Project Details
Projekt
Electrical and thermoelectric properties of Bi and Bi2Te3 nanowires: novel and high-efficiency thermoelectric devices
Applicant
Professor Dr. Reinhard Neumann
Subject Area
Experimental Condensed Matter Physics
Term
from 2006 to 2010
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 25843653
Our project aims at investigating the electrical and thermoelectric properties of Bi nanowires, as well as their band structure. Bi is a semimetal with unique properties. It possesses one anisotropic hole pocket at the T point and three highly anisotropic electron pockets at the L point. Due to the highly anisotropic Fermi surface, all transport properties depend on the crystal orientation. Furthermore, Bi exhibits a very small effective electron mass, a large Fermi wavelength (F (40 nm at 300 K) and a large electron mean free path le (100 nm at 300 K). These properties make bismuth nanowires very suitable for studying both mesoscopic and quantum size effects. In the mesoscopic regime, we want to understand the influence of electron scattering at both wire surface and grain boundaries on the increased electrical resistivity of the nanowires in comparison to bulk. This increase in resistivity is of tremendous importance for the implementation of nanostructures in electronic devices.For Bi nanowires with diameters in the Fermi wavelength range, we will study the semimetalto- semiconductor transition predicted for wires with diameters below ~ 40 nm, caused by quantum confinement, which make the band edges shift against each other, the small band overlap changes into a band gap. Infrared spectroscopy measurements will provide valuable novel information on the bands shifts as a function of wire diameter and temperature. Furthermore, measurements on short and thin Bi wires (l < le, d < (F) will provide the possibility to study quantum conductance effects on nanowires with well-defined shape, size and crystallinity. Additionally, we plan to measure the thermoelectric efficiency of arrays of Bi and Bi2Te3 nanowires, and to analyze their possible application in novel and promising thermoelectric nanodevices, which can be used for low-power generation and/or refrigeration.
DFG Programme
Priority Programmes
Participating Person
Dr. Maria Eugenia Toimil-Molares
