University of Pittsburgh,
Keywords: nanoelectronics, monolayer electrolyte
Summary: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 in the monolayer electrolyte memory 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 a ~1.34 eV increase in the absolute value of the adsorption energy compared to vacuum. The threshold voltage shift between the two states corresponds to a change in charge density of ~ 2.5 × 1012 cm-2, and an on-off ratio exceeding 104 at a 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). Switching times down to 50 nanoseconds has been demonstrated. The data suggest that faster switching times and lower switching voltages could be feasible by top gating. The research is supported by the National Science Foundation (NSF, U.S.) under Grant No. ECCS-GOALI-1408425 and DMR-CAREER-1847808.