With increasing attention in Majorana physics for possible quantum bit applications, a large interest has been developed to understand the properties of the interface between an $s$-type superconductor and a topological insulator. Up to this point the interface analysis was mainly focused on in situ prepared Josephson junctions, which consist of two coupled single interfaces or to ex situ fabricated single interface devices. In our work we utilize a fabrication process, combining selective area growth and shadow evaporation which allows the characterization of a single in situ fabricated $\mathrm{Nb}/{\left({\mathrm{Bi}}_{0.15}{\mathrm{Sb}}_{0.85}\right)}_2{\mathrm{Te}}_3$ nanointerface. The resulting high interface transparency is apparent by a zero bias conductance increase by a factor of 1.7. Furthermore, we present a comprehensive differential conductance analysis of our single in situ interface for various magnetic fields, temperatures, and gate voltages. Additionally, density functional theory calculations of the superconductor/topological insulator interface are performed in order to explain the peaklike shape of our differential conductance spectra and the origin of the observed smearing of conductance features.

• Received 10 January 2024
• Revised 16 February 2024
• Accepted 28 February 2024

DOI:https://doi.org/10.1103/PhysRevMaterials.8.034205