BSc forsvar for Emil Møller Olsen

Title: Characterization of Superconductor-Semiconductor Junctions in Al/InAs Nanowires - AFM study of etched and shadowed nanowires

Abstract: Superconductor–semiconductor nanowire hybrid structures have gained significant interest due to their applications in quantum devices. One such application is the fabrication of Josephson junctions, which can be realized using several approaches.

These include selective wet etching of nanowire regions and in situ shadowing during growth. While SEM micrographs have been used to study etched and shadowed nanowires, they do not provide sufficient detail on surface roughness.

The aim of this project is to investigate the surface morphology of these nanowires using atomic force microscopy (AFM) and compare the results with previously obtained SEM images. This analysis will help determine whether AFM is a useful tool for characterizing nanostructures grown at NBI. In addition, root mean square (RMS) roughness values have been determined for both etched and shadowed nanowires.

The results show that shadowed nanowires exhibit lower RMS roughness, and are therefore smoother, compared to etched ones, and that unshadowed/unetched crystal regions are smoother than shadowed/etched regions in general. Regions with zincblende and wurtzite crystal phases have also been identified using AFM, opening up a use for the technique to be useful in characterizing nanostructures.

Supervisor: Jesper Nygård