Entropy generation in silicon thin film: Influence of film thickness on entropy generation rate

Thermodynamic irreversibility in thin silicon film is considered and entropy generation in the film is predicted. The Boltzmann equation is incorporated to formulate the phonon transport in the film due to temperature disturbance across the film edges. Frequency-dependent and frequency-independent phonon transport are introduced to compare the entropy predictions due to both cases. The study is extended to include the effect of the film thickness on the entropy generation in the film. A numerical code is developed using the discrete ordinate method and the predictions are validated with the data presented in our previous study. It is found that entropy generation is higher in the close region of the high temperature film edge. As the film thickness increases towards the cold temperature of the film edge, entropy generation rate becomes gradual. Entropy generation due to the frequency-independent case is higher than that corresponding to the frequency-dependent case. This behavior is attributed to the ballistic phonons, which do not contribute to the film resistance; therefore, they do not contribute to entropy generation in the film.