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.

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 and Interface Effects on Thermal Conductivity of Superlattices and Periodic Thin-Film Structures

1997 ◽  
Vol 119 (2) ◽  
pp. 220-229 ◽  
Author(s):  
G. Chen
Keyword(s):  
Thin Film ◽  
Thermal Conductivity ◽  
Effective Thermal Conductivity ◽  
Amorphous Materials ◽  
High Efficiency ◽  
Interface Roughness ◽  
Atomic Scale ◽  
Diffuse Interface ◽  
Boltzmann Transport ◽  
Diffuse Interfaces

Superlattices consisting of alternating layers of extremely thin films often demonstrate strong quantum size effects that have been utilized to improve conventional devices and develop new ones. The interfaces in these structures also affect their thermophysical properties through reflection and transmission of heat carriers. This work develops models on the effective thermal conductivity of periodic thin-film structures in the parallel direction based on the Boltzmann transport equation. Different interface conditions including specular, diffuse, and partially specular and partially diffuse interfaces, are considered. Results obtained from the partially specular and partially diffuse interface scattering model are in good agreement with experimental data on GaAs/AlAs superlattices. The study shows that the atomic scale interface roughness is the major cause for the measured reduction in the superlattice thermal conductivity. This work also suggests that by controlling interface roughness, the effective thermal conductivity of superlattices made of bulk materials with high thermal conductivities can be reduced to a level comparable to those of amorphous materials, while maintaining high electrical conductivities. This suggestion opens new possibilities in the search of high efficiency thermoelectric materials.

Thin Film In-Plane Silicon Thermal Conductivity Dependence on Molecular Dynamics Surface Boundary Conditions

2004 ◽  
Author(s):  
Carlos J. Gomes ◽  
Marcela Madrid ◽  
Cristina H. Amon
Keyword(s):  
Thin Film ◽  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Film Thickness ◽  
Boundary Conditions ◽  
Mean Free Path ◽  
Surface Boundary ◽  
Repulsive Potential ◽  
Surface Boundary Conditions ◽  
Weber Potential

The in-plane thermal conductivity of thin silicon films is predicted using equilibrium molecular dynamics, the Stillinger-Weber potential and the Green-Kubo relationship. Film thicknesses range from 2 to 200 nm. Periodic boundary conditions are used in the directions parallel to the thin film surfaces. Two different strategies are evaluated to treat the atoms on the surfaces perpendicular to the thin film direction: adding four layers of atoms kept frozen at their crystallographic positions, or restraining the atoms near the surfaces with a repulsive potential. We show that when the thin-film thickness is smaller than the phonon mean free path, the predictions of the in-plane thermal conductivity at 1000K differ significantly depending on the potential applied to the atoms near the surfaces. In this limit, the experimentally observed trend of decreasing thermal conductivity with decreasing film thickness is predicted when the surface atoms are subject to a repulsive potential in addition to the Stillinger-Weber potential, but not when they are limited by frozen atoms.

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 Conductivity Measurement of In0.10Ga0.90As0.96N0.04 Thin Film

2017 ◽  
Author(s):  
Antony Jan ◽  
Ramez Cheaito ◽  
Kenneth E. Goodson ◽  
Bruce M. Clemens
Keyword(s):  
Thin Film ◽  
Thermal Conductivity ◽  
Indium Gallium Arsenide ◽  
Optical Fibers ◽  
Conductivity Measurement ◽  
Chemical Vapor ◽  
Mean Free Path ◽  
Thermal Conductivity Measurement ◽  
Optical Fiber Communications ◽  
Fiber Communications

Dilute indium gallium arsenide nitrides (InxGa1-xAs1-yNy) are valuable in photonic applications as long wavelength emitters and for pairing with silica optical fibers for low attenuation optical fiber communications. The reliable operation of these devices is tied to a precise temperature control and the knowledge of the thermal properties of their components. However, the thermal conductivity of bulk or thin film InGaAsN of any composition are, to the best of our knowledge, not available in literature. In response, we use time-domain thermoreflectance (TDTR) to measure the thermal conductivity of a 78 nm In0.10Ga0.90As0.96N0.04 film grown by metalorganic chemical vapor deposition (MOCVD) on GaAs substrate. The thermal conductivity of In0.10Ga0.90As0.96N0.04 is found to be 6 +/− 0.5 Wm−1K−1, a factor of two lower than that of bulk In0.10Ga0.90As. To our knowledge this is the first reported thermal conductivity measurement on InGaAsN. We also present an analytical model for predicting the thermal conductivity of InGaAsN for any composition. Using this model, we find that the reduction in thermal conductivity can be attributed to the scattering of phonons by nitrogen impurities and boundary scattering of long mean free path phonons from the film thickness.

scholarly journals Deterministic Phonon Transport Predictions of Thermal Conductivity in Uranium Dioxide With Xenon Impurities

2018 ◽  
Vol 140 (5) ◽  
Author(s):  
Jackson R. Harter ◽  
Laura de Sousa Oliveira ◽  
Agnieszka Truszkowska ◽  
Todd S. Palmer ◽  
P. Alex Greaney
Keyword(s):  
Thermal Conductivity ◽  
Uranium Dioxide ◽  
Neutron Transport ◽  
Mean Free Path ◽  
Phonon Transport ◽  
Multiscale Approach ◽  
First Principles Calculations ◽  
Boltzmann Transport ◽  
Experimental Heat ◽  
Transport Code

We present a method for solving the Boltzmann transport equation (BTE) for phonons by modifying the neutron transport code Rattlesnake which provides a numerically efficient method for solving the BTE in its self-adjoint angular flux (SAAF) form. Using this approach, we have computed the reduction in thermal conductivity of uranium dioxide (UO2) due to the presence of a nanoscale xenon bubble across a range of temperatures. For these simulations, the values of group velocity and phonon mean free path in the UO2 were determined from a combination of experimental heat conduction data and first principles calculations. The same properties for the Xe under the high pressure conditions in the nanoscale bubble were computed using classical molecular dynamics (MD). We compare our approach to the other modern phonon transport calculations, and discuss the benefits of this multiscale approach for thermal conductivity in nuclear fuels under irradiation.

A Rapid Method to Measure Thermal Conductivity of Dielectric Thin Films: Thermal Resistance Method

2005 ◽  
Author(s):  
Da-Jeng Yao ◽  
Heng-Chieh Chien ◽  
Ming-Hsi Tseng
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Thermal Conductivity ◽  
Thermal Resistance ◽  
Dielectric Film ◽  
Electrical Heating ◽  
New Technique ◽  
Simple Method ◽  
Dielectric Thin Films ◽  
Resistance Method

A new and relatively simple method, described for thermal conductivity measurement of dielectric thin films, is presented in this paper. This new technique, the thermal resistance method, can be applied to determine cross-plane thermal conductivity of thin film by electrical heating and sensing techniques without traditional free standing structure design. A slender metal line, deposited on top of dielectric film, is used to measure and extract thermal resistance (Rc) of composite structure, including substrate and dielectric film. A 2-D analytical solution is derived to get thermal resistance (Rs) of substrate. Therefore, the thermal resistance of thin film (Rf) is calculated by subtracting Rs form Rc and thermal conductivity of thin film can also be extracted from thermal resistance. The measurement data of silicon dioxide with difference thickness are verified by using previous scientific literatures. In addition, the measuring results also show good agreement with those measured by 3 omega method. According to advantages of rather rapid and accuracy, this new technique has potential to develop to be an in-line test key for MEMS and IC relative industries.

Phonon transport characteristics across silicon thin film pair: Presence of a gap between the films

2015 ◽  
Vol 40 (3) ◽  
Author(s):  
Haider Ali ◽  
Bekir S. Yilbas
Keyword(s):  
Thin Film ◽  
Experimental Data ◽  
Thermal Conductivity ◽  
Temperature Difference ◽  
Radiation Heat Transfer ◽  
Phonon Transport ◽  
Radiative Energy ◽  
Gap Size ◽  
Boltzmann Transport ◽  
Silicon Thin Film

AbstractPhonon transport across silicon thin film pair with minute gap (Casimir limit) between the films is studied. Phonon transport characteristics across the gap are examined for various gap sizes, and the transient solution of the frequency-dependent Boltzmann transport equation is presented according to relevant boundary conditions incorporating the gap between the film pair. Since the gap size is minute (Casimir limit), the radiative energy transport between the edges of the film pair is incorporated. In addition, phonon transmission and reflection is introduced at the gap edges, thus satisfying energy conservation. The thermal conductivity predicted is validated through experimental data reported in the open literature. Predicted thermal conductivity data agree well with the experimental data reported in the open literature. Increasing gap size alters the phonon transport characteristics across the film pair. Increasing gap size enhances temperature difference between the edges of the gap; in which case, the effect of phonon transmittance is more significant on the temperature difference than that corresponding to the radiation heat transfer due to Casimir limit.

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.

scholarly journals First-Principles Study of Structure, Elastic Properties, and Thermal Conductivity of Monolayer Calcium Hydrobromide

2021 ◽  
Vol 2021 ◽  
pp. 1-7
Author(s):  
Si-Hua Li ◽  
Cui-E Hu ◽  
Xiao-Lu Wang ◽  
Yan Cheng
Keyword(s):  
Thermal Conductivity ◽  
Elastic Properties ◽  
First Principles ◽  
Lattice Thermal Conductivity ◽  
Mechanical Stability ◽  
Iterative Solution ◽  
Mean Free Path ◽  
Hydrogen Atmosphere ◽  
Theoretical Studies ◽  
Boltzmann Transport

In recent years, some laboratories have been able to prepare calcium hydrobromide (CaHBr) by melting hydride and anhydrous bromide or metal and bromide in a hydrogen atmosphere at 900°C and have studied some of its properties. But there are few theoretical studies, especially the theoretical studies of monolayer CaHBr. We use the first-principles method to calculate the structure, elastic properties, and lattice thermal conductivity of the monolayer CaHBr based on the Boltzmann transport equation. We obtain a stable crystal structure by the optimization of monolayer CaHBr. By calculating the elastic constant of monolayer CaHBr, its mechanical stability is proved, and the elastic limit of monolayer CaHBr is obtained by biaxial tensile strain on monolayer CaHBr. And the corresponding phonon spectra show no imaginary frequency, indicating the dynamic stability of the monolayer CaHBr. By the ShengBTE code, we calculate the lattice thermal conductivity of the monolayer CaHBr, the iterative solution of BTE and RTA at 300 K–1200 K is obtained, and the lattice thermal conductivity at room temperature is κ ι BTE = 2.469   W / m ⋅ K and κ ι RTA = 2.201   W / m ⋅ K , respectively. It can be seen that the lattice thermal conductivity of monolayer CaHBr is low. And by analyzing the phonon spectrum, the scattering rate, and the mean free path of the phonons, the lattice thermal conductivity of monolayer CaHBr mainly depends on the acoustic modes. We hope this study can provide theoretical guidance for the experiments and practical application of monolayer CaHBr.

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