Dresden 2017 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 83: Topological Insulators III (joint session DS, HL, MA, O, TT, organized by HL)

TT 83.5: Vortrag

Freitag, 24. März 2017, 10:30–10:45, POT 251

Stencil lithography of MBE grown superconductors on top of topological insulator thin films — •Michael Schleenvoigt, Peter Schüffelgen, Daniel Rosenbach, Tobias W. Schmitt, Martin Lanius, Benjamin Bennemann, Stefan Trellenkamp, Elmar Neumann, Gregor Mussler, Thomas Schäpers, and Detlev Grützmacher — Peter Grünberg Institute 9, Forschungszentrum Jülich & JARA-FIT, 52425 Jülich, Germany

A stack of the two binary 3D topological insulators Bi2Te3 (n-type doped) and Sb2Te3 (p-type) forms a PN-heterostructure. Growing those topological heterostructures by means of MBE offers the possibility to tune the Fermi level of the upper surface to the Dirac-point. To protect the delicate Dirac system from degradation and oxidation we cap our heterostructures with a thin Al layer, before taking the sample to ambient conditions. We further developed this process to allow for in-situ growth of two different Al layers, i.e. a thin 1-2 nm Al layer on the full wafer followed by a thick Al film on well-defined areas by means of stencil lithography. The thin Al layer will subsequently oxidize after exposure to air and protect the delicate topological surface, whereas the thick Al layer with spatial extent in the (sub-)micrometer range will serve as superconducting contacts. Superconductor-Topological Insulator-Superconductor junctions with lateral dimensions in the nm range have then been fabricated. Despite the in-situ deposition, transport measurements and transmission electron microscope analysis indicate a low transparency, due to an intermixed region at the interface between topological insulator thin film and metallic Al.