Thermal conductivity measurement of amorphous Si/SiGe multilayer films by 3 omega method

The cross-plane thermal conductivities of five amorphous Si/Si0.75Ge0.25 multilayer films deposited by magnetron sputtering with period thicknesses ranging from 2.5 nm to 50 nm were investigated by a differential 3ω method at room temperature. The measurement results demonstrate that the thermal conductivities of amorphous Si/Si0.75Ge0.25 multilayer films are independent of period thickness and are comparable to the corresponding result calculated according to the Fourier heat conduction theory using constituent materials' thermal conductivities. Structure disorder and sharp interfaces of multilayer films were confirmed by X-ray diffraction and scanning electron microscopy. The results indicate that in amorphous Si/Si0.75Ge0.25 multilayer system interface effects do not play a key factor to thermal transport at room temperature due to significant reduction of phonon mean free path induced by the structure disorder.

► The thermal conductivity of amorphous Si/SiGe multilayer films was studied.
► The synthesized films were systematically characterized by XRD and SEM.
► The thermal conductivities of films are independent of period thickness.
► Fourier theory and Debye model was used to analyze the outcome.
► The interface effect could be negligible due to the phonon MFP limitation.