An analysis of the thermal conductivity in silicon vertical nanowire arrays using 3ω method

Abstract

We report the influence of dimension or doping concentration on thermal conductivity of silicon nanowire for thermoelectric application. Vertical silicon nanowire composite films, in which vertical nanowire array is embedded in dielectric materials, are fabricated by CMOS technology. The vertical nanowires have highly uniform dimension with diameters of 180 nm and 350 nm and heights of about 3 m. The differential 3ω method is used to measure the thermal conductivity of composite film. The thermal conductivity of nanowires with the diameter of 350 nm and 180 nm are 48.85 W/m∙K and 35.42 W/m∙K, respectively, which are 67 % and 75 % lower than that of bulk silicon. In addition, the boron and phosphorus doped silicon nanowires show the thermal conductivity of 14.54 W/m∙K and 17.15 W/m∙K, respectively, which are lower than that of un-doped nanowires. It turns out that thermal conductivity of nanowire decreases with shrinking diameter or increasing doping concentration. These results come from phonon-boundary scattering and phonon-impurity scattering. Consequently, the silicon nanowire can be very promising for thermoelectric device by tuning phonon scattering.