Thermal boundary resistance at Au/Ge/Ge and Au/Si/Ge interfaces

Abstract

Amorphous Ge (a-Ge), crystalline Ge (c-Ge), and amorphous Si (a-Si) thin films were deposited on a Ge substrate at different temperatures by magnetron sputtering. We measured thermal boundary resistance (TBR) in Au/Ge/Ge and Au/Si/Ge three-layer samples. The measured TBR in Au/a-Ge/Ge and Au/a-Si/Ge decreased slightly with increasing deposition temperature. The measured TBR values were larger than the values predicted by the diffuse mismatch model. Furthermore, it is interesting to note that the measured TBR in Au/c-Ge/Ge was twofold larger than that in Au/a-Ge/Ge. Cross-sectional transmission electron microscopy was conducted to investigate interfacial morphology of the samples. The results indicate that the crystalline state of the deposited thin films play an important role in TBR by modifying phonon density of states and interfacial properties. Our findings are of great importance for applications involving thermal management of micro- and optoelectronic devices, and for the development of thermal barrier coatings and thermoelectric materials with high figures-of-merit.