Heat Diffusion Imaging: In-Plane Thermal Conductivity Measurement of Thin Films in a Broad Temperature Range

This work combines the principles of the heat spreader method and imaging capability of the thermoreflectance measurements to measure the in-plane thermal conductivity of thin-films without the requirement of film suspension or multiple thermometer deposition. We refer to this hybrid technique as heat diffusion imaging. The thermoreflectance imaging system provides a temperature distribution map across the film surface. The in-plane thermal conductivity can be extracted from the temperature decay profile. By coupling the system with a cryostat, we were able to conduct measurements from 40 K to 400 K. Silicon thin film samples with and without periodic holes were measured and compared with in-plane time-domain thermoreflectance (TDTR) measurement and literature data as validation for heat diffusion imaging.