title: Wide bandgap tunability in complex transition metal oxides by site-specific substitution.
abstract: Fabricating complex transition metal oxides with a tunable bandgap without compromising their intriguing physical properties is a longstanding challenge. Here we examine the layered ferroelectric bismuth titanate and demonstrate that, by site-specific substitution with the Mott insulator lanthanum cobaltite, its bandgap can be narrowed by as much as 1 eV, while remaining strongly ferroelectric. We find that when a specific site in the host material is preferentially substituted, a split-off state responsible for the bandgap reduction is created just below the conduction band of bismuth titanate. This provides a route for controlling the bandgap in complex oxides for use in emerging oxide optoelectronic and energy applications.
authors.affiliation: Oak Ridge National Laboratory, Materials Science and Technology Division, Oak Ridge, Tennessee 37831, USA.
authors.forename: Woo Seok
authors.initials: WS
authors.lastname: Choi
authors.forename: Matthew F
authors.initials: MF
authors.lastname: Chisholm
authors.forename: David J
authors.initials: DJ
authors.lastname: Singh
authors.forename: Taekjib
authors.initials: T
authors.lastname: Choi
authors.forename: Gerald E
authors.initials: GE
authors.lastname: Jellison
authors.forename: Ho Nyung
authors.initials: HN
authors.lastname: Lee