Optical Characterization of Undoped and Au-doped MoS2 Single Crystals

Single crystals of undoped and Au-doped MoS2 were grown by the chemical vapor transport method using iodine as a transporting agent. The doping effect of the Au was characterized by temperature-dependent piezoreflectance (PzR) spectroscopy measurements in broad range of temperatures from 25 to 300 K. The temperature dependent PzR spectra revealed prominent features in the vicinity of direct-band-edge excitons for both investigated samples. The energies and broadening parameters of the A and B excitons were determined via a detailed line shape fit of the PzR spectra. We observed that Au doping strongly reduces the splitting between A and B excitons as well as it causes the redshift of observed transitions in relation to the undoped MoS2. The origin of observed excitons was discussed.