title: Crystallinity of tellurium capping and epitaxy of ferromagnetic topological insulator films on SrTiO3.
abstract: Thin films of topological insulators are often capped with an insulating layer since topological insulators are known to be fragile to degradation. However, capping can hinder the observation of novel transport properties of the surface states. To understand the influence of capping on the surface states, it is crucial to understand the crystal structure and the atomic arrangement at the interfaces. Here, we use x-ray diffraction to establish the crystal structure of magnetic topological insulator Cr-doped (Bi,Sb)2Te3 (CBST) films grown on SrTiO3 (1 1 1) substrates with and without a Te capping layer. We find that both the film and capping layer are single crystal and that the crystal quality of the film is independent of the presence of the capping layer, but that x-rays cause sublimation of the CBST film, which is prevented by the capping layer. Our findings show that the different transport properties of capped films cannot be attributed to a lower crystal quality but to a more subtle effect such as a different electronic structure at the interface with the capping layer. Our results on the crystal structure and atomic arrangements of the topological heterostructure will enable modelling the electronic structure and design of topological heterostructures.
authors.affiliation: 1] London Centre for Nanotechnology, University College London, London WC1H 0AH, United Kingdom [2] Swiss Light Source, Paul Scherrer Institut, Villigen PSI, CH-5232, Switzerland.
authors.forename: Jihwey
authors.initials: J
authors.lastname: Park
authors.affiliation: London Centre for Nanotechnology, University College London, London WC1H 0AH, United Kingdom.
authors.forename: Yeong-Ah
authors.initials: YA
authors.lastname: Soh
authors.affiliation: 1] London Centre for Nanotechnology, University College London, London WC1H 0AH, United Kingdom [2] Swiss Light Source, Paul Scherrer Institut, Villigen PSI, CH-5232, Switzerland [3] Laboratory for Solid State Physics, ETH Zurich, Zurich, CH-8093, Switzerland [4] Institut de la Matiere Complexe, EPF Lausanne, Lausanne, CH-1015, Switzerland.
authors.forename: Gabriel
authors.initials: G
authors.lastname: Aeppli
authors.affiliation: Department of Physics, Tsinghua University, Beijing 100084, People's Republic of China.
authors.forename: Xiao
authors.initials: X
authors.lastname: Feng
authors.affiliation: Institute of Physics, Chinese Academy of Sciences, Beijing 100190, P. R. China.
authors.forename: Yunbo
authors.initials: Y
authors.lastname: Ou
authors.affiliation: 1] Department of Physics, Tsinghua University, Beijing 100084, People's Republic of China [2] Institute of Physics, Chinese Academy of Sciences, Beijing 100190, P. R. China.
authors.forename: Ke
authors.initials: K
authors.lastname: He
authors.affiliation: Department of Physics, Tsinghua University, Beijing 100084, People's Republic of China.
authors.forename: Qi-Kun
authors.initials: QK
authors.lastname: Xue