Vanadium-Doped Molybdenum Disulfide Monolayers with Tunable Electronic and Magnetic Properties: Do Vanadium-Vacancy Pairs Matter?

TL;DR

This study investigates how sulfur vacancies and vanadium-vacancy pairs influence the magnetic and electronic properties of V-doped MoS2 monolayers, revealing defect engineering as a key to tuning 2D magnetic semiconductors.

Contribution

The paper combines microscopy, theoretical calculations, and device fabrication to elucidate the role of vacancies and dopant-vacancy pairs in magnetic ordering of V-doped MoS2 monolayers.

Findings

Sulfur vacancies and V-vacancy pairs significantly affect magnetic properties.

V-doping induces p-type behavior in MoS2 transistors.

Defect engineering can tune electronic and magnetic properties of 2D TMDs.

Abstract

Monolayers of molybdenum disulfide (MoS2) are the most studied two-dimensional (2D) transition-metal dichalcogenides (TMDs), due to its exceptional optical, electronic, and opto-electronic properties. Recent studies have shown the possibility of incorporating a small amount of magnetic transition metals (e.g., Fe, Co, Mn, V) into MoS2 to form a 2D dilute magnetic semiconductor (2D-DMS). However, the origin of the observed ferromagnetism has remained elusive, due to the presence of randomly generated sulfur vacancies during synthesis that can pair with magnetic dopants to form complex dopant-vacancy configurations altering the magnetic order induced by the dopants. By combining high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) imaging with first-principles density functional theory (DFT) calculations and magnetometry data, we demonstrate the critical effects of sulfur vacancies and their pairings with vanadium atoms on the magnetic ordering in V-doped MoS2 (V-MoS2) monolayers. Additionally, we fabricated a series of field effect transistors on these V-MoS2 monolayers and observed the emergence of p-type behavior as the vanadium concentration increased. Our study sheds light on the origin of ferromagnetism in V-MoS2 monolayers and provides a foundation for future research on defect engineering to tune the electronic and magnetic properties of atomically thin TMD-based DMSs.