Electron and Phonon Thermal Conduction in Epitaxial High-Tc Superconducting Films

1993 ◽  
Vol 115 (1) ◽  
pp. 17-25 ◽  
Author(s):  
K. E. Goodson ◽  
M. I. Flik
Keyword(s):  
Experimental Data ◽  
Thermal Conductivity ◽  
Size Effect ◽  
Free Path ◽  
Fluid Model ◽  
Mean Free Path ◽  
Boundary Scattering ◽  
High Tc ◽  
Two Fluid Model ◽  
Electron Mean Free Path

Electrons and phonons are the carriers of heat in the a-b plane of the high-Tc superconductor YBa2Cu3O7. In the absence of boundary scattering, the a-b plane thermal conductivity and the mean free path of each carrier type are calculated as functions of temperature using kinetic theory, the two-fluid model of the superconducting state, and experimental data for the thermal conductivity and electrical resistivity of a single crystal. The reduction by boundary scattering of the effective a-b plane thermal conductivity along an epitaxial YBa2Cu3O7 film is predicted as a function of temperature and film thickness. The size effect on the phonon conductivity dominates over the size effect on the electron conductivity. The predicted electron mean free path is limited by scattering on defects and is in very good agreement with experimental data from infrared spectroscopy.

Size Effect on the Thermal Conductivity of Thin Metallic Films Investigated by Scanning Joule Expansion Microscopy

2008 ◽  
Vol 130 (8) ◽  
Author(s):  
Siva P. Gurrum ◽  
William P. King ◽  
Yogendra K. Joshi ◽  
Koneru Ramakrishna
Keyword(s):  
Thermal Conductivity ◽  
Size Effect ◽  
Three Dimensional ◽  
Mean Free Path ◽  
Local Temperature ◽  
Metallic Films ◽  
Dielectric Interface ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element ◽  
Electron Mean Free Path

A technique to extract in-plane thermal conductivity of thin metallic films whose thickness is comparable to electron mean free path is described. Microscale constrictions were fabricated into gold films of thicknesses 43nm and 131nm. A sinusoidal voltage excitation across the constriction results in a local temperature rise. An existing technique known as scanning joule expansion microscopy, measures the corresponding periodic thermomechanical expansion with a 10nm resolution and determines the local temperature gradient near the constriction. A three-dimensional finite-element simulation of the frequency-domain heat transfer fits the in-plane thermal conductivity to the measured data, finding thermal conductivities of 82±7.7W∕mK for the 43nm film and 162±16.7W∕mK for the 131nm film, at a heating frequencies of 100kHz and 90kHz, respectively. These values are significantly smaller than the bulk thermal conductivity value of 318W∕mK for gold, showing the electron size effect due to the metal-dielectric interface and grain boundary scattering. The obtained values are close to the thermal conductivity values, which are derived from electrical conductivity measurements after using the Wiedemann–Franz law. Because the technique does not require suspended metal bridges, it captures true metal-dielectric interface scattering characteristics. The technique can be extended to other films that can carry current and result in Joule heating, such as doped single crystal or polycrystalline semiconductors.

Thermal Transport Property of Silicon Membranes With Asymmetric Porous Structure

2015 ◽  
Author(s):  
Harutoshi Hagino ◽  
Koji Miyazaki
Keyword(s):  
Thermal Conductivity ◽  
Free Path ◽  
Thermal Conduction ◽  
Transport Theory ◽  
Mean Free Path ◽  
Phonon Transport ◽  
Boundary Scattering ◽  
Rectification Effect ◽  
Thermal Rectification ◽  
Asymmetric Pores

The size effect on thermal conduction due to phonon boundary scattering in films was studied as controlling heat conduction. Thermal rectifier was proposed as a new heat control concept by a ballistic rectifier relies on asymmetric scattering of phonons in asymmetric linear structure. We focus on the thermal rectification effect in membrane with asymmetric pores. We discussed on the thermal rectification effect from the calculation and thermal conductivity measurement of asymmetric structured membrane. Thermal conduction was calculated by using radiation calculation of ANSYS Fluent based on Boltzmann transport theory which is development of equation of phonon radiative transfer from view point of phonon mean free path and boundary scattering condition. In-plane thermal conductivities of free standing membranes with microsized asymmetric pores were measured by periodic laser heating measurement. From the result of calculation, phonons were transition to ballistic transport in the membranes with asymmetric shaped pores and thermal rectification effect was obtained on the condition of specular scattering because of the asymmetric back-scattering of ballistic phonons from asymmetric structure. The thermal rectification effect was increased with decreasing thickness of membrane shorter and shorter than mean free path of phonon. From the result of measurements, we were able to confirm the reduction of thermal conductivity based on ballistic phonon transport theory, but the strong thermal rectification effect was not confirmed.

Size Effect on the Thermal Conductivity of High-Tc Thin-Film Superconductors

1990 ◽  
Vol 112 (4) ◽  
pp. 872-881 ◽  
Author(s):  
M. I. Flik ◽  
C. L. Tien
Keyword(s):  
Thin Film ◽  
Thermal Conductivity ◽  
Size Effect ◽  
Mean Free Path ◽  
Boltzmann Transport ◽  
Simple Method ◽  
High Tc ◽  
Theory Approximation ◽  
Lead Films ◽  
Reported Data

Using the kinetic theory approximation and reported data, this study shows that at low temperatures, the phonon mean free path in polycrystalline ceramic YBa2Cu3O7 can be of the order of the thickness of thin-film superconductors. In this case, boundary scattering reduces the thermal conductivity with decreasing film thickness. A simple method accounts for the size effect on conduction in thin films. This analysis rests solely on geometric arguments and does not consider the effect of grain boundaries. For conduction along the film, this model approximates well an analytical solution of the Boltzmann transport equation, and is in good agreement with experimental data for thin lead films. The model is also employed to analyze the size effect on conduction across the film and the influence of anisotropy.

The thermal conductivity of tin and indium below 1°K

1958 ◽  
Vol 248 (1255) ◽  
pp. 522-538 ◽  
Keyword(s):  
Thermal Conductivity ◽  
Free Path ◽  
Superconducting State ◽  
Size Dependence ◽  
Mean Free Path ◽  
Fermi Velocity ◽  
Boundary Scattering ◽  
Simple Analysis ◽  
Phonon Field ◽  
Size Dependent

An experimental study has been made of some aspects of the thermal conductivity of superconducting tin and indium below 1°K. Experiments at the lowest temperatures, where the thermal conductivity of the lattice is dominant, and for tin varies as T 3 , have been mainly directed towards studying the size effect in the conductivity due to the scattering of phonons at the specimen surface. Electropolishing tin has been found to increase the thermal conductivity considerably; a simple analysis of the results shows that almost complete specular reflexion of phonons is attainable. The analysis confirms the existence of an internal scattering of phonons, describable at the lowest temperatures by a temperature-independent mean free path which does not vary when the diameter of the specimen is reduced, but is very sensitive to any damage suffered by the crystal. The lattice conductivity of indium, which is anomalous in having a T 4 rather than a T 3 variation, appears to be limited mainly by internal scattering and it is tentatively suggested that the internal scattering is mainly due to the reradiation from dislocations oscillating in the phonon field. At somewhat higher temperatures (above about 0.7 but below 1°K) the thermal conductivity is predominantly electronic and the results indicate that here too the ‘effective’ electronic mean free path is size-dependent due to boundary scattering. From an analysis of this size-dependence in tin, the ‘intrinsic’ electronic mean free path in the superconducting state is deduced and found to be between ten and thirty times as long as in the normal state. The results suggest also that the electronic velocity in the superconducting state is something like one-third of the Fermi velocity.

SIZE-DEPENDENT MELTING TEMPERATURE AND THERMAL CONDUCTIVITY OF NANOSCALE SEMICONDUCTORS

2007 ◽  
Vol 21 (23n24) ◽  
pp. 4026-4029 ◽  
Author(s):  
L. H. LIANG ◽  
BAOWEN LI
Keyword(s):  
Thermal Conductivity ◽  
Size Effect ◽  
Free Path ◽  
Melting Temperature ◽  
Mean Free Path ◽  
Debye Model ◽  
Size Dependent ◽  
Si Nanoparticles ◽  
Nanoscale Semiconductors ◽  
Phonon Velocity

A model describing size-dependent melting temperature and thermal conductivity of nanosemiconductors is proposed based on Lindermann's melting criterion and Debye model. By the atomic thermal vibration consideration and by introducing intrinsic size effect of phonon velocity and mean free path combined with surface scattering effect, the model predicts that the melting temperature and thermal conductivity of nanosemiconductors decrease as the size reduces. The size effect depends on such material parameters as the vibration entropy, mean free path, the characteristic crystal size and surface roughness. The predictions are in agreement with experimental results of Si nanoparticles, nanowires and thin films.

Thermal and Electrical Conductivities of Polycrystalline Metallic Nanofilms Based on the Kinetic Theory

2008 ◽  
Author(s):  
Bo Feng ◽  
Zhixin Li ◽  
Xing Zhang
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Grain Boundary ◽  
Kinetic Theory ◽  
Size Effect ◽  
Free Path ◽  
Coulomb Blockade ◽  
Mean Free Path ◽  
Surface Scattering ◽  
Inelastic Electron

A model is developed for in-plane thermal conductivity of nanostructured metallic films based on the kinetic theory, which attributes the reduced thermal conductivity to the reduced mean free path of electrons. The partially inelastic electron-surface scattering and grain-boundary impedance by quantum mechanical treatment are elaborately included. Meanwhile, the mean free path of electrons is also used to study in-plane electrical conductivity of nanofilms. Both electrical conductivity and thermal conductivity, varying with film thickness and temperature, are observed to be lower than corresponding bulk values, agreeing well with the experimental data. The grain-boundary scattering is theoretically found to dominate over surface scattering to enhance the size effect on electrical and thermal conductivities. In addition, the size effect in low temperature appears more dramatic due to larger electron Knudsen number. We further examine the Lorenz number of nanofilms and find the Wiedemann-Franz law is seriously violated. The Coulomb blockade and the neutral excitation of electron-hole pair are used to offer a more detailed picture. Excessive thermal conductivity is also evaluated resorting to concepts in granular metals to show the validity of this account.

Electron Mean Free Path and Orbit Aspect Ratio from the Dependence of the Strength of the rf Size Effect on Specimen Width

1971 ◽  
Vol 27 (14) ◽  
pp. 929-932 ◽  
Author(s):  
J. E. Neighbor ◽  
C. A. Shiffman ◽  
D. G. Chatjigiannis ◽  
S. P. Jacobsen
Keyword(s):  
Aspect Ratio ◽  
Size Effect ◽  
Free Path ◽  
Mean Free Path ◽  
Specimen Width ◽  
Electron Mean Free Path
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