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[March 2007]
New Electronic Devices Created from Bent Nanowires
Researchers have taken advantage of the unique coupled semiconducting and piezoelectric properties of zinc oxide nanowires to create a new class of electronic components and devices that could provide the foundation for a broad range of new applications.So far, the researchers have demonstrated field-effect transistors, diodes, sensors – and current-producing nanogenerators – that operate by bending zinc oxide nanowires and nanobelts. The new components take advantage of the relationship between the mechanical and electronic coupled behaviour of piezoelectric nanomaterials, a mechanism the researchers call 'nano-piezotronics™'.
"Nano-piezotronics utilizes the coupling of piezoelectric and semiconducting properties to fabricate novel electronic components," said Zhong Lin Wang, a Regents Professor in the School of Materials Science & Engineering at the Georgia Institute of Technology (Atlanta, GA, USA). "These devices could provide the fundamental building blocks that would allow us to create a new area of electronics."
For example, in a nano-piezotronic transistor, bending a one-dimensional zinc oxide nanostructure alters the distribution of electrical charges, providing control over the current flowing through it. By measuring changes in current flow through them, piezotronic sensors can detect forces in the
nano- or even pico-Newton range. Other piezotronic sensors can determine blood pressure within the body by measuring the current flowing through the nanostructures. Moreover, an electrical connection made to one side of a bent zinc oxide nanostructure creates a piezotronic diode that limits current flow to one direction.The nano-piezotronic mechanism takes advantage of the fundamental property of nanowires or nanobelts made from piezoelectric materials: bending the structures creates a charge separation – positive on one side and negative on the other. The connection between bending and charge creation has also been used to create nanogenerators that produce measurable electrical currents when an array of zinc oxide nanowires is bent and then released.
Development of a piezotronic gated diode based on zinc oxide nanowires was reported on 13 February 2007 in the online advance issue of the journal Advanced Materials. Other nano-piezotronic components have been reported in the journals Nano Letters and Science. The research has been sponsored by the National Science Foundation (NSF), Defense Advanced Research Projects Agency (DARPA), the National Institutes of Health (NHI) and NASA.
www.gatech.edu
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