Nanoscale Electromechanical and Conductive Properties of a Layered Two-Dimensional Hybrid Perovskite
Abstract
Two-dimensional (2D) organic–inorganic hybrid perovskites exhibit coupled ionic, electronic, and electromechanical responses that can strongly influence local charge transport. Here, solution-processed mixed-halide butylammonium lead perovskite crystals were mechanically exfoliated and investigated using X-ray diffraction, atomic force microscopy, piezoresponse force microscopy (PFM), and conductive atomic force microscopy (c-AFM). PFM measurements under −5, 0, and +5 V revealed clear bias-dependent changes in amplitude and phase, indicating an electric field-sensitive local electromechanical response. Local c-AFM measurements showed nonlinear bipolar hysteresis, with a pronounced increase in current near +7–8 V and a decrease near −7 to −6 V during the subsequent negative sweep. Because the crystals are mixed ionic–electronic conductors and the nanoscale tip–sample junction introduces substantial injection and contact barriers, the observed behavior is interpreted as resistive switching-like conductivity modulation, rather than definitive ferroelectric switching. The results are consistent with the combined contributions of charge injection, trap filling, possible ionic redistribution, and piezoelectricity-associated modulation of the local transport barrier. These findings provide nanoscale insight into electric field-dependent electromechanical and out-of-plane conductive behaviors in layered 2D hybrid perovskites.