Thermal conductivity measurements of single-crystalline bismuth nanowires by the four-point-probe 3-ω technique at low temperatures

Abstract

We have successfully investigated the thermal conductivity (κ) of single-crystalline bismuth nanowires (BiNWs) with [110] growth direction, via a straightforward and powerful four-point-probe 3-ω technique in the temperature range 10-280 K. The BiNWs, which are well known as the most effective material for thermoelectric (TE) device applications, were synthesized by compressive thermal stress on a SiO2/Si substrate at 250-270 °C for 10 h. To understand the thermal transport mechanism of BiNWs, we present three kinds of experimental technique as follows, (i) a manipulation of a single BiNW by an Omni-probe in a focused ion beam (FIB), (ii) a suspended bridge structure integrating a four-point-probe chip by micro-fabrication to minimize the thermal loss to the substrate, and (iii) a simple 3-ω technique system setup. We found that the thermal transport of BiNWs is highly affected by boundary scattering of both phonons and electrons as the dominant heat carriers. The thermal conductivity of a single BiNW (d ~ 123 nm) was estimated to be ~2.9 W m(-1) K(-1) at 280 K, implying lower values compared to the thermal conductivity of the bulk (~11 W m(-1) K(-1) at 280 K). It was noted that this reduction in the thermal conductivity of the BiNWs could be due to strongly enhanced phonon-boundary scattering at the surface of the BiNWs. Furthermore, we present temperature-dependent (10-280 K) thermal conductivity of the BiNWs using the 3-ω technique.

Reduced temperature-dependent thermal conductivity of magnetite thin films by controlling film thickness

“…In the current study, we utilized a four-point probe 3- ω method based on the application of an alternating current (AC) with angular modulation frequency (1- ω ), which was first developed by Cahill in 1990 [20] to measure the temperature-dependent thermal conductivities of as-grown Fe 3 O 4 thin films. It has been proved the most promising technique to extract thermal conductivities of 1D nanostructures such as nanowires [21,22] and carbon nanotubes [23,24] and thin films [25-27]. We have also proved this technique to be one of the powerful methods to extract the thermal conductivity of most low-dimensional materials [21].…”

Reduction in thermal conductivity of Bi thin films with high-density ordered nanoscopic pores

“…Thus, the lattice thermal conductivity is dominant thermal transport at low temperature, whereas the electronic thermal conductivity becomes progressively more important as temperature increase. Similarly, we observed that the thermal conductivity was almost constant up to 200 K and then slightly increased above 200 K in BiNW by enhanced boundary scattering via electrons [20]. As shown in Figure 4b, the length of the charge carrier MFP is longer than the neck size of the nanoporous Bi thin films with approximately 135- and approximately 200-nm pore diameters suggesting that the boundary scattering by charge carriers and bipolar diffusion at the pore surfaces, as the neck size decrease, could play a significant role in the suppression of the thermal conductivity of nanoporous Bi thin films at 300 K. Moreover, the nanoporous Bi thin film exhibits a lower thermal conductivity than 1D Bi NWs.…”

“…As shown in Figure 4b, the length of the charge carrier MFP is longer than the neck size of the nanoporous Bi thin films with approximately 135- and approximately 200-nm pore diameters suggesting that the boundary scattering by charge carriers and bipolar diffusion at the pore surfaces, as the neck size decrease, could play a significant role in the suppression of the thermal conductivity of nanoporous Bi thin films at 300 K. Moreover, the nanoporous Bi thin film exhibits a lower thermal conductivity than 1D Bi NWs. The thermal conductivity of a single-crystalline BiNW (approximately 120 nm in diameter) was measured to be approximately 2.9 W/m∙K at 280 K, confirming that nanoporous Bi thin films exhibit a lower thermal conductivity than 1D Bi NWs [20]. Consequently, the nanoporous architecture should provide promising scalable TE materials with low thermal conductivities, which have advantages over 1D nanostructure, such as nanowires and nanotubes.…”

“…A lock-in amplifier (A − B mode) connected to the two electrodes in the middle receives the 3 ω voltage fluctuation along the narrow metal strip; that gives the information about the thermal conductivity of the films. A few early studies by our group showed that the thermal conductivities of 1D silicon carbide nanowires (SiC NWs) [16] and Bi NWs [20] were measured successfully with our experimental setup and equipment. For the measurement of the thermal conductivity of nonporous and nanoporous Bi thin films, the third-harmonic voltage ( V 3 ω ) must be plotted against the natural logarithm of the applied frequencies ln ω resulting in a linear relationship.…”

Effect of grain size on thermal transport in post-annealed antimony telluride thin films

“…Cross-plane thermal conductivity measurements were conducted using four-point-probe 3- ω measurements in the 20 to 300 K temperature range in a vacuum of 5 × 10 −5  Torr, which has been proven to be a promising measurement technique for both 1D nanostructures [7,8,32] and 2D thin films [28]. Figure 3 shows the temperature oscillation of the in-phase component, Δ T s+f ( ω ), for the 400-nm-thick Sb 2 Te 3 thin films annealed at temperatures of 200°C to 350°C, with the Δ T s ( ω ) value of the substrates (SiO 2 /Si) also added as a reference.…”