One pot chemical vapor deposition of high optical quality large area monolayer Janus transition metal dichalcogenides

TL;DR

This paper presents a one-pot chemical vapor deposition method to synthesize large-area, high-quality Janus monolayer transition metal dichalcogenides with asymmetric chalcogen layers, characterized by advanced spectroscopic techniques.

Contribution

It introduces a novel CVD process for creating Janus TMD monolayers with asymmetric layers, supported by experimental and theoretical analysis.

Findings

Successful synthesis of large-area Janus monolayers

High optical quality demonstrated by optical measurements

Strong exciton-phonon coupling observed

Abstract

We report one-pot chemical vapor deposition (CVD) growth of large-area Janus SeMoS monolayers, with the asymmetric top (Se) and bottom (S) chalcogen atomic planes with respect to the central transition metal (Mo) atoms. The formation of these two-dimensional semiconductor monolayers takes place upon the thermodynamic equilibrium-driven exchange of the bottom Se atoms of the initially grown MoSe2 single crystals on gold foils with S atoms. The growth process is characterized by complementary experimental techniques including Raman and X-ray photoelectron spectroscopy and the growth mechanisms are rationalized by first principle calculations. The remarkably high optical quality of the synthesized Janus monolayers is demonstrated by optical and magneto-optical measurements which reveal the strong exciton-phonon coupling and enable to obtain the exciton g-factor of -3.3.