We recently demonstrated in collaboration with the LPENS (Emmanuel Baudin’s team) that when graphenebased transistors encapsulated in boron nitride (hBN) are subjected to a large bias voltage, electroluminescent radiation is produced in the mid-infrared spectral range [Abou-Hamdan2024]. The phenomenon of non-incandescent infrared emission is accompanied by efficient evacuation of the electrical power applied to the devices mediated by the excitation of hyperbolic polariton phonons in hBN. The measurements we have carried out to date to investigate this phenomenon are far-field measurements involving an infrared microscope coupled to a Fourier transform infrared spectrometer, using a method called infrared spatial modulation spectroscopy [Li2018 ; Abou-Hamdan2022].
As part of this post-doctoral fellowship, we wish to extend our knowledge of the phenomenon by carrying out super-resolved near-field measurements in the infrared using a local scanning probe called TRSTM (thermal radiation scanning tunnelling microscope). The instrument developed by our team is similar to an infrared scanning near-field optical microscope (SNOM), which detects the electromagnetic fields produced by the sample itself through thermal fluctuations or other processes, rather than using external illumination. It uses a tungsten tip as a local scatterer of the infrared radiation emitted at the sample surface [DeWilde2006]. The scattered electromagnetic field is then collected and guided in free space towards a mid-infrared detector coupled to a commercial Fourier transform infrared spectrometer (FTIR).
Since graphene-based transistors have a typical width of 10 – 30 µm and nanostructured electrodes, the spatial resolution of far-field measurements is insufficient to observe the exact location of the infrared electroluminescent signal they produce. The aim of the near-field TRSTM measurements is then to obtain super-resolved images and spectra of the infrared radiation emitted by the graphene-based device in operation, with a spatial resolution of 100 nm. A similar approach was successfully used in our team to investigate non-Planckian near-field thermal radiation [Babuty2013].
In addition, the post-doctoral research will also aim to use intense laser illumination to excite thermally some specific electromagnetic modes of infrared plasmonic nano-antennas [Langevin2024] in order to produce optically programmable infrared sources. Such optically programmable devices produced in collaboration with ONERA and C2N could be of use in the future for free space infrared telecommunications.
This post-doctorate is part of the ELuSeM project funded by the French National Research Agency. The postdoc will be carried out at Institut Langevin (Yannick De Wilde’s team) in collaboration with the Physics Laboratory of the Ecole Normale Supérieure (LPENS) in Paris, the Laboratoire Charles Fabry-IOGS, the ONERA, among others. The graphene devices are produced and characterized electrically by the team of Emmanuel Baudin at ENS (PI of the project), while the optical measurements are performed at Institut Langevin. The infrared plasmonic antenna devices are conceived at ONERA by the team of Patrick Bouchon, and fabricated at C2N. Theoretical modeling is performed at Laboratory Charles Fabry by the team of Jean-Jacques Greffet.
REFERENCES:
- [Abou-Hamdan2024] L. Abou-Hamdan et al., manuscript under revision (2024).
- [Li2018] C. Li et al. , Phys. Rev. Lett. 121, 243901 (2018).
- [Abou-Hamdan2022] L. Abou-Hamdan et al., ACS Photonics 9, 7, 2295–2303 (2022).
- [DeWilde2006] Y. De Wilde et al., Nature 444, 740–743 (2006).
- [Babuty2013] A. Babuty et al., Phys. Rev. Lett. 110, 146103 (2013).
- [Langevin2024] D. Langevin et al., Phys. Rev. Lett. 132, 043801 (2024).
ACTIVITIES:
Main tasks in experimental physics:
- Ultra-sensitive infrared measurements
- TRSTM measurements (infrared SNOM without external source) – SNOM (homemade setup with RHK control electronics)
- FTIR spectroscopy; IR SMS (spatially-modulated infrared spectroscopy)
- Setting up laser heating of plasmonic antennas on measurement bench
- Electromagnetic modeling
Secondary tasks:
- Design of plasmonic antenna samples for lithography
- Contribution to other experimental studies
Required skills:
- Mastery of near-field microscopy techniques. Desirable experience: manipulation with infrared SNOM; manipulation, preferably with RHK control electronics; FTIR spectroscopy.
- FTIR spectroscopy; infrared nano-spectroscopy
- Electromagnetic modeling
