Adhesive Tape Helps Create Innovative THz Photodetector
It is 10,000 times thinner than a sheet of paper and has been inspired by the discovery made by Nobel Prize winners Andre Geim and Konstantin Novoselov.
An international team of researchers, including scientists at HSE University and Moscow Pedagogical State University (MPGU), has developed a novel photodetector composed of a thin superconducting film, capable of detecting weak terahertz (THz) radiation. This discovery holds promise for studying objects in space, developing wireless broadband communication systems, and making advancements in spectroscopy. The study has been published in Nano Letters.
The study was conducted with support from the Russian Science Foundation (RSF), Projects No. 21-72-10117 and No. 23-72-00014.
Superconducting Hot-Electron Bolometers are a type of highly sensitive photodetectors capable of capturing low-intensity electromagnetic radiation in the terahertz range. These detectors find application in astronomy for studying space objects such as stars, galaxies, and cosmic microwave radiation. Additionally, they are sought after in security and medical diagnostic systems, as they facilitate the visualisation of concealed objects with resolutions reaching hundreds of micrometres.
When the photosensitive element of such a detector absorbs electromagnetic radiation, it undergoes local heating, leading to the formation of thermalised electrons with kinetic energy surpassing the material's average electron energy. The emergence of overheated electrons causes a shift in the resistance of the photosensitive element, thereby generating an electrical signal that can be measured.
Current commercial superconducting bolometers employing overheated electrons are manufactured using films produced through magnetron sputtering techniques. This technology presently lacks the capability to produce materials thinner than a few nanometres, whereas the detector's performance is directly influenced by the deposition quality.
An international team of researchers, including scientists at MIEM HSE, have proposed using a thinner material and an alternative method for applying the detector’s photosensitive element. Taking inspiration from Nobel Prize winners Andre Geim and Konstantin Novoselov, who produced graphene by repeatedly cleaving graphite with adhesive tape, the study authors successfully obtained ultrathin films of niobium diselenide (NbSe2) by delaminating atomic layers from the material using polymer adhesive tape.
Research Fellow, MIEM HSE
We worked as part of a large international collaboration consisting of specialists in photodetectors and experts in two-dimensional materials. We pooled our expertise to develop a sensitive and compact terahertz radiation detector with a thickness of just a few atomic layers of niobium diselenide, which is 10,000 times thinner than a standard sheet of office paper. Furthermore, this technology enables us to obtain materials with an optimal structure. It is easy to apply and does not require specialised equipment.
The authors also investigated the reaction of NbSe2 to THz radiation. They examined how the material heats up upon exposure to an electromagnetic wave and how the detector's properties vary depending on its environment—the substrate and electrodes—given that two-dimensional materials are sensitive to their surroundings. The scientists have also identified the mechanisms that constrain the sensitivity and speed of the detector.
The scientists emphasise that their pioneering work to develop a bolometric THz radiation detector demonstrates the potential for such a device to eventually surpass existing commercial solutions.
Doctoral student and Research Fellow, MIEM HSE
We have demonstrated that using the proposed technology makes it possible to manufacture a bolometric THz radiation detector with characteristics similar to those of existing commercial counterparts.
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