Thermal Boundary Conductance in Heterostructures Studied by Ultrafast Electron Diffraction,
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.
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