Thermal conductivity of ZrO2 thin films

The thermal conductivity of thin solid films may be considerably lower than bulk material ones. We have recently developed a new photothermal method which enables the determination of the thermal conductivity of the dielectric films, on various kind of substrates, with an accuracy better than 10%. In this paper, we present the thermal conductivity of two kinds of ZrO2 thin films (stabilized with Y2O3 or not). We observe that a decrease in the dielectric thickness leads to a drastic drop of the thermal conductivity lambda(a). The drop in the thermal conductivity has a similar shape for the two ZrO2 phases. Phonons boundary scattering cannot contribute so significantly to the reduction of lambda(a). The most satisfactory explanation is that the thermal conductivity lambda(a) is affected by an additional thermal resistance R, especially between ZrO2 and alumina substrate. In the future, we intend to study in more detail the structures of the interfaces. (C) 2000 Editions scientifiques et medicates Elsevier SAS.