A microprobe technique for simultaneously measuring thermal conductivity and Seebeck coefficient of thin films

摘要

We demonstrate a microprobe technique that can simultaneously measure thermal conductivity u0001nand Seebeck coefficient u0002 of thin films. In this technique, an alternative current joule-heatednV-shaped microwire that serves as heater, thermometer and voltage electrode, locally heats the thinnfilm when contacted with the surface. The u0001 is extracted from the thermal resistance of thenmicroprobe and u0002 from the Seebeck voltage measured between the probe and unheated regions ofnthe film by modeling heat transfer in the probe, sample and their contact area, and by calibrationsnwith standard reference samples. Application of the technique on sulfur-doped porous Bi2Te3 andnBi2Se3 films reveals u0002 =−105.4 and 1.96 u0003V/K, respectively, which are within 2% of the valuesnobtained by independent measurements carried out using microfabricated test structures. Thenrespective u0001 values are 0.36 and 0.52 W/mK, which are significantly lower than the bulk values duento film porosity, and are consistent with effective media theory. The dominance of air conduction atnthe probe-sample contact area determines the microscale spatial resolution of the technique andnallows probing samples with rough surfaces.