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Whereas thin films of topological insulators grown by molecular beam epitaxy often display regular, triangular features, Bi2Se3 films grown onto yttrium iron garnet (YIG) display much greater disorder. Here, we present observations of various types of disorder present in these films using atomic force microscopy and scanning transmission electron microscopy. The investigation reveals the presence of an amorphous metal oxide layer between the substrate and the film, which appears to smooth out the nanometer-scale undulations in the YIG surface. It also shows the existence of quasiordered arrays of heavy atoms in some interfacial regions, as well as rotations and tilting between adjacent grains and basal twinning at various heights in the film. Using density functional theory, we explore the impact of these prominent basal twins on the electronic structure of the film.
Bibliographical noteFunding Information:
This work is supported in part by SMART, one of seven centers of nCORE, a Semiconductor Research Corporation program, sponsored by National Institute of Standards and Technology (NIST). This work utilized the College of Science and Engineering (CSE) Characterization Facility, University of Minnesota (UMN), supported in part by the NSF through the UMN MRSEC program (Grant No. DMR-1420013), and the CSE Minnesota Nano Center, UMN, supported in part by NSF through the NNIN program. The work at CSU was also supported by NSF (Grant No. EFMA-1641989) and the Department of Energy (Grant No. DE-SC0018994). We also acknowledge computational support from the Minnesota Supercomputing Institute (MSI). A.R. and N.S. acknowledge support from The Pennsylvania State University Two-Dimensional Crystal Consortium-Materials Innovation Platform (2DCC-MIP) which is supported by NSF cooperative Agreement No. DMR-1539916.
© 2019 American Physical Society.
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- Period 6
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11/1/14 → …
Project: Research project