Thermal Conductivity Measurements on Challenging Samples by the 3 Omega Method

The 3 omega method is the best established method for measuring the thermal properties of thin films (> 100 nm) and nanowires. Theoretically, the method could be applied to many more types of samples, leading to new knowledge, but to date little effort has been made to extend its applicability. An enabling set of technologies has been tested at the Fraunhofer-IPM. The technologies developed encompass a new design of microheater, the measurement of bulk samples with a prefabricated microheater on adhesive tapes and polymer sheets, the measurement of tiny bulk samples glued to the underside of polymer sheets, a fully automated experimental setup, and a new numerical tool adapted to the new type of heater. The new design of microheater and software were validated using float glass as a reference material. A microheater on adhesive tape was used to measure accurately the thermal properties of sintered thermoelectric materials. The thermal conductivity of a very small melt-spun nanocomposite sample glued to the underside of a Kapton (TM) sheet was measured. The potential of the new design of microheater to measure very thin (similar to nm) films is discussed.