High-throughput characterization of transition metal dichalcogenide alloys: Thermodynamic stability and electronic band alignment

TL;DR

This paper uses first principles calculations to analyze the thermodynamic stability and electronic properties of 72 transition metal dichalcogenide alloys, revealing phase behavior and tunable band edges.

Contribution

It provides a comprehensive thermodynamic and electronic characterization of TMD alloys, including phase diagrams and band alignment, which was previously incomplete.

Findings

Ordered phases are generally absent at room temperature.

Some alloys exhibit stable Janus phases at room temperature.

Band edge positions can be continuously tuned through alloying.

Abstract

Alloying offers a way to tune many of the properties of the transition metal dichalcogenide (TMD) monolayers. While these systems in many cases have been thoroughly investigated previously, the fundamental understanding of critical temperatures, phase diagrams and band edge alignment is still incomplete. Based on first principles calculations and alloy cluster expansions we compute the phase diagrams 72 TMD monolayer alloys and classify the mixing behavior. We show that ordered phases in general are absent at room temperature but that there exists some alloys, which have a stable Janus phase at room temperature. Furthermore, for a subset of these alloys, we quantify the band edge bowing and show that the band edge positions for the mixing alloys can be continuously tuned in the range set by the boundary phases.