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Tunable Radiation Tolerant 2D Terahertz bolometer

Periodic Reporting for period 1 - TURANDOT (Tunable Radiation Tolerant 2D Terahertz bolometer)

Reporting period: 2019-09-01 to 2021-08-31

THz fingerprints of space objects are of a great value as they provide the insights into history of the Universe, formation and evolution of galaxies and their central supermassive black holes, and other fundamental problems of astrophysics. Detection and decoding of these ultra-weak signals currently rely on bolometers, the most sensitive detectors of the sub-millimetre wavelengths radiation. In particular, THz bolometers are key elements of Herschel Space Observatory, James Clerk Maxwell Telescope and Stratospheric Observatory for Infrared Astronomy . Since the durability and robustness are vital for these systems , in “The 2017 terahertz science and technology roadmap” ultrafast and ultrasensitive THz detectors for continuous and pulsed radiation are listed among the most important challenges.

Bolometers require materials capable to efficiently absorb radiation and having a low heat capacitance. Correspondingly, the thermal resistance and heat capacity, which ultimately defines sensitivity and response time of the bolometer, respectively, are materials parameters of crucial importance. Another important issue for THz astronomy is necessity to tune the detection wavelength in a wide range in which the radiation of the astrophysics objects may occur. Finally, detection of the THz signals by space telescopes implies high resistance of the bolometer to ionizing radiation. Concluding, only materials that combine (i) high absorption ability, (ii) frequency tunability and (iii) radiation hardness can offer efficient platform for ultrafast and ultrasensitive THz bolometer for space applications.

The primary goal of TURANDOT was to combine advantages of graphene and transition metals dichalcogenides (TMD) monolayers to approach the design concept for ultrathin, ultrasensitive and ultrafast THz bolometer, which paves the way towards new generation of THz detectors for space application having unprecedented tunability and remarkable radiation tolerance.
We have established a solid theoretical background that enables utilizing thin carbon films (graphene and other graphitic materials) in THz bolometers. The numerical simulation allowed us to develop carbon-based metasurfaces of enhanced absorption ability that can be employed for detecting ultraweak electromagnetic radiation in a broad frequency range. We demonstrate that in order to achieve perfect absorption, the metasurface should possess low reflectivity and transmissivity, while the material used should allow excitation of a dark plasmon.

We observed nearly zero THz transmittivity and zero reflectivity was observed for free standing graphene metasurface film organized in the regular array of hemispheres. The fabricated metasurface demonstrate almost perfect absorption in the broad THz range spanning over more than one decade from 100 GHz. It is worth noting that the obtained transmittivity is four times lower than that can be achieved in the flat free standing graphene sheet of the same conductivity.

In order to understand the radiation tolerance of the graphene-based bolometers we investigated both theoretically and experimentally the formation of the defects under irradiation of the heterostructures with energetic ion beams. It has been shown that particles’ flux at the geostationary orbit cannot cause tangible damage of the graphene-based THz bolometer. In particular, the damaging of the graphene/hBN multilayer due to the ions’ bombardment should not affect the performance of the fabricated THz detector, which remains unchanged for more than ten years.

Polarization-sensitive THz plasmonic interferometer was fabricated using exfoliated graphene/hBN heterostructures and validated in THz range. The proof-of-concept experiments with heterostructures made of Gr/hBN and Gr/TDMs as well as graphene based metasurfaces have been carried out. The optimal absorbing element configuration has been selected in view of its robustness vs graphene defects.

Know-how related to fabrication of free-standing corrugated graphene/polymer nanomembranes are analyzed to be used as technological basis of UEF spin-off company.

In the course of the project implementation Dr Polina Kuzhir has published 28 papers in peer-reviewed journals and made 3 invited presentations at the international conferences on discipline. She also delivered a series of invited lectures (on-line) within ERASMUS+ programme (24-30 May 2021) at the University of Cassino and Southern Lazio, Italy Active participation (with oral presentations) in a series of meetings "Photonics research community (RC) meets Cancer RC, Water RC, DrugTech RC" facilitated establishing collaboration between UEF research communities.
Research and innovation results of the TURANDOT project, in particular the synthesis routes for fabrication of graphitic membranes and graphene corrugated metasurface highly absorptive in THz range and having substantial robustness against the fabrication defects have been used as an input for the submission of innovation project funded by large infrastructural project funded by EC, ATTRACT phase 2, Theme 3: Breakthrough Terahertz Imaging or Ranging Systems, Modality B (IA) ‘Micromechanical Bolometers arrays for Terahertz hyperspectral imaging’ (h-cube), coordinated by Marco Lazzarino, Pisa University, CNR.

The h-cube project addresses the emerging need for low-cost, portable solutions for hyperspectral imaging in the terahertz (THz) region of the electromagnetic spectrum. Factors such as the cost of THz cameras (often > 50k€) and the lack of multi-frequency sensing (“color imaging”) capabilities still prevent wide deployment of THz sensing. h-cube aims at tackling these challenges and producing a game-changing, affordable (<2k€) solution that can be manufactured at scale.

ER and Supervisor have arrived at preliminary agreement with the Department administration on organizing UEF spin-off company under support of Photonics Finland Scaling up the TURANDOT uptakes to a wider industrial level will employ market proven, highly effective Business Finland tools: such as Startup hub, Open Business Environment Ecosystem, Government funding and support for fast companies’ growth. This activity is in progress.

The TURANDOT outcomes can be used for THz imaging from body scanners in airports, production quality control to larger-volume, every-day applications such as crop monitoring, building control and weapon identification in crowded environments. Thereby indirectly TURANDOT contributes to promotion of peace and the well-being of EU citizens, security and sustainable development of Europe.

In view of promoting equality, the influence of TURANDOT implementation to the female researcher career development cannot be overestimated. The project impact to the ER career development is incredibly high. Along with achieved scientific results Polina Kuzhir got Professorship in nanomaterials at the Department of Physics and Mathematics, University of Eastern Finland. She is the only female off 10 Professors in the department.

ER substantially improved her teaching profile being the primary supervisor of 7 MS thesis, 2 PhD thesis and co-supervisor of 1 PhD thesis at the Department of Physics and Mathematics in 2019-2021.
Performance of phase-sensitive room temperature THz detector.