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MBE Growth of Al/InAs and Nb/InAs Superconducting Hybrid Nanowire Structures

Abstract

We report on in situ growth of crystalline Aluminum (Al) and Niobium (Nb) shells on indium arsenide (InAs) nanowires. The nanowires are grown on Si(111) substrates by molecular beam epitaxy (MBE) without foreign catalysts in the vapor-solid (VS) mode. The metal shells are deposited by electron-beam evaporation in a metal MBE. High quality supercondonductor/semiconductor (SC/SM) hybrid structures such as Al/InAs and Nb/InAs are of interest for ongoing research in the fields of gateable Josephson junctions and quantum information related research. Systematic investigations of the deposition parameters suitable for metal shell growth are conducted. In case of Al, the substrate temperature, the growth rate and the shell thickness are considered. The substrate temperature as well as the angle of the impinging deposition flux are explored for Nb shells. The core-shell hybrid structures are characterized by electron microscopy and x-ray spectroscopy. Our results show that the substrate temperature is a crucial parameter in order to enable the deposition of smooth Al layers. Contrary, Nb films are less dependent on substrate temperature but strongly affected by the deposition angle. At a temperature of 200 °C Nb reacts with InAs, dissolving the nanowire crystal. Our investigations result in smooth metal shells exhibiting an impurity and defect free, crystalline superconductor/InAs interface. Additionally, we find that the superconductor crystal structure is not affected by stacking faults present in the InAs nanowires.

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Publication details

The article was received on 05 Jun 2017, accepted on 01 Oct 2017 and first published on 02 Oct 2017


Article type: Paper
DOI: 10.1039/C7NR03982D
Citation: Nanoscale, 2017, Accepted Manuscript
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    MBE Growth of Al/InAs and Nb/InAs Superconducting Hybrid Nanowire Structures

    N. A. Güsken, T. Rieger, P. Zellekens, B. Bennemann, E. Neumann, M. I. Lepsa, T. Schäpers and D. Gruetzmacher, Nanoscale, 2017, Accepted Manuscript , DOI: 10.1039/C7NR03982D

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