Extension of the 3ω method to measure the thermal conductivity of thin films without a reference sample

The 3ω method has been extensively used to measure the thermal conductivity of bulk and thin film dielectric materials. In practice it is basically a differential technique since it is necessary to process two samples that are identical except for the layer of interest, and in some cases the reference sample may not be available. In this contribution we show that it is possible to simultaneously measure the thermal conductivity of both the substrate and the thin film without the need for a reference sample. Two sensors of different widths are used to extract values from the substrate and the layer of interest. This method is applied to measure the out-of-plane thermal conductivity of a-SiO2 and a-SiNx films grown on a Si substrate.