Thermal Conductivity of an Individual Bismuth Nanowire Covered with a Quartz Template Using a 3-Omega Technique
Thermal conductivity is estimated using a 3-omega technique for an individual bismuth nanowire (diameter: 595 nm, length: 2.24 mm) covered with a quartz template. To evaluate the thermal conductivity of the nanowire, we propose a simple model of thermal and electrical transfer functions for the nanowire that assumes a linear combination of that of the line heater on the substrate and a suspended wire. Since the out-of-phase third-harmonic component of the electrical transfer function depends only on the thermal diffusivity of the nanowire, measurement of the frequency dependence is carried out. A distinct extreme value of the frequency has been observed, as expected, and estimation of the thermal conductivity of the nanowire covered with the quartz is attempted. Although the thermal conductivity at 300 K is 9.8 W/mK, somewhat smaller than that of bulk bismuth, the temperature dependence of the thermal conductivity is quite different from that of bulk bismuth, and decreased linearly with decreasing temperature. In particular, this shows that the thermal conductivity obtained is suppressed in the low-temperature region by phonon confinement in the nanowire.