The investigation of electron-phonon coupling on thermal transport across metal-semiconductor periodic multilayer films

The cross-plane thermal conductivities of four X/Si (X = SiGe, Au, Cr, Ti) periodic multilayer films deposited by magnetron sputtering with period thicknesses of about 20 nm were investigated by a differential 3 omega method at room temperature. Structure characterization and sharp interfaces of multilayer films were confirmed by grazing incidence small angle X-ray scattering and field emission scanning electron microscopy. The measured thermal conductivities were compared with the classic heat conduction model and the two temperature model (TTM). The interfacial thermal resistance is the sum of the phonon interfacial thermal resistance and electron-phonon thermal resistance. The experimental results show great agreement with the theoretical results calculated by the TTM. It indicates that in metal-semiconductor periodic multilayered system for a relatively low coupling factor G (10(16) - 10(17) Wm(-3) K-1), the thermal conductivity of the samples is significantly affected by the electron-phonon coupling, providing a more insightful understanding of the thermal transport mechanism of the thin-film system.