Nanotechnology Now

While some researchers try to figure out how to create really tiny electrical devices, others take on the practical task of figuring out how to make wires small enough to connect them up to silicon chips with. Penn State University has figured a way of not only making very fine wires, but of spacing them out regularly while they're at it. "We have known how to make smaller and smaller structures by using techniques that have been developed for the fabrication of computer chips, and we also have known how to make molecules bigger and bigger," says Paul Weiss, associate professor of chemistry at Penn State. "But that intermediate region between the two approaches has been essentially inaccessible, and our technique of using 'molecular rulers' represents a step toward bridging that gap."

The way they make these rulers is a bit tricky to get your head around, so I've made this picture. It starts off with a trick called "electron beam lithography," which is basically etching things with a very fine beam of electrons. It's not practical to etch thick wires with this trick, but a strip (1) of the base material can be 'seeded' by it. A layer of unpleasant organic stuff (2) called mercaptoalkanoic acid grows on the seed, spreading out like an ANZAC biscuit on a baking sheet. They know how fast it spreads, so they know how much of the base it has covered. Finally, gold (3) is used to fill in the gaps, and the gold nanowires are complete. The bigger the biscuit, the thinner the wires.

The wires in the picture are 15 nanometers wide, or roughly 70,000 to the millimeter. So that's not a lot of gold. The next trick is to figure out how to move the other end around and stick it to the right place on a silicon chip, but they're working on that in other places.