Fig. 2

Material imaging and crystal structure characterization. a Raman spectra of CVD monolayer (black line) and bilayer MoS₂ (magenta line). For monolayer one, the E_2g¹ peak is at 385.8 cm⁻¹ and the A_1g peak is at 404.7 cm⁻¹, corresponding to a delta of 18.9 cm⁻¹. For bilayer MoS₂, the E_2g¹ peak is at 384.8 cm⁻¹ and the A_1g peak is at 407.2 cm⁻¹, corresponding to a delta of 22.4 cm⁻¹. b, c Raman spectroscopy maps of the peaks at 385 cm⁻¹ and 405 cm⁻¹. Scale bars are both 20 μm. d Photoluminescence spectra of CVD monolayer (black line) and bilayer (magenta line) MoS₂. The peaks corresponding to the A1 and B1 direct excitonic transitions with the energy split from valence band spin–orbital coupling. e PL spectroscopy map of the peak at 1.85 eV. Scale bar is 20 μm. f Low-resolution TEM image of the boundary between bilayer (right) and monolayer (left). Scale bar is 1 μm. g Typical SAED pattern image in the bilayer region in f. Scale bar is 5 nm⁻¹. h HRTEM image and atomic configuration of AA stacked bilayer MoS₂. Scale bar is 2 nm. i HRTEM image recorded from the folded edge of bilayer MoS_2. Scale bar is 5 nm