On the Stability and Electronic Structure of Transition-Metal Dichalcogenide Monolayer Alloys Mo1−xXxS2−ySey with X = W, Nb

Agnieszka Kuc,Thomas Heine

doi:10.3390/electronics5010001

On the Stability and Electronic Structure of Transition-Metal Dichalcogenide Monolayer Alloys Mo1−xXxS2−ySey with X = W, Nb

Agnieszka Kuc, Thomas Heine

Open Access

https://doi.org/10.3390/electronics5010001

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Journal: Electronics	Publication Date: Dec 30, 2015
Citations: 39	License type: CC BY 4.0

Affiliation: Leipzig University, Constructor University

Abstract

Layered transition-metal dichalcogenides have extraordinary electronic properties, which can be easily modified by various means. Here, we have investigated how the stability and electronic structure of MoS 2 monolayers is influenced by alloying, i.e., by substitution of the transition metal Mo by W and Nb and of the chalcogen S by Se. While W and Se incorporate into the MoS 2 matrix homogeneously, forming solid solutions, the incorporation of Nb is energetically unstable and results in phase separation. However, all three alloying atoms change the electronic band structure significantly. For example, a very small concentration of Nb atoms introduces localized metallic states, while Mo 1 - x W x S 2 and MoS 2 - y Se y alloys exhibit spin-splitting of the valence band of strength that is in between that of the pure materials. Moreover, small, but evident spin-splitting is introduced in the conduction band due to the symmetry breaking. Therefore, transition-metal dichalcogenide alloys are interesting candidates for optoelectronic and spintronic applications.

Highlights

The electronic structure of two-dimensional (2D) layered materials, in particular transition-metal chalcogenides (TMCs), have gained enormous interest in the past five years
Results on TMC nanotubes suggest that doping small quantities of Group 13 or Group 15 atoms results in a metallic character [16]; Nb doping of MoS2 tubes was found to be unfavorable energetically [17,18,19]
The incorporation of a dilute impurity concentration into a host material results in significant changes to the band structure, which was shown in the cases of III-V semiconductors, e.g., the As impurity in GaN leads to a significant band gap reduction, and such a GaNAs alloy can be used for green emission [20,21]

Summary

Introduction

The electronic structure of two-dimensional (2D) layered materials, in particular transition-metal chalcogenides (TMCs), have gained enormous interest in the past five years. Special attention is paid to semiconducting TMCs of the 2H TX2 type (T, transition metal; X, chalcogen atom), because their electronic properties can be tuned by various factors, such as quantum confinement, external electric field, strain modulations or doping [1,2,3,4,5,6,7,8,9,10,11]. The interest in spintronic applications of TMCs arises from the hexagonal symmetry and the finite band gap, which, depending on the stoichiometry and number of layers, is in the range of. Hexagonal symmetry of TMCs imposes the existence of inequivalent energy valleys in the Brillouin zone

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Conclusion