(662g) Molecularly Thin All-Solid-State Non-Volatile Memory Gated By a Monolayer Electrolyte

A non-volatile, solid-state, one-transistor (1T) memory is demonstrated based on electric double layer (EDL) gating of a WSe₂ field-effect transistor (FET) using an electrolyte that is a single molecular layer thick. The “monolayer electrolyte” consists of cobalt crown ether phthalocyanine and lithium ions, which are positioned by field-effect at either the surface of the WSe₂ channel or a h-BN capping layer to achieve ‘1’ or ‘0’, respectively. Bistability is significantly improved by the h-BN cap, with density functional theory (DFT) calculations showing an enhanced trapping of Li⁺ near h-BN due to an adsorption energy increase of 1.345 eV compared to vacuum. The threshold voltage shift between the two states corresponds to a change in sheet carrier density of ~ 2.5 × 10¹² cm^-2, and an on-off ratio exceeding 10⁴ at the back gate voltage of 0 V. The on-off ratio remains stable after 1000 cycles and the retention time for each state exceeds 6 hours (max measured). When the write time approaches 1 ms, the on-off ratio remains > 10², showing that monolayer electrolyte-gated, 2D non-volatile FET can respond on timescales similar to existing flash memory. The data suggest that faster switching times, and lowing switching voltages will be achievable by top gating the device – work that is currently in progress.

This research is supported by the NSF under Grant No. ECCS-GOALI-1408425 and DMR-EPM(CAREER)- 1847808