Probing planar defects in nanoparticle superlattices by 3D small-angle electron diffraction tomography and real space imaging.

Lennart Bergström,Dong Wang,Arnaud Mayence,Peter Oleynikov,German Salazar-Alvarez

doi:10.1039/c4nr04156a

Lennart Bergström, Dong Wang + Show 3 more

Open Access

https://doi.org/10.1039/c4nr04156a

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Journal: Nanoscale	Publication Date: Jan 1, 2014
Citations: 12	License type: cc-by

Affiliation: Stockholm University, Karolinska University Hospital

Abstract

We demonstrate how the acquisition and processing of 3D electron diffraction data can be extended to characterize structural features on the mesoscale, and show how lattice distortions in superlattices of self-assembled spherical Pd nanoparticles can be quantified by three-dimensional small-angle electron diffraction tomography (3D SA-EDT). Transmission electron microscopy real space imaging and 3D SA-EDT reveal a high density of stacking faults that was related to a competition between fcc and hcp arrangements during assembly. Information on the orientation of the stacking faults was used to make analogies between planar defects in the superlattices and Shockley partial dislocations in metallic systems.

Highlights

The structural diversity of single- and multiple-component nanoparticle superlattices[1,2,3,4,5,6] is rapidly expanding and the ability to tune the electronic, optical and magnetic properties by the composition, size, and shape of the nanoparticles and their packing arrangements is attracting great interest.[7,8,9,10,11] For instance, thin films of binary PbTe/Ag2 nanoparticle superlattices can show a high p-type conductivity,[12] whereas planar iron oxide (γ-Fe2O3) nanoparticle assemblies display a 2D to 3D crossover of the magnetic properties that depend on the layer thickness.[13]
We show that 31 Three-dimensional electron diffraction tomography (3D EDT), operating in the smallangle diffraction mode, can be used to study mesoscopic structures, e.g. 3D packing arrangements and lattice distortions in nanoparticle superlattices
We show that the Pd nanoparticle superlattices display a high density of stacking faults that is related to the competition between the two densest ways to pack spheres, namely face-centered cubic and hexagonal closed-packed arrangements, and discuss the similarities to metallic systems

Summary

Introduction

The structural diversity of single- and multiple-component nanoparticle superlattices[1,2,3,4,5,6] is rapidly expanding and the ability to tune the electronic, optical and magnetic properties by the composition, size, and shape of the nanoparticles and their packing arrangements is attracting great interest.[7,8,9,10,11] For instance, thin films of binary PbTe/Ag2 nanoparticle superlattices can show a high p-type conductivity,[12] whereas planar iron oxide (γ-Fe2O3) nanoparticle assemblies display a 2D to 3D crossover of the magnetic properties that depend on the layer thickness.[13]. We show that 3D EDT, operating in the smallangle diffraction mode, can be used to study mesoscopic structures, e.g. 3D packing arrangements and lattice distortions in nanoparticle superlattices.

Results

Conclusion