Wide bandgap tunability in complex transition metal oxides by site-specific substitution

• DOI: 10.1038/ncomms1690
• Publication Date: 2012-02-21T09:26:02Z
• Authors: Ho Nyung Lee; Taekjib Choi; Gerald E. Jellison; David J. Singh; Matthew F. Chisholm; Woo Seok Choi
• Keywords: Bismuth titanate; Bismuth

Fabricating complex transition metal oxides with a tuneable band gap 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 band gap can be narrowed as much as one electron volt, 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 band gap reduction is created just below the conduction band of bismuth titanate. This provides a route for controlling the band gap in complex oxides for use in emerging oxide opto-electronic and energy applications.