Non-destructive detection of cross-sectional strain and defect structure in an individual Ag five-fold twinned nanowire by 3D electron diffraction mapping

Xin Fu,Jun Yuan

doi:10.1038/s41598-017-06485-5

Abstract

Coherent x-ray diffraction investigations on Ag five-fold twinned nanowires (FTNWs) have drawn controversial conclusions concerning whether the intrinsic 7.35° angular gap could be compensated homogeneously through phase transformation or inhomogeneously by forming disclination strain field. In those studies, the x-ray techniques only provided an ensemble average of the structural information from all the Ag nanowires. Here, using three-dimensional (3D) electron diffraction mapping approach, we non-destructively explore the cross-sectional strain and the related strain-relief defect structures of an individual Ag FTNW with diameter about 30 nm. The quantitative analysis of the fine structure of intensity distribution combining with kinematic electron diffraction simulation confirms that for such a Ag FTNW, the intrinsic 7.35° angular deficiency results in an inhomogeneous strain field within each single crystalline segment consistent with the disclination model of stress-relief. Moreover, the five crystalline segments are found to be strained differently. Modeling analysis in combination with system energy calculation further indicates that the elastic strain energy within some crystalline segments, could be partially relieved by the creation of stacking fault layers near the twin boundaries. Our study demonstrates that 3D electron diffraction mapping is a powerful tool for the cross-sectional strain analysis of complex 1D nanostructures.

Highlights

Strain and defects, usually coexisting in nanostructures, are known as very important structural factors influencing the mechanical1–4, electronic and photonic5–7 properties of one-dimensional (1D) nanostructures employed as building blocks for nanoscale devices
Sun et al claimed to have found a novel body-centered tetragonal phase in the core of Ag FTNWs46, and it has recently been challenged through quantitative investigation of coherent x-ray diffraction combined with atomistic simulation that suggested the presence of star-disclination strain field instead29
Through the quantitative analysis of the diffracted beam intensity distribution about specific reflection reconstructed by 3D electron diffraction mapping, we confirm that the cross-sectional strain distribution in an individual Ag fold twinned nanowires (FTNWs) is inhomogeneous in accordance with the disclination model9, but the five single crystallites in such Ag nanowire could be differently strained

Summary

Introduction

Usually coexisting in nanostructures, are known as very important structural factors influencing the mechanical, electronic and photonic properties of one-dimensional (1D) nanostructures employed as building blocks for nanoscale devices. Through the quantitative analysis of the diffracted beam intensity distribution about specific reflection reconstructed by 3D electron diffraction mapping, we confirm that the cross-sectional strain distribution in an individual Ag FTNW is inhomogeneous in accordance with the disclination model, but the five single crystallites in such Ag nanowire could be differently strained. Such difference is attributed to internal strain energy relaxation by introducing variable defect microstructures. Our study case demonstrates that 3D electron diffraction mapping is applicable to the non-destructive determination of the transverse strain distribution and defective microstructure in complex 1D nanostructures

Methods

Results

Conclusion