Perfect quintuple layer Bi2Te3 nanowires: Growth and thermoelectric properties

P Schönherr,D Kojda,S F Fischer,V Srot,T Hesjedal,P A Van Aken

doi:10.1063/1.4986524

Abstract

Bi2Te3 nanowires are promising candidates for thermoelectric applications. Vapor-liquid-solid growth of these nanowires is straightforward, but the traditional Au-catalyzed method is expected to lead to Au contamination and subsequently crystal defects. Here, we present a comparison of the Au-catalyzed growth method with an alternative method using TiO2. We observe that the latter approach results in perfect quintuple layer nanowires, whilst using Au leads to mixed quintuple and septuple layer structures. Despite these differences, we surprisingly find only a negligible effect on their thermoelectric properties, namely conductivity and Seebeck coefficient. This result is relevant for the further optimization and engineering of thermoelectric nanomaterials for device applications.

Highlights

The efficiency of thermoelectric (TE) materials is quantified by the figure of merit ZT = S2σT /κ, a function of the temperature T, the Seebeck coefficient S, the electrical conductivity σ, and the thermal conductivity κ
The high ZT of Bi2Te3 is supported by poor thermal conductivity due to heavy atoms and good electrical conductivity due to the topological surface states
The Au-catalyzed sample was grown at a gas flow of 150 SCCM and the TiO2-catalyzed sample was grown at 300 SCCM

Summary

Introduction

Perfect quintuple layer Bi2Te3 nanowires: Growth and thermoelectric properties TiO2-catalyzed sample which is shown in Fig. 1(a) is characterized by broad, ribbon-like nanowires. We found previously that small Au-catalyzed Bi2(Se,Te)[3] nanowires grow by the vapor-liquidsolid mechanism.[13] The functioning of the TiO2 catalyst particle remains rather elusive beyond the initial nucleation stage.[7] The findings above suggest identical growth mechanisms for thin nanowires given the identical distribution at low diameters.

Results

Conclusion