Australian researchers have been able to place a single phosphorous atom with extreme accuracy inside a silicon crystal, making a working transistor and paving the way for advances in quantum computing.
The researchers, based at the University of New South Wales (UNSW) in Sydney, used a scanning tunneling microscope (STM) to create the tiny, fully functional electronic device.
Previously, scientists have created single-atom transistors by chance or a process of fine tuning, which have a margin of error of around 10 nanometers. This is the first time such a device has been created with perfect accuracy, say the researchers.
“If you want to make a practical computer in the long term, you need to be able to put lots of individual atoms in, and there you find that the separation between the atoms is quite critical, so you need to have atomic precision to do that,” said researcher Michelle Simmons in a UNSW video.
“Our group has proved that it is really possible to position one phosphorus atom in a silicon environment—exactly as we need it—with near-atomic precision, and at the same time register gates,” said study co-author Martin Fuechsle from UNSW in a press release.
These transistors could one day form the building blocks of a quantum computer.
In their paper, published online in Nature Nanotechnology on Feb. 19, the researchers describe how they used the STM to manipulate atoms at the surface of a silicon crystal in an ultra-high vacuum chamber to build the device.
Using a lithographic technique, phosphorous atoms were patterned onto the silicon crystal and coated with a layer of nonreactive hydrogen.
Hydrogen atoms were then selectively removed using the superfine metal tip of the STM, and the phosphorous atoms were combined with the silicon in a controlled chemical reaction. The structure was then coated with a layer of silicon.
An intricate system of tiny, visible markers was etched into the surface to allow the researchers to align metal contacts with the device and hook up an electricity supply.
The researchers found that the electronic properties of the transistor matched the theoretical predictions made by the team’s co-authors.
In order to keep pace with Moore’s Law—which describes a long-term trend in computing where the number of transistors that can be added to an integrated circuit doubles approximately every 18 months—subatomic transistors would need to be in use by 2020.
The development of this new single-atom transistor well ahead of schedule could therefore mean a huge leap in the capabilities of computers and digital devices may be possible much sooner than expected.