$WSe_2$ Monolayers Grown by Molecular Beam Epitaxy on hBN

TL;DR

This paper presents a novel three-step MBE growth process for high-quality, optically uniform WSe2 monolayers on hBN, demonstrating improved optical properties and reproducibility over exfoliated samples, advancing TMD device fabrication.

Contribution

Developed a three-step MBE method for growing high-quality WSe2 monolayers on hBN with enhanced optical uniformity and reproducibility, surpassing traditional exfoliation techniques.

Findings

High optical uniformity of WSe2 monolayers achieved

Reproducible growth process established

Optical and structural properties comparable to exfoliated samples

Abstract

A three-step process was developed for growing high-quality, optically uniform WSe2 monolayers by molecular beam epitaxy (MBE) with advantage of using hexagonal boron nitride (hBN). The process was optimized to maximize the efficiency of photoluminescence and promote formation of hexagonal WSe2 domains. Atomic force microscopy (AFM) was employed to estimate the dispersion of WSe2 hexagonal domains orientation. Monolayer character of the film was identified using optical methods and verified with high-resolution transmission electron microscopy (TEM) cross-section. Temperature-and-magnetic-field-dependent studies revealed the behaviour of exciton complexes to be analogical to that of exfoliated counterparts. Direct growth on hBN combined with uniform optical response proves this WSe2 superior to mechanically exfoliated WSe2 in terms of convenience of use and reproducibility. Provided results establish a significant progress in optical quality of epitaxially grown transition metal dichalcogenides (TMDs) monolayers and fabrication of large-scale functional devices.