The smallest transistor has been created using a single phosphorus atom
by an international team of researchers at the University of New South Wales,
Purdue University and the University of Melbourne.
Michelle Simmons, group leader and director of the ARC Centre for
Quantum Computation and Communication at the University of New South Wales,
says the development is less about improving current technology than building
future tech.
This is a beautiful demonstration of controlling matter at the atomic
scale to make a real device, Simmons says. "Fifty years ago when the first
transistor was developed, no one could have predicted the role that computers
would play in our society today. As we transition to atomic-scale devices, we
are now entering a new paradigm where quantum mechanics promises a similar
technological disruption. It is the promise of this future technology that
makes this present development so exciting.
Gerhard Klimeck, who directed the Purdue group that ran the simulations,
says this is an important development because it shows how small electronic
components can be engineered.
Moore’s Law simply stated that the number of transistors that can be
placed on a processor will double approximately every 18 months. The latest
Intel chip, the "Sandy Bridge," uses a manufacturing process to place
2.3 billion transistors 32 nanometers apart. A single phosphorus atom, by
comparison, is just 0.1 nanometers across, which would significantly reduce the
size of processors made using this technique, although it may be many years
before single-atom processors actually are manufactured. The single-atom
transistor does have one serious limitation: It must be kept very cold, at
least as cold as liquid nitrogen, or minus 391 degrees Fahrenheit (minus 196
Celsius).
The atom sits in a well or channel, and for it to operate as a
transistor the electrons must stay in that channel. At higher temperatures, the
electrons move more and go outside of the channel. For this atom to act like a
metal you have to contain the electrons to the channel. If someone develops a
technique to contain the electrons, this technique could be used to build a
computer that would work at room temperature. But this is a fundamental
question for this technology.
Although single atoms serving as transistors have been observed before, this is the first time a single-atom transistor has been controllably engineered with atomic precision. The structure even has markers that allow researchers to attach contacts and apply a voltage. The thing that is unique about what is done here, with atomic precision, individual atom is positioned within the device.
Simmons says this control is the key step in making a single-atom
device. By achieving the placement of a single atom, we have, at the same time,
developed a technique that will allow us to be able to place several of these
single-atom devices towards the goal of a developing a scalable system.
The single-atom transistor could lead the way to building a quantum
computer that works by controlling the electrons and thereby the quantum
information, or quantum bits. Some scientists, however, have doubts that such a
device can ever be built.
