ICT2014 Abstracts

We have studied on thermoelectric properties of suspended individual stoichiometric bismuth telluride (Bi₂Te₃) nanotube at temperatures ranging from 50 K to 300K. The wall thickness of nanotube is between 10 nm and 15 nm. A microfabricated thermoelectric workbench was developed to measure electrical and thermal conductivity and Seebeck coefficient. Electron beam induced deposition of platinum was used to provide mechanical anchors and good electrical and thermal contact between the nanotube and the workbench. Rapid thermal annealing was performed in the atmosphere of forming gas (4% H₂/96% N₂) at 200 °C to further improve the electrical contact. The measured Seebeck coefficient was positive, which indicates that hole is majority carrier and is consistent with a previous report that the bulk bismuth telluride is p-type when the atomic ratio of tellurium is below 63%. We measured 4 samples and the Seebeck coefficient of the nanotubes varied between 275 µV/K and 357 µV/K at 300 K which is 1.10 and 1.43 times larger than the reported value of bulk Bi₂Te₃ (249 µV/K) respectively. We measured the thermal conductivity using 3ω method. The thermal conductivity was on one of the Bi₂Te₃ nanotubes was measured to be 0.95 W/m-K at 300 K. However, since this measurement was performed on a separate workbench, all the three transport measurements were not performed on the same nanotube. However, this value of thermal conductivity was typical for nanotubes with diameters in the range of 100 – 120 nm where we expect the tellurium core to be completely consumed and used to form the bismuth telluride nanotube. Based on these measurements, Bi₂Te₃ nanotubes are expected to have ZT value between 1.16 and 0.69 at 300 K which is 2.76 and 1.64 times larger than reported value of bulk Bi₂Te₃ (0.42), respectively.