The analysis of lattice thermal conductivity in thin film
Date Issued
2005
Date
2005
Author(s)
Chang, Tai-Ming
DOI
zh-TW
Abstract
The lattice thermal conductivity of a thin film structure is a critical issue to improve the figure of merit of thermoelectric materials. The main purpose of this thesis is to re-establish a theory for calculating the in-plane lattice thermal conductivity of a thin film. The theory is constructed based on the particle-concept. The phonon Boltzmann transport equation with the relaxation time approximation is solved. For completeness and consistency, the proposed theory takes into account (i) the modification of the acoustic phonon dispersion relation due to spatial confinement, (ii) the change in the non-equilibrium phonon distribution due to partially diffuse boundary scattering, (iii) the frequency -dependence of the phonon group velocity, and (iv) the adoption of the maximum allowed wave vector in order to calculate the Debye temperature according to the modified phonon dispersion relation. From the calculations, we predict that the decrease of the phonon group velocity and the Debye temperature, the increase of the boundary roughness and the enhanced phonon scattering lead to a significant reduction of the lattice thermal conductivity. The sensitivities of the thermal conductivity on the temperature, the boundary roughness, and the film thickness agree well recent theoretical and experimental investigations.
Subjects
薄膜
聲子波茲曼方程式
晶格熱傳導係數
Thin-film
Phonon Boltzmann transport equation
Lattice thermal conductivity
Type
thesis
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