Researchers at the US National Institute of Standards and Technology (Nist) have demonstrated a technique that could pave the way for bulk manufacture of nanowires for atomic-scale electronics devices.

The team has selectively grown nanowires on sapphire wafers in specific positions and orientations accurately enough to attach contacts and layer other circuit elements, all with conventional lithography techniques.

Researchers have used wires just tens of nanometres wide to create transistors similar to those used in memory devices, as well as prototype sensors for gases or biomolecules.

Previous methods of producing such materials have not been suitable for mass production.

But building on earlier work to grow nanowires horizontally on the surface of wafers, 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 form nano-droplets that act as nucleation points for crystals of zinc oxide, a semiconductor.

"A slight mismatch in the crystal structures of zinc oxide and sapphire induces the semiconductor to grow as a narrow nanowire in one particular direction across the wafer," said the researchers.

"Because the starting points and the growth direction are both well known, it is relatively straightforward to add electrical contacts and other features with additional lithography steps."

As a proof of concept, the Nist researchers have used this procedure to create more than 600 nanowire-based transistors, a circuit element commonly used in digital memory chips, in a single process.