Radiation detector made from graphene could be scaled up for mass production
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US researchers have developed a new, simpler radiation detector which exploits the extraordinary properties of graphene.
Graphene – an atom-thick layer of carbon atoms in a hexagonal lattice – is known for its unparalleled qualities: it is the strongest known material, light, an exceptionally good conductor of heat and electricity, and almost completely transparent. It also has a useful thermoelectric property: it can convert heat to electricity.
“The discovery of graphene in 2004 was anticipated to herald a whole new type of technology but, unfortunately, there are some strong fundamental limitations for this material,” said Grigory Skoblin, a PhD student at Chalmers University of Technology, Sweden. “Nowadays, the real industrial applications of graphene are quite limited.”
So far, the researchers say, most applications of graphene make use of its mechanical properties rather than its other physical properties, such as its electrical conductivity.
“But our device shows that more fundamental properties can be used in actual applications.”
Graphene’s ability to convert heat to electricty was exploited by researchers in order to create a new radiation detector.
This detector is a bolometer, a device for measuring the power of electromagnetic radiation through the heating of a material that has resistance which changes with temperature. In this new device, radiation heats part of the device, causing electrons to move and generating an electric field. This creates a potential difference across the device, which can be measured.
This device is particularly useful in that it responds very quickly (thanks to using a very small piece of graphene), and works over a great range of temperatures up to 200°C. Most bolometers – which rely on the generation of a current or change in resistance by incoming radiation – only work at very low temperatures.
While graphene has previously been used to create bolometers, these other models tend to contain double layers of graphene. In comparison, this design is particularly simple and cheap, and would be easier to scale up for commercial applications thanks to its coating of Parylene, which offers both high performance and scalability.
In the future, Skoblin and his collaborators aim to widen the frequency range of the detector (which currently only works with 94GHz microwave radiation), and use chemical vapour deposition to create larger pieces of graphene for the device.