Prediction of high zT in thermoelectric silicon nanowires with axial germanium heterostructures
The Thomas Young Centre for Theory and Simulation of Materials, Imperial College London London SW7 2AZ, UK
Accepted: 5 May 2011
We calculate the thermoelectric figure of merit, zT=S2GT/(κl+κe), for p-type Si nanowires with axial Ge heterostructures using a combination of first-principles density-functional theory, interatomic potentials, and Landauer-Buttiker transport theory. We consider nanowires with up to 8400 atoms and twelve Ge axial heterostructures along their length. We find that introducing heterostructures always reduces S2G, and that our calculated increases in zT are predominantly driven by associated decreases in κl. Of the systems considered, ⟨111⟩ nanowires with a regular distribution of Ge heterostructures have the highest figure of merit: zT=3, an order of magnitude larger than the equivalent pristine nanowire. Even in the presence of realistic structural disorder, in the form of small variations in length of the heterostructures, zT remains several times larger than that of the pristine case, suggesting that axial heterostructuring is a promising route to high-zT thermoelectric nanowires.
PACS: 73.63.Nm – Quantum wires / 72.20.Pa – Thermoelectric and thermomagnetic effects / 63.22.Gh – Nanotubes and nanowires
© EPLA, 2011