The thermal conductivity of optical coatings of SiO2 and TiO2 were measured. The novel measurement method based on an extension of the 3ω method gave precise results over temperatures 80-400K. The accuracy of the procedure was assessed by measuring the thermal conductivity of a 1-μm-thick film of SiO2 grown on a Si wafer. It was noted that reduction in the thermal conductivity of an evaporated film relative to a sputtered film observed in SiO2 was also observed in TiO2. For SiO2, the temperature dependence of the thermal conductivity for the sputtered and evaporated films were the same. The similarity of the behavior of SiO2 and TiO2 films was remarkable and indicated that the cause of the reduction in thermal conductivity of evaporated oxide thin films has a common origin. However, the source of thermal conductivity reduction of sputtered SiO2 relative to sputtered films cannot be readily accounted by variations in film density.
ASJC Scopus subject areas
- Physics and Astronomy (miscellaneous)