title: Optical absorption and spectral photoconductivity in α-(Fe₁-xCrx)₂O₃ solid-solution thin films.
abstract: Hematite, α-Fe2O3, is an attractive narrow gap oxide for consideration as an efficient visible light photocatalyst, with significant potential for band gap engineering via doping. We examine optical absorption in α-(Fe1-xCrx)2O3 epitaxial films and explain the observed excitations, and the nature of the band gap dependence on x, through first-principles calculations. The calculated and measured optical band gap becomes smaller than that of bulk α-Fe2O3 and reaches a minimum as the Cr cation fraction increases to 50%. The lowest energy transitions in the mixed-metal alloys involve electron excitation from occupied Cr 3d orbitals to unoccupied Fe 3d orbitals, and they result in a measurable photocurrent. The onset of α-Fe2O3 photoconductivity can be reduced by nearly 0.5 eV (to 1.60 eV) through addition of Cr.
authors.affiliation: Fundamental and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, WA 99352, USA.
authors.forename: Sara E
authors.initials: SE
authors.lastname: Chamberlin
authors.forename: Yong
authors.initials: Y
authors.lastname: Wang
authors.forename: Kenneth
authors.initials: K
authors.lastname: Lopata
authors.forename: Tiffany C
authors.initials: TC
authors.lastname: Kaspar
authors.forename: Alicia W
authors.initials: AW
authors.lastname: Cohn
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Gamelin
authors.forename: Niranjan
authors.initials: N
authors.lastname: Govind
authors.forename: Peter V
authors.initials: PV
authors.lastname: Sushko
authors.forename: Scott A
authors.initials: SA
authors.lastname: Chambers