Optical properties of molybdenum disulfide on different substrates affected by spin-orbit coupling

Molybdenum disulfide (MoS2) films have been widely used in many optical devices owing to their excellent optical properties. In this paper, inch-scale MoS2 films were grown on sapphire substrates through chemical vapor deposition (CVD) and transferred to SiO2/Si substrates. Analysis of Raman spectroscopy shows the transfer process releases uniaxial stress and introduces weak n-type doping. Using spectroscopic ellipsometry to analyze the refractive index, extinction coefficient and the dielectric function of monolayer MoS2 on sapphire substrates and SiO2/Si substrates, the electron transition energies were calculated on this basis. Combined with the first principle calculation based on density functional theory (DFT), the physical origins of electron transition peak were obtained. Computational and experimental tests show that monolayer MoS2 on sapphire substrates show spin-orbit coupling phenomena, which leads to the splitting of an electron-jumping peak, while MoS2 on SiO2/Si substrates did not exhibit spin-orbit coupling. This work can provide a reference for the application of MoS2 on different substrates.