Three-dimensional imaging of dislocations in a nanoparticle at atomic resolution

Abstract

Dislocations and their interactions strongly influence many material properties, ranging from the strength of metals and alloys to the efficiency of light-emitting diodes and laser diodes. Several experimental methods can be used to visualize dislocations. Transmission electron microscopy (TEM) has long been used to image dislocations in materials, and high-resolution electron microscopy can reveal dislocation core structures in high detail, particularly in annular dark-field mode. A TEM image, however, represents a two-dimensional projection of a three-dimensional (3D) object (although stereo TEM provides limited information about 3D dislocations). X-ray topography can image dislocations in three dimensions, but with reduced resolution. Using weak-beam dark-field TEM and scanning TEM, electron tomography has been used to image 3D dislocations at a resolution of about five nanometres (refs 15, 16). Atom probe tomography can offer higher-resolution 3D characterization of dislocations, but requires needle-shaped samples and can detect only about 60 per cent of the atoms in a sample. Here we report 3D imaging of dislocations in materials at atomic resolution by electron tomography. By applying 3D Fourier filtering together with equal-slope tomographic reconstruction, we observe nearly all the atoms in a multiply twinned platinum nanoparticle. We observed atomic steps at 3D twin boundaries and imaged the 3D core structure of edge and screw dislocations at atomic resolution. These dislocations and the atomic steps at the twin boundaries, which appear to be stress-relief mechanisms, are not visible in conventional two-dimensional projections. The ability to image 3D disordered structures such as dislocations at atomic resolution is expected to find applications in materials science, nanoscience, solid-state physics and chemistry.

Polymorphism of dislocation core structures at the atomic scale

“…Although high-resolution atomic force microscopy enables individual dislocations to be identified at the surfaces, it falls short of providing atomic resolution of their cores 9 , impeding a ready inference of their core properties. In contrast, advanced transmission electron microscopy (TEM) is in principle able to directly resolve individual embedded dislocation cores with single-atom sensitivity [10][11][12][13] , particularly in the annular darkfield mode 10,11 . This leads to a far greater understanding on the correlation between the dislocation cores in real materials and their mechanical, optical, and electronic behaviours 12,14 .…”

Formation of bimetallic clusters in superfluid helium nanodroplets analysed by atomic resolution electron tomography

“…For polycrystalline or amorphous materials, such approaches are not applicable and a full tomographic tilt series needs to be carried out. Near-atomic resolution of single-metallic polycrystalline particles has been first demonstrated on gold nanoparticles 15 , and more recently Chen et al 16 have mapped 3D dislocations in platinum nanoparticles at atomic resolution using very strong filtering in the Fourier domain. This approach has been used to some success, but has also led to some controversy 17 and, moreover, is not necessary when careful considerations in the reconstruction are applied to low-noise experimental data.…”

Rational synthesis and the structure-property relationships of nanoheterostructures: a combinative study of experiments and theory

“…33 In this study, the Pt atomic columns were clearly observed and the Fe Kagomé layer (3/4 monolayer) and the 1/4 monolayer were also 34 Recently, a resolution of 2.4 Å was obtained for Au single crystalline NP 35 and Pt nanodecahedra 36 with twin boundaries. Some advanced algorithms, such as the Compressive Sensing algorithm, were utilized to achieve better resolution for Au nanorods (NRs).…”