Berlin 2018 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 11: Topological insulators II (joint session HL/TT)

HL 11.1: Talk

Monday, March 12, 2018, 15:00–15:15, A 151

Advanced MBE techniques for improved Bi2Se3 thin film growth — •Sarah Schmitt, Peter Schüffelgen, Abdur Jalil, Michael Schleenvoigt, Tobias Schmitt, Jonas Kölzer, Daniel Rosenbach, Thomas Schäpers, Gregor Mussler, and Detlev Grützmacher — Peter Grünberg Institut, Forschungszentrum Jülich & JARA Jülich-Aachen Research Alliance, D-52425 Jülich, Germany

Topological Insulators (TIs) are semiconductors with an inverted bulk band gap, but topologically protected states at their surface. The surface states exhibit promising features, useful for example for spintronic and quantum computing applications. In this study, we focus on the binary 3D TI Bi2Se3, which is unique due to its large bulk band gap and its freestanding Dirac point that lies in between valence and conduction band. However, binary compounds suffer from high back ground doping due to crystal defects in the bulk. To reduce defects in Bi2Se3, the quality of the thin films grown by molecular beam epitaxy (MBE) on Si(111) has been optimized. By varying the Bi, Se and substrate temperature as well as using InP as alternative substrate. The best conditions for low roughness, homogeneous domains and reduction of defects were investigated.

For transport measurements Hall bar structures were designed. To avoid defect formation during device fabrication, electrodes were deposited in-situ via stencil lithography. Still in-situ, the stencil mask was removed and the thin film capped with a thin dielectric layer to conserve the sample before taking it to ambient conditions. This technique allows the access to clean ultra-thin TI films by means of MBE.