Grain size and its effect on thermal conductivity of Pt nanofilms

Six Pt films with thicknesses of 15-62 nm have been fabricated by electron beam-physical vapor deposition (EB-PVD). The grain sizes of the Pt nanofilms and its effect on the thermal conductivity have been studied experimentally. It is found that the grain size increases with the nanofilm thickness increasing and goes to a constant about 20 nm. The grain size is nearly comparable with the nanofilm thickness with the thickness less than 30 nm, while becomes much less than the nanofilm thickness with the thickness larger than 30 nm. Influenced by the surface and grain boundary effects, the thermal conductivity of the Pt nanofilms is greatly lower than that of the Pt bulk. It is noted that the thermal conductivity of the studied platinum nanofilms increases with the thickness increasing and runs to 35 W/mK, which is much lower than that of the bulk material.