Combined Thermoelectric and Structure Characterizations of Patterned Nanowires

Abstract

Theoretical studies have suggested that Bi-based and III-V nanowire structures may have high thermoelectric figure of merit (ZT). It was found in a previous measurement that the thermoelectric properties of individual electro-deposited bismuth telluride nanowires are largely influenced by the crystal structure including crystalline quality, chemical composition, doping concentration, and surface roughness, all of which cannot be controlled readily in various bottom-up nanowire synthesis method. We have developed a top-down fabrication process of suspended indium arsenide (InAs) nanowires. Based on nanolithography and reactive ion etching, the nanowires are patterned from an epitaxial thin film deposited by molecular beam epitaxy with well-controlled doping concentration, which can be determined from Hall measurement. The thermoelectric properties of these top-down patterned III-V nanowires have been characterized using a new design of a suspended microdevice. The new device allows for transmission electron microscopy and energy dispersive X-ray spectroscopy analysis of the same nanowire assembled on the microdevice so as to establish the structure-thermoelectric properties relationships. This paper reports the measured thermoelectric properties of a patterned InAs nanowire with a rectangular cross section of 150 nm in width and 40 nm thickness in a temperature range between 100 K and 400 K. The obtained Seebeck coefficient, thermal conductivity, electrical conductivity, and ZT are -57.2 muV/K, 4.11 W/m K, 1350 S/m, and 0.00032, respectively, at temperature 300 K