Magnetoexcitons in large area CVD-grown monolayerMoS2andMoSe2on sapphire

Magnetotransmission spectroscopy was employed to study the valley Zeeman effect in large area monolayer ${\mathrm{MoS}}_{2}$ and ${\mathrm{MoSe}}_{2}$. The extracted values of the valley $g$ factors for both A and B excitons were found to be similar with ${g}_{v}\ensuremath{\simeq}\ensuremath{-}4.5$. The samples are expected to be strained due to the CVD growth on sapphire at high temperature ($700{\phantom{\rule{0.16em}{0ex}}}^{\ensuremath{\circ}}\mathrm{C}$). However, the estimated strain, which is maximum at low temperature, is only $\ensuremath{\simeq}0.2%$. Theoretical considerations suggest that the strain is too small to significantly influence the electronic properties. This is confirmed by the measured value of the valley $g$ factor, and the measured temperature dependence of the band gap, which are almost identical for CVD and mechanically exfoliated ${\mathrm{MoS}}_{2}$.