NIST demos industrial-grade nanowire device fabricationOctober 29, 2007In the growing catalog of nanoscale technologies, nanowires-tiny rows of conductor or semiconductor atoms-have attracted a great deal of interest for their potential to build unique atomic-scale electronics. But before you can buy some at your local Nano Depot, manufacturers will need efficient, reliable methods to build them in quantity. Researchers at the National Institute of Standards and Technology (NIST) believe they have one solution-a technique that allows them to selectively grow nanowires on sapphire wafers in specific positions and orientations accurately enough to attach contacts and layer other circuit elements, all with conventional lithography techniques. They detailed their results in a recent paper.* Despite their name, nanowires are more than just electrical connectors. Researchers have used nanowires to create transistors like those used in memory devices and prototype sensors for gases or biomolecules. However working with objects only tens of nanometers wide is challenging. A common approach in the lab is to grow nanowires like blades of grass on a suitable substrate, mow them off and mix them in a fluid to transfer them to a test surface, using some method to give them a preferred orientation. When the carrier fluid dries, the nanowires are left behind like tumbled jackstraws. Using scanning probe microscopy or similar tools, researchers hunt around for a convenient, isolated nanowire to work on, or place electrical contacts without knowing the exact positions of the nanowires. It's not a technique suitable for mass production. Building on earlier work to grow nanowires horizontally on the surface of wafers (see "Gold Nano Anchors Put Nanowires in Their Place"), NIST researchers used conventional semiconductor manufacturing techniques to deposit small amounts of gold in precise locations on a sapphire wafer. In a high-temperature process, the gold deposits bead up into nanodroplets that act as nucleation points for crystals of zinc oxide, a semiconductor. A slight mismatch in the crystal structures of zinc oxide and sapphire induces the semiconductor to grow as a narrow nanowire in one particular direction across the wafer. Because the starting points and the growth direction are both well known, it is relatively straightforward to add electrical contacts and other features with additional lithography steps. As proof of concept, the NIST researchers have used this procedure to create more than 600 nanowire-based transistors, a circuit element commonly used in digital memory chips, in a single process. In the prototype process, they report, the nanowires typical grew in small bunches of up to eight wires at a time, but finer control over the size of the initial gold deposits should make it possible to select the number of wires in each position. The technique, they say, should allow industrial-scale production of nanowire-based devices. National Institute of Standards and Technology (NIST) |
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| Related Nanowire Current Events and Nanowire News Articles LANL Roadrunner simulates nanoscale material failure Very tiny wires, called nanowires, made from such metals as silver and gold, may play a crucial role as electrical or mechanical switches in the development of future-generation ultrasmall nanodevices. Transforming Nanowires Into Nano-Tools Using Cation Exchange Reactions A team of engineers from the University of Pennsylvania has transformed simple nanowires into reconfigurable materials and circuits, demonstrating a novel, self-assembling method for chemically creating nanoscale structures that are not possible to grow or obtain otherwise. Nanowire biocompatibility in the brain: So far so good The biological safety of nanotechnology, in other words, how the body reacts to nanoparticles, is a hot topic. Researchers at Lund University in Sweden have managed for the first time to carry out successful experiments involving the injection of so-called 'nanowires.' Harvard scientists bend nanowires into 2-D and 3-D structures Taking nanomaterials to a new level of structural complexity, scientists have determined how to introduce kinks into arrow-straight nanowires, transforming them into zigzagging two- and three-dimensional structures with correspondingly advanced functions. Nanoelectronic transistor combined with biological machine could lead to better electronics If manmade devices could be combined with biological machines, laptops and other electronic devices could get a boost in operating efficiency. Caltech physicists create first nanoscale mass spectrometer Using devices millionths of a meter in size, physicists at the California Institute of Technology (Caltech) have developed a technique to determine the mass of a single molecule, in real time. A quicker, cheaper SARS virus detector -- one easily customizable for other targets Members of a USC-led research team say they've made a big improvement in a new breed of electronic detectors for viruses and other biological materials - one that may be a valuable addition to the battle against epidemics. Scientists demonstrate effect of confining dielectrics on semiconductor nanowire conductivity Researchers at the Harvard School of Engineering and Applied Sciences (SEAS), in collaboration with researchers from Worcester Polytechnic Institute (WPI), have demonstrated, for the first time, that the activation energy of impurities in semiconductor nanowires is affected by the surrounding dielectric and can be modified by the choice of the nanowire embedding medium. Self-assembled nanowires could make chips smaller and faster Researchers at the University of Illinois have found a new way to make transistors smaller and faster. The technique uses self-assembled, self-aligned, and defect-free nanowire channels made of gallium arsenide. New 'near-field' radiation therapy promises relief for overheating laptops Our modern age has become accustomed to regular improvements in information technology, says Slava Rotkin, but these advances do not come without a cost. More Nanowire Current Events and Nanowire News Articles |
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