Atomistic Design of Thermoelectric Properties of Silicon Nanowires

• Published in: Nano letters Vol. 8; no. 4; pp. 1111 - 1114
• Main Authors: Vo, Trinh T.M, Williamson, Andrew J, Lordi, Vincenzo, Galli, Giulia
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01.04.2008
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Electronic structure of nanoscale materials : clusters, nanoparticles, nanotubes, and nanocrystals; Exact sciences and technology; Low-dimensional structures (superlattices, quantum well structures, multilayers): structure, and nonelectronic properties; Materials science; Nanocrystalline materials; Nanoscale materials and structures: fabrication and characterization; Physics; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Thermal properties of condensed matter; Thermal properties of small particles, nanocrystals, nanotubes; Ionic conductivity; Theoretical study; Nanostructures; Thermoelectric properties; Thermoelectric materials; Surface reconstruction; Electronic structure; Growth mechanism; Thermal conductivity; Property structure relationship; Silicon; Ab initio calculations; Nanowires; Nanostructured materials; Figure of merit
• ISSN: 1530-6984; 1530-6992
• DOI: 10.1021/nl073231d

We present predictions of the thermoelectric figure of merit (ZT) of Si nanowires with diameter up to 3 nm, based upon the Boltzman transport equation and ab initio electronic structure calculations. We find that ZT depends significantly on the wire growth direction and surface reconstruction, and we discuss how these properties can be tuned to select silicon based nanostructures with combined n-type and p-type optimal ZT. Our calculations show that only by reducing the ionic thermal conductivity by about 2 or 3 orders of magnitudes with respect to bulk values, one may attain ZT larger than 1, for 1 or 3 nm wires, respectively. We also find that ZT of p-doped wires is considerably smaller than that of their n-doped counterparts with the same size and geometry.