Second-order resonant Raman scattering in single-layer tungsten disulfide WS2

Resonant Raman spectra of single-layerWS(2) flakes are presented. A second-order Raman peak (2LA) appears under resonant excitation with a separation from the E-2g(1) mode of only 4 cm(-1). Depending on the intensity ratio and the respective linewidths of these two peaks, any analysis that neglects the presence of the 2LA mode can lead to an inaccurate estimation of the position of the E-2g(1) mode, leading to a potentially incorrect assignment for the number of layers. Our results show that the intensity of the 2LA mode strongly depends on the angle between the linear polarization of the excitation and detection, a parameter that is neglected in many Raman studies.