Thermal Conductivity of Thin Metallic Films

1994 ◽  
Vol 116 (1) ◽  
pp. 28-34 ◽  
Author(s):  
Sunil Kumar ◽  
George C. Vradis
Keyword(s):  
Experimental Data ◽  
Thermal Conductivity ◽  
Boltzmann Equation ◽  
Electron Transport ◽  
Temperature Gradient ◽  
Grain Boundary ◽  
Electron Scattering ◽  
Boundary Scattering ◽  
Electron Motion ◽  
Metallic Films

This study examines the effect of transverse thickness on the in-plane thermal conductivity of single crystal, defect-free, thin metallic films. The imposed temperature gradient is along the film and the transport of thermal energy is predominantly due to free electron motion. The small size necessitates an evaluation of the Boltzmann equation of electron transport along with appropriate electron scattering boundary conditions. Simple expressions for the reduction of conductivity due to increased dominance of boundary scattering are presented and the results are compared with other simplified approaches and experimental data from the literature. Grain boundary scattering is also considered via simple arguments.

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.

Thermal Conductivity of N-Type Si-Ge

1991 ◽  
Vol 234 ◽  
Author(s):  
Paul G. Klfmens
Keyword(s):  
Thermal Conductivity ◽  
Grain Boundary ◽  
Figure Of Merit ◽  
Lattice Thermal Conductivity ◽  
Electronic Conductivity ◽  
Boundary Scattering ◽  
Low Frequencies ◽  
Free Carriers ◽  
Anharmonic Interactions ◽  
Debye Frequency

ABSTRACTThe lattice thermal conductivity of 80-20 Si-Ge is treated theoretically for the case of the Fermi energy positioned for optimum figure of merit. The spectral distribution of the lattice conductivity is limited by anharmonic interactions, by the randomness of the Si-Ge lattice and, at low frequencies, by the interaction with free carriers and neutral donors. The two latter processes dominate over grain boundary scattering. The spectral conductivity is sharply peaked around 0.1 of the Debye frequency. A further reduction in lattice conductivity can be obtained by small insulating inclusions. This is partially offset by a reduction in electronic conductivity, but results in some improvement in the figure of merit.

Modeling Grain Boundary Scattering and Thermal Conductivity of Polysilicon Using an Effective Medium Approach

2011 ◽  
Author(s):  
Timothy S. English ◽  
Justin L. Smoyer ◽  
John C. Duda ◽  
Pamela M. Norris ◽  
Thomas E. Beecham ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Grain Boundary ◽  
Polycrystalline Silicon ◽  
Phonon Scattering ◽  
Effective Medium ◽  
Boundary Scattering ◽  
Total Thermal Conductivity ◽  
New Model ◽  
Grain Boundary Scattering ◽  
Effective Medium Approach

This work develops a new model for calculating the thermal conductivity of polycrystalline silicon using an effective medium approach which discretizes the contribution to thermal conductivity into that of the grain and grain boundary regions. While the Boltzmann transport equation under the relaxation time approximation is used to model the grain thermal conductivity, a lower limit thermal conductivity model for disordered layers is applied in order to more accurately treat phonon scattering in the grain boundary regions, which simultaneously removes the need for fitting parameters frequently used in the traditional formation of grain boundary scattering times. The contributions of the grain and grain boundary regions are then combined using an effective medium approach to compute the total thermal conductivity. The model is compared to experimental data from literature for both undoped and doped polycrystalline silicon films. In both cases, the new model captures the correct temperature dependent trend and demonstrates good agreement with experimental thermal conductivity data from 20 to 300K.

scholarly journals The role of grain boundary scattering in reducing the thermal conductivity of polycrystalline XNiSn (X = Hf, Zr, Ti) half-Heusler alloys

2017 ◽  
Vol 7 (1) ◽  
Author(s):  
Matthias Schrade ◽  
Kristian Berland ◽  
Simen N. H. Eliassen ◽  
Matylda N. Guzik ◽  
Cristina Echevarria-Bonet ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Grain Boundary ◽  
Heusler Alloys ◽  
Boundary Scattering ◽  
Grain Boundary Scattering
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