Measurement of thermal conductivity of thin films with a Si-N membrane-based microcalorimeter

We describe a method of measuring thermal conductivity of films as thin as 15 nm from 2-300 K and in magnetic fields up to at least 8 T using a silicon-nitride membrane based microcalorimeter. The thermal transport in the membrane is measured before and after a sample film is deposited on the membrane. Accurate knowledge of the geometry of the microcalorimeter allows the thermal conductivity of the sample film to be determined from the difference of these measurements. We demonstrate the method for two thin film samples, a 16 nm thick Au film and a 200 nm Pb film. Results are in good agreement with the expected thermal conductivity. Below 10 K, surface scattering effects in the nitride membrane become important and limit the usefulness of this technique in some cases. Above 100 K radiative loss becomes important; we describe a method for correcting for this, taking advantage of its temperature dependence. (C) 2005 American Institute of Physics.