Thomas Kanne Nordqvist

Growth and Characterization of Semiconductor-Superconductor Nanowire Hybrids

This thesis constitutes a collection of projects that are ruggedly intertwined by the joint theme of hybrid nanowires designed for quantum transport experiments. Considerations of key phases in the metal thin film growth evolution are used as a conceptual background for predicting the crystallinity and morphological nature of the as-grown films. From this analysis we find Pb deposited on InAs nanowires to be structurally the most optimal elemental superconductor for experiments utilizing hybrid nanowires. We show how Pb forms single crystals all along the nanowire length with an epitaxial relationship to InAs. These highly ordered structures are shown electrically to widely expand the parameter space in respect to state-of-the-art material combinations.

Additionally, we investigate how to transform hybrid wires into hybrid devices and present two different strategies for preparing in-situ junctions in superconducting films. Efforts are made to grow multiple nanowires in close proximity and subsequently conjoining the structures with a metal film. These endeavors allow for investigations of novel quantum states proposed as a model system for next generation quantum hardware. In the end, we present a new method for utilizing nanowires for devices based on cutting cross sections of the nanowires. With this technique we are able to make up-scaled devices which could potentially make arrayed nanowire structures highly relevant for industrial applications.

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