Structural characterization and thermoelectric transport properties of uniform single-crystalline lead telluride nanowires

Uniform single-crystalline PbTe nanowires with average diameter of about 30 nm, below its average excitonic Bohr radius of 46 nm, were successfully synthesized in large quantity by a two-step hydrothermal process using tellurium nanowires as templates and Pb(NO₃)₂ as a precursor. It is shown that the reaction temperature, duration, and concentration of Pb(NO ₃)₂ play important roles in the formation of the PbTe nanowires. An in situ diffusion and growth mechanism together with a nontopotactic transformation process was proposed to explain the formation of the PbTe nanowires. The thermoelectric transport measurement indicates a high Seebeck coefficient of about 628 μV/K in the thin film sample composed of the obtained PbTe nanowires, about 137% exceeding that of the state-of-the-art bulk PbTe. The calculated local density of states (LDOS) by the density functional theory shows a strong increase with decreasing nanowire diameter, which is consistent with the measured large enhancement in Seebeck coefficient in the PbTe nanowire sample.