Fig. 6: TR-MP-STM measurement results obtained at a grain boundary.
a STM image corresponding to the area shown in Fig. 3a and TR-MP-STM measurement results obtained over the surface for the delay times of 1, 10, 100, 500, 1000, and 1950 ps. 1950 ps is the limit of the delay time of our system used here. Here, the values in the image obtained for 1950 ps was subtracted from the other images. The measurement conditions were Vs = −3 V, Iset = 10 pA, fluence 13 μJ/cm2 and center wavelength 633 nm, and the excitation energy was adjusted to the peak of the exciton resonance spectrum of WS2. b TR-MP-STM spectra obtained in the white square shown in a. x indicates the distance from the boundary. The 56 spectra for each x were averaged. Lifetimes obtained by fitting are shown in each figure. c Lifetime as a function of x. As can be seen in Fig. 3a, Id was measured when the probe was in the area to the right of the right GB edge. Therefore, to reduce the influence of the structures in GB, this measurement was performed on the right side of the GB edge. The error bars in b are the standard deviation of the 56-point values in the y direction at each x point in the white square shown in a. The error bars in c are the fitting errors obtained in b.
