Growth, stabilization and conversion of semi-metallic and semiconducting phases of MoTe2 monolayer by molecular-beam epitaxy

TL;DR

This paper demonstrates the growth and phase control of monolayer MoTe2 using molecular-beam epitaxy, showing how growth conditions and surface adsorption influence the stabilization of different structural phases with potential applications in phase-change electronics.

Contribution

It introduces a method to grow and tune both 2H and 1T' phases of MoTe2 monolayers via MBE, highlighting the role of Te surface adsorption in phase stabilization.

Findings

Successful growth of 2H and 1T' MoTe2 monolayers by MBE

Structural domain tunability through growth conditions and annealing

Te surface adsorption stabilizes the metastable 1T' phase

Abstract

Monolayer (ML) transition-metal dichalcogenides exist in different phases, such as the hexagonal (2H) and distorted octahedral or monoclinic (1T') phases. The different structures show vastly different properties. For example, the 2H MoTe2 ML is a direct-gap semiconductor while 1T' MoTe2 is a semi-metal. It has been suggested that the formation energies between 2H and 1T' MoTe2 differ very little, so there is a high chance to tune the structures of MoTe2 and thereby to bring in new applications such as phase-change electronics. In this work, we report growth of both 2H and 1T' MoTe2 ML by molecular-beam epitaxy (MBE). We demonstrate the tunability of the structural domains in epitaxial MoTe2 by changing the growth conditions of MBE and by annealing. We present experimental and theoretical evidences showing the important role of Te surface adsorption in promoting and stabilizing the otherwise metastable 1T'-MoTe2 during MBE.