Proximitized Topological Insulator Charge Island Fabricated via In Situ Multi-Angle Stencil Lithography

Benedikt Frohn; Tobias Schmitt; Vanessa Serrano; Anne Schmidt; Michael Schleenvoigt; Albert Hertel; Benjamin Bennemann; Abdur Rehman Jalil; Detlev Grützmacher; Peter Schüffelgen

arXiv · 2604.18736

Proximitized Topological Insulator Charge Island Fabricated via In Situ Multi-Angle Stencil Lithography

Benedikt Frohn·Tobias Schmitt·Vanessa Serrano·Anne Schmidt·Michael Schleenvoigt·Albert Hertel·Benjamin Bennemann·Abdur Rehman Jalil·Detlev Grützmacher·Peter Schüffelgen

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Abstract

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)$_2$Te$_3$ 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.

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Benedikt Frohn, Tobias Schmitt, Vanessa Serrano, Anne Schmidt, Michael Schleenvoigt, Albert Hertel, Benjamin Bennemann, Abdur Rehman Jalil, Detlev Grützmacher, Peter Schüffelgen. 2026-04-20. Proximitized Topological Insulator Charge Island Fabricated via In Situ Multi-Angle Stencil Lithography. https://arxiv.org/abs/2604.18736

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