Numerical simulation of transient thermoreflectance of thin films in the picosecond regime

Gregory J. Kowalski

doi:10.1117/12.259826

21 November 1996 Numerical simulation of transient thermoreflectance of thin films in the picosecond regime

Gregory J. Kowalski

Proceedings Volume 2855, High Heat Flux Engineering III; (1996) https://doi.org/10.1117/12.259826
Event: SPIE's 1996 International Symposium on Optical Science, Engineering, and Instrumentation, 1996, Denver, CO, United States

Abstract

Transient thermoreflectance techniques, especially the picosecond transient thermoreflectance method (PTTR), provide a means of determining the thermo-physical properties of a thin film and of measuring thin film properties and temperature during manufacturing. In these techniques a pump and probe method is used to heat the sample and to measure the reflectance from it. It has been shown using a plane wave analysis and a 1D thermal analysis based on uniform spatial irradiation that internal reflections caused by the spatial temperature field significantly affect the accuracy of the method in some materials. The internal reflection mechanism alters the temperature field as compared to that predicted without it. Criteria to define the range of importance of the internal reflection mechanism have been developed based on these assumptions. THese results are extended using numerical analysis to investigate the effects of an incident Gaussian beam instead of uniform irradiation. The code includes mechanism to describe the temperature and intensity dependent absorption coefficients and index of refraction. It is found that the 2D effects decrease the 1D normalized reflectance change by 24 percent. A technique for the incorporating the code into the analysis of the PTTR is described.

Citation Download Citation

Gregory J. Kowalski "Numerical simulation of transient thermoreflectance of thin films in the picosecond regime", Proc. SPIE 2855, High Heat Flux Engineering III, (21 November 1996); https://doi.org/10.1117/12.259826

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