Interfacial thermal resistance of metal-nonmetal interfaces under bidirectional heat fluxes

Abstract

Interfacial thermal resistance (ITR) at metal/nonmetal interfaces is a crucial issue affecting the efficiency of electronic devices. We investigated the ITR of Ni/Al2O3 and W/Al2O3 interfaces under the influence of bidirectional heat fluxes, with the heat flowing from the metal to the nonmetal and vice versa, using the time domain thermoreflectance technique. An asymmetric ITR was first experimentally observed such that the ITR was larger by a factor of 1.4–1.9 when the heat was applied from the nonmetal side, relative to the metal side. The additional interfacial electron–phonon couplings induced by the temperature difference between the hot electrons and phonons, which occur upon heating from the metal side, could be one of the plausible reasons causing the asymmetry. The thermal contribution of the interfacial electron–phonon coupling is found to be comparable with the phonon–phonon coupling. This new approach may allow us to elucidate thermal rectification at metal/nonmetal interfaces, thus leading to the development of light-controlled thermal diodes.