Engineering the structural and electronic phases of MoTe2 through W substitution

TL;DR

This study demonstrates how W substitution in MoTe2 can control its structural phases, enabling the engineering of its electronic properties for potential optoelectronic and topological applications.

Contribution

It reveals the phase diagram of Mo$_{1-x}$W$_x$Te$_2$ and shows that W doping stabilizes the $T_d$-phase at room temperature, combining semiconducting and topological features.

Findings

Only ~8% W stabilizes the $T_d$-phase at room temperature.

The $T_d$-phase has a Fermi surface similar to WTe$_2$.

Phase transition from semiconducting to semimetallic occurs with W doping.

Abstract

MoTe$_2$ is an exfoliable transition metal dichalcogenide (TMD) which crystallizes in three symmetries, the semiconducting trigonal-prismatic $2H-$phase, the semimetallic $1T^{\prime}$ monoclinic phase, and the semimetallic orthorhombic $T_d$ structure. The $2H-$phase displays a band gap of $\sim 1$ eV making it appealing for flexible and transparent optoelectronics. The $T_d-$phase is predicted to possess unique topological properties which might lead to topologically protected non-dissipative transport channels. Recently, it was argued that it is possible to locally induce phase-transformations in TMDs, through chemical doping, local heating, or electric-field to achieve ohmic contacts or to induce useful functionalities such as electronic phase-change memory elements. The combination of semiconducting and topological elements based upon the same compound, might produce a new generation of high performance, low dissipation optoelectronic elements. Here, we show that it is possible to engineer the phases of MoTe$_2$ through W substitution by unveiling the phase-diagram of the Mo$_{1-x}$W$_x$Te$_2$ solid solution which displays a semiconducting to semimetallic transition as a function of $x$. We find that only $\sim 8$ \% of W stabilizes the $T_d-$phase at room temperature. Photoemission spectroscopy, indicates that this phase possesses a Fermi surface akin to that of WTe$_2$.