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ISSN Online: 2377-424X

ISBN Print: 978-1-56700-421-2

International Heat Transfer Conference 15
August, 10-15, 2014, Kyoto, Japan

Investigation of Nanoscale Heat Transfer with Highly Versatile Phase-Locked Thermoreflectance

Get access (open in a dialog) DOI: 10.1615/IHTC15.kn.000025
pages 449-460

Sinopsis

The precision of Time Domain Thermoreflectance (TDTR) measurements is often limited by the small data signal relative to a larger background noise. In order to reduce this noise, we propose the implementation of low-cost digital logic circuitry to phase-lock the optical detection scheme with the source laser frequency. Materials with small coefficients of thermoreflectivity, for example, yield a low signal, while experimental conditions, such as low modulation frequencies, may yield large noise levels. Either case leads to low signalto-noise results preventing precise TDTR measurement results. The digital phase-locking procedure discussed in this paper can increase the signal-to-noise ratio by nearly a factor of four, thus making a wider array of measurements possible. The importance of a phase-locked system is discussed experimentally and theoretically and the design of the digital circuit is described. Thermoreflectance measurements of Al and Ni on Si are presented to display the significant improvement in the results after the phase-locking procedure is conducted.