Visible light carrier generation in co-doped epitaxial titanate films
Abstract
Perovskite titanates such as SrTiO3 (STO) exhibit a wide range of important functional properties, including ferroelectricity and excellent photocatalytic performance. The wide optical band gap of titanates limits their use in these applications; however, making them ill-suited for integration into solar energy harvesting technologies. Our recent work has shown that by doping STO with equal concentrations of La and Cr, we can enhance visible light absorption in epitaxial thin films while avoiding any compensating defects. In this work, we explore the optical properties of photoexcited carriers in these films. Using spectroscopic ellipsometry, we show that the Cr3+ dopants, which produce electronic states immediately above the top of the O 2p valence band in STO reduce the direct band gap of the material from 3.75 eV to 2.4–2.7 eV depending on doping levels. Transient reflectance spectroscopy measurements are in agreement with the observations from ellipsometry and confirm that optically generated carriers are present for longer than 2 ns. Finally, through photoelectrochemical methylene blue degradation measurements, we show that these co-doped films exhibit enhanced visible light photocatalysis when compared to pure STO.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Mar 02, 2015
- Source ID
- 10.1063/1.4913930
Entities
People
- Brent A. Apgar
- Jason B Baxter
- Lane W Martin
- Mark E Bowden
- Ran Gao
- Ryan B. Comes
- Scott A. Chambers
- Sergey Y. Smolin
- Tiffany C. Kaspar
Organizations
- Air Force Office of Scientific Research
- Drexel University
- Environmental Molecular Sciences Laboratory
- Lawrence Berkeley National Laboratory
- National Science Foundation
- Pacific Northwest National Laboratory
- United States Department of Energy
- University of California, Berkeley
- University of Illinois Urbana–Champaign