Substrate-induced interfacial interactions in MOCVD-grown monolayer MoSe2

Abstract

Transition metal dichalcogenides (TMDCs) have garnered considerable interest for next-generation optoelectronic applications. However, the atomically thin properties of TMDCs make them highly sensitive to the environment. Therefore, the substrate becomes a key ingredient that affects the film growth and properties. In this work, we investigate the interactions between metal organic chemical vapor deposition-grown monolayer MoSe2 and substrates by spectroscopic analyses and theoretical calculations. It is shown that, during the growth process, there is an ∼1% tensile strain between MoSe2 and the substrate owing to the thermal coefficient of expansion mismatch, which leads to a redshift of peak positions in both photoluminescence (PL) and Raman spectra. Furthermore, after transferring monolayer MoSe2 films to sapphire and SiO2/Si substrates, we found that the strong substrate-dependent charge transfer results in different ratios of various excitonic emission intensities by analyzing the temperature-dependent PL spectra and x-ray photoelectron spectroscopy. Our findings reveal strong surface-dependent interactions between TMDC films and their substrates that affect the growth and optical properties of the films, which shed light on the selection of substrates during atomically thin TMDC film growth.