Energy Transport across the Thin Films Pair with Presence of Minute Vacuum Gap at Interface

Cross-plane energy transport in aluminum and silicon films pair with presence of minute vacuum gap in between them is investigated. Laser short-pulse heating is introduced in the aluminum film and energy transfer in the films pair is formulated using the Boltzmann equation. Energy exchange between the electron and lattice subsystems is expressed in terms of the electron-phonon coupling. The vacuum gap size is considered to be less than the mean-free path silicon and the Casimir limit is applied to incorporate the thermal radiation contribution to the overall energy transport across the vacuum gap. It is found that ballistic phonon contribution to energy transfer across the vacuum gap is significant and the contribution of the thermal radiation, due to Casimir limit, to energy transfer is small. The vacuum gap size has significant effect on the energy transfer from aluminum film to the silicon film; in which case, increasing vacuum gap size enhances temperature difference across the interface of the vacuum gap.