nanotehnoloogia, nanoteknologia, nanotechnologija, nanotehnologijas, nanoteknologija,
nanotechnologii, nanotecnologia, nanotehnologijo, nanoteknik
Electronics based on amorphous materials is the key to large area low cost driver
circuitry in flat panel displays, but their operating speed has been limited
by the difficulty with which electrons move through disordered amorphous materials.
Now, the observation of negative resistance in amorphous semiconductors offers
the prospect of low-cost devices switching at Gighertz rates, and opens up applications
from large area display drivers to high-speed electronics for mobile communications.
These devices are suitable to be used in combination with plastic electronics
due to the room temperature deposition process.
breakthrough at Surrey has been to make devices with layers only a few nanometres
thick, through which electrons can pass by quantum-mechanical tunnelling. In
a three-layer structure, the composition and thickness of the layers control
the energies at which electrons are allowed to tunnel, and can give rise to
a region of negative resistance. Such ‘resonant tunnelling diodes' have been
extensively studied in highly ordered crystalline semiconductors such as gallium
arsenide, and account for some of the highest-speed electronic devices ever
demonstrated. However, previous attempts to realise negative resistance in amorphous
materials (e.g. amorphous silicon) have proved unsuccessful.
The Surrey devices are made from thin layers of diamond-like carbon, a material
which has the added advantage of chemical robustness, thermal stability, high
resistance to electrical breakdown, and biocompatibility. It can be deposited
over large areas at room temperature, which makes it compatible with low-cost,
flexible plastic substrates. The newly demonstrated suitability of diamond-like
carbon for quantum electronics may give rise to the establishment of a new family
of high speed carbon based high power devices such as tunnel transistors, oscillators
and hybrid devices. These devices would offer the possibility of high speed nano-electronics
circuits, stable against chemical attack and suitable for high temperature operation,
compatible with large area low cost production.
The work was sponsored by the Portfolio Partnership and Carbon Based Electronics
Programmes of the Engineering and Physical Sciences Research Council (EPSRC)
in the UK.
"This work extends the potential of amorphous carbon electronics to high speed
switching at GHz rates, and follows our earlier demonstration of room temperature
processing of carbon electronics on plastic" said the lead investigator of the
team, Professor Ravi Silva. "Such ground breaking work was only possible due
to the flexible funding afforded by the 5 year Portfolio Partnership between
the University of Surrey and EPSRC".
Resonant tunnelling and fast switching in amorphous carbon quantum well
S. Bhattacharyya, S.J. Henley, E. Mendoza, L. Gomez-Rojas, J. Allam and S.R.P.
Silva, Nature Materials 5, 19–22 (January 2006)
Published online: 25 December 2005
Press release 25/12/05
Media enquiries: Peter La, Press Office at the University of Surrey, Tel: 01483
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