Ionic Control over Ferroelectricity in 2D Layered van der Waals Capacitors

Journal Article · 04 January 2022 · ACS Applied Materials and Interfaces

DOI: https://doi.org/10.1021/acsami.1c18683 · OSTI ID:1841505

Neumayer, Sabine  ^[1]; Si, Mengwei ^[2]; Li, Junkang ^[2]; Liao, Pai-Ying ^[2]; Tao, Lei ^[3]; O'Hara, Andrew ^[3]; Pantelides, Sokrates T. ^[3]; Ye, Peide ^[2]; Maksymovych, Petro  ^[1]; Wisinger, Nina Balke  ^[4]

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1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
2. Purdue Univ., West Lafayette, IN (United States)
3. Vanderbilt Univ., Nashville, TN (United States)
4. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); North Carolina State Univ., Raleigh, NC (United States)

The van der Waals layered material CuInP₂S₆ features interesting functional behavior, including the existence of four uniaxial polarization states, polarization reversal against the electric field through Cu ion migration, a negative-capacitance regime, and reversible extraction of Cu ions. At the heart of these characteristics lies the high mobility of Cu ions, which also determines the spontaneous polarization. Therefore, Cu migration across the lattice results in unusual ferroelectric behavior. Here, we demonstrate how the interplay of polar and ionic properties provides a path to ionically controlled ferroelectric behavior, achieved by applying selected DC voltage pulses and subsequently probing ferroelectric switching during fast triangular voltage sweeps. Using current measurements and theoretical calculations, we observe that increasing DC pulse duration results in higher ionic currents, the buildup of an internal electric field that shifts polarization loops, and an increase in total switchable polarization by ~50% due to the existence of a high polarization phase which is stabilized by the internal electric field. Apart from tuning ferroelectric behavior by selected square pulses, hysteretic polarization switching can even be entirely deactivated and reactivated, resulting in three-state systems where polarization switching is either inhibited or can be performed in two different directions.

• Research Organization: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES). Materials Sciences & Engineering Division
• Grant/Contract Number: AC05-00OR22725; FG02-09ER46554
• OSTI ID: 1841505
• Journal Information: ACS Applied Materials and Interfaces, Journal Name: ACS Applied Materials and Interfaces Journal Issue: 2 Vol. 14; ISSN 1944-8244
• Publisher: American Chemical Society (ACS)Copyright Statement
• Country of Publication: United States
• Language: English