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.
@article{arxiv.1202.4785,
title = {Wide band gap tunability in complex transition metal oxides by site-specific substitution},
author = {Woo Seok Choi and Matthew F. Chisholm and David J. Singh and Taekjib Choi and Gerald E. Jellison and Ho Nyung Lee},
journal= {arXiv preprint arXiv:1202.4785},
year = {2012}
}