Switching devices used in electronic components such as memory chips and microprocessors preferably provide high density, non-volatile storage at high speed, low power consumption, and low cost. The use of nanotechnology has promised improvements in all of these areas. For example, WO 01/03208 describes the use of single-walled carbon nanotubes (SWNT) in crossbar junctions as memory devices. In a nanoscale crossbar memory device, a nanowire such as a SWNT is suspended over other nanowires at a junction. An electrical current in one or both nanowires causes either attraction or repulsion of the wires, resulting in the stable closing or opening of an electrical circuit. However, such devices are considered difficult to produce reliably and to use commercially, because of the problems inherent in using directed growth or chemical assembly of the nanowires at the scale required. In other proposed nanoscale switching devices, such as described in U.S. Pat. No. 6,919,592, sheets of nanoelements such as SWNT are used as actuation elements. With such devices, the ratio of the voltage required to switch to one state is on the order of six-fold higher than the voltage required to switch to the other state, adding significant complexity to the operation of such devices. Thus, there remains a need to develop nanoscale switching devices that are simple to construct and to operate, and that provide high density, low power non-volatile storage.
USPTO Backgrounds
USPTO Backgrounds