitaxy and characterized using x-ray photoelectron spectroscopy and x-ray absorption near-edge spectroscopy to show that the Cr dopants are almost exclusively in the Cr3+ oxidation state. Extended x-ray absorption fine structure measurements and theoretical modeling suggest that it is thermodynamically preferred for La and Cr dopants to occupy nearest neighbor A- and B-sites in the lattice. Transport measurements show that the material exhibits variable-range hopping conductivity with high resistivity. These results create new opportunities for the use of doped STO films in photovoltaic and photocatalytic applications.
Revised: December 28, 2018 |
Published: December 3, 2014
Citation
Comes R.B., P.V. Sushko, S.M. Heald, R.J. Colby, M.E. Bowden, and S.A. Chambers. 2014.Band-Gap Reduction and Dopant Interaction in Epitaxial La,Cr Co-doped SrTiO3 Thin Films.Chemistry of Materials 26, no. 24:7073-7082.PNNL-SA-105536.doi:10.1021/cm503541u