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Heat sensors tunnelling the gap

Nanotechnologies require sensitive instrumentation to monitor both internal temperature fluxes as well as to allow for optimal performance. In both cases, tunnel junctions are often used. New developments with tunnel junctions may now offer far more improved features.
Heat sensors tunnelling the gap
A tunnel junction is precisely what it suggests; a bridge that is formed from two electrodes separated by a thin tunnel barrier of magnesium oxide or aluminium oxide for example. They are used in a multitude of nano-technologies, from sensors to biomedical instruments to computer hard drives and circuitry.

Temperature fluxes within nano-scale structures are often too minute for standard sensors to detect accurately. This complicates matters when such structures are complex and require certain temperature allowances. As such, a Finnish nano-technology company has developed a temperature sensing technique utilising tunnel junctions.

Through lithographic fabrication they are able to construct a tunnel junction of minute proportions and operate on temperature-dependent tunnelling resistance of metal-insulator-metal tunnel junctions. It can furthermore detect miniscule fluctuations in temperatures, with a variant scale from approximately -200 degrees Celsius to 200 degrees Celsius.

A typical junction is around one hundred square nanometres in size and is capable of having a tailored impedance factor that can be made as high as the MOhm-level that results in extremely low excitation levels. The only restriction to such sensors is the limits of the lithography itself. The fabrication of these tunnels has been effected with electron beam lithography and these can be arranged in either 1D or 2D arrangements capable of detecting temperature gradients or distributions in a sub-micron scale.

These tunnel junction sensors have a wide range of applications and can be further integrated with optical sensors for use in the life sciences. The developers are currently looking for partners both in life science and biotechnology for further development and integration.
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