title: Infrared optical absorption in low-spin Fe(2+)-doped SrTiO3.
abstract: Band gap engineering in SrTiO3 and related titanate perovskites has long been explored due to the intriguing properties of the materials for photocatalysis and photovoltaic applications. A popular approach in the materials chemistry community is to substitutionally dope aliovalent transition metal ions onto the B site in the lattice to alter the valence band. However, in such a scheme there is limited control over the dopant valence, and compensating defects often form. Here we demonstrate a novel technique to controllably synthesize Fe(2+)- and Fe(3+)-doped SrTiO3 thin films without formation of compensating defects by co-doping with La(3+) ions on the A site. We stabilize Fe(2+)-doped films by doping with two La ions for every Fe dopant, and find that the Fe ions exhibit a low-spin electronic configuration, producing optical transitions in the near infrared regime and degenerate doping. The novel electronic states observed here offer a new avenue for band gap engineering in perovskites for photocatalytic and photovoltaic applications.
authors.affiliation: Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, 902 Battelle Blvd, Richland, WA 99352, USA.
authors.forename: Ryan B
authors.initials: RB
authors.lastname: Comes
authors.forename: Tiffany C
authors.initials: TC
authors.lastname: Kaspar
authors.forename: Steve M
authors.initials: SM
authors.lastname: Heald
authors.forename: Mark E
authors.initials: ME
authors.lastname: Bowden
authors.forename: Scott A
authors.initials: SA
authors.lastname: Chambers