third int. conf. quantum, nano, and micro tech. (icqnm 2009) february 1-6, 2009 — cancun, mexico...
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Third Int. Conf. Quantum, Nano, and Micro Tech. (ICQNM 2009) February 1-6, 2009 — Cancun, Mexico
Heat Transferin
Thin Films
Thomas Prevenslik
Berlin, GermanyHong Kong, China
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Third Int. Conf. Quantum, Nano, and Micro Tech. (ICQNM 2009) February 1-6, 2009 — Cancun, Mexico
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.
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Third Int. Conf. Quantum, Nano, and Micro Tech. (ICQNM 2009) February 1-6, 2009 — Cancun, Mexico
Experiment
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Pulse Method (Thin Solid Films, Kelemen, 36 (1976) 199-203)
Thermal Diffusivity
c
K
T/Tlnt4
xx
21
21
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K = thermal conductivity = density, c = specific heat
X1
X2 T1
T2
Wire
F
Data Shows K 0 as 0
Substrate
Film
Problem
Diffusivity diverges as c 0 Can conductivity K be measured
by Pulse Method?
S
W
Third Int. Conf. Quantum, Nano, and Micro Tech. (ICQNM 2009) February 1-6, 2009 — Cancun, Mexico
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).
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Third Int. Conf. Quantum, Nano, and Micro Tech. (ICQNM 2009) February 1-6, 2009 — Cancun, Mexico
Experiment and BTE Theory
Bulk Copper
0
100
200
300
400
500
10 100 1000 10000
Film Thickeness - - nm
The
rmal
Con
duct
ivity
- W
/ m
-K
.
Keff BTE PredictionsCopper Films
Electronics Cooling, 2007
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Third Int. Conf. Quantum, Nano, and Micro Tech. (ICQNM 2009) February 1-6, 2009 — Cancun, Mexico
Purpose
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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
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
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Third Int. Conf. Quantum, Nano, and Micro Tech. (ICQNM 2009) February 1-6, 2009 — Cancun, Mexico
Nanoparticle or Quantum Dot
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•
NP, QD
• •
Molecular
Collisions
No Temperature change
EM
Emission
Laser
Radiation
Third Int. Conf. Quantum, Nano, and Micro Tech. (ICQNM 2009) February 1-6, 2009 — Cancun, Mexico
Thin Film
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QED Heat Transfer QCond = QJoule -QQED
Standard Mixing Rules
eff= Keff /effceff ceff = cS and cF = 0 eff =(FKF+SKS)[(F/S)+1]/[cS(FF+SS] KF = eff cS [F +S(S/F)] - (S/F)KS
KF ~ KBulk
QQED
QCond
T1
T2
Current Approach QCond =QJoule
Kelemen
KF = KS [(F+S/S)-1SFKF << KBulk
QJoule
x2-x1
Third Int. Conf. Quantum, Nano, and Micro Tech. (ICQNM 2009) February 1-6, 2009 — Cancun, Mexico
EM Confinement
2r2r
2r
2 n2
1
Ln2
1
Wn2
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c
f rn2
rP n2
hcE
For << W and L, 2nr
Photons in Rectangular cavity resonator, nr > 1
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Third Int. Conf. Quantum, Nano, and Micro Tech. (ICQNM 2009) February 1-6, 2009 — Cancun, Mexico
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 the thin film.
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Third Int. Conf. Quantum, Nano, and Micro Tech. (ICQNM 2009) February 1-6, 2009 — Cancun, Mexico
QM Restrictions
0.00001
0.0001
0.001
0.01
0.1
1 10 100 1000
Wavelength - - microns
Pla
nck
Ene
rgy
- E -
eV
1
kT
hcexp
hc
E
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Film
Free Molecule
Third Int. Conf. Quantum, Nano, and Micro Tech. (ICQNM 2009) February 1-6, 2009 — Cancun, Mexico
Thin Film as an Einstein Solid
1
kThc
exp
hc
N3U A
NA = Number of Atoms in Film 3 NA Degrees of Freedom
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Third Int. Conf. Quantum, Nano, and Micro Tech. (ICQNM 2009) February 1-6, 2009 — Cancun, Mexico
Einstein Specific Heat
T
UC
2
2
A1
kT
hcexp
kT
hcexp
kT
hc
kN3
C*C
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0*Cas0 Einstein
1*Cas
Debye & Einstein
Third Int. Conf. Quantum, Nano, and Micro Tech. (ICQNM 2009) February 1-6, 2009 — Cancun, Mexico
Thin Film Specific Heat
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3 microns0
0.2
0.4
0.6
0.8
1
1.2
0.001 0.01 0.1 1 10 100 1000
Thin Fim Thickness - nr microns
Dim
ensi
onle
ss S
peci
fic H
eat
C* EM
Emission Temp
Increase
Third Int. Conf. Quantum, Nano, and Micro Tech. (ICQNM 2009) February 1-6, 2009 — Cancun, Mexico
QED Induced Heat Transfer
QEDJouleCond QQQ
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dt
dNEQ PPQED
Non Thermal Emission
EP = Photon Planck Energy
dNP/dt = Photon Rate
Third Int. Conf. Quantum, Nano, and Micro Tech. (ICQNM 2009) February 1-6, 2009 — Cancun, Mexico
Conductivity – Response Kelemen - 1976
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Copper Film
Glass SubstrateMixing Rule
Substrate
Experiment
Third Int. Conf. Quantum, Nano, and Micro Tech. (ICQNM 2009) February 1-6, 2009 — Cancun, Mexico
QED induced Heat Transfer
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0
100
200
300
400
500
10 100 1000 10000
Film Thickeness - - nm
The
rmal
Con
duct
ivity
- W
/ m
-K
.
0510152025303540
E(d
N/d
t) /
A (
T-T
o)
x10
9 W
/ m
2- K.
Kbulk - Keff
Keff
EMEmission
Third Int. Conf. Quantum, Nano, and Micro Tech. (ICQNM 2009) February 1-6, 2009 — Cancun, Mexico
QED induced Heat Transfer
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0
10
20
30
40
10 100 1000 10000
Film Thickness - - nm
Pla
nck
Ene
rgy
- E
- e
V
1.E+25
1.E+26
1.E+27
1.E+28
(dN
/dt)
/A(T
-To)
/ m2- K
dN / dt
Ep Photomultiplier
Third Int. Conf. Quantum, Nano, and Micro Tech. (ICQNM 2009) February 1-6, 2009 — Cancun, Mexico
UV Laser Emission
Zinc Oxide
Sapphire
He-Cd
Laser
325 nm
QED radiation ~ 388 nm
~ 388/2(2.03 ) = 95 nm
< 100 nm
Mat. Sci. Eng. B56 (1998) 239-245 (QED cavity by Refractive Indices-Not Film Conductivity )
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QLaser ~ QQED
QCond ~ 0
Third Int. Conf. Quantum, Nano, and Micro Tech. (ICQNM 2009) February 1-6, 2009 — Cancun, Mexico
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.
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Third Int. Conf. Quantum, Nano, and Micro Tech. (ICQNM 2009) February 1-6, 2009 — Cancun, Mexico
Extensions
Nanocatalysts
Surface Chemical Reactions
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Third Int. Conf. Quantum, Nano, and Micro Tech. (ICQNM 2009) February 1-6, 2009 — Cancun, Mexico
Nanocatalysts
Reactants A, B kT ~ 0.0258 eV
VUVRadiation
A
A
B
B
NP Au kT ~ 0.0 eV
BA
VUVRadiation
Reactants A, B kT ~ 0.0258 eV
TiO2 Particle
VUVRadiation
A
B
B
NP Au/TiO2
kT ~ 0.0
BA
A
A
B
B VUVRadiation
A
UnsupportedSupported
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Third Int. Conf. Quantum, Nano, and Micro Tech. (ICQNM 2009) February 1-6, 2009 — Cancun, Mexico
Surface Chemical Reactions
Substrate
NPs
Gas Molecules
QED radiation
QEDradiation
A
A
A
A
A AA-
A-EEE+PE
EEE+PE
exo A -
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“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
Questions & Papers
Email: [email protected]
http://www.nanoqed.net
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