Quantum size effects in layered VX2 (X=S, Se, Te) materials: Manifestation of metal to semimetal or semiconductor transition

TL;DR

This study uses DFT calculations to explore how quantum size effects in layered VX2 materials cause transitions from metallic to semimetallic or semiconducting states when reducing from bilayer to monolayer, revealing phase-dependent properties.

Contribution

It provides the first detailed analysis of quantum size effects in VX2 materials, highlighting phase-dependent electronic and magnetic property changes upon layer reduction.

Findings

Quantum size effects induce metal to semimetal or semiconductor transitions.

Properties differ significantly between 2H and 1T phases.

Monolayer VX2 exhibits distinct electronic behavior from bilayer.

Abstract

Most of the 2D transition metal dichalcogenides (TMDC) are nonmagnetic in pristine form. However, 2D pristine VX2 (X=S, Se, Te) materials are found to be ferromagnetic. Using spin polarized density functional theory (DFT) calculations, we have studied the electronic, magnetic and surface properties of this class of materials in both trigonal prismatic 2H- and octahedral 1T-phase. Our calculations reveal that they exhibit materially different properties in those two polymorphs. Most importantly, detailed investigation of electronic structure explored the quantum size effect in 2H-phase of these materials thereby leading to metal to semimetal (2H-VS2) or semiconductor (2H-VSe2, 2H-VTe2) transition when downsizing from bilayer to corresponding monolayer.