Multilevel Memory Based on Nanowire / Molecule Heterostructures
C. Li, B. Lei, W. Fan, M. Meyyapan, J. Han and C. Zhou
University of Southern California, US
multilevel memory, nonvolatile, In2O3 nanowire
We have been working on building high-performance nanoscale memory devices. Our work has directly addressed the above-mentioned difficulties by exploiting a novel devices structure: nanowire field effect transistors with self-assembled redox molecules. This approach combines the charge storage properties of molecules with the charge sensing capability of nanowires. We have constructed the first multilevel molecular memory by coating In2O3 nanowire FETs with a self-assembled monolayer of Fe2+-terpyridine compound. This bottom-up process takes advantage of both the nanowire and the redox-active molecules, as discrete multilevels naturally exist in an ensemble of redox-active molecules, while precise charge sensing can be carried out with a semiconducting nanowire transistor. In the demonstration, charges were precisely placed at up to eight discrete levels by altering the population of reduced / oxidized molecules. Gate voltage pulses and current sensing were used for writing and reading operations, respectively. More importantly, these devices exhibited ultralong retention up to 600 hours and great reliability. Our approach solved the long-standing reliability issue by moving molecules outside the conduction path, and multilevel memory represents a conceptual breakthrough for molecular devices.
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Nanotech 2005 Conference Program Abstract