Modulating Electronic Structure of Monolayer Transition Metal Dichalcogenides by Substitutional Nb-Doping

TL;DR

This study demonstrates in-situ Nb doping of monolayer WS2 during chemical vapor deposition, effectively tuning its electronic properties, inducing p-type behavior, and enhancing electrocatalytic hydrogen evolution performance.

Contribution

It introduces a controlled in-situ Nb doping method for TMDCs, enabling tunable electronic structures and improved catalytic activity.

Findings

Nb doping changes WS2 bandgap from 1.98 eV to 1.65 eV

Doping induces n to p-type conversion in WS2

Enhanced hydrogen evolution performance due to reduced energy barrier

Abstract

Modulating electronic structure of monolayer transition metal dichalcogenides (TMDCs) is important for many applications and doping is an effective way towards this goal, yet is challenging to control. Here we report the in-situ substitutional doping of niobium (Nb) into TMDCs with tunable concentrations during chemical vapour deposition. Taking monolayer WS2 as an example, doping Nb into its lattice leads to bandgap changes in the range 1.98 eV to 1.65 eV. Noteworthy, electrical transport measurements and density functional theory calculations show that the 4d electron orbitals of the Nb dopants contribute to the density of states of Nb-doped WS2 around the Fermi level, resulting in an n to p-type conversion. Nb-doping also reduces the energy barrier of hydrogen absorption in WS2, leading to an improved electrocatalytic hydrogen evolution performance. These results highlight the effectiveness of controlled doping in modulating the electronic structure of TMDCs and their use in electronic related applications.