Sensing depths in frequency domain thermoreflectance

A method is developed to calculate the length into a sample to which a Frequency Domain Thermoreflectance (FDTR) measurement is sensitive. Sensing depth and sensing radius are defined as limiting cases for the spherically spreading FDTR measurement. A finite element model for FDTR measurements is de...

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Bibliographic Details
Published in:Journal of applied physics 2022-06, Vol.131 (24)
Main Authors: Hodges, Wyatt, Jarzembski, Amun, McDonald, Anthony, Ziade, Elbara, Pickrell, Greg W.
Format: Article
Language:English
Subjects:
Applied physics
Finite element method
Frequency domain analysis
Mathematical models
Silicon dioxide
Thickness
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Summary:A method is developed to calculate the length into a sample to which a Frequency Domain Thermoreflectance (FDTR) measurement is sensitive. Sensing depth and sensing radius are defined as limiting cases for the spherically spreading FDTR measurement. A finite element model for FDTR measurements is developed in COMSOL multiphysics and used to calculate sensing depth and sensing radius for silicon and silicon dioxide samples for a variety of frequencies and laser spot sizes. The model is compared to experimental FDTR measurements. Design recommendations for sample thickness are made for experiments where semi-infinite sample depth is desirable. For measurements using a metal transducer layer, the recommended sample thickness is three thermal penetration depths, as calculated from the lowest measurement frequency.
ISSN:0021-8979
1089-7550
DOI:10.1063/5.0088594