Measurement of thermal conductivity and contact resistance using the photoacoustic and thermoreflectance methods

Thermal conductivity and contact resistance were measured using the photoacoustic and thermoreflectance methods. The photoacoustic method uses a sinusoidally modulated infrared laser to cyclically heat a sample surface. A microphone picks up the acoustic response, which is characteristic of certain thermal properties. The thermoreflectance method uses a pulsed nanosecond laser to heat a spot on the surface of a sample and a continuous wavelength HeNe laser to probe the heated spot. The reflectivity is directly proportional to the temperature, so the normalized change in reflected probe power on the time domain is compared to a finite volume model of the temperature. The sensitivity of each method to relevant parameters is discussed, and samples are tested to show the capabilities of each apparatus. A case study of carbon nanotubes was performed to show the potential of both methods