Size effects on the thermal conductivity of polycrystalline platinum nanofilms

摘要: The surface and grain-boundary effects on the in-plane thermal conductivity of polycrystalline platinum nanofilms have been investigated. thicknesses range from 15.0 to 63.0 nm mean grain sizes measured by x-ray diffraction vary 9.5 26.4 nm. conductivities a direct electrical heating method are greatly reduced bulk values. results compared with values predicted Qiu Tien model Kumar Vradis theory. It is found that reduction in mainly caused scattering reflection coefficient electrons striking boundaries around 0.35. relaxation time also applied study size check whether Matthiessen rule still valid predicting metallic nanofilms. indicate considering only background valid. If scattering, however, included, deviations other theories mentioned above found.