GBTD - Graphene Based Thermal Detector
We develop a thermal detector of light based on graphene, a two-dimensional material made of a single atomic layer of carbon atoms. In a thermal detector, the energy of the incident radiation is estimated by the temperature change of the absorber. The smaller is the absorber, the bigger is the temperature increase. The graphene flake is the ideal material but it is so tiny (a few millionth of millimeter square) that we cannot attach a thermometer to it because the thermometer, however small, is million times larger than the flake. The only possibility is to use the graphene as absorber and thermometer at the same time. The temperature of the graphene is related to the intensity of the random motion of its electrons that we can measure with a particular superconducting sensor, the SQUID, that works well at very low temperatures (near the absolute zero, -273°C).
The Science
The project GBTD (2014-2016) concerns the development of a thermal detector of photons based on graphene, a material made of a single atomic layer of carbon atoms arranged in a regular hexagonal lattice to form a two-dimensional crystal.
In a thermal detector, the energy of the incident radiation is estimated by the temperature change of the absorber. Low temperature and small heat capacity permit better performance.
The electronic and thermal properties of graphene at low temperatures make it an ideal candidate for absorbing electromagnetic radiation with energy less than 3 eV (λ> 400 nm).
By means of noise thermometry techniques, we intend to measure the heating of an absorber made of graphene by using low noise amplifiers such as SQUID and HEMT amplifiers down to temperatures of the order of some tens of mK. The Johnson voltage noise VTh=4kBTRgraph associated with the graphene foil resistance Rgraph is proportional to the temperature T of the charge carriers (electrons). Thanks to its very low noise temperature a SQUID amplifier (see figure) is able to measure the thermal noise VTh. From the measured values of VTh and Rgraph the temperature of the absorber constituted by the graphene electrons can be evaluated.
The sensitivity of the detector depends on many factors such as the dimensions and purity of the graphene foil, the mechanisms of the heat flow from the graphene electron gas, the operating temperature, the sensitivity of the used amplifier etc.
The first goal of the project is the evaluation of the limit of the performance of this detector by also considering possible schemes to improve the quantum efficiency and the scalability.
The second objective is to test the device as a detector of weak visible light in view of its use in ultracryogenic experiments of the type Double Beta Decay and/or Dark Matter.
The development of the project will be based on a close collaboration between INFN, University of Trento and the Fondazione Bruno Kessler (FBK) as regards the involved researchers, the equipment and the facilities in accordance with the recent agreement which aims to support TIFPA.
The project will also benefit from the recently started collaborations in the framework of the important European initiative “Graphene Flagship”, in which the Bruno Kessler Foundation is responsible of two research activities.
TEAM
• Involved external institutions: /
• INFN groups: Laboratori Nazionali di Legnaro, TIFPA, Catania, Milano, Padova
• Principal Investigator: Paolo Falferi (FBK Trento)
• INFN Project: CSN V
• Duration: 3 years (2014-2016)
TIFPA Team
• Local responsible for TIFPA: Paolo Falferi (FBK Trento)
• Involved TIFPA people: Benno Marghesin, Renato Mezzena, Nicola Pugno, Giorgio Speranza
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