R. Padhan, P. Malik, R.R. Srivastava, A. Wali, M. Susner, R. Rao, D.K. Pradhan, R. Divan, D. Rosenmann, A.V. Sumant, N.R. Pradhan
Jackson State University,
United States
Keywords: 2D ferroelectricity, 2D materials, CuInP₂S₆, frequency enhanced PFM
Summary:
Van der Waals layered copper indium thiophosphate (CuInP2S6, CIPS) has emerged as a perfect 2D ferroelectric material; however, precise tuning of its polarization of ferroelectric domains remains challenging due to the dominant Cu-ion migration that often obscures ideal ferroelectric switching. For characterizing ferroelectric property of CIPS, We have used frequency enhanced PFM imaging technique to identify the ferroelectric domains at the surface of CIPS. PFM-amplitude and PFM-phase hysteresis loop further confirms the switching property of these domains at different thickness. We also present an contact-AFM based measurement integrated with a ferroelectric tester, enabling direct characterization of current–voltage, capacitance–voltage, polarization–electric field (P–E), and PUND signal. The experimental configuration employs a conductive AFM tip electrically coupled to an external ferroelectric measurement circuit. A few-layer graphene (FLG) flake is transferred onto the CIPS flake serving as the top electrode and Au-coated SiO2/Si substrate acts as the bottom contact. This approach enables reliable polarization detection in the presence of mobile Cu+ ions. The measured P–E hysteresis loops exhibit robust opening and frequency-tunable remanent polarization. At the same trend, the current-voltage measurement loops reveal the a dominant ferroelectric transition without resistive effect. Furthermore, the PUND signal confirm the intrinsic switchable ferroelectric domains within the exfoliated layers which are tunable as a function of pulse voltage and pulse width. These findings demonstrate an effective strategy to characterize intrinsic ferroelectric switching in 2D van der Waals systems, providing a versatile route for exploring and engineering nanoscale ferroelectric phenomena in several layered ferroelectric materials. Acknowledgement: Department of Defense U.S. Army Contracting Command, Award number: W911NF2510121 and Office of Basic Energy Sciences program under award number DE-SC0024072 and Airforce Research Laboratory, award # FA8650-20-2-5853