Heat Transfer in Thin Films Thomas Prevenslik Berlin
Heat Transfer in Thin Films Thomas Prevenslik Berlin, Germany Hong Kong, China Third Int. Conf. Quantum, Nano, and Micro Tech. (ICQNM 2009) February 1 -6, 2009 — Cancun, Mexico 1
Background Over the past 30 years, heat transfer in thin films has been based on classical methods. However, for films less than about 100 nm, classical heat transfer cannot explain the reduced thermal conductivity found in experiments. Third Int. Conf. Quantum, Nano, and Micro Tech. (ICQNM 2009) February 1 -6, 2009 — Cancun, Mexico 2
Experiment Pulse Method (Thin Solid Films, Kelemen, 36 (1976) 199 -203) F W S Thermal Diffusivity Substrate Film T 2 X 1 T 1 Wire K = thermal conductivity = density, c = specific heat Problem Diffusivity diverges as c 0 Can conductivity K be measured by Pulse Method? Data Shows K 0 as 0 Third Int. Conf. Quantum, Nano, and Micro Tech. (ICQNM 2009) February 1 -6, 2009 — Cancun, Mexico 3
Current Approach To explain reduced conductivity data, Fourier heat conduction theory is thought not applicable to thin films having thickness smaller than the mean free paths of phonons. Heat Transfer in thin films is modified to treat phonons as particles in the Boltzmann Transport Equation (BTE). Third Int. Conf. Quantum, Nano, and Micro Tech. (ICQNM 2009) February 1 -6, 2009 — Cancun, Mexico 4
Experiment and BTE Theory Bulk Copper Third Int. Conf. Quantum, Nano, and Micro Tech. (ICQNM 2009) February 1 -6, 2009 — Cancun, Mexico 5
Purpose To provide a QM explanation for thin film heat transfer based on QED induced EM radiation using Standard Mixing Rules. QM = Quantum Mechanics QED = Quantum Electro Dynamics EM = Electromagnetic Third Int. Conf. Quantum, Nano, and Micro Tech. (ICQNM 2009) February 1 -6, 2009 — Cancun, Mexico 6
QED induced EM radiation Classically, heat is conserved by an increase in temperature. But at the nanoscale, QM forbids heat to be conserved by an increase in temperature because specific heat vanishes. QED allows heat to be conserved at the nanoscale by the emission of nonthermal EM radiation Third Int. Conf. Quantum, Nano, and Micro Tech. (ICQNM 2009) February 1 -6, 2009 — Cancun, Mexico 7
Nanoparticle or Quantum Dot NP, QD EM Emission Laser Radiation • • • No Temperature change Molecular Collisions Third Int. Conf. Quantum, Nano, and Micro Tech. (ICQNM 2009) February 1 -6, 2009 — Cancun, Mexico 8
Thin Film QCond QQED Current Approach QCond =QJoule Kelemen KF = KS [( F+S/ S)-1]( S / F) KF << KBulk QED Heat Transfer T 2 x 2 -x 1 T 1 QJoule QCond = QJoule -QQED Standard Mixing Rules eff= Keff / effceff = c. S and c. F = 0 eff =( FKF+ SKS)[( F/ S)+1]/[c. S( F F+ S S] KF = eff c. S [ F + S( S/ F)] - ( S/ F)KS KF ~ KBulk Third Int. Conf. Quantum, Nano, and Micro Tech. (ICQNM 2009) February 1 -6, 2009 — Cancun, Mexico 9
EM Confinement Photons in Rectangular cavity resonator, nr > 1 For << W and L, 2 nr Third Int. Conf. Quantum, Nano, and Micro Tech. (ICQNM 2009) February 1 -6, 2009 — Cancun, Mexico 10
Specific Heat Thin films cannot conserve the Joule heat by an increase in temperature because specific heat vanishes Specific heat by Debye/Einstein Model for atomic vibration gives slow phonon (ps) response. Excitons in QDs produced promptly (fs). Modify Einstein Model for atom vibration to photon vibration inside thin film. Third Int. Conf. Quantum, Nano, and Micro Tech. (ICQNM 2009) February 1 -6, 2009 — Cancun, Mexico 11
QM Restrictions Free Molecule Film Third Int. Conf. Quantum, Nano, and Micro Tech. (ICQNM 2009) February 1 -6, 2009 — Cancun, Mexico 12
Thin Film as an Einstein Solid NA = Number of Atoms in Film 3 NA Degrees of Freedom Third Int. Conf. Quantum, Nano, and Micro Tech. (ICQNM 2009) February 1 -6, 2009 — Cancun, Mexico 13
Einstein Specific Heat Einstein Debye & Einstein Third Int. Conf. Quantum, Nano, and Micro Tech. (ICQNM 2009) February 1 -6, 2009 — Cancun, Mexico 14
Thin Film Specific Heat 3 microns Third Int. Conf. Quantum, Nano, and Micro Tech. (ICQNM 2009) February 1 -6, 2009 — Cancun, Mexico 15
QED Induced Heat Transfer Non Thermal Emission EP = Photon Planck Energy d. NP/dt = Photon Rate Third Int. Conf. Quantum, Nano, and Micro Tech. (ICQNM 2009) February 1 -6, 2009 — Cancun, Mexico 16
Conductivity – Response Kelemen - 1976 Experiment Copper Film Glass Substrate Mixing Rule Substrate Third Int. Conf. Quantum, Nano, and Micro Tech. (ICQNM 2009) February 1 -6, 2009 — Cancun, Mexico 17
QED induced Heat Transfer Third Int. Conf. Quantum, Nano, and Micro Tech. (ICQNM 2009) February 1 -6, 2009 — Cancun, Mexico 18
QED induced Heat Transfer Third Int. Conf. Quantum, Nano, and Micro Tech. (ICQNM 2009) February 1 -6, 2009 — Cancun, Mexico 19
UV Laser Emission Mat. Sci. Eng. B 56 (1998) 239 -245 (QED cavity by Refractive Indices-Not Film Conductivity ) He-Cd Laser 325 nm QED radiation ~ 388 nm d ~ 388/2(2. 03 ) = 95 nm QLaser ~ QQED QCond ~ 0 Zinc Oxide d < 100 nm Sapphire Third Int. Conf. Quantum, Nano, and Micro Tech. (ICQNM 2009) February 1 -6, 2009 — Cancun, Mexico 20
Conclusions Thin film specific heat vanishes. Transient film temperatures follow the substrate allowed by QM to have specific heat. Bulk conductivity is maintained in the film, but there is no conductive heat loss parallel to the surface. The film loses heat normal to the surface by EM emission. Pulse Method requires modification using Standard Mixing Rules to measure thin film thermal conductivity QED induced EM emission can and should be measured with standard photomultipliers for 100 nm films. Third Int. Conf. Quantum, Nano, and Micro Tech. (ICQNM 2009) February 1 -6, 2009 — Cancun, Mexico 21
Extensions Nanocatalysts Surface Chemical Reactions Third Int. Conf. Quantum, Nano, and Micro Tech. (ICQNM 2009) February 1 -6, 2009 — Cancun, Mexico 22
Nanocatalysts Unsupported Supported Third Int. Conf. Quantum, Nano, and Micro Tech. (ICQNM 2009) February 1 -6, 2009 — Cancun, Mexico 23
Surface Chemical Reactions “God made solids, but surfaces are the work of the Devil. ” W. Pauli (1900 -1958) Third Int. Conf. Quantum, Nano, and Micro Tech. (ICQNM 2009) February 1 -6, 2009 — Cancun, Mexico 24
Questions & Papers Email: thomas@nanoqed. net http: //www. nanoqed. net Third Int. Conf. Quantum, Nano, and Micro Tech. (ICQNM 2009) February 1 -6, 2009 — Cancun, Mexico 25
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