Frequency domain thermoreflectance technique for measuring the thermal conductivity of individual micro-particles

The thermal properties of micron scale particles are an important factor in the design of composite materials and other applications. Here we present an optical technique based on frequency domain thermoreflectance (FDTR) that is capable of measuring the thermal conductivity of individual particles a few microns across. In addition, the technique can provide values for a particle's effective volume which is a new capability compared to conventional FDTR applied to multilayer samples. We also show and explain the response of systems that constrain heat flow along the in-plane direction due to a boundary. We tested this technique with natural diamond and doped silicon particles of different sizes. For the diamond particles, the thermal conductivity values obtained were within the range of reported literature values, while for the silicon particles, the thermal conductivities were slightly lower than the bulk sample they were fabricated from, possibly due to defects introduced during the fabrication process.