Probing Thermal conductivity of Group-IV thin film alloys by the 3ω method

Short-range order (SRO), a deviation from random atomic arrangement in alloys, could significantly influences electronic and phonon properties in group-IV alloys like SnGe and SiGeSn. Owing to the challenges in growing bulk crystals for group-IV alloys, epitaxial thin film synthesis has been extensively explored and developed. Unlike the impact of SRO on electronic properties that can be relatively easily probed via spectroscopy and transport measurements, correlating SRO phonons and the associated thermal transport, which is essential for designing advanced electronic and thermoelectric materials, remains a challenge in thin flims. This work utilizes the 3ω method to determine the in-plane thermal conductivity of SnGe and SiGeSn thin films. By analyzing the third-harmonic voltage response from a patterned metal heater, we directly extract the thermal conductivity of the film layer. Our results not only validate the 3ω technique for complex multilayer systems but also establish a foundational framework for linking atomic-scale structure to phonon dynamics in group-IV alloys.