Structural investigation of cryogenic-grown Sn thin films on InSb substrates*

Superconductor-semiconductor hybrid structures fabricated by optimizing interface formation recipes contribute to better topological superconducting devices. Lately, we measured superconductivity and 2e parity charging in crystalline tin islands grown at cryogenic temperatures on InSb nanowire facets. To further understand the structural properties of those heterostructures, we deposited tin layers on InSb (110) and (001) substrates using different growth recipes, including the one used for nanowires. First of all, X-ray diffraction spectroscopy performed at room temperature shows that tin thin films grown on InSb are epitaxial and in the cubic alpha phase. Depending on the capping strategy to prevent thin film dewetting, some films may contain beta tin grains that are superconducting. We finally propose a mechanism responsible for the formation of the beta grains in the thin films.