New publication from the SUNLAB: Nano Letters
A multidisciplinary initiative between the University of Ottawa SUNLAB, Micro and Nano Systems Lab & Krich Lab, Princeton University and Polytechnique Montréal resulted in a recent publication first-authored by PhD candidate Mathieu Giroux, in Nano Letters. In this manuscript, the authors demonstrate the potential of using a silicon nitride (SiN) nanomechanical resonator as a sensing element to study near-field radiative heat transfer.
Near-field radiative heat transfer (NFRHT) has demonstrated great theoretical potential for applications such as energy conversion and heat transfer control. NFRHT consists of evanescent coupling occurring between two bodies at sub-wavelength distances, increasing the radiative heat transfer beyond the conventional laws of thermal radiation. Despite a large amount of promising theoretical work, experimental progress on the topic is relatively scarce due to challenges of precision alignment at high temperature. NFRHT measurements often rely on custom microdevices that can be difficult to reproduce after their original demonstration. In this work, the authors study NFRHT using plain SiN membrane nanomechanical resonators, a widely available substrate used in applications such as electron microscopy and optomechanics and on which other materials can easily be deposited.
Relying on a high precision 5-axis positioning system, a heated spherical sample was aligned with a SiN resonator, enabling radiative heat transfer measurement down to a minimal distance of 180 nm. The NFRHT is measured by tracking the highly temperature-sensitive mechanical resonance frequency of the membrane as the distance between the two surfaces is decreased. Comparison with the theoretical model demonstrate that, at the achieved deep subwavelength distance of 180 nm, the heat transfer is highly dominated by surface polariton resonances over an area comparable to plane-plane experiments employing custom microfabricated devices. This results in a quasi-monochromatic radiative heat transfer, desirable in most NFRHT applications.
The authors expect that the reproducibility and flexibility of this platform will facilitate investigation of new materials for NFRHT – such as graphene, thin-film metals, lossy materials, hyperbolic materials and metamaterials – which can all be easily deposited on SiN membranes. The fact that nanomechanical resonators are sensitive to both force and temperature also creates an opportunity to investigate thermal corrections to the Casimir effect.
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M. Giroux, M. Stephan, M. Brazeau, S. Molesky, A. W. Rodriguez, J. J. Krich, K. Hinzer, and R. St-Gelais, Measurement of near-field radiative heat transfer at deep sub-wavelength distances using nanomechanical resonators, Nano Lett. 23 (18), 8490-8497 (2023). DOI: 10.1021/acs.nanolett.3c02049