Wednesday, March 04, 2009

US Patent 7498215 - Fabrication of silicon nanowire sheets

There are two primary methodologies used to incorporate silicon nanowires into electronics -
1) growing the nanowires directly on the substrate (usually requiring high temperature processing that limit the choice of substrate) or 2) prefabricating the silicon nanowires and depositing the nanowires in a solution on the substrate using a printing or coating method (usually requiring an additional step for orienting the nanowires during or after deposition). This patent from Canon teaches a third alternative based on the fabrication of aligned silicon nanowire monolayers in a technique similar to Langmuir-Blodgett deposition. Claim 1 reads:

1. A method of producing a product including silicon wires, comprising:

dispersing the silicon wires, which are covered with a hydrophobic insulating polymer solution, in a solvent having a polarity opposite to that of the silicon wires;

arranging longitudinal directions of the silicon wires so that each one of the silicon wires is positioned end to end to one another;

fixing the silicon wires whose longitudinal directions are arranged end to end to one another by using one of a crosslinking reaction and a polymerization reaction of the polymer, and collecting the silicon wires fixed in accordance with said fixing step by forming one of a silicon wire monolayer sheet and a silicon wire monolayer ribbon on a substrate.