Piezoreflectance Study of Band-Edge Excitons of ReS2:Au

The optical properties of Au-doped rhenium disulphide (ReS 2 :Au) have been investigated by temperature- and polarization-dependent piezoreflectance (PzR) measurements. In comparison with the undoped ReS 2 , ReS 2 :Au shows not only the main excitonic transitions of E 1 ex , E 2 ex , E 3 ex , and E 4 ex near the direct band edge but also two extra transitions E A ex and E B ex owing to the doping effects. From temperature-dependent 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 ReS 2 :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.