Laser repetition rate in time-domain thermoreflectance techniques

• Published in: International journal of heat and mass transfer 2017-06, Vol.109, p.786-790
• Main Authors: Larkin, L.S., Smoyer, J.L., Norris, P.M.
• Format: Article
• Language: English
• Subjects: Heat conductivity; Heat transfer; Multilayered thin films; Oscillators; Repetition; Silicon dioxide; Thermal conductivity; Thermodynamic properties; Thin film thermal properties; Thin films; Time domain analysis; Time-domain thermoreflectance
• ISSN: 0017-9310; 1879-2189
• DOI: 10.1016/j.ijheatmasstransfer.2017.02.047

•The thermal properties measured by TDTR are independent of laser repetition rate.•TDTR’s sensitivity to thermal properties is altered by laser repetition rate.•First reported values of conductance at Al/SiC and Al/PECVD SiO2/SiC interfaces. 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 SiO2 film, and the interfacial conductances of Al/SiO2 and Al/SiC systems.