IWNET12
IWNET12
Thermodynamic analysis of irreversibilities in thin heat conducting
lms
Federico Vázquez1, J. Antonio del Río2
1 Facultad de Ciencias, Universidad Autónoma del Estado de Morelos, México
2 Centro de Investigación en Energía, Universidad Nacional Autónoma de México, México
Abstract
The size of dielectric and semiconductor based devices has become of the order of the phonon's mean free path
or smaller with new technologies. Their performance however is aected by the high operation temperatures
reached due to their reduced sizes. The sources of irreversible processes must then be studied in order to
improve operation conditions to assure an optimal functioning. In this work we undertake the theoretical
analysis of the entropy production in heat conducting thin lms from the point of view of Linear Irreversible
thermodynamics. The experimentally observed reduction of the thermal conductivity with the thickness of the
lm is considered in the description through the use of an expression obtained on Boltzmann equation grounds.
The uctuating nature of heat ux is described by introducing proper stochastic terms in the constitutive heat
ux equation. Besides the entropy generation for dierent thickness of the conducting lm we study the group
velocity of Fourier modes, the response of the system under external temperature gradients and the spectrum
of temperature uctuations. Our ndings allow us to feature a kind of dynamical phase transition when the
lm thickness equals the mean free path of phonons.
E-mail: vazquez@uaem.mx

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