1. www.ee.surrey.ac.uk/NEC 300 nm The Nano-Electronics Centre Researchers in Professor Ravi Silva’s NEC group specialise in Nanoelectronics. They are interested in exploring, simulating and characterising the properties of materials at the nanoscale. They intend to exploit these novel materials by engineering useful electronic devices. Work in the NEC covers a wide range of activities, including carbon based electronics (especially diamond-like carbon and carbon nanotubes), nano-biology, nano- manipulation & characterisation, microwave electronics & devices, optical devices and large area electronics. These activities are carried out by scientists specialising in a wide variety of academic disciplines including physics, electronic engineering, chemistry and biology. At the nanoscale, the properties of materials change in interesting and potentially useful ways. Materials with nano-sized dimensions can be stronger, more reactive, lighter or optically active to a greater extent than in the bulk. The idea behind nanotechnology is to exploit this unusual behaviour to produce new materials, which can be used to make novel, efficient, small, durable and fast devices. Put simply, nanotechnology is engineering on a tiny scale. Other activities within the group include: memory switching in amorphous silicon alloys, low temperature polysilicon active matrix electron field emission displays, characterisation of a new source gated transistor based on hydrogenated amorphous silicon and polysilicon, RF response of carbon nanotubes for fabrication of active and passive devices and several projects on devices for microwave applications, amongst many others. The group has moved from strength to strength and has quadrupled in size over the past five years. They have received over £7 million funding from EPSRC alone and are promising to remain a formidable force at the forefront of research in nanoelectronics for many years to come. Contact: s.silva@surrey.ac.uk © The Nanoelectronics Centre 2005, produced by Stephen Lyth Just some of the forty-strong NEC group. Right: Carbon-based high speed electronic devices of the future could be based on amorphous carbon superlattices. The figure shows a band-gap modulated superlattice, consisting of layers of diamond-like carbon with alternating sp 3 bond fractions; the superlattice’s electronic properties are tailored simply by altering the barrier and well widths. Left: Transmission electron micrograph of a 100 nm thick stratified layer of nano- crystalline silicon, formed by excimer laser crystallization of amorphous silicon. Films such as these are studied as potential absorber materials for photovoltaics. Nanostructured materials including silicon, carbon, gallium nitride and organics are studied extensively within the group. Manufacturing techniques such vacuum evaporation, rf and reactive sputtering, chemical vapour deposition, plasma treatment, focussed ion beam milling, nanomanipulation, photolithography, spin coating, chemical etching and laser ablation are routinely used. An array of characterisation techniques are utilised, including scanning electron microscopy, x-ray and ultraviolet photoelectron spectroscopy, ion beam microscopy, scanning capacitance microscopy, transmission electron microscopy, scanning tunnelling microscopy, atomic force microscopy, and a wide range of optical and electrical characterisation techniques. Solar cells, light emitting diodes, thin film transistors, electron field emitters, biosensors, memory switching elements, superlattices, resonant tunnelling structures, quantum capacitors and gas sensors are some of the structures that are designed, fabricated and characterised using the facilities in the Advanced Technology Institute. Above: The NEC created this false colour SEM image for the Science Museum in London. They wrote on a grain of pollen just 15 microns across, using gallium ion beam milling. More information about the nanotechnology exhibit at the Science Museum can be found at: www.sciencemuseum.org.uk Researchers at the NEC can make organic light emitting diodes incorporating carbon nanotubes, like the one pictured above. Similar devices are made as organic solar cells, which are extensively studied within the group, alongside inorganic solar cells based on nanocrystalline silicon and gallium nitride. Silver-Silicon Dioxide (Ag-SiO 2 ) nanocomposites are promising candidates for electron field emission device applications. They give an emission current at very low threshold fields (< 20 V/  m) due to the electrical inhomogeneity effect. Above left: High- resolution transmission electron microscopy image of Ag-SiO 2 nanocomposites. Above right: Simulation of local electric field enhancement within the Ag-SiO 2 nanocomposites. Carbon nanotubes (CNTs) are cylindrical molecules made up of concentric hollow tubes of flat graphite-like layers of carbon. They are stronger than steel, more conductive than copper and less dense than aluminium. If their unique properties can be utilised on a macroscale, CNTs will have a huge impact on the modern world. The NEC leads the world in many areas of CNT research, including pioneering methods for growing carbon nanofibres at room temperature. This makes it possible to grow CNTs on temperature sensitive substrates such as plastic and paper and also allows us to functionalise CNTs with biological materials more easily and to look at novel biosensors. Potential applications for CNTs are as wide ranging as flat screen field-emission displays, high speed electronic components, gas sensors, water filters, biosensors, reinforced polymer composite materials, artificial light sources and single electron transistors. Left: Aligned CNTs can be grown over large areas in the labs at the Advanced Technology Institute. Thin films of nickel are deposited on silicon substrates, and these films are broken into nanoscale islands using high temperatures, or a high power excimer laser. CNTs begin to grow from the nickel islands when the substrate is heated up to 700°C in a methane and hydrogen gas plasma. By applying 700 volts, aligned CNTs can be grown. The conduction properties of CNTs are affected by gas adsorbents onto their surface, so gas sensors can be fabricated from CNT ropes (left). The graph (right) shows the room temperature response of a fibre to small quantities of nitrogen dioxide (which can cause severe coughing, choking, nausea and abdominal pain). Above: A computer gen- erated image of a short segment of a single-wall CNT. This CNT would be around 0.75 nm in diameter, and 3 nm long. Left: Researchers in the NEC are able to create CNTs that are filled with iron, or silver. Using these CNTs in polymer composites could lead to plastics with frequency dependant conductivity, or magnetic memory elements for computing. 10nm “Nanotechnology will change the way the world operates. The effects will be all pervasive, and will hopefully be of benefit to humanity.” Prof Ravi Silva “Leading edge expertise in metrology at NPL coupled with the best researchers in academia…will make an unbeatable team capable of tackling the most challenging areas of research.” Dr. Kamal Hossain, NPL Carbon nanotubes and DNA are both similar sized molecules and have a natural affinity towards one another. Carbon nanotubes are hydrophobic (insoluble in water) and DNA is hydrophilic (soluble in water). Wrapping DNA around nanotubes is therefore an excellent way to improve the solubility of nanotubes. The atomic force microscope images (below) show tangled DNA ropes (left) and carbon nanotubes wrapped in short single stranded DNA (right), This technique has potential for functionalisation of the surface of nanotubes for use as DNA hybridisation biosensors. Above: An atomic force microscope image of a DNA network formed on silicon. DNA (or deoxyribonucleic acid) is a molecule found primarily in the nucleus of cells, and carries genetic information about cell growth, division, and function. DNA consists of two long nucleotide strands twisted into a double helix, held together by weak hydrogen bonds. The sequence of nucleotides determines hereditary characteristics. Nature has been developing biological nanotechnology through evolution for billions of years. Evolution has created diverse nano- sized proteins, organelles and complex molecules that can assemble, sense, reproduce and cooperate with incredible efficiency. Researchers at the NEC intend to exploit these processes along with the impressive electronic properties of carbon nanotubes to develop devices that incorporate biomolecular and biocompatible components. Such devices could be used as novel biosensors that could increase the efficiency and reduce the cost of medical diagnoses, health monitoring and biosensing. 500nm