Nano-Switch Memory Element (24054)
The invention is a switchable nano-electromechanical system (NEMS) for memory applications. Whereas current nano-switches of this type can “stick” irreversibly in the lower (closed position), the invention is stable in both switch positions – top and bottom. For this invention, a carbon nanotube (CNT) cantilever deflects under an applied voltage. When the CNT tip is very close to the base electrode, substantial tunneling current results. Due to the feedback resistor shown in the below figure, the voltage drops substantially, and the cantilever retracts upward – but only a bit. Due to hysteresis effects, it does not return to the upper position until voltage is shut off. Because contact is never really made between cantilever and electrode, the system is reversible. Current methods do not incorporate the feedback circuit, so the cantilever can crash into the base electrode with sticking as the result – an irreversible condition not suitable for a switch in a memory element.
STAGE OF DEVELOPMENT: Analysis shows that the invention has two well-defined stable equilibrium positions. For details, see C. Ke, and H. Espinosa, Applied Physics Letters, 85, 681 (2004). The inventors have since run in situ, SEM experiments, successfully verifying the bistability of the device (See C.Ke and H. Espinosa, In Situ Electron Microscopy Electromechanical Characterization of a Bistable NEMS Device, Small, 2006).
Horacio Espinosa, Changhong Ke
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