based layers investigated by the 3ω method *

Aim of the project is to develop a diagnostic technique to measure the thermal conductivity of thin Zr_xO_y layers which are deposited via PECVD and can be used for galvanic isolation. The 3ω method was selected as a surface-sensitive technique with high accuracy and short equilibration time.

This method can be applied to bulk amorphous solids and crystals as well as to amorphous films tens of microns thick. A thin electrically conductive wire is deposited onto the specimen to measure its thermal conductivity. The wire serves both, as a heater and as a temperature sensor. Joule heating at a 2ω frequency occurs when an ac current with angular modulation frequency ω is applied to the wire. The generated thermal wave diffuses into the specimen. This causes a modulation of the resistance at 2ω due to the temperature dependence of the resistance. The voltage drop along the wire contains a contribution from a third harmonic that depends on the modulated temperature rise of the heater and could be used to calculate the thermal conductivity of the sample.

We will present the setup, its characterization by using reference samples and first results on Zr_xO_y layers and the influence of the structure and morphology of these layers on the thermal conductivity.