Fig. 1: Ferroelectric domains in marginally twisted bilayer MoS₂.

a, Example of BSECCI acquired on unencapsulated twisted bilayer MoS₂ placed onto a graphite substrate. Light and dark domain contrast corresponds to the two dominant stacking orders referred as Mo^tS^b and S^tMo^b. Scale bar, 1 μm. b, Centre: schematic demonstrating the transition from Mo^tS^b to S^tMo^b with perfectly stacked bilayer regions separated by a partial dislocation. Side panels: the cross-sectional alignment of the MoS₂ monolayers, viewed along the armchair direction, assembled within the double-gated device structure. Colour maps overlayed on top of the TMD atomic schematics show calculated charge density transferred between top and bottom layers, with red and blue corresponding to positive and negative charges, respectively. c–g, Domain switching visualized by BSECCI under different values of transverse electric field \(D/\varepsilon _0\) applied in situ. Measurements have been performed on marginally twisted MoS₂ encapsulated in hBN from both sides, placed on a graphite back gate and covered with graphene top gate as shown schematically in b. Large domains mostly retain their shape when the field is removed and practically disappear when the field is inverted; the arrows in e indicate partial dislocations colliding when neighbouring domains of the same orientation try to merge. Micrographs are presented in chronological order. The white oval feature in a and black ring features in c–g are where the intralayer contamination has segregated to form a bubble. Scale bars, 1 μm.