Dataset for Figure 1

Reflection contrast imaging of ferroelectric domains in few-layer 3R-MoS2. a. Optical micrograph of a 3R-MoS2 flake on Si/SiO2/hBN. Topographical steps and edges of the bottom hBN have been marked by white dotted lines. b. Surface potential map within the area enclosed by the black rectangle in a. Two domains, marked by ◦ and □, can be identified by the difference in contrast. c. Integrated intensity map of ΔR/R at the XA spectral region, i.e., from 1906 to 1918meV (gray bar in inset of panel d). d. Low-temperature reflectance contrast spectra from various spatial locations marked by symbols of corresponding color in c (black - 5L domain I, red - 5L domain II, and blue - 7L). Inset shows high-resolution spectra collected from domain I and II. e-f. Two crystal configurations of 5L 3R-MoS2 overlayed on layer-projected KVB and KCB band-edges. To first order, the band edge variation along Z and the degeneracies, highlighted for the XM-XM-MX-XM stacking by dotted lines, result from the ferroelectricity-induced electrostatic considerations (SI Fig. S12-13 for other configurations). Arrows represent polarization vectors at the interfaces.