Cyclic twinning and internal defects of boron-rich nanowires revealed by three-dimensional electron diffraction mapping

Xin Fu,Jun Yuan

doi:10.1039/c3nr01839c

Abstract

Structural characterization of individual nanosized boron-rich nanowires has been carried out through analysing the three-dimensional (3D) electron diffraction intensity distribution. Not only can the cyclic twinning structure of these nanowires be easily determined, the new approach also reveals the heterogeneous strain relaxation within the intact nanowire, through the accurate determination of the orientation relationship between the constituent crystallites. The quantitative analysis of the fine structure in the 3D diffraction dataset indicates that this may be related to the distribution of defects such as stacking faults, microtwins and dislocations. It is envisaged that the non-destructive nature of this approach could open the way for the in situ study of the structural evolution of complex nanomaterials and polycrystalline materials in general.

Highlights

In recent years, both material growth energetics and kinetics have been explored to produce a wide range of nanomaterials with interesting structures and form factors, such as nanotetrapods,[1] icosahedral nanoparticles,[2] decahedral nanoparticles,[2,3] nanowires,[4,5,6,7,8] and nanostars,[9] to just name a few well-known examples
Real-space imaging through transmission electron microscopy is the conventional tool of choice to study the internal structure of materials, but it cannot be realized routinely with atomic resolution even using state-of-the-art aberration corrected microscopic techniques because of the large dimensions of the nanostructures involved in many cases
We will show that the retrieval of 3D diffraction intensity distribution allows us to identify the cyclic twinned structure directly, but the technique reveals quantitatively the orientation relationship of the internal crystallites and information about deformation and defects associated with the internal strain relaxation, all non-destructively

Summary

Introduction

Both material growth energetics and kinetics have been explored to produce a wide range of nanomaterials with interesting structures and form factors, such as nanotetrapods,[1] icosahedral nanoparticles,[2] decahedral nanoparticles,[2,3] nanowires,[4,5,6,7,8] and nanostars,[9] to just name a few well-known examples. The cyclic twinning nanostructure can have real or pseudo ve-fold symmetry that is not seen in the bulk materials, usually it is always due to the result of a balance between the surface energy minimization and the reduction of the strain energy associated with such polycrystalline structures.[21,22] The twinning structure may be a factor in uencing the mechanical properties of nanomaterials. Ve-fold cyclic twinned silver nanowires exhibit anomalous strength and brittle failure.[12] We will show that the retrieval of 3D diffraction intensity distribution allows us to identify the cyclic twinned structure directly, but the technique reveals quantitatively the orientation relationship of the internal crystallites and information about deformation and defects associated with the internal strain relaxation, all non-destructively

Methods

Results

Conclusion