エバネッセント光による面方向熱輸送促進

抄録

Thermal conductivity of a thin film decreases due to the strong phonon scattering at the film surface with decreasing the film thickness. However, it is shown theoretically that the thermal conductivity of a thin film with several tens nano-meter thickness can be increased due to the Surface Phonon-Polaritons (SPhPs) effects. SPhPs are surface evanescent electromagnetic waves resulting from the coupling between optical phonons and photons. In this regard, silicon dioxide films are made by thermal oxidization to have high density films compared to those grown by other methods. Further, standard micro-fabrication processes were used to fabricate suspended thin film for thermal conductivity measurement by steady state method and diffusivity by 3ω method. We also measured temperature dependence of thermal conductivity of 50 and 200 nm thick suspended thin films from 300 K to 370 K. Experimental results is comparable with analytical thermal conductivity enhanced due to surface phonon-polaritons. Result shows that the thermal transport in suspended thin films was increased with decreasing the film thickness while it increased with increasing the temperature.