Transient heat conduction in dielectric thin films

Abstract

This paper discusses transient heat transfer phenomena in solid dielectric thin films from both macroscopic and microscopic points of view. Phonon radiative transfer model as well as Fourier's law and thermal wave theory are utilized to analyze the transient heat conduction phenomena in dielectric thin films. Diamond and GaAs thin films are chosen as the examples to demonstrate the differences between the macroscale and microscale heat transfer models. The phonon radiative transfer model is partially ballistic, partially wavelike, and partially diffusive depends on the film thickness. Phonon radiative transfer model predicts temperature jumps at boundaries due to its ballistic nature when the film thickness is less than the mean free path, A. In contrast, the results predicted by the phonon radiative transfer model approaches to that of Fourier's law when the film thickness is larger than 10 times of the mean free path. The results show that as the ratio of thin film thickness to phonon mean free path, L/Lambda, is greater than 100, Fourier's law is a good approximation to deal with the transient heat transfer problems in dielectric thin films.