Temperature dependent thermal conductivity of polycrystalline ZnO films

We report on measurements of the thermal conductivity of atomic layer depositedpolycrystalline zinc oxide (ZnO)films between 30 and 300 K. The room temperature thermal conductivity of the films is found to be twofold less than that of single-crystal ZnO. The maximum thermal conductivities of the polycrystalline samples occur at about 60 K and their values are almost an order of magnitude lower than bulk ZnO. The effect of the grain size and the transparency of the intergrain boundary on the thermal conductivity are analyzed within the framework of the phonon-hopping transport model.