Versatile Large-Area Custom-Feature van der Waals Epitaxy of Topological Insulators

TL;DR

This paper introduces a versatile van der Waals epitaxy method for growing large-area, high-quality topological insulator films with custom features, enabling scalable device integration and improved electronic properties.

Contribution

The study presents a novel, adaptable vdWE process for custom-feature TI growth on mica, with detailed surface migration modeling and demonstration of high electronic quality.

Findings

Epitaxial growth of large single-crystal TI domains with controlled orientations.

Topological surface states contribute significantly to room-temperature conductance.

The process allows for arbitrary shape and array fabrication of TIs.

Abstract

As the focus of applied research in topological insulators (TI) evolves, the need to synthesize large-area TI films for practical device applications takes center stage. However, constructing scalable and adaptable processes for high-quality TI compounds remains a challenge. To this end, a versatile van der Waals epitaxy (vdWE) process for custom-feature Bismuth Telluro-Sulfide TI growth and fabrication is presented, achieved through selective-area fluorination and modification of surface free-energy on mica. The TI features grow epitaxially in large single-crystal trigonal domains, exhibiting armchair or zigzag crystalline edges highly oriented with the underlying mica lattice and only two preferred domain orientations mirrored at $180^\circ$. As-grown feature thickness dependence on lateral dimensions and denuded zones at boundaries are observed, as explained by a semi-empirical two-species surface migration model with robust estimates of growth parameters and elucidating the role of selective-area surface modification. Topological surface states contribute up to 60% of device conductance at room-temperature, indicating excellent electronic quality. High-yield microfabrication and the adaptable vdWE growth mechanism with readily alterable precursor and substrate combinations, lend the process versatility to realize crystalline TI synthesis in arbitrary shapes and arrays suitable for facile integration with processes ranging from rapid prototyping to scalable manufacturing.