3D Domain Arrangement in van der Waals Ferroelectric α‐In2Se3

AbstractOne of the exceptional features of the van der Waals (vdW) ferroelectrics is the existence of stable polarization at a level of atomically thin monolayers. This ability to withstand a detrimental effect of the depolarization fields gives rise to complex domain configurations characterized, among others, by the presence of layered “antipolar” head‐to‐head (H‐H) or tail‐to‐tail (T‐T) dipole arrangements. In this study, tomographic piezoresponse force microscopy (TPFM) is employed to study the 3D polarization arrangement in vdW ferroelectric α‐In2Se3. Sequential removal of thin layers from the polar surface using the PFM tip reveals a complex 3D profile of the domain walls in the α‐In2Se3 crystals. Antiparallel domain layers stacked along the polar direction are also observed by PFM imaging of the non‐polar surfaces showing that H‐H and T‐T domain boundaries are commonly present in α‐In2Se3. Application of TPFM to the electrically written domains allows evaluation of their geometrical lateral‐to‐vertical size aspect ratio, which shows a strong prevalence for the sidewise expansion in comparison to the forward growth. Local I–V measurements reveal a strong polarization direction dependence of conductivity due to the modulation of the energy barrier height as corroborated by theoretical modeling.