Shreyas Pandit
Thu, 22 Sep 2005 11:48:32 -0700
http://research.nottingham.ac.uk/Vision/display.aspx?id=801&pid=190 In a spinYou know the routine. You turn on your computer and let it chug away while you make a cup of tea and chat to your colleagues about what they did the night before. It may be a gentle way to start the day, but when your trusty machine decides to crash mid project, the precious minutes it takes to re-boot can seem like hours.
However, waiting for your computer to come to life could soon be a thing of the past thanks to current research in Nottingham's Semiconductor Physics Group. For the last two years, the group has been applying cutting-edge physics to the fabrication of materials, which could bring together the hard disk and processor as the basis of the next generation of computers. Currently the only such group in the UK doing this kind of work, it's just been awarded over £2 million from the Engineering and Physical Sciences Research Council (EPSRC) and the Higher Education Funding Council for England (HEFCE), to develop materials which could lead to computers you can flick on as easily as turning on the television.
The reason that even the fastest and most up-to-date computer can't seem to wake up in the morning is that some of the components also need to chat amongst themselves for a while. 'Broadly speaking, the two most important bits of your computer are the processor, which carries out electronic operations using combinations of transistors, and the hard disk, which stores bits of information as tiny magnetic dots,' says Professor Bryan Gallagher of Nottingham's Semiconductor Physics Group. 'No matter how fast the processor, it still needs to carry all the information from the hard disk and read the software before it can operate.'
The key to building a processor that can also act as a hard disk is a relatively new area of physics called spintronics, and it aims to takes electronics research to another level. 'In electronics all you do is move electrons around using electric fields. Electrons have a charge and as they respond to an applied electrical field, you create currents or switch electronic gates on and off. So what you're exploiting is the ability to push electrons around,' explains Professor Gallagher. But as well as having a charge, electrons also have a property known as spin, which means they act like tiny bar magnets that point in a specific direction. 'Normally these bar magnets just tumble around, but if you can make the material they are in ferromagnetic - permanently magnetic in the same way as iron - they all start lining up,' he explains further.
'It's a bit like moving iron filings around with a magnet; it's a way of controlling them. You can also move electrons around, which means that you can store information in spin and move that information around with an electric field.'
The upshot of all this clever physics is the prospect of a processor that is also the computer's memory, and the very real possibility of an instant-on computer. But that's not all. With this new type of processor it would be possible to effectively rewrite the electronic circuits using software, rather than buying a new chip and plugging it in. This would be perfect for upgrading inaccessible computers like those on satellites, not to mention the humble earthbound PC.
In fact, the spintronics revolution is likely to make itself felt in every aspect of life, as computer chips begin to be included in all kinds of products. Personal organisers, mobile phones and gaming will all benefit from spintronic technology, as will the motor industry. Modern cars not only have an onboard computer, but also something in the region 200 magnetic sensors, which monitor and control everything from air-conditioning to the firing of the engine itself. Replaced with a spintronics computer and a network of spintronic sensors, tomorrow's intelligent car would make today's electronic efforts look like a horse-drawn carriage. The future intelligent home, with interconnected sensors to control lighting, heat and even tell you when you have run out of milk, could all make use of spintronic technology.
All this may be a few years down the line, but the Semiconductor Physics Group has already made considerable progress in building a range of materials to act as the new ferromagnetic semiconductor.
Key to this process has been Professor Tom Foxon, an international expert in molecular beam epitaxy - the method used to make the semiconductors. 'We're looking at materials including Galium Arsenide, where we replace one in 20 of the atoms in the semiconductor with manganese, which is magnetic. So, what we end up with is a dilute magnetic semiconductor with electrons which talk to each other and line up nicely. You could use this material to store information, or you could use it to make transistors. What it means is that you could have a processor where parts of it would be storing information, parts would be processing information, and these would be integrated so you wouldn't need wires to connect them up,' remarks Professor Gallagher.
The group has gained the reputation as a world leader in the fabrication of these ferromagnetic semiconductors, and already supplies them to university and industry laboratories all over the world. While the semiconductors initially only operated at a third of room temperature, a recent breakthrough enabled the team to get them working at around half room temperature. 'It's a big step forward,' says Professor Gallagher. 'But a key challenge now is to get it working properly at room temperature. There's a huge amount of materials development to do.'
In the meantime, a collaboration with Hitachi is simultaneously working to make spintronic devices on a nanoscale - a field known as nanospintronics. The Nottingham group intends to move well beyond current state-of-the-art technology by making ferromagnetic semiconductor devices on the scale of 10nm or less, something that raises even more challenges for the team. 'What seems to be the case is that there are completely different phenomena occurring at the nanoscale, where there is the promise of making fantastically sensitive devices,' explains Professor Gallagher. 'It's very long term, but some of this technology could be a revolution in the magnetic recording industry.' In support of this research, the University has committed £1.15 million for nanospintronics facilities.
And, as if two computer revolutions weren't enough, their work could also provide a means to the all-important end of quantum computing. A quantum computer would work by processing information using interactions at the level of a single atom or smaller, and in terms of processing power would take computing into another realm. 'It has been established that the most powerful computers possible would be quantum computers,' he says. 'This kind of computer could be small, but it would have a computing power bigger than any conventional computer you could imagine building. The holy grail is to find a way to replace standard units of memory with quantum units called qu-bits.'
Spintronics may hold the answer. 'The spin of an electron is the result of quantum mechanics,' says Professor Gallagher. 'The great thing about spin is that it's quite robust, so if you set the spin of a particular electron to point upwards, it will stay up for a reasonably long time - long enough for you to do your quantum computation. So, there's the possibility that you could manipulate and store information at the level of single spins and this might well be a route to quantum computing.'
But don't throw out the old computer just yet. 'That won't happen any sooner than 20 years from now!' believes Professor Gallagher.
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