The experimental investigation of thermal conductivity and the Wiedemann–Franz law forsingle metallic nanowires

Abstract

A new method for the measurement of thermal conductivity of electrically conductingsingle nanowires is presented. First experimental investigations are focused on the thermalconductivity of metallic Pt nanowires with a diameter of (typically) 100 nm and a length of 10 µm. Thermal conductivity data are compared with measurements of electrical conductivity inorder to test the Wiedemann–Franz law for metallic nanowires. Compared to the bulkvalues at room temperature, electrical and thermal conductivities of the nanowire aredecreased by a factor of 2.5 and 3.4, respectively. Consequently, the Lorenz numberL = λ/σT = 1.82 × 10−8 V2 K−2 of the nanowire is smaller than the bulk Lorenz numberLbulk = (π2/3)(k/e)2 = 2.44 × 10−8 V2 K−2 of metals. Furthermore, the temperature coefficientβ of electrical resistivity is also reduced compared to the bulk value. These decreases ofλ,σ andβ can be attributed to size effects, mainly caused by grain boundary scattering of electrons.