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Engineers from the University of Glasgow are presenting work this week at the 56th International Conference on electron, Ion and Photon Beam Technology and Nanofabrication demonstrating a reproducible process for making silicon nanowires with widths down to 4 nm. These are the smallest silicon nanowires ever produced using top down electron beam lithography.

The nanowires were produced in the James Watt Nanofabrication Centre in the School of Engineering using state-of-the-art electron beam lithography to define the pattern in a resist before reactive ion etching transferred the pattern into the silicon substrate. The key breakthrough being reported at the conference is the low damage etch process where a very low dc bias is used to minimise process damage. This allows far smaller silicon nanowires which still have high electrical conductivity and high performance at such small length scales.

The wire was fabricated by PhD student Muhammad Mirza working under the direction of Prof Douglas Paul in the School of Engineering.

"The technology is being developed for a range of sensing applications. The electrical conductivity of the wire is very sensitive to molecules that are deposited onto the sidewalls of the nanowire and by choosing ligands that adhere to the nanowire and then selectively bind to specific molecules in the breath, there is the potential for detection of specific disease from breath analysis. Whilst the research is at an early stage, it is being undertaken using technologies that could be transferred to commercial silicon foundries for manufacture in volume. There are also potential applications for using similar nanowires to enhance thermoelectric generators which convert heat into electricity."

Nanowire Tall

The James Watt Nanofabrication Centre houses more than £20 M of nanofabrication tools in a 750 square-metre clean room environment. The Centre is collaborating with more than 90 different universities and research institutes around the world. Kelvin Nanotechnology Ltd. provides commercial access to the Centre’s facilities and expertise. More than 250 companies have benefited from nanofabrication services delivered by Kelvin Nanotechnology Ltd.

For further details please e-mail: Douglas.Paul@ glasgow.ac.uk. The work was funded by the EPSRC.