Created: A One-Atom Transistor!
By on February 20th, 2012

Scientists have hit a new low when it comes to size! The newest size of a transistor is just one atomic radius and it is made of phosphorus. A group of physicists from the University of New South Wales and Purdue University have created a transistor out of a single phosphorus atom embedded in a silicon crystal. Moore’s law has been broken, once and for all!

An STM image of the phosphorus atom placed on a Silicon substrate. The surrounding electrodes are the drain and source (see next image). (Courtesy: Arstechnica)

Quantum Mechanics and Choices!

What more, the transistor, instead of relying on the binary electronic states of ‘on’ and ‘off’ can rely on a superposition of quantum states, using so-called qubits. Qubits don’t represent just one of the two positions, but a multitude of all the possibilities, as prescribed by quantum mechanics.

Qubits will help realize the making of quantum computers, and of this, scientists are sure! The computers will be extremely small (for obvious reasons), very fast (information relay over tiny scales and the huge number of qubit states to utilize), energy efficient (no heat dissipation) and be able to solve a huge number of problems within a fraction of a second.

Moore’s Law

Even Moore’s law is happily in trouble! Moore’s law states that every eighteen months, the density of transistors on a chip doubles! Moore’s law has been scaled down to the scale of one atom! It is safe to say that it cannot go down any further.

The colour gradient image of the potential across the neighbourhood of the single phosphorus atom. The G, S and D refer to the gate, source and drain. So-called Field Effect Transistor (FET's) are supposed to regulate the passage of current from the source to the drain, using the voltages applied at the gates (Courtesy: Nature article)

Andreas Heinrich, a physicist at IBM, says the following about this work:

This is at least a 10-year effort to make very tiny electrical wires and combine them with the placement of a phosphorus atom exactly where they want them.

The deposition of the single atom at a precise position was done using a scanning tunneling microscope (STM). The STM was used to ‘cut’ the ‘groove’ into the silicon. Phosphine gas was then used to deposit one atom of phosphorus. It was then covered with a few layers of silicon.

The work appears in an issue in Nature Nanotechnology (link).

Dreams of using a device to relocate just one atom of a substance on a substrate are finally coming true! One of the principal dreamers was Richard Feynman. He would be proud!

Implementing these gated devices as an array of switches to make a working circuit is the present challenge. The Next is already here!

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Author: Debjyoti Bardhan Google Profile for Debjyoti Bardhan
Is a science geek, currently pursuing some sort of a degree (called a PhD) in Physics at TIFR, Mumbai. An enthusiastic but useless amateur photographer, his most favourite activity is simply lazing around. He is interested in all things interesting and scientific.

Debjyoti Bardhan has written and can be contacted at debjyoti@techie-buzz.com.

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