2 . B Thermal Conductivity in Dielectric Thin Films In 1984

In 1984 Decker et al.' reported the measurement of thermal conductivity for freestanding thin films of Si02 and A1203. Values were found to be one to two orders of magnitude lower than those for the corresponding bulk materials. The authors attributed this difference to the unique microstructure of dielectric thin films (primarily columnar for vapor-deposited coatingsz), which, along with defects and impurities, would be expected to reduce the phonon mean-free path, and thus the conductivity. Work by others has recently reinforced these findings for other dielectric coatings.3.4