Martin Courtney explores how future nanotechnology will support a new generation of computer systems. Academics and large corporations all over the world are busy pouring money into nanotechnology research. Finding new ways to build smaller, more powerful CPUs; low-power, flexible computer displays and touchscreens; and longer-life device batteries are just some of the applications high on their agendas.
Not all nanotechnology implementations will have an impact on IT, however – arguably the majority of applications are being designed for use in the field of medical science, biofuel production, solar energy, pharmaceuticals and even paper manufacturing, among others.
What is nanotechnology?
Nanotechnology is the logical successor to microtechnology – a term commonly used to define miniature circuits around a single micrometre (one millionth of a metre) in size, which have been used to form part of micro-electromechanical systems (MEMS).
Perhaps the best example of MEMS usage in IT is in the formation of integrated circuits (ICs) that consist of tiny processors and passive components manufactured within a thin substrate of semiconductor material. Typical material examples include silicon and metals such as gold, nickel and titanium, with various etching processes used to put burn patterns on the chips, and which are already found in many forms of electronic equipment today.
MEMs are also used in optical switching equipment and digital cameras, as well as accelerometer chips in small electronic devices such as smartphones, handheld PCs and MP3 players. They are also used in PC hard drives to stabilise the read head to prevent disk damage and data loss.
Nanotechnology takes microtechnology further by miniaturising technology either to an atomic or molecular scale, or to structures fewer than 100 nanometres in size (to put things in perspective, a nanometre is roughly equivalent to a billionth of a metre).
One idea is that molecular structures can be used to replace electronic components, producing switches and ICs only a few atoms wide, which can be used in electronic devices to greatly reduce their size, without affecting speed or performance.
In other words, smaller, faster computers, with larger memories and more powerful CPUs than silicon-based chips currently allow, using techniques such as soft lithography to produce cheap and effective nanoscale circuits based on alternative materials.
Carbon nanotubes in CPUs
Much of the work being done with nanotechnology revolves around semiconductors, which is the reason why many companies are putting considerable financial resources into researching a specific area of nanotechnology called carbon nanotubes.
These are made when carbon atoms form hollow, open-ended cylinders that have diameters between 0.4nm and 1.8nm, and vary in length up to several hundred nanometres depending on how they are made. Electrons flow through these nanotubes 10 times faster than they do through silicon circuits found in most CPUs, while they can carry up to 100 times the current and dissipate up to 20 times the heat.
Intel obtained a US patent for its carbon nanotube-coated capacitor electrodes and their manufacturing method, and the resultant capacitors, intended to provide power to electronic devices such as desktop PCs, servers, laptops, handhelds, gaming devices and telephones.
Nanowires in memory
Intel, HP, IBM and others are also exploring semiconductor nanowires for use in CMOS memory – up to 100 bits of data could be stored on a single nanowire, says the company, delivering between 10 and 100 times more data than other solid-state memory such as Flash, at lower cost.
To this end, IBM researchers recently announced the creation of a ring oscillator out of field-effect transistors based on 3nm-diameter nanowires, demonstrating that engineers can build a working circuit from transistors at much smaller channel lengths than today’s devices.
Researchers at Samsung Electronics had previous demonstrated a similar circuit based on 13nm nanowires, and HP has promised a 4.5nm wire by next year – but it is expected to be several years before either version of the technology makes it into memory chips.
HP is also experimenting with a new system architecture that allows multiple layers of memory to be stacked 3D-fashion. Details remain vague to date, and nor is it clear if the “nanostore” operates on a nanoscale, in the same way that Apple’s Nano doesn’t. But it is intended as a stack of processor cores connected to HP’s non-volatile memristor cores in datacentre servers, meaning much of the processing is performed within memory rather than CPU, resulting in up to a tenfold increase in performance, said HP.
Carbon nanotubes can also be used as either conducting or semiconducting material for use in data storage, while scanning probe microscopes may eventually be used as a tool for data transfer.
IBM’s millipede storage system, for example, uses an array of atomic force microscope (AFM) tips to make indentations in materials such as polymer and read them similar to the way that lasers read CDs, but at considerably smaller scale and much higher density of information.
Hitachi Maxell has partnered with the Institute of Technology in Tokyo to create new tape storage technology which would allow products to reach capacity of more than 50TB, using what it calls the facing targets sputtering method, an ultra-thin nano-structured magnetic film (magnetic particles are fewer than 10 nanometres), allowing it to fit more information into a much smaller area and raising the number of bits that can be stored.
Researchers at the Pohang University of Science Technology in South Korea last year achieved an areal storage density of 1.03TB per inch, using the same AFM-based lithography to write, read and delete nanoscopic indentations which can hold data on a specialised polymeric film surface. This was achieved at room temperature and with no heating of the AFM tip required, thereby using far less power.
Hard drive maker Seagate is also partnering Queen’s University in Belfast to research new coatings and materials for use in hard disk drives, investing £7.5m of funding in equipment and financial support for researchers at the School of Mathematics and Physics studying the use of both microtechnology and nanotechnology in data storage.
Displays and graphene
Using carbon nanotubes in computer monitors and electronic device displays may eventually replace existing CRT and LCD technology. Much research is being done with a nanotechnology material called graphene, which has long been regarded as one of the most promising technologies to emerge. Scientists have recently created nanowires by capturing the electronic properties of reduced graphene oxide on a nanoscale, allowing it to be used as a conducting, as well as an insulating material.
The latest development saw researchers at Samsung and Sungkyunkwan University in Korea produce a continuous layer of pure graphene the size of a television, on top of a flexible, transparent, 63cm-wide polyester sheet which could be used to conduct electricity across flexible, transparent touchscreens based on a sheet of carbon just one atom thick that can be folded like paper.
The same material can also be used to make displays lighter and more power efficient. One manufacturer, Nanosys, has developed screen technology that incorporates nanomaterials called quantum dots that convert light from the backlight into narrowly defined colour bands that are matched to the display’s filter, improving both power efficiency by more than 10 per cent and the colour range of the display, the company said.
Using nanotechnology as the building blocks for low-power computer systems is also something of a Holy Grail for equipment manufacturers. Researchers at MIT have made some headway here, arming a lithium-ion battery with a positive electrode made of carbon nanotubes that they say can deliver up to 10 times more power than a conventional battery and can store up to five times more energy than a conventional ultracapacitor.
Most methods of making carbon nanotubes require a binding agent that reduces the electrode’s conductivity and creates lumps of material that shrink the surface area needed to store and react with lithium in the battery. MIT’s electrodes have a much higher surface area, which increases capacity and allows lithium to move in and out of the electrode more rapidly, enabling faster charging and discharging.
The nanotube-based battery could deliver longer battery life not only to next-generation portable electronic devices such as laptops and smartphones, but also extend the currently limited range of electric vehicles.
Given its ability to pack high processing power into much smaller systems, nanotechnology is heavily tipped to support the emergence of quantum computers, those that are able to number crunch much larger volumes of information much more quickly than current high-performance computers based on current silicon technology.
Rather than encoding data as zeroes and ones in the same way as binary computers, quantum computers store data as Qubits which can represent both zeroes and ones simultaneously. This reduces the number of computations needed in a single process to find all possible permutations, potentially churning out more accurate data using less power and in a fraction of the time; particularly useful for encryption and security applications.
Researchers at the University of Cambridge, in collaboration with Toshiba, recently revealed an entangled light emitting diode (LED) containing a quantum dot using voltage, rather than a laser-driven power source. The latter are generally considered to be impractical for quantum computing applications due to their bulk and complexity, and it is hoped that entangled LEDs will eventually form the basis of optical quantum computer systems.
Elsewhere, researchers at the University of New South Wales have demonstrated what they say are the world’s first electronic devices in silicon created on an individual atom scale – on chips where the components are 22nm in size, with individual transistor gates about 42 atoms across. Two previous groups have managed to produce working single-atom transistors, and hope these will form the basis of solid-state quantum computing.
That is not to say that molecular nanoscale components using alternative substrate materials are a dead cert to form the basis of all quantum computers in the future. Rival scientists are also exploring silicon-based alternatives, with a combined team from the University of Surrey, Heriot-Watt University in Edinburgh, and the FOM institute for Plasma Physics in the Netherlands having demonstrated that elements of quantum engineering can be implemented within silicon transistors.
Manufacturing and modelling issues
The big challenge for nanotechnology in IT is how to create nanoscale switches inside those computer chips that turn the flow of electrons on or off, and make the logical gates that create electrical circuits, not least because of the problems involved in actually building something so small, then controlling it, and producing those necessary components at sufficiently low cost to make them commercially viable.
Scientists also face the obstacle of how to test and design nanoscale components and microchips, especially given the variability within the billions of tiny transistors they often comprise.
Glasgow University has developed NanoCMOS simulation software, which uses grid computing to harness the CPU power from thousands of computers, to simulate how hundreds of thousands of transistors function within a circuit.
In partnership with a consortium called Tere-scale Reliable Adaptive Memory Systems, the project will focus on CMOS microchips using transistors less than 16nm in size, as well as look at nanowire transistors, quantum devices, carbon nanotubes and molecular electronics which may use components as small as 5nm.
IBM’s nanoscale Matterhorn
IBM’s latest nanotechnology breakthrough has seen its scientists develop a silicon mapping technique which could replace current electron beam lithography (e-beam) to accelerate the introduction of nanotechnology into electronics, microchips, medicine, life sciences and opto-electronics at less cost.
To demonstrate just how tiny its precision instrument can operate, IBM created a representation of the Matterhorn in Switzerland (below), 1,000 copies of which could be fitted in a 0.3mm grain of salt, said the firm.
It is still in the advanced proof-of-principle stage and is unlikely to be commercially available for another five years. But IBM says it shows the technology works and the company is now actively trying to partner with universities and research laboratories to pioneer its usage in the meantime.
Current e-beam-based lithography equipment designed to create nanoscale optical lenses or circuits on silicon chips can cost about $5m (£3.3m), which IBM says could be reduced by up to 400 per cent.
“The problem with e-beam technology is that it is a serial method and not really suitable for mass production, and you have to go through complicated development steps to define and produce patterns,” said Urs Duerig, a physicist with IBM Research in Zurich. “This is a tabletop tool which is much smaller and costs up to five times less.”
Potential applications for the new IBM technique include fast prototyping for CMOS nanoelectronics, optical components and meta-materials, to fabricating 3D nanoparticles such as nanorods and nanotubes in bioscience.
Written by Martin Courtney