Thermal transport: Breaking through barriers

Nanocrystal arrays (NCA) play a key role in unlocking the mystery of understanding heat flow across interfaces. An optical pump-probe technique known as frequency domain thermoreflectance was used to measure thermal conductivity in nanocrystal arrays. These are a hybrid organic inorganic material composed of crystalline nanoparticles of up to 20 nm in diameter arranged in self-assembled three-dimensional arrays. By using nanocrystals with higher Debye temperatures, such as Fe₂O₃, the researcher show more than a twofold increase in thermal conductivity of the NCA. Beyond the tuning of the thermal conductivity itself, these results provide evidence that inelastic scattering is minimal at organic/inorganic interfaces. Its presence would allow two low-frequency modes to excite a high-frequency mode or vice versa thereby reducing thermal resistance between two vibrationally dissimilar materials.