In Situ Measurement of Strain-Dependent Thermal Conductivity in Emerging Functional Materials

Semiconductor devices and sensors often contend with a range of mechanical stresses or strains. This is particularly pertinent in emerging domains like flexible electronics and thermoelectric devices, which find application in the renewable energy sector and experience these stresses in practical operating environments. The existing body of literature on experimental measurements of the strain dependence of materials are limited and still in the process of refinement. There are no steady-state measurement techniques used to measure the thermal conductivity. The measurements done are transient and performed through either Raman Spectroscopy or the 3w method. Both have limitations in terms of stability and duration of experiments as well as for investigating bulk materials due to geometrical and size constraints. Another critical constraint in transient measurements is that heat diffusion is measured, making it difficult to distinguish the strain dependence of thermal conductivity and heat capacity separately. Whereas in steady state we can have stable and continuous long-duration measurements, bulk material experiments, and can measure the temperature gradient of the material, from which we can directly calculate its thermal conductivity. We demonstrate this by measuring the thermal conductivity dependence on strain of bulk Silicon, GaN and GaAs. This study opens up a potential direction towards controlling thermal conductivity in semiconductors. This work is based on research supported by the U.S. Office of Naval Research under the award number N00014-22-1-2262.