In-situ Quasi-Instantaneous e-beam Driven Catalyst-Free Formation Of Crystalline Aluminum Borate Nanowires

Ignacio G Gonzalez-Martinez,Mark H Rümmeli,Jürgen Eckert,Gianaurelio Cuniberti,Thomas Gemming,Alicja Bachmatiuk,Jens Kunstmann,Viktor Bezugly,Rafael Mendes

doi:10.1038/srep22524

Abstract

The catalyst-assisted nucleation and growth mechanisms for many kinds of nanowires and nanotubes are pretty well understood. At times, though, 1D nanostructures form without a catalyst and the argued growth modes have inconsistencies. One such example is the catalyst-free growth of aluminium borate nanowires. Here we develop an in-situ catalyst-free room temperature growth route for aluminium nanowires using the electron beam in a transmission electron microscope. We provide strong experimental evidence that supports a formation process that can be viewed as a phase transition in which the generation of free-volume induced by the electron beam irradiation enhances the atomic mobility within the precursor material. The enhanced atomic mobility and specific features of the crystal structure of Al5BO9 drive the atomic rearrangement that results in the large scale formation of highly crystalline aluminium borate nanowires. The whole formation process can be completed within fractions of a second. Our developed growth mechanism might also be extended to describe the catalyst-free formation of other nanowires.

Highlights

The use of catalysts is avoided in almost all reports, a growth mechanism other than the vapor-liquid-solid (VLS) mechanism must be considered
We show strong experimental evidence that supports a universal formation process that can be viewed as a phase transition in which a sudden liberation of free-volume generated by an energy input results in the crystallization of nanowires within a precursor particle
This growth mechanism can be extended to describe the formation of other nanowires, for example, WO3 nanowires produced inside a TEM14 as well as other synthesis routes[8,9,10,11]

Summary

Introduction

The use of catalysts is avoided in almost all reports, a growth mechanism other than the vapor-liquid-solid (VLS) mechanism must be considered. The process continues until the precursor runs out of B2O3 and the persistent droplets evaporate Sometimes this logic is “reversed”, and the argument proposes a sea of liquid boron oxide in which small Al droplets are formed. We show strong experimental evidence that supports a universal formation process that can be viewed as a phase transition in which a sudden liberation of free-volume generated by an energy input (an electron beam in this case) results in the crystallization of nanowires within a precursor particle This growth mechanism can be extended to describe the formation of other nanowires, for example, WO3 nanowires produced inside a TEM14 as well as other synthesis routes[8,9,10,11]

Methods

Results

Discussion

Conclusion