Fig. 1. Controlled synthesis of AA- and AB′-stacked SnSe₂.

a Schematic illustration of the CVD setup for the phase control in SnSe₂. Optical images (b), Raman spectra (c), and SHG (d) of AA- and AB′- stacked SnSe₂ flakes, respectively. e Atomic models (top and side views) of AA- and AB′-stacked SnSe₂. Pink atoms represent Sn atoms, the orange atoms represent the upper-layer Se atoms bonded to Sn, and the yellow spheres represent the lower-layer Se atoms bonded to Sn. Scale bar: b 10 μm.