Magneto-excitons in large area CVD grown monolayer MoS$_{2}$ and MoSe$_{2}$ on sapphire

TL;DR

This study uses magneto transmission spectroscopy to analyze the valley Zeeman effect in large-area CVD-grown monolayer MoS₂ and MoSe₂ on sapphire, revealing similar g-factors to exfoliated samples and minimal strain effects.

Contribution

It demonstrates that CVD-grown monolayer MoS₂ and MoSe₂ on sapphire exhibit valley Zeeman effects comparable to exfoliated samples, with negligible strain influence on electronic properties.

Findings

Valley g-factors are approximately -4.5 for both materials.

Strain in CVD samples is minimal (~0.2%), not affecting electronic properties.

Temperature dependence of band gap matches that of exfoliated samples.

Abstract

Magneto transmission spectroscopy was employed to study the valley Zeeman effect in large-area monolayer MoS$_{2}$ and MoSe$_{2}$. The extracted values of the valley g-factors for both A- and B-exciton were found be similar with $g_v \simeq -4.5$. The samples are expected to be strained due to the CVD growth on sapphire at high temperature ($700^\circ$C). However, the estimated strain, which is maximum at low temperature, is only $\simeq 0.2\%$. Theoretical considerations suggest that the strain is too small to significantly influence the electronic properties. This is confirmed by the measured value of valley g-factor, and the measured temperature dependence of the band gap, which are almost identical for CVD and mechanically exfoliated MoS$_2$.