Pulsed current-voltage electrodeposition of stoichiometric Bi2Te3 nanowires and their crystallographic characterization by transmission electron backscatter diffraction

Cristina V Manzano,Mikhail N Polyakov,Jon Maiz,Myriam H Aguirre,Xavier Maeder,Marisol Martín-González

doi:10.1080/14686996.2019.1671778

Abstract

ABSTRACT Bi2Te3 nanowires with diameters ranging from 25 to 270 nm, ultra-high aspect ratio, and uniform growth front were fabricated by electrodeposition, pulsing between zero current density during the off time and constant potential during the on time (pulsed-current-voltage method, p-IV). The use of zero current density during the off time is to ensure no electrodeposition is carried out and the system is totally relaxed. By this procedure, stoichiometric nanowires oriented perpendicular to the c-axis is obtained for the different diameters of porous alumina templates. In addition, the samples show a uniform growth front with ultra-high aspect ratio single crystal nanowires. The high degree of crystallinity was verified by transmission electron backscatter diffraction. This characterization revealed that the nanowires present both large single crystalline areas and areas with alternating twin configurations.

Highlights

Bismuth telluride is an attractive semiconductor whose principal application is as a thermoelectric material around room temperature
The nanowires are mainly single crystalline according to transmission electron microscopy (TEM) study, with a few inclusions of different nanocrystals
The high degree of crystallinity in these nanowires was verified by transmission electron backscatter diffraction (t-EBSD)

Summary

Introduction

Bismuth telluride is an attractive semiconductor whose principal application is as a thermoelectric material around room temperature. By changing the types of pulses and allowing the system to relax, we are influencing: a) the electrical double layer at the electrode-electrolyte interface, b) the mass transport, and c) the Bi2Te3 crystallization This process influences the crystallographic quality of the deposit and the properties of the semiconducting material obtained. Deposition conditions from the literature are listed, and the preferred wire axis orientations are reported [12,13,14,15], based on X-ray diffraction (XRD) and transmission electron microscopy (TEM) measurements In some of these studies, single crystal Bi2Te3 nanowires were reported. Bi2Te3 nanowires with different diameters (25, 60, 70, and 270 nm) were fabricated at 4°C by alternating periods of pulsed electrodeposition reduction potential and zero current density This method enables the fabrication of oriented Bi2Te3 nanowires with a high aspect ratio, uniform stoichiometry, and large single crystal areas. The nanowires are studied by XRD, TEM and t-EBSD measurements

Experimental details

Results and discussion

Conclusions