# MBE growth of 2H-MoTe2 and 1T'-MoTe2 on 3D substrates

## TL;DR

This study explores the molecular beam epitaxy growth of 2H and 1T' phases of MoTe2 on 3D substrates, analyzing phase boundaries, grain size, and stability to advance understanding of this less-explored material.

## Contribution

It demonstrates controlled MBE growth of MoTe2 phases, characterizes their structural properties, and investigates their stability and phase boundaries on different substrates.

## Key findings

- Successful MBE growth of 2H and 1T' MoTe2 phases.
- Identification of grain size and twinned grains via GI-XRD.
- Observation of excess Te incorporation affecting electrical properties.

## Abstract

MoTe2 is the least explored material in the Molybdenum-chalcogen family, which crystallizes in thermodynamically stable semiconducting 2H phase at \textless 500 C and 1T' metallic phase at higher temperatures. Molecular beam epitaxy (MBE) provides an unique opportunity to tackle the small electronegativity difference between Mo and Te while growing layer by layer away from thermodynamic equilibrium. For a few-layer MoTe2 grown at a moderate rate of $\sim$6 mins per monolayer under varied Te:Mo flux ratio and substrate temperature, the boundary between the 2 phases in MBE grown MoTe2 on CaF2 is characterized using Reflection high-energy electron diffraction (RHEED), Raman spectroscopy and X-ray photoemission spectroscopy (XPS). Grazing incidence X-ray diffraction (GI-XRD) reveals a grain size of $\sim$90 {\AA} and presence of twinned grains. XRD, transmission electron miscroscopy, RHEED, low energy electron diffraction along with lack of electrical conductivity modulation by field effect in MBE 2H-MoTe2 on GaAs (111) B show likelihood of excess Te incorporation in the films. Finally, thermal stability and air sensitivity of MBE 2H-MoTe2 is investigated by temperature dependent XRD and XPS, respectively.