Large-area synthesis of continuous two-dimensional MoTexSe2-x alloy films by chemical vapor deposition

TL;DR

This paper reports a method for large-area synthesis of 2D MoTexSe2-x alloy films with controllable tellurium content, confirmed by Raman spectroscopy and DFT calculations, enabling potential optoelectronic applications.

Contribution

A modified alkali metal halides assisted chemical vapor deposition method for synthesizing large-scale 2H phase Te-based 2D TMDs alloys with controllable composition.

Findings

Millimeter-scale continuous alloy films achieved.

Raman spectra confirmed phase and composition changes.

Phonon confinement model explains vibrational mode shifts.

Abstract

Great achievements have been made in alloying of two-dimensional (2D) semiconducting transition metal dichalcogenides (TMDs), which can allow tunable band gaps for practical applications in optoelectronic devices. However, telluride-based TMDs alloys were less studied due to the difficulties of sample synthesis. Here, in this work we report the large-area synthesis of 2D MoTexSe2-x alloy films with controllable Te composition by a modified alkali metal halides assisted chemical vapor deposition method. The as-prepared films have millimeter-scale transverse size. Raman spectra experiments combining calculated Raman spectra and vibrational images obtained by density functional theory (DFT) confirmed the 2H-phase of the MoTexSe2-x alloys. The A1g mode of MoSe2 shows a significant downshift accompanied by asymmetric broadening to lower wavenumber with increasing value of x, while E12g mode seems unchanged, which were well explained by a phonon confinement model. Our work provides a simple method to synthesize large-scale 2H phase Te-based 2D TMDs alloys for their further applications.