Figure 4.

a) Illustration of WTe₂ /MoTe₂ growth modes via CVD system. b) Side and top views of the crystal structure of 1T′ W(Mo)Te₂, respectively. c) Optical image of a large single crystalline WTe₂ monolayer. d) WTe₂ monolayer film and an optical image of a large bilayer WTe₂ with grain boundary, highlighting the location of the grain boundary. e) Optical image of a single crystalline MoTe₂ monolayer, with the length and width of 150 and 8 µm, respectively. f) Optical image of a MoTe₂ flake containing 1L, 2L, and 3L MoTe₂. The number of layer can be easily identified by their contrast. g) Scanning transmission electron microscopy (STEM) Z‐contrast image of a monolayer WTe₂. The coordinate and structural model are overlaid on the image. Insets: Fast Fourier‐transform (FFT) pattern and simulated STEM image of the monolayer WTe₂. h) Line intensity profile file of the region highlighted by red rectangle in panel (g). i) STEM Z‐contrast image of an atomically sharp stacking boundary between the 2H (left) and 2H′ (right) stacking. j) The structural model is optimized by DFT calculations. Reproduced with permission.146