Laser repetition rate in time-domain thermoreflectance techniques

摘要

Pump-probe thermoreflectance techniques have been utilized extensively to measure the thermal properties; such as, thermal conductivity and interfacial conductances of thin film systems. While there have been many implementations of transient measurements, the most commonly operated systems utilize a near-IR femtosecond pulsed system as the fundamental laser source. The repetition rate of these femtosecond pulsed systems can vary from kHz to MHz. Thus, we perform an in-depth comparison of the implementation and analysis of low-repetition rate and high-repetition rate time-domain thermoreflectance (TDTR), demonstrating that despite varying the repetition-rate, the measured thermal properties are consistent. To illustrate the universality of these systems, we selected a range of materials to study on both TDTR set-ups, including the thermal conductivity of a SiC film, a SiO_2 film, and the interfacial conductances of Al/SiO_2 and Al/SiC systems.