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Direct and indirect methods for calculating thermal emission from layered structures with nonuniform temperatures / L. P. Wang in Journal of heat transfer, Vol. 133 N° 7 (Juillet 2011) 

Public ISBD [article]  in Journal of heat transfer > Vol. 133 N° 7 (Juillet 2011) . - pp. [072701/1-7] Titre : Direct and indirect methods for calculating thermal emission from layered structures with nonuniform temperatures Type de document : texte imprimé Auteurs : L. P. Wang, Auteur ; S. Basu, Auteur ; Z. M. Zhang, Auteur Année de publication : 2011 Article en page(s) : pp. [072701/1-7] Note générale : Physique Langues : Anglais (eng) Mots-clés : Generalizes  Kirchhoff's  law  Thermal  emission  Fluctuational  electrodynamics  Multilayers Index. décimale : 536 Chaleur. Thermodynamique Résumé : The determination of emissivity of layered structures is critical in many applications, such as radiation thermometry, microelectronics, radiative cooling, and energy harvesting. Two different approaches, i.e., the “indirect” and “direct” methods, are commonly used for computing the emissivity of an object. For an opaque surface at a uniform temperature, the indirect method involves calculating the spectral directional-hemispherical reflectance to deduce the spectral directional emissivity based on Kirchhoff's law. On the other hand, a few studies have used a combination of Maxwell's equations with the fluctuation-dissipation theorem to directly calculate the emissivity. The present study aims at unifying the direct and indirect methods for calculating the far-field thermal emission from layered structures with a nonuniform temperature distribution. Formulations for both methods are given to illustrate the equivalence between the indirect and the direct methods. Thermal emission from an asymmetric Fabry–Pérot resonance cavity with a nonuniform temperature distribution is taken as an example to show how to predict the intensity, emissivity, and the brightness temperature. The local density of states, however, can only be calculated using the direct method. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO00013300 [...] [article] Direct and indirect methods for calculating thermal emission from layered structures with nonuniform temperatures [texte imprimé] / L. P. Wang, Auteur ; S. Basu, Auteur ; Z. M. Zhang, Auteur . - 2011 . - pp. [072701/1-7]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 7 (Juillet 2011) . - pp. [072701/1-7] Mots-clés : Generalizes  Kirchhoff's  law  Thermal  emission  Fluctuational  electrodynamics  Multilayers Index. décimale : 536 Chaleur. Thermodynamique Résumé : The determination of emissivity of layered structures is critical in many applications, such as radiation thermometry, microelectronics, radiative cooling, and energy harvesting. Two different approaches, i.e., the “indirect” and “direct” methods, are commonly used for computing the emissivity of an object. For an opaque surface at a uniform temperature, the indirect method involves calculating the spectral directional-hemispherical reflectance to deduce the spectral directional emissivity based on Kirchhoff's law. On the other hand, a few studies have used a combination of Maxwell's equations with the fluctuation-dissipation theorem to directly calculate the emissivity. The present study aims at unifying the direct and indirect methods for calculating the far-field thermal emission from layered structures with a nonuniform temperature distribution. Formulations for both methods are given to illustrate the equivalence between the indirect and the direct methods. Thermal emission from an asymmetric Fabry–Pérot resonance cavity with a nonuniform temperature distribution is taken as an example to show how to predict the intensity, emissivity, and the brightness temperature. The local density of states, however, can only be calculated using the direct method. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO00013300 [...]

Direct measurement of thermal emission from a fabry–perot cavity resonator / L. P. Wang in Journal of heat transfer, Vol. 134 N° 7 (Juillet 2012) 

Public ISBD [article]  in Journal of heat transfer > Vol. 134 N° 7 (Juillet 2012) . - 09 p. Titre : Direct measurement of thermal emission from a fabry–perot cavity resonator Type de document : texte imprimé Auteurs : L. P. Wang, Auteur ; S. Basu, Auteur ; Z. M. Zhang, Auteur Année de publication : 2012 Article en page(s) : 09 p. Note générale : heat transfer Langues : Anglais (eng) Mots-clés : high  temperature;  thermal  emission;  thin  films;  wave  interference Index. décimale : 536 Chaleur. Thermodynamique Résumé : There have been growing interests in selective control of thermal emission by using micro/nanostructures. The present study describes direct measurements of infrared thermal emission at elevated temperatures of an asymmetric Fabry–Perot resonator at variable angles for each polarization. The multilayered structure mainly contains a SiO2 optical cavity sandwiched between a thick (opaque) Au film and a thin Au film. Metallic adhesive and diffusion-barrier layers were deposited on a Si substrate before depositing the thick Au film. A dielectric protection layer was deposited atop the thin Au film to prevent oxidation at high temperatures. A SiC wafer was used as the reference to test the emittance measurement facility, which includes a heated sample holder, a blackbody source, mirror assembly, a polarizer, and a Fourier-transform infrared spectrometer with different detectors. The measured emittance spectra of the Fabry–Perot structure exhibit peak broadening and shifting as temperature increases; the mechanisms are elucidated by comparison with theoretical modeling. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000134000007 [...] [article] Direct measurement of thermal emission from a fabry–perot cavity resonator [texte imprimé] / L. P. Wang, Auteur ; S. Basu, Auteur ; Z. M. Zhang, Auteur . - 2012 . - 09 p. heat transfer Langues : Anglais (eng) in Journal of heat transfer > Vol. 134 N° 7 (Juillet 2012) . - 09 p. Mots-clés : high  temperature;  thermal  emission;  thin  films;  wave  interference Index. décimale : 536 Chaleur. Thermodynamique Résumé : There have been growing interests in selective control of thermal emission by using micro/nanostructures. The present study describes direct measurements of infrared thermal emission at elevated temperatures of an asymmetric Fabry–Perot resonator at variable angles for each polarization. The multilayered structure mainly contains a SiO2 optical cavity sandwiched between a thick (opaque) Au film and a thin Au film. Metallic adhesive and diffusion-barrier layers were deposited on a Si substrate before depositing the thick Au film. A dielectric protection layer was deposited atop the thin Au film to prevent oxidation at high temperatures. A SiC wafer was used as the reference to test the emittance measurement facility, which includes a heated sample holder, a blackbody source, mirror assembly, a polarizer, and a Fourier-transform infrared spectrometer with different detectors. The measured emittance spectra of the Fabry–Perot structure exhibit peak broadening and shifting as temperature increases; the mechanisms are elucidated by comparison with theoretical modeling. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000134000007 [...]

Entropy generation in thin films evaluated from phonon radiative transport / T. J. Bright in Journal of heat transfer, Vol. 132 N° 10 (Octobre 2010) 

Public ISBD [article]  in Journal of heat transfer > Vol. 132 N° 10 (Octobre 2010) . - pp. [101301-1/9] Titre : Entropy generation in thin films evaluated from phonon radiative transport Type de document : texte imprimé Auteurs : T. J. Bright, Auteur ; Z. M. Zhang, Auteur Année de publication : 2010 Article en page(s) : pp. [101301-1/9] Note générale : Physique Langues : Anglais (eng) Mots-clés : Conduction  Entropy  Phonon  radiative  transfer  Thermodynamics  Thin  film Index. décimale : 536 Chaleur. Thermodynamique Résumé : One of the approaches for micro/nanoscale heat transfer in semiconductors and dielectric materials is to use the Boltzmann transport equation, which reduces to the equation of phonon radiative transfer under the relaxation time approximation. Transfer and generation of entropy are processes inherently associated with thermal energy transport, yet little has been done to analyze entropy generation in solids at length scales comparable with or smaller than the mean free path of heat carriers. This work extends the concept of radiation entropy in a participating medium to phonon radiation, thus, providing a method to evaluate entropy generation at both large and small length scales. The conventional formula for entropy generation in heat diffusion can be derived under the local equilibrium assumption. Furthermore, the phonon brightness temperature is introduced to describe the nature of nonequilibrium heat conduction. A diamond film is used as a numerical example to illustrate the distribution of entropy generation at the walls and inside the film at low temperatures. A fundamental knowledge of the entropy generation processes provides a thermodynamic understanding of heat transport in solid microstructures; this is particularly important for the performance evaluation of thermal systems and microdevices. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...] [article] Entropy generation in thin films evaluated from phonon radiative transport [texte imprimé] / T. J. Bright, Auteur ; Z. M. Zhang, Auteur . - 2010 . - pp. [101301-1/9]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 132 N° 10 (Octobre 2010) . - pp. [101301-1/9] Mots-clés : Conduction  Entropy  Phonon  radiative  transfer  Thermodynamics  Thin  film Index. décimale : 536 Chaleur. Thermodynamique Résumé : One of the approaches for micro/nanoscale heat transfer in semiconductors and dielectric materials is to use the Boltzmann transport equation, which reduces to the equation of phonon radiative transfer under the relaxation time approximation. Transfer and generation of entropy are processes inherently associated with thermal energy transport, yet little has been done to analyze entropy generation in solids at length scales comparable with or smaller than the mean free path of heat carriers. This work extends the concept of radiation entropy in a participating medium to phonon radiation, thus, providing a method to evaluate entropy generation at both large and small length scales. The conventional formula for entropy generation in heat diffusion can be derived under the local equilibrium assumption. Furthermore, the phonon brightness temperature is introduced to describe the nature of nonequilibrium heat conduction. A diamond film is used as a numerical example to illustrate the distribution of entropy generation at the walls and inside the film at low temperatures. A fundamental knowledge of the entropy generation processes provides a thermodynamic understanding of heat transport in solid microstructures; this is particularly important for the performance evaluation of thermal systems and microdevices. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...]

Infrared radiative properties of heavily doped silicon at room temperature / S. Basu in Journal of heat transfer, Vol. 132 N° 2 (n° spécial) (Fevrier 2010) 

Public ISBD [article]  in Journal of heat transfer > Vol. 132 N° 2 (n° spécial) (Fevrier 2010) . - pp. [023301-1/8] Titre : Infrared radiative properties of heavily doped silicon at room temperature Type de document : texte imprimé Auteurs : S. Basu, Auteur ; B. J. Lee, Auteur ; Z. M. Zhang, Auteur Article en page(s) : pp. [023301-1/8] Note générale : Physique Langues : Anglais (eng) Mots-clés : Microscale  Doped  silicon  Radiative  properties  Thin  films Index. décimale : 536 Chaleur. Thermodynamique Résumé : This paper describes an experimental investigation on the infrared radiative properties of heavily doped Si at room temperature. Lightly doped Si wafers were ion-implanted with either boron or phosphorus atoms, with dosages corresponding to as-implanted peak doping concentrations of 1020 and 1021 cm−3; the peak doping concentrations after annealing are 3.1×1019 and 2.8×1020 cm−3, respectively. Rapid thermal annealing was performed to activate the implanted dopants. A Fourier-transform infrared spectrometer was employed to measure the transmittance and reflectance of the samples in the wavelength range from 2 µm to 20 µm. Accurate carrier mobility and ionization models were identified after carefully reviewing the available literature, and then incorporated into the Drude model to predict the dielectric function of doped Si. The radiative properties of doped Si samples were calculated by treating the doped region as multilayer thin films of different doping concentrations on a thick lightly doped Si substrate. The measured spectral transmittance and reflectance agree well with the model predictions. The knowledge gained from this study will aid future design and fabrication of doped Si microstructures as wavelength selective emitters and absorbers in the midinfrared region. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...] [article] Infrared radiative properties of heavily doped silicon at room temperature [texte imprimé] / S. Basu, Auteur ; B. J. Lee, Auteur ; Z. M. Zhang, Auteur . - pp. [023301-1/8]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 132 N° 2 (n° spécial) (Fevrier 2010) . - pp. [023301-1/8] Mots-clés : Microscale  Doped  silicon  Radiative  properties  Thin  films Index. décimale : 536 Chaleur. Thermodynamique Résumé : This paper describes an experimental investigation on the infrared radiative properties of heavily doped Si at room temperature. Lightly doped Si wafers were ion-implanted with either boron or phosphorus atoms, with dosages corresponding to as-implanted peak doping concentrations of 1020 and 1021 cm−3; the peak doping concentrations after annealing are 3.1×1019 and 2.8×1020 cm−3, respectively. Rapid thermal annealing was performed to activate the implanted dopants. A Fourier-transform infrared spectrometer was employed to measure the transmittance and reflectance of the samples in the wavelength range from 2 µm to 20 µm. Accurate carrier mobility and ionization models were identified after carefully reviewing the available literature, and then incorporated into the Drude model to predict the dielectric function of doped Si. The radiative properties of doped Si samples were calculated by treating the doped region as multilayer thin films of different doping concentrations on a thick lightly doped Si substrate. The measured spectral transmittance and reflectance agree well with the model predictions. The knowledge gained from this study will aid future design and fabrication of doped Si microstructures as wavelength selective emitters and absorbers in the midinfrared region. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...]

Near-field radiation calculated with an improved dielectric function model for doped silicon / S. Basu in Journal of heat transfer, Vol. 132 N° 2 (n° spécial) (Fevrier 2010) 

Public ISBD [article]  in Journal of heat transfer > Vol. 132 N° 2 (n° spécial) (Fevrier 2010) . - pp. [023302-1/7] Titre : Near-field radiation calculated with an improved dielectric function model for doped silicon Type de document : texte imprimé Auteurs : S. Basu, Auteur ; B. J. Lee, Auteur ; Z. M. Zhang, Auteur Article en page(s) : pp. [023302-1/7] Note générale : Physique Langues : Anglais (eng) Mots-clés : Doped  silicon  Lateral  shift  Near-field  radiation Index. décimale : 536 Chaleur. Thermodynamique Résumé : This paper describes a theoretical investigation of near-field radiative heat transfer between doped silicon surfaces separated by a vacuum gap. An improved dielectric function model for heavily doped silicon is employed. The effects of doping level, polarization, and vacuum gap width on the spectral and total radiative transfer are studied based on the fluctuational electrodynamics. It is observed that increasing the doping concentration does not necessarily enhance the energy transfer in the near-field. The energy streamline method is used to model the lateral shift of the energy pathway, which is the trace of the Poynting vectors in the vacuum gap. The local density of states near the emitter is calculated with and without the receiver. The results from this study can help improve the understanding of near-field radiation for applications such as thermophotovoltaic energy conversion, nanoscale thermal imaging, and nanothermal manufacturing. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...] [article] Near-field radiation calculated with an improved dielectric function model for doped silicon [texte imprimé] / S. Basu, Auteur ; B. J. Lee, Auteur ; Z. M. Zhang, Auteur . - pp. [023302-1/7]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 132 N° 2 (n° spécial) (Fevrier 2010) . - pp. [023302-1/7] Mots-clés : Doped  silicon  Lateral  shift  Near-field  radiation Index. décimale : 536 Chaleur. Thermodynamique Résumé : This paper describes a theoretical investigation of near-field radiative heat transfer between doped silicon surfaces separated by a vacuum gap. An improved dielectric function model for heavily doped silicon is employed. The effects of doping level, polarization, and vacuum gap width on the spectral and total radiative transfer are studied based on the fluctuational electrodynamics. It is observed that increasing the doping concentration does not necessarily enhance the energy transfer in the near-field. The energy streamline method is used to model the lateral shift of the energy pathway, which is the trace of the Poynting vectors in the vacuum gap. The local density of states near the emitter is calculated with and without the receiver. The results from this study can help improve the understanding of near-field radiation for applications such as thermophotovoltaic energy conversion, nanoscale thermal imaging, and nanothermal manufacturing. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...]

Near-field radiative transfer between heavily doped SiGe at elevated temperatures / Z. M. Zhang in Journal of heat transfer, Vol 134 N° 9 (Septembre 2012) 

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