Thermal boundary conductance in heterostructures studied by ultrafast electron diffraction

Abstract

Ultrafast electron diffraction (UED) at surfaces is used to study the energy dissipation in ultrathin epitaxial Bi-films on Si(001) subsequent to fs laser pulse excitation. The temperature of the Bi-film is determined from the drop in diffraction intensity due to the Debye–Waller effect. A temperature rise from 80 to 200 K is followed by an exponential cooling with a time constant of 640 ps. The cooling rate of the Bi-film is determined by the reflection of phonons at the Bi/Si interface and is slower than expected from the acoustic and diffusive mismatch model.