Nanoscale heat conduction at a silicon?superfluid helium boundary

Abstract

The boundary between silicon crystal and superfluid helium-4 (1–2 K) is an interesting configuration for studying heat transfer mechanisms at very small length scales. This may prove useful in future heat conduction analysis in microstructures. We define two possible heat conduction regimes, namely a classical surface effect regime and a scattering effect regime. The distinction between these regimes depends upon the (ℓ/λ) ratio, where the surface roughness length is ℓ and the phonon wavelength is λ. In a preliminary experiment we show that heat conduction across a silicon–superfluid helium interface at ∼2 K can be entirely explained by the scattering effect regime where diffuse phonon scattering from surface irregularities of nanometric scale lengths play a dominant role.