Monday, August 14, 2006

US Patent 7087920 - Conductively Switchable Nanowire

http://www.freepatentsonline.com/7087920.pdf

An emerging area which may be less familar then nanotechnology, but which may have more near term economic impact, is morphware, otherwise referred to as reconfigurable electronics. Traditionally electronics has been divided into hardware, which refers to the physical electrical components such as specific logical or analog circuits, and software, which refers to the instructions in the form of binary patterns to be carried out by the hardware. However, the emergence of materials whose conductivity/resistance can be programmed allows for not just the software to be altered but for the actual electronic hardware to be adjusted and adaptable to different conditions. As an example, using "morphware" technology a circuit originally configured as an FM radio receiver can change into a circuit for a cell phone at a push of a button. Also there is the potential for circuit optimization under different conditions (temperature, frequency of use, etc.) and to learn user preferences in the same way a device such as TIVO learns to anticipates a user's prefered television programs. Currently the Dept. of Defense (specifically DARPA) is investing in the development of this technology, but private enterprise such as Hewlett Packard is also making some practical headway.

This patent from HP uses a doped nanowire with conductivity selectively programmable in accordance with temperature to configure a circuit. Claim 1 reads:

1. A nanowire comprising: a single crystalline semiconductor material having an exterior surface and an interior region; and one or more dopant atoms, wherein at least a portion of the nanowire thermally switches between two conductance states, the two conductance states being a high conductance state and a low conductance state, and wherein in the high conductance state, a first fraction of the dopant atoms are in the interior region and a second fraction of the dopant atoms are at the exterior surface, and wherein in the low conductance state, a third fraction of the dopant atoms are in the interior region and a fourth fraction of the dopant atoms are at the exterior surface, the first fraction being greater than the third fraction and the second fraction being less than the fourth fraction.