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

TL;DR

This paper presents an in situ multi-angle stencil lithography method for fabricating clean superconductor-topological insulator nanostructures, enabling exploration of proximity-induced superconductivity with high control.

Contribution

The authors introduce a novel in situ fabrication technique combining selective growth and angle-controlled deposition for hybrid TI-superconductor devices.

Findings

Demonstrated robust Coulomb blockade in fabricated islands

Observed suppression of low-energy conductance with magnetic field

Established a scalable platform for TI-based hybrid quantum devices

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.