A new thermometry method for measuring the thermal conductivity of materials – Congrats Dr. Jeff Braun (and congrats on successful PhD defense on 4/12/19!)

The recently deemed “Dr.” Jeff Braun recently published his work on steady state thermoreflectance (SSTR), an optical pump-probe technique based on continuous wave lasers in which the steady state temperature rise of a solid is monitored as a function of laser power to measure the thermal conductivity of the material.  SSTR is capable of measuring the thermal conductivity of materials over length scales from just a few microns to hundreds of microns, filling an important void in the landscape of thermal conductivity measurement capabilities.

Braun, J.L., Olson, D.H., Gaskins, J.T., Hopkins, P.E., “A steady-state thermoreflectance method to measure thermal conductivity,” Review of Scientific Instruments 90, 024905 (2019). PDF.

We demonstrate a steady-state thermoreflectance-based optical pump-probe technique to measure the thermal conductivity of materials using a continuous wave laser heat source. The technique works in principle by inducing a steady-state temperature rise in a material via long enough exposure to heating from a pump laser. A probe beam is then used to detect the resulting change in reflectance, which is proportional to the change in temperature at the sample surface. Increasing the power of the pump beam to induce larger temperature rises, Fourier’s law is used to determine the thermal conductivity. We show that this technique is capable of measuring the thermal conductivity of a wide array of materials having thermal conductivities ranging from 1 to >2000 W m−1 K−1, in excellent agreement with literature values.