Molecularly Thin Electrolyte for All Solid-State Nonvolatile Two-Dimensional Crystal Memory.
basic_science · Level V
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- Record sourced from PubMed, PMID 31661286.
- Also identified by DOI 10.1021/acs.nanolett.9b03792.
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Abstract
A molecularly thin electrolyte is developed to demonstrate a nonvolatile, solid-state, one-transistor (1T) memory based on an electric-double-layer (EDL) gated WSe<sub>2</sub> field-effect transistor (FET). The custom-designed monolayer electrolyte consists of cobalt crown ether phthalocyanine and lithium ions, which are positioned by field-effect at either the surface of the WSe<sub>2</sub> channel or an 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 enhanced trapping of Li<sup>+</sup> 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 × 10<sup>12</sup> cm<sup>-2</sup>, and an On/Off ratio exceeding 10<sup>4</sup> 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 h (max measured). When the write time approaches 1 ms, the On/Off ratio remains >10<sup>2</sup>, showing that the monolayer electrolyte-gated FET can respond on time scales similar to existing flash memory. The data suggest that faster switching times and lower switching voltages could be feasible by top gating.