Locally resolved influence of the dielectric environment on the ferroelectric domains in marginally twisted 2D semiconductors

Twisting transition metal dichalcogenide (TMD) layers in the limit of very small angles, relaxes the moiré lattice into areas of energetically favorable stacking, creating a regime of triangular domains with alternating stacking of metal atoms aligned over chalcogen (MX), and chalcogens aligned over metal atoms (XM). Broken inversion symmetry in these domains leads to vertical polarization. Here, we explore the question of how this spatially varying polarization is influenced by and influences a proximal electrostatic environment. We show Scanning Tunneling Microscopy/Spectroscopy (STM/S) on graphene placed on top of marginally twisted WSe₂. In addition, using Kelvin Probe Force Microscopy (KPFM) we study how polarization depends on the substrate on which the marginally twisted layers are placed.