From diffusive in-plane to ballistic out-of-plane heat transport in thin non-crystalline films

By means of Scanning Near-field Thermal Microscopy and with the support of equivalent thermal circuit modelling the transition from diffusive in-plane heat flux to ballistic Stefan-Boltzmann like out-of-plane heat flux from a nanoscale heat source is demonstrated. The results obtained on atomic layer deposited thin amorphous films with a thickness larger than the phonon mean-free path will significantly influence the thermal management and reliability investigations of modern devices based on thin film technology.