Electronic structure of molecular beam epitaxy grown 1T$^\prime$-MoTe$_2$ film and strain effect

TL;DR

This study investigates the electronic properties of MBE-grown 1T' MoTe2 films, revealing metallic behavior and suggesting strain engineering as a pathway to induce topological insulating states for quantum spin Hall effect realization.

Contribution

First experimental characterization of MBE-grown 1T'-MoTe2 electronic structure and analysis of strain effects for topological phase transition.

Findings

MBE growth depends critically on substrate temperature.

The as-grown film exhibits metallic behavior with band overlap.

Strain engineering can induce a band gap for topological insulating states.

Abstract

Atomically thin transition metal dichalcogenide films with distorted trigonal (1T$^\prime$) phase have been predicted to be candidates for realizing quantum spin Hall effect. Growth of 1T$^\prime$ film and experimental investigation of its electronic structure are critical. Here we report the electronic structure of 1T$^\prime$-MoTe$_2$ films grown by molecular beam epitaxy (MBE). Growth of the 1T$^\prime$-MoTe$_2$ film depends critically on the substrate temperature, and successful growth of the film is indicated by streaky stripes in the reflection high energy electron diffraction and sharp diffraction spots in low energy electron diffraction. Angle-resolved photoemission spectroscopy measurements reveal a metallic behavior in the as-grown film with an overlap between the conduction and valence bands. First principles calculation suggests that a suitable tensile strain along the a-axis direction is needed to induce a gap to make it an insulator. Our work not only reports the electronic structure of MBE grown 1T$^\prime$-MoTe$_2$ films, but also provides insights for strain engineering to make it possible for quantum spin Hall effect.