Layer-by-layer epitaxial growth of scalable WSe2 on sapphire by molecular-beam epitaxy

TL;DR

This paper demonstrates a novel layer-by-layer epitaxial growth method for scalable WSe2 thin films on sapphire using molecular-beam epitaxy, enabling high-quality 2D material fabrication on insulating substrates.

Contribution

It introduces a new MBE growth protocol for 2D TMDCs on insulators, advancing the fabrication of van der Waals heterostructures with potential for novel properties.

Findings

Successful epitaxial growth of WSe2 on sapphire

Demonstration of ambipolar transistor operation

Broad applicability to other TMDCs

Abstract

Molecular-beam epitaxy (MBE) provides a simple but powerful way to synthesize large-area high-quality thin films and heterostructures of a wide variety of materials including accomplished group III-V and II-VI semiconductors as well as newly-developing oxides and chalcogenides, leading to major discoveries in condensed-matter physics. For two-dimensional (2D) materials, however, main fabrication routes have been mechanical exfoliation and chemical-vapor deposition by making good use of weak van der Waals bonding nature between neighboring layers, and MBE growth of 2D materials, in particular on insulating substrates for transport measurements, has been limited despite its fundamental importance for future advanced research. Here we report layer-by-layer epitaxial growth of scalable transition-metal dichalocogenide (TMDC) thin films on insulating substrates by MBE, and demonstrate ambipolar transistor operation. The proposed growth protocol is broadly applicable to other TMDC, providing a key milestone toward fabrication of van der Waals heterostructures with various 2D materials for novel properties and functionalities.