Control of Epitaxial BaFe2As2 Atomic Configurations with Substrate Surface Terminations

Jong-Hoon Kang; Lin Xie; Yi Wang; Hyungwoo Lee; Neil Campbell; Jianyi Jiang; Philip J Ryan; David J Keavney; Jung-Woo Lee; Tae Heon Kim; Xiaoqing Pan; Long-Qing Chen; Eric E Hellstrom; Mark S Rzchowski; Zi-Kui Liu; Chang-Beom Eom

doi:10.1021/acs.nanolett.8b02704

Control of Epitaxial BaFe₂As₂ Atomic Configurations with Substrate Surface Terminations

Nano Lett. 2018 Oct 10;18(10):6347-6352. doi: 10.1021/acs.nanolett.8b02704. Epub 2018 Sep 11.

Authors

Jong-Hoon Kang¹, Lin Xie^{2

3}, Yi Wang⁴, Hyungwoo Lee¹, Neil Campbell⁵, Jianyi Jiang⁶, Philip J Ryan⁷, David J Keavney⁷, Jung-Woo Lee¹, Tae Heon Kim¹, Xiaoqing Pan², Long-Qing Chen⁴, Eric E Hellstrom⁶, Mark S Rzchowski⁵, Zi-Kui Liu⁴, Chang-Beom Eom¹

Affiliations

¹ Department of Materials Science and Engineering , University of Wisconsin-Madison , Madison , Wisconsin 53706 , United States.
² Department of Materials Science and Engineering and Department of Physics and Astronomy , University of California-Irvine , Irvine , California 92679 , United States.
³ National Laboratory of Solid State Microstructures and College of Engineering and Applied Sciences , Nanjing University , Nanjing , Jiangsu 210093 , People's Republic of China.
⁴ Department of Materials Science and Engineering , The Pennsylvania State University , University Park , Pennsylvania 16802 , United States.
⁵ Department of Physics , University of Wisconsin-Madison , Madison , Wisconsin 53706 , United States.
⁶ Applied Superconductivity Center, National High Magnetic Field Laboratory , Florida State University , 2031 East Paul Dirac Drive , Tallahassee , Florida 32310 , United States.
⁷ Advanced Photon Source , Argonne National Laboratory , Argonne , Illinois 60439 , United States.

PMID: 30149722
DOI: 10.1021/acs.nanolett.8b02704

Abstract

Atomic layer controlled growth of epitaxial thin films of unconventional superconductors opens the opportunity to discover novel high temperature superconductors. For instance, the interfacial atomic configurations may play an important role in superconducting behavior of monolayer FeSe on SrTiO₃ and other Fe-based superconducting thin films. Here, we demonstrate a selective control of the atomic configurations in Co-doped BaFe₂As₂ epitaxial thin films and its strong influence on superconducting transition temperatures by manipulating surface termination of (001) SrTiO₃ substrates. In a combination of first-principles calculations and high-resolution scanning transmission electron microscopy imaging, we show that Co-doped BaFe₂As₂ on TiO₂-terminated SrTiO₃ is a tetragonal structure with an atomically sharp interface and with an initial Ba layer. In contrast, Co-doped BaFe₂As₂ on SrO-terminated SrTiO₃ has a monoclinic distortion and a BaFeO_{3- x} initial layer. Furthermore, the superconducting transition temperature of Co-doped BaFe₂As₂ ultrathin films on TiO₂-terminated SrTiO₃ is significantly higher than that on SrO-terminated SrTiO₃, which we attribute to shaper interfaces with no lattice distortions. This study allows the design of the interfacial atomic configurations and the effects of the interface on superconductivity in Fe-based superconductors.

Keywords: BaFe2As2; Superconducting Tc; heterostructures; interfacial atomic structure; surface termination; thin films.

Publication types

Research Support, U.S. Gov't, Non-P.H.S.