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Current research is based on the design, research and development
of devices required to successfully recover waste heat and convert it into
electrical power through the use of Microsystems Technology. This takes place
using optical nano-antennas, in the same way a standard radio antenna picks up a
radio station. These 'nantenna' arrays scale in size with the wavelength of the radiation.
In the temperature range 250-300°C, radiation in the region of 60 THz is emitted,
which has an associated wavelength of 5 µm.
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Initial work focussed on ensuring a maximum output from the heat source, which involved research into emissivity and,
in particular, black body emitters. COMSOL Multiphysics was used to simulate the heating of a section of car exhaust pipe
to analyse the temperature of the surface of the pipe:
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- Left - Slice plot of temperature of pipe
- Right - 3D Representation of pipe
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The main aim of this project is the rectification of this signal into a useful DC voltage.
This will take place using high speed metal-oxide-metal diodes, which involve the use of two
dissimilar metals separated by a native oxide, whose thickness and surface area must be strictly
controlled to ensure that the diode has a high enough cut-off frequency in order to successfully
rectify the signal, through the use of electron tunnelling. A 2D array of such antenna-coupled
diodes will allow, through parallel and series connections, a current sufficiently high that it
can be used successfully in existing electrical systems.
In order to make successful metal-oxide-metal (MOM) diodes, the following must be considered:
- Maximise the work function difference between the metals for asymmetry in I-V characteristics
- Produce a uniform oxide layer that is sufficiently thin (a few nm) for electron tunnelling to occur
- Reduce the diode size to sub-micron dimensions to increase the cut-off frequency
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- I-V Characteristics of a Ti-TiOx-Pt Diode
- TEM image of (bottom to top) SiO2, Ti, TiOx and Pt structure
- SEM image of an array of sub-micron lines created via phase shift lithography
- SEM image of a single line created via phase shift lithography
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© Copyright Durham University 2012
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