Hybrid superconductor-topological insulator (TI) nanostructures constitute a promising materials platform for exploring proximity-induced superconductivity in systems with topologically protected surface states. A key obstacle has been the realization of clean and well-controlled superconductor-TI interfaces, as TI surfaces rapidly degrade under ambient conditions. Here, we introduce a fully in situ, multi-angle stencil lithography technique that enables the fabrication of proximitized charge islands in TIs. The approach combines selective-area growth of (Bi,Sb)2Te3 nanoribbons with angle-controlled deposition of diffusion barriers, superconducting Al, and ultrathin oxide tunnel barriers, allowing scalable fabrication of hybrid nanostructures without post-growth processing. Low-temperature transport measurements reveal robust Coulomb blockade and a pronounced suppression of low-energy conductance which vanishes with magnetic field, consistent with proximity-induced superconductivity in the island. These results establish a versatile nanofabrication platform that enables access to previously unexplored TI-based hybrid quantum devices and opens new routes for investigating superconductivity in topological nanostructures.
@article{arxiv.2604.18736,
title = {Proximitized Topological Insulator Charge Island Fabricated via In Situ Multi-Angle Stencil Lithography},
author = {Benedikt Frohn and Tobias Schmitt and Vanessa Serrano and Anne Schmidt and Michael Schleenvoigt and Albert Hertel and Benjamin Bennemann and Abdur Rehman Jalil and Detlev Grützmacher and Peter Schüffelgen},
journal= {arXiv preprint arXiv:2604.18736},
year = {2026}
}