Browsing by Author "Francoeur, M."

Now showing 1 - 14 of 14

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Coexistence of multiple regimes for near-field thermal radiation between two layers supporting surface phonon polaritons in the infrared
(American Physical Society, 2011) Francoeur, M.; Mengüç, Mustafa Pınar; Vaillon, R.; Mechanical Engineering; MENGÜÇ, Mustafa Pınar
We demonstrate the coexistence of different near-field thermal radiation regimes between two layers supporting surface phonon polaritons (SPhPs) in the infrared. These regimes existwhen the distance of separation between the media d is much smaller than the dominant emission wavelength. This coexistence is noticed after computations of the near-field radiative heat transfer coefficient hr for silicon carbide films using fluctuational electrodynamics and following an asymptotic analysis of hr . We show that the emergence of these regimes is a function of a dimensionless variable D defined as the ratio of the layer thickness t to d. When D _ 1 for both films, SPhPs dominating near-field radiant energy exchange do not couple within the layers, such that hr follows a d−2 power law as for the case of two planar half-spaces.When D_1 for both layers, the dominant SPhPs couple within the films, thus resulting in a splitting of the spectral distribution of flux into two distinct modes. Despite this splitting, the asymptotic expansion reveals that hr varies as d−2 due to the fact that the spectral bands of high emission and absorption are essentially the same for both films. However, when both layers have a thickness of the order of a nanometer or less, a purely theoretical regime emerges where hr follows a d−4 asymptote. Also, when one layer has D _ 1 while the other one is characterized by D _ 1, there is an important mismatch between the spectral bands of high emission and absorption of the films, thus resulting in a hr varying as d−3. These various near-field thermal radiation regimes are finally summarized in a comprehensive regime map. This map provides a clear understanding of near-field thermal radiation regimes between two layers, which are particularly important for designing highly efficient nanoscale-gap thermophotovoltaic power generation devices.
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Concluding remarks and future directions
(Elsevier, 2023-01-01) Francoeur, M.; Mengüç, Mustafa Pınar; Mechanical Engineering; MENGÜÇ, Mustafa Pınar
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Control of near-field radiative heat transfer via surface phonon-polariton coupling in thin films
(Springer Business+Media, 2011-06) Francoeur, M.; Mengüç, Mustafa Pınar; Vaillon, R.; Mechanical Engineering; MENGÜÇ, Mustafa Pınar
The possibility of controlling near-field radiative heat transfer with the use of silicon carbide thin films supporting surface phonon–polaritons in the infrared spectrum is explored. For this purpose, the local density of electromagnetic states is calculated and analyzed within the nanometric gap formed between two SiC films as well as the radiative heat flux exchanged between the thin layers.
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Coupling of near-field thermal radiative heating and phonon Monte Carlo simulation: Assessment of temperature gradient in n-doped silicon thin film
(Elsevier, 2014-08) Wong, B. T.; Francoeur, M.; Bong, V. N.-S.; Mengüç, Mustafa Pınar; Mechanical Engineering; MENGÜÇ, Mustafa Pınar
Near-field thermal radiative exchange between two objects is typically more effective than the far-field thermal radiative exchange as the heat flux can increase up to several orders higher in magnitudes due to tunneling of evanescent waves. Such an interesting phenomenon has started to gain its popularity in nanotechnology, especially in nano-gap thermophotovoltaic systems and near-field radiative cooling of micro-/nano-devices. Here, we explored the existence of thermal gradient within an n-doped silicon thin film when it is subjected to intensive near-field thermal radiative heating. The near-field radiative power density deposited within the film is calculated using the Maxwell equations combined with fluctuational electrodynamics. A phonon Monte Carlo simulation is then used to assess the temperature gradient by treating the near-field radiative power density as the heat source. Results indicated that it is improbable to have temperature gradient with the near-field radiative heating as a continuous source unless the source comprises of ultra-short radiative pulses with a strong power density.
Open Access
Credible intervals for nanoparticle characteristics
(Elsevier, 2012-01) Charnigo, R.; Francoeur, M.; Kenkel, P.; Mengüç, Mustafa Pınar; Hall, B.; Srinivasan, C.; Mechanical Engineering; MENGÜÇ, Mustafa Pınar
Solving the inverse problem of nanoparticle characterization has the potential to advance science and benefit society. While considerable progress has been made within a framework based on the scattering of surface plasmon-polaritons, an aspect not heretofore considered is the quantification of uncertainty in the estimation of a nanoparticle characteristic. Therefore, the present article offers a technique by which an investigator may augment an estimate of a nanoparticle characteristic with a companion “credible interval”. Analogous to the familiar confidence interval but arising from within the Bayesian statistical paradigm, a credible interval allows the investigator to make a statement such as “the nanoparticle diameter lies between 36 and 48 nm with 95% probability” instead of merely “the nanoparticle diameter is estimated to be 42 nm”. Our technique may even be applied outside of the surface plasmon-polariton scattering framework, as long as the investigator specifies his/her prior beliefs about the nanoparticle characteristic and indicates which potential outcomes are likely or unlikely in whatever experiment he/she designs to estimate the nanoparticle characteristic. Two numerical studies illustrate the implementation and performance of our technique in constructing ranges of likely values for nanoparticle diameters and agglomeration levels, respectively.
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Estimating quantitative features of nanoparticles using multiple derivatives of scattering profiles
(Elsevier, 2011-05) Charnigo, R.; Francoeur, M.; Kenkel, P.; Mengüç, Mustafa Pınar; Hall, B.; Srinivasan, C.; Mechanical Engineering; MENGÜÇ, Mustafa Pınar
Characterization of nanoparticles on surfaces is a challenging in verse problem whose solution has many practical applications. This article proposes a method, suitable for in situ characterization systems, for estimating quantitative features of nanoparticles on surfaces from scattering profiles and their derivatives. Our method enjoys a number of advantages over competing approaches to this inverse problem. One such advantage is that only a partial solution is required for the companion direct problem. For example, estimating the average diameter of nanoparticles to be 53 nm is possible even when a researcher’s existing scattering data pertain to nanoparticles whose average diameters are in multiples of 5 nm. Two numerical studies illustrate the implementation and performance of our method for inferring nanoparticle diameters and agglomeration levels respectively.
Open Access
Local density of electromagnetic states within a nanometric gap formed between two thin films supporting surface phonon polaritons
(AIP Publishing, 2010) Francoeur, M.; Mengüç, Mustafa Pınar; Vaillon, R.; Mechanical Engineering; MENGÜÇ, Mustafa Pınar
We present a detailed physical analysis of the near-field thermal radiation spectrum emitted by a silicon carbide (SiC) film when another nonemitting SiC layer is brought in close proximity. This is accomplished via the calculation of the local density of electromagnetic states (LDOS) within the gap formed between the two thin films. An analytical expression for the LDOS is derived, showing explicitly that (i) surface phonon polariton (SPhP) coupling between the layers leads to four resonant modes, and (ii) near-field thermal radiation emission is enhanced due to the presence of the nonemitting film. We study the impact of the interfilm separation gap, the distance where the fields are calculated, and the thickness of the nonemitting layer on the spectral distribution of the LDOS. Results show that for an interfilm gap of 10 nm, the near-field spectrum emitted around the SPhP resonance can increase more than an order of magnitude as compared to a single emitting thin layer. Interfilm SPhP coupling also induces a loss of spectral coherence of resonance, mostly affecting the low frequency modes. The effect of the nonemitting film can be observed on LDOS profiles when the distance where the fields are calculated is close to the interfilm gap. As the LDOS is calculated closer to the emitter, the near-field spectrum is dominated by SPhPs with small penetration depths that do not couple with the modes associated with the nonemitting film, such that thermal emission is similar to what is observed for a single emitting layer. Spectral distribution of LDOS is also significantly modified by varying the thickness of the nonemitting film relative to the thickness of the emitting layer, due to an increasing mismatch between the cross-coupled SPhP modes. The results presented here show clearly that the resonant modes of thermal emission by a polar crystal can be enhanced and tuned, between the transverse and longitudinal optical phonon frequencies, by simply varying the structure of the system. This analysis provides the physical grounds to tune near-field thermal radiation emission via multilayered structures, which can find application in nanoscale-gap thermophotovoltaic power generation.
Open Access
A Monte Carlo simulation for phonon transport within silicon structures at nanoscales with heat generation
(Elsevier, 2011-04) Wong, B. T.; Francoeur, M.; Mengüç, Mustafa Pınar; Mechanical Engineering; MENGÜÇ, Mustafa Pınar
Nanoscale phonon transport within silicon structures subjected to internal heat generation was explored. A Monte Carlo simulation was used. The simulation procedures differed from the current existing methods in which phonons below a predefined “reference temperature” were not accounted to reduce memory storage and computational resources. Results indicated that the heat diffusion equation significantly underestimates temperature distribution at nanoscales in the presence of an external heat source. Discussions on temperature distribution inside silicon thin film when heated by a pulsed laser, an electron beam or due to near-field thermal radiation effects were also provided.
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Overview of light, plasmonics, and particles
(Elsevier, 2023-01-01) Mengüç, Mustafa Pınar; Francoeur, M.; Mechanical Engineering; MENGÜÇ, Mustafa Pınar
In this chapter, we present a short discussion about light and its importance in nature, human civilizations, and society, and provide some cultural discussions. We briefly mention the interconnections between electromagnetic wave propagation, absorption, scattering, plasmonics, thermal emission, and near-field radiative transfer. We also provide an overview of the chapters in the book to help the reader to start their pursuit of interdisciplinary studies of light, plasmonics, and particles.
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Preface
(Elsevier, 2023-01-01) Mengüç, Mustafa Pınar; Francoeur, M.; Mechanical Engineering; MENGÜÇ, Mustafa Pınar
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Solution of near-field thermal radiation in one-dimensional layered media using dyadic Green's functions and the scattering matrix method
(Elsevier, 2009-12) Francoeur, M.; Mengüç, Mustafa Pınar; Vaillon, R.; Mechanical Engineering; MENGÜÇ, Mustafa Pınar
A general algorithm is introduced for the analysis of near-field radiative heat transfer in one-dimensional multi-layered structures. The method is based on the solution of dyadic Green's functions, where the amplitude of the fields in each layer is calculated via a scattering matrix approach. Several tests are presented where cubic boron nitride is used in the simulations. It is shown that a film emitter thicker than 1 μm provides the same spectral distribution of near-field radiative flux as obtained from a bulk emitter. Further simulations have pointed out that the presence of a body in close proximity to an emitter can alter the near-field spectrum emitted. This algorithm can be employed to study thermal one-dimensional layered media and photonic crystals in the near-field in order to design radiators optimizing the performances of nanoscale-gap thermophotovoltaic power generators.
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Special issue on the Third International Workshop on Nano-micro Thermal Radiation (NanoRad’17)
(Elsevier, 2019-11) Lee, B. J.; Shuai, Y.; Francoeur, M.; Mengüç, Mustafa Pınar; Mechanical Engineering; MENGÜÇ, Mustafa Pınar
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Spectral tuning of near-field radiative heat flux between two thin silicon carbide films
(Institute of Physics, 2010) Francoeur, M.; Mengüç, Mustafa Pınar; Vaillon, R.; Mechanical Engineering; MENGÜÇ, Mustafa Pınar
Spectral distributions of radiative heat flux between two thin silicon carbide films separated by sub-wavelength distances in vacuum are analysed. An analytical expression for the near-field flux between two layers of finite thicknesses in terms of film reflection and transmission coefficients is derived for the first time. The resulting equation clearly shows the resonant modes of thermal emission, absorption and the cross-coupling of surface phonon-polaritons (SPhPs) between the layers. When the films are of the same thickness, the resonant frequencies maximizing near-field thermal emission almost match those of absorption. The small discrepancies, due to SPhP coupling between the films, lead to loss of spectral coherence affecting mostly the low frequency mode. The flux profiles also show that splitting of the resonance into two distinct frequencies happens when the ratio thickness of the film over the separation gap is less than unity. When the thickness of one film increases relative to the other, spectral distributions of flux are significantly altered due to an important mismatch between the resonant frequencies of high emission and absorption. This modification of the near-field flux is mostly due to weaker SPhP coupling within the layer of increasing thickness. Based on an asymptotic analysis of the dispersion relation, an approximate approach is proposed to predict the resonant modes maximizing the flux between two films, which can be potentially extended to multiple thin layers. The outcome of this work would allow tailoring near-field radiative heat transfer, and can eventually be used to design customized nanostructures for energy harvesting applications.
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Thermal impacts on the performance of nanoscale-gap thermophotovoltaic power generators
(IEEE, 2011-06) Francoeur, M.; Vaillon, R.; Mengüç, Mustafa Pınar; Mechanical Engineering; MENGÜÇ, Mustafa Pınar
The thermal impacts on the performance of nanoscale-gap thermophotovoltaic (nano-TPV) power generators are investigated using a coupled near-field thermal radiation, charge, and heat transport formulation. A nano-TPV device consisting of a tungsten radiator, maintained at 2000 K, and cells made of indium gallium antimonide (In0.18Ga0.82 Sb) are considered; the thermal management system is modeled assuming a convective boundary with a fluid temperature fixed at 293 K. Results reveal that nano-TPV performance characteristics are closely related to the temperature of the cell. When the radiator and the junction are separated by a 20 nm vacuum gap, the power output and the conversion efficiency of the system are respectively 5.83 × 105 Wm−2 and 24.8% at 300 K, whereas these values drop to 8.09 × 104 Wm−2 and 3.2% at 500 K. In order to maintain the cell at room temperature, a heat transfer coefficient as high as 105 Wm−2 K−1 is required for nanometer-size vacuum gaps. The reason for this is that thermal radiation since thermal radiation enhancement beyond the blackbody from a bulk radiator of tungsten is broadband in nature, while only a certain part of the spectrum is useful for maximizing nano-TPV performance. In future studies, near-field radiation spectral conditions leading to optimal performance characteristics of the device will be investigated.