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Recent advances in the exploration of two-dimensional (2D) van der Waals (vdW) ferroelectrics revealed not only a wealth of fundamentally exciting properties but also a strong potential for nanoelectronic applications facilitated by their semiconducting nature and tunable polarization-coupled physical properties. Here, using scanning probe microscopy techniques, we investigate the effects of mechanical stress and optical illumination on the transport behavior of one of the most actively studied 2D ferroelectrics, α-In2Se3. Local I–V measurements reveal a strongly asymmetric polarization-dependent conductivity of α-In2Se3, which can be continuously tuned by the tip-induced mechanical pressure. While the local conductivity increases up to two orders of magnitude for both polarization states, the upward polarization displays a much sharper change. Further enhancement of conductivity by an order of magnitude is observed under optical illumination, resulting from a cumulative modulation of the junction barrier via polarization, strain, and optical excitation. The obtained results make α-In2Se3 a promising material for application in electronic devices with optomechanical functionality. 

Abstract One 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 ferroelectricα‐In₂Se₃. Sequential removal of thin layers from the polar surface using the PFM tip reveals a complex 3D profile of the domain walls in theα‐In₂Se₃crystals. 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 inα‐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. LocalI–Vmeasurements reveal a strong polarization direction dependence of conductivity due to the modulation of the energy barrier height as corroborated by theoretical modeling.