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Transient thermoreflectance techniques are based on the phenomenon that the optical reflectance of a surface is directly proportional to the surface temperature.

They can be broadly categorised into two types, both of which are available from TherMap Solutions:

Time Domain (TDTR) and Frequency Domain (FDTR) thermoreflectance.

Whilst there are differences in the implementation of TDTR and FDTR, all thermoreflectance measurement techniques:

  • Are pump-probe laser techniques, which utilise one high power laser to heat the sample (pump laser) and another to detect changes in the sample reflectivity (probe laser) induced by this heating.

  • Can perform thermal characterisation of anisotropic materials through measurement of cross-plane and in-plane thermal conductivity.

  • Require the topmost surface material to possess a high thermoreflectance coefficient, as well as, ideally, high reflectance of the probe laser wavelength and high absorbance of the pump laser wavelength. Samples that do not fulfil this criteria require deposition of a thin (<0.2μm) layer of transducer material.

  • Can perform thermal conductivity surface mapping.

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