Moore’s Law states that the number of transistors on an integrated circuit for minimum component cost doubles every 24 months; however, even Gordon Moore himself has said, “It can’t continue forever. The nature of exponentials is that you push them out and eventually disaster happens.” As more and more transistors are crammed on a single chip, the chance that the chip will not work due to unstable materials rises.
But the speed at which these transistors are crammed is now decreasing. According to the semiconductor industry roadmap, the further miniaturization of electronics will find its greatest challenge in the next 10 to 20 years.
One of the major obstacles behind packing transistors on a chip lies in the materials that are used. Silicon, as with other materials, will oxidize, decompose, and become highly unstable when cut down to smaller sizes; these ‘barriers’ have threatened their use in the future and development of electronic devices.
In July of 2005, Scientists at the University of Manchester discovered a new class of materials which, today, are hoping to use to solve the puzzle behind getting more transistors on a smaller chip.
Professor Andre Geim, Director of The Manchester Center for Mesoscience & Nanotechnology, at the time noted, “This discovery opens up practically infinite possibilities for applications which people have never even thought of yet. These materials are lightweight, strong and flexible, and there is a huge choice of them. This is not only about smart gadgets. Like polymers whose pervasiveness changed our everyday life forever, one-atom-thick materials could be used in a myriad of routine applications from clothing to computers.”
The materials were created by extracting individual atomic planes from conventional bulk crystals by using a technique called ‘micromechanical cleavage’. Depending on the parent crystal, their one-atom-thick counterparts can be metals, semiconductors, insulators, magnets, etc.
Using carbon as the parent crystal in ‘micromechanical cleavage,’ Professor Geim and his colleagues were able to create graphene, a one-atom-thick material that is rapidly becoming one of the hottest topics in modern physics.
The first graphene-based transistor was reported by The University of Manchester team at the same time as the discovery of graphene, and other groups such as the Georgia Institute of Technology and AMO have recently reproduced the result.
Despite the creation of these graphene transistors, they were reported to be very ‘leaky’ (Electrical flow could not be turned off to zero) which has severely limited applying this technology to devices such as computer chips and electronic circuits with a high transistor count.
Today, the Manchester team has found a better solution which will allow graphene-based transistors eligible for use in future computer chips. For the first time, Professor Geim and his colleagues have shown that graphene will remain highly stable and conductive when it is cut into strips that are just a few nanometers wide. (a single human hair is about 80,000 nanometers in width)
These super-small strips of graphene will remain stable where it’s counterpart would break down at sizes ten times larger. “We have made ribbons only a few nanometers wide and cannot rule out the possibility of confining graphene even further – down to maybe a single ring of carbon atoms,” says Professor Geim.
Geim’s team has currently made a number of single-electron-transistor devices that will work under ambient conditions and show a high-quality transistor action; In addition, Geim and his team suggest future circuits will be carved out of a single sheet of graphene, and believes this innovation will allow for substantially quicker miniaturization of electronic circuits when the current silicon-based technology reaches its limits.
“To make transistors at the true-nanometer scale is exactly the same challenge that modern silicon-based technology is facing now. The technology has managed to progress steadily from millimeter-sized transistors to current microprocessors with individual elements down to tens nanometers in size,” says Dr Leonid Ponomarenko, who is leading this research at The University of Manchester. “The next logical step is true nanometer-sized circuits and this is where graphene can come into play because it remains stable – unlike silicon or other materials – even at these dimensions.”
Professor Geim does not expect graphene-based circuits to be readily available until 2025, but believes graphene is probably the only viable approach when silicon-based methods come to an end.
In terms of transistor size, you can see that we’re slowly approaching the size of atoms; which, in chip technology, seems to be the ideological barrier. Though it may be 15 years off, graphene-based transistors are the future, and will one day be credited to saving Moore’s Law.