Strong In-plane Anisotropy in the Electronic Properties of Doped Transition Metal Dichalcogenides exhibited in W1-xNbxS2

TL;DR

This study reveals significant in-plane anisotropy in the electronic properties of Nb-doped WS2 monolayers, driven by dopant distribution and growth kinetics, affecting conductivity and mobility.

Contribution

It demonstrates the origin of anisotropic electronic behavior in doped transition metal dichalcogenides through combined microscopy and theoretical modeling.

Findings

High anisotropy in conductivity and mobility observed

Dopant distribution influences electronic anisotropy

Growth kinetics contribute to symmetry-breaking

Abstract

In this work, we study the electronic properties of monolayer transition metal dichalcogenide materials subjected to aliovalent doping, using Nb-doped WS2 as an exemplar. Scanning transmission electron microscopy imaging of the as-grown samples reveals an anisotropic Nb dopant distribution, prompting our investigation of anisotropy in electronic properties. Through electronic structure calculations on supercells representative of observed structures, we confirm that local Nb-atom distributions are consistent with energetic considerations, although kinetic processes occurring during sample growth must be invoked to explain the overall symmetry-breaking. We perform effective bandstructure and conductivity calculations on realistic models of the material that demonstrate that a high level of anisotropy can be expected in electronic properties including conductivity and mobility.