Piezoreflectance study of band-edge excitons of res2:au

The optical properties of Au-doped rhenium disulphide (ReS2:Au) have been investigated by temperature- and polarization-dependent piezoreflectance (PzR) measurements. In comparison with the undoped ReS2, ReS2:Au shows not only the main excitonic transitions of Eex 1, Eex 2, Eex 3, and Eex 4 near the direct band edge but also two extra transitions Eex A and Eex B owing to the doping effects. From temperaturedependent PzR spectra in the temperature range from 40 to 300 K, the least-squares fits are used to extract the parameters that describe the temperature variations of the band-edge excitonic transitions. The excitonic transitions show a strong polarization dependence in the near-infrared region. The polarization-dependent PzR measurement in the range between 0 and 180° was used to characterize the unique polarization property of ReS2:Au, and identify the origin of the excitonic transitions. However, the variation in the amplitude of PzR excitonic transitions with different polarization characteristics follows the Malus rule.