Abstract

The thermal conductivities of several dielectric thin films have been evaluated with a high precision thermal comparator. Our technique works in air at 36°C and is rapid and nondestructive. Measurements can be performed on any thin film-substrate combination, but high conductivity substrates like single crystal Si, Al₂O₃, and MgF₂ are preferred. By measuring the apparent conductivity of coated substrates as a function of coating thickness we derive both the film conductivity and the conductivity of any interface or barrier layer. We report our results for e-beam deposited films of SiO₂, Al₂O₃, and MgF₂ on optical substrates. As an example, Al₂O₃ on Si exhibits a thermal conductivity of 5 × 10⁻⁵ cal cm⁻¹ s⁻¹ °C⁻¹ for films varying in thickness from 0.5 to 2.0 µm. The conductivity of the coating-substrate interface is lower than 5 × 10⁻⁶ cal cm⁻¹ s⁻¹ °C⁻¹. For comparison, Decker reported¹ a value of conductivity for a free-standing film of Al₂O₃, produced by ion beam sputtering, of 8.6 × 10⁻⁵ cal cm⁻¹ s⁻¹ °C⁻¹.

© 1986 Optical Society of America