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We have spectroscopically determined the optical bandgaps and band offsets at epitaxial interfaces of BaSnO3 with SrTiO3(001) and LaAlO3(001). 28 u.c. BaSnO3 epitaxial films exhibit direct and indirect bandgaps of 3.56 ± 0.05 eV and 2.93 ± 0.05 eV, respectively. The lack of a significant Burstein-Moss shift corroborates the highly insulating, defect-free nature of the BaSnO3 films. The conduction band minimum is lower in electron energy in 5 u.c. films of BaSnO3 than in SrTiO3 and LaAlO3 by 0.4 ± 0.2 eV and 3.7 ± 0.2 eV, respectively. This result bodes well for the realization of oxide-based, high-mobility, two-dimensional electron systems that can operate at ambient temperature, since electrons generated in the SrTiO3 by modulation doping, or at the BaSnO3/LaAlO3 interface by polarization doping, can be transferred to and at least partially confined in the BaSnO3 film.
Bibliographical noteFunding Information:
The thin film growth and characterization work at the University of Minnesota was supported primarily by the National Science Foundation through DMR-1410888 and, in part, by the MRSEC under Award No. # DMR-1420013. We also acknowledge use of facilities at the UMN Minnesota Nano Center. Parts of this work were carried out in the Characterization Facility, University of Minnesota, which receives partial support from NSF through the MRSEC program. The XPS and SE work at PNNL was supported by the U.S. Department of Energy, Office of Science, Division of Materials Sciences and Engineering under Award No. #10122. The PNNL work was performed in the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at PNNL.
© 2016 Author(s).
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