High, Multiple, and Nonvolatile Polarizations in Organic–Inorganic Hybrid [(CH3)3(CH2CH2Cl)N]2InCl5·H2O for Memcapacitor

Dielectrics with high, nonvolatile, and multiple polarizations are required for fabricating memcapacitors that enable high parallelism and low energy consumption in artificial neuromorphic computing systems as artificial synapses. Conventional ferroelectric materials based on displacive and order-disorder types generally have difficulty meeting these requirements due to their low polarization values (∼150 μC/cm²) and persistent electrical hysteresis loops. In this study, we report a novel organic-inorganic hybrid (CETM)₂InCl₅·H₂O (CETM = (CH₃)₃(CH₂CH₂Cl)N) exhibiting an intriguing polarization vs electric field (charge vs voltage) "hysteresis loop" and a record-high nonvolatile polarization over 30 000 μC/cm² at room temperature. The polarization is highly dependent on the period and amplitude of the ac voltage, showing multiple nonvolatile states. Electrochemical impedance spectroscopy, time-dependent current behavior, disparate resistor response in the dehydrated derivative (CETM)₂InCl₅, and the negative temperature dependence of ionic conductance support that the memcapacitor behavior of (CETM)₂InCl₅·H₂O stems from irreversible long-range migration of protons. First-principles calculations further confirm this and clarify the microscale mechanism of anisotropic polarization response. Our findings may open up a new avenue for developing memcapacitors by harnessing the benefits of ion migration in organic-inorganic hybrids.