Master's Defense: Martin Espiñeira

Structural Characterization of Superconductor-Semiconductor Hybrid Crystals


Hybrid III-V semiconductor-supeconductor nanowires are candidates to become qubits in a universal quantum computer. Vapour-Liquid-Solid and Selective Area Growth are the two most used techniques to grow these NWs. With the increasing interest on fabricating these structures comes the necessity to understand the hybrid structure formed in the interface between the superconductor and the semiconductor. This thesis focus on the study of the structure of this hybrid interface in both VLS and SAG nanowires. VLS nanowires showed a perfect epitaxy between the InAs and Al at the interface with the development of twin grains in the Al. As well it is presented the Geometric Phase Analysis technique to study crystal strain in SAG nanowires. This technique shows the dilatation and rotation of a selected set of planes along the transition between the buffer and the NW, as well as the appearance of misfit dislocations in the interface. The Al deposition was found to be monocrystalline along the SAG nanowire facet.