Fig. 3: Characterizations of R-stacked bilayer WS2 single crystals.
From: Remote epitaxy of single-crystal rhombohedral WS2 bilayers
a Optical image of aligned bilayer WS2 islands. b Second harmonic generation (SHG) spectra of monolayer WS2, bilayer R-WS2 and bilayer H-WS2 samples. c SHG mapping of the as-grown WS2 samples in (a). d Optical image of the sapphire substrate, monolayer (1 L) WS2 and bilayer (2 L) WS2 samples. e Typical selected area electron diffraction (SAED) pattern of the bilayer WS2 samples. f Typical AFM image of the bilayer WS2 samples. g Atomically-resolved scanning transmission electron microscopy (STEM) image from the merged area of two aligned bilayer WS2 islands (namely, 2 L WS2-1 and 2 L WS2-2), showing that no boundary was formed. The dashed lines represent the edges of 2 L WS2-1 and 2 L WS2-2. The box labelled ‘A’ represents a merged area. h Atomically-resolved STEM image of the high-quality R-stacked bilayer WS2 lattice. The yellow and blue balls represent the W and S atoms, respectively.
