Structure and basal twinning of topological insulator $\mathrm{B}{\mathrm{i}}_{2}\mathrm{S}{\mathrm{e}}_{3}$ grown by MBE onto crystalline ${\mathrm{Y}}_{3}\mathrm{F}{\mathrm{e}}_{5}{\mathrm{O}}_{12}$

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Structure and basal twinning of topological insulator $B i_{2} S e_{3}$ grown by MBE onto crystalline $Y_{3} F e_{5} O_{12}$

Danielle Reifsnyder Hickey, Javad G. Azadani, Anthony R. Richardella, James C. Kally, Joon Sue Lee, Houchen Chang, Tao Liu, Mingzhong Wu, Nitin Samarth, Tony Low, and K. Andre Mkhoyan

Phys. Rev. Materials 3, 061201(R) – Published 25 June 2019

Abstract

Whereas thin films of topological insulators grown by molecular beam epitaxy often display regular, triangular features, $B i_{2} S e_{3}$ 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.

Received 12 March 2019

DOI:https://doi.org/10.1103/PhysRevMaterials.3.061201

Physics Subject Headings (PhySH)

Band gap Electronic structure Twinning

Solid-solid interfaces Topological materials

Density functional calculations Scanning transmission electron microscopy

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Danielle Reifsnyder Hickey^1,2, Javad G. Azadani³, Anthony R. Richardella⁴, James C. Kally⁴, Joon Sue Lee^4,5, Houchen Chang⁶, Tao Liu⁶, Mingzhong Wu⁶, Nitin Samarth⁴, Tony Low³, and K. Andre Mkhoyan ^1,*

¹Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, USA
²Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
³Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, Minnesota 55455, USA
⁴Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
⁵California NanoSystems Institute, University of California, Santa Barbara, California 93106, USA
⁶Department of Physics, Colorado State University, Fort Collins, Colorado 80523, USA