Fig. 4: Measurement of the defect density in TMDs using HRTEM.
From: Giant persistent photoconductivity in monolayer MoS2 field-effect transistors
60 kV chromatic (Cc) and spherical (Cs) aberration-corrected HRTEM images of CVD grown ML-MoS2 (a, b) and ML-WS2 (c, d). a shows the raw image of the ML-MoS2. The area within the white square is magnified in the lower left. A few red circles mark vacancies, which are difficult to see even in the magnified image. Thus, Fourier-filtering was applied to remove the frequencies of the MoS2 lattice, which is shown in (b). In b, the same area as in (a) is magnified. Due to the Fourier-filtering, the vacancies are better visible (black dots, surrounded by red circles). The same procedure was also applied for WS2 (c) raw image and (d) Fourier-filtered image). Due to the filtering, contaminations become also more visible outside the framed area, thus only clean areas were evaluated with certainty for the defect concentration. The scale bars in (a–d) is 5 nm. The scale bars in the inset of (a) and (b) is 1 nm.
