Memcapacitors are emerging as an attractive candidate for high-density information storage due to their multilevel and adjustable capacitances and long-term retention without a power supply. However, knowledge of their memcapacitive mechanism remains unclear and accounts for the limited implementation of memcapacitors for multilevel memory technologies. Here, repeatable and reproducible quaternary memories fabricated from hybrid perovskite (CH3 NH3 SnBr3 ) memcapacitors are reported. The device can be modulated to at least four capacitive states ranging from 0 to 169 pF with retention for 104 s. Impressively, an effective device yield approaching 100% for quaternary memory switching is achieved by a batch of devices; each state has a sufficiently narrow distribution that can be distinguished from the others and is superior to most multilevel memories that have a low device yield as well as an overlapping distribution of states. The memcapacitive switching stems from the modulated p-i-n junction capacitance triggered by Br- migration, as demonstrated by in situ element mapping, X-ray photoelectron spectra, and frequency-dependent capacitance measurements; this mechanism is different from the widely reported memristive switching involving filamentary conduction. The results provide a new way to produce high-density information storage through memcapacitors.
Keywords: MASnBr3; lead-free hybrid perovskites; memcapacitors; multilevel information storage; quaternary memory.
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