Phonon escape from electrically heated metal films on silicon

Abstract

Electric field heating of electrons in thin metal films deposited on silicon substrates has been used to determine the phonon transmission across the metal-silicon interface. A simple rate equation model is used to fit the electron temperature as a function of applied field. From the fit the authors have established that the phonon transmission deviates from the usual acoustic mismatch model. The authors find the phonon escape to comprise two components: ballistic escape of phonons from the film and strong scattering close to the interface.

Micro-SQUIDs with controllable asymmetry via hot-phonon controlled junctions

“…From the work of Nabity and Wybourne 43 on the phonon escape from electrically heated metal films on silicon dioxide, it is found that the transport at low temperatures consists of ballistic transport of the phonons out of the metallic film with strong scattering at the interface between the materials. After generation, the low-frequency phonons escape from the film with a time scale that is faster than the time scale for the phonon to be scattered from an electron.…”

Acoustic-phonon decoherence and electron transport in metallic nanostructures

“…We characterize this loss by a phonon escape time τ s . It has been shown experimentally [26] that the rate of energy loss from a film at low temperatures depends on the details of the phonon escape time. In the strong acoustic coupling limit between a supported wire and the substrate, the phonons remain nearly in equilibrium at a substrate temperature T s and this implies a very short phonon escape time from the wire compared to the phonon relaxation time on the electrons.…”