In the growing catalog of nanoscale technologies, nanowirestiny rows of conductor or semiconductor atomshave attracted a great deal of interest for their potential to build unique atomic-scale electronics. But before you can buy some at your local Nano Depot, manufacturers will need efficient, reliable methods to build them in quantity. Researchers at the National Institute of Standards and Technology (NIST) believe they have one solutiona technique that allows them to selectively grow nanowires on sapphire wafers in specific positions and orientations accurately enough to attach contacts and layer other circuit elements, all with conventional lithography techniques. They detailed their results in a recent paper.*
Despite their name, nanowires are more than just electrical connectors. Researchers have used nanowires to create transistors like those used in memory devices and prototype sensors for gases or biomolecules. However working with objects only tens of nanometers wide is challenging. A common approach in the lab is to grow nanowires like blades of grass on a suitable substrate, mow them off and mix them in a fluid to transfer them to a test surface, using some method to give them a preferred orientation. When the carrier fluid dries, the nanowires are left behind like tumbled jackstraws. Using scanning probe microscopy or similar tools, researchers hunt around for a convenient, isolated nanowire to work on, or place electrical contacts without knowing the exact positions of the nanowires. Its not a technique suitable for mass production.
Building on earlier work to grow nanowires horizontally on the surface of wafers (see Gold Nano Anchors Put Nanowires in Their Place), NIST researchers used conventional semiconductor manufacturing techniques to deposit small amounts of gold in precise locations on a sapphire wafer. In a high-temperature process, the gold deposits bead up into nanodroplets that act as nucleation points
|Contact: Michael Baum|
National Institute of Standards and Technology (NIST)