Silicon Nanowires as Efficient Thermoelectric Materials
Abstract
Thermoelectric materials interconvert thermal gradients and electric fields for power generation or for refrigeration1,2. Thermoelectrics currently find only niche applications because of their limited efficiency, which is measured by the dimensionless parameter ZTa function of the Seebeck coefficient or thermoelectric power, and of the electrical and thermal conductivities. Maximizing ZT is challenging because optimizing one physical parameter often adversely affects another3. Several groups have achieved significant improvements in ZT through multi-component nanostructured thermoelectrics46, such as Bi2Te3/Sb2Te3 thin-filmsuperlattices, or embedded PbSeTe quantum dot superlattices. Here we report efficient thermoelectric performance from the single-component system of silicon nanowires for cross-sectional areas of 10 nm x 20 nm and 20 nm x 20 nm. By varying the nanowire size and impurity doping levels, ZT values representing anapproximately 100-fold improvement over bulk Si are achieved over a broad temperature range, including ZT~1 at 200 K. Independent measurements of the Seebeck coefficient, the electrical conductivity and the thermal conductivity, combined with theory, indicate that the improved efficiency originates from phonon effects. These results are expected to apply to other classes of semiconductor nanomaterials.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 10, 2008
- Accession Number
- AD1020067
Entities
People
- Akram I. Boukai
- James R. Heath
- Jamil Tahir-kheli
- Jen-kan Yu
- William Iii A. Goddard
- Yuri Bunimovich
Organizations
- California Institute of Technology