Thermal conductance of metal-metal interfaces

The thermal conductance of interfaces between Al and Cu is measured in the temperature range 78<T<298 K using time-domain thermoreflectance. The samples are prepared by magnetron sputter deposition of a 100 nm thick film of Al on top of layers of Cu on sapphire substrates. The chemical abruptness of the Al-Cu interface is systematically varied by ion-beam mixing using 1 MeV Kr ions. The thermal conductance of the as-deposited Al-Cu interface is 4 GW m-2 K-1 at room temperature, an order-of-magnitude larger than the phonon-mediated thermal conductance of typical metal-dielectric interfaces. The magnitude and the linear temperature dependence of the conductance are described well by a diffuse-mismatch model for electron transport at interfaces.