Tilt-structure and high-performance of hierarchical Bi1.5Sb0.5Te3 nanopillar arrays

Ming Tan,Dali Yan,Yanming Hao,Zehua Wu,Yuan Deng

doi:10.1038/s41598-018-24872-4

Ming Tan, Dali Yan + Show 3 more

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https://doi.org/10.1038/s41598-018-24872-4

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Abstract

The uniquely tilted nanopillar array favorably influence carrier and phonon transport properties. We present an innovative interfacial design concept and a novel tilt-structure of hierarchical Bi1.5Sb0.5Te3 nanopillar array comprising unique interfaces from nano-scaled open gaps to coherent grain boundaries, and tilted nanopillars assembled by high-quality nanowires with well oriented growth, utilizing a simple vacuum thermal evaporation technique. The unusual structure Bi1.5Sb0.5Te3 nanopillar array with a tilt angle of 45° exhibits a high thermoelectric performance ZT = 1.61 at room temperature. The relatively high ZT value in contrast to that of previously reported Bi1.5Sb0.5Te3 materials and the Bi1.5Sb0.5Te3 nanopillar array with a tilt angle of 60° or 90° evidently reveals the crucial role of the unique interface and tilt-structure in favorably influencing carrier and phonon transport properties, resulting in a significantly improved ZT value. This method opens a new approach to optimize nano-structure film materials.

Highlights

Thermoelectric (TE) materials can directly interconvert thermal energy and electrical energy by on the basis of Seebeck effect and Peltier effect
Stranz and Sun reported that a wafer-scale vertical nanopillar arrays or nanowire arrays can be realized by lithography and anisotropic etching for improving the performance of TE cross-plane devices as proposed recently[17,18]
The SEM images (Fig. 1a,b) reveal that the hierarchical Bi1.5Sb0.5Te3 nanopillar array with a tilt angle of 45° has been perfectly prepared by a simple thermal evaporation technique, which indicates a tilted growth when the tilt angle of the substrate plane to the horizontal plane is 45°

Summary

Introduction

Thermoelectric (TE) materials can directly interconvert thermal energy and electrical energy by on the basis of Seebeck effect and Peltier effect. Bi2Te3 and its alloy are the best TE materials near room temperature, which are anisotropic with a layered structure Their thermal and electrical conductivities along the a-axis (in the c-plane) are approximately two and four times higher, respectively, than those along the c-axis of Bi2Te3-based materials. Some vertically aligned nanowire arrays or nanopillar arrays have been synthesized by the electrochemical deposition with templates or the anisotropic etching and lithography method, this kind of hierarchical nanopillar arrays with tilt-structure have never been reported, let alone the tilted Bi1.5Sb0.5Te3 material. This motivates us to further explore the effect of tilt-structure on the hierarchical Bi1.5Sb0.5Te3 nanopillar arrays. It provides a new avenue to control the structural configuration of materials with possible relevance to improvement of their properties

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