skip to main content

Title: Visible light carrier generation in co-doped epitaxial titanate films

Perovskite titanates such as SrTiO{sub 3} (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 Cr{sup 3+} 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.
Authors:
; ;  [1] ; ;  [2] ;  [3] ;  [3] ;  [4] ;  [3] ;  [4] ;  [5]
  1. Fundamental and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington 99354 (United States)
  2. Department of Chemical and Biological Engineering, Drexel University, Philadelphia, Pennsylvania 19104 (United States)
  3. Department of Materials Science and Engineering, University of California-Berkeley, Berkeley, California 94720 (United States)
  4. (United States)
  5. Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99354 (United States)
Publication Date:
OSTI Identifier:
22412762
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 106; Journal Issue: 9; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ABSORPTION; CHARGE CARRIERS; CHROMIUM IONS; COMPARATIVE EVALUATIONS; CONCENTRATION RATIO; DOPED MATERIALS; ELLIPSOMETRY; EPITAXY; EV RANGE; METHYLENE BLUE; OPTICAL PROPERTIES; PEROVSKITE; PHOTOCATALYSIS; SOLAR ENERGY; SPECTROSCOPY; STRONTIUM TITANATES; THIN FILMS; TRANSIENTS; VALENCE; VISIBLE RADIATION