Three-Dimensional Imaging of Microstructure in Au Nanocrystals

X-ray diffraction using a coherent beam involves the mutual interference among all the extremities of small crystals. The continuous diffraction pattern so produced can be phased because it can be oversampled. We have thus obtained three-dimensional images of the interiors of Au nanocrystals that show 50 nm wide bands of contrast with $\{111\}$ orientation that probably arise from internal twinning by dynamic recrystallization during their formation at high temperature.

Figure 1

Experimental geometry. As the sample is rocked, 2D slices are collected through the 3D CXD pattern.

Figure 2

Typical slices through the 3D CXD pattern of a Au crystal near the $(11\overline{1})$ reflection with spacing $2.8\times {10}^{-3}{\mathrm{n}\mathrm{m}}^{-1}$.

Figure 3

Top: The 2D slices through the best fit 3D reconstructed density separated as labeled. Bottom: (a) SEM image of a Au nanocrystal prepared as described in the text. (b) $z=0.00\mu \mathrm{m}$ slice from the second best fit showing good agreement between fits. (c) Coordinate system for the reconstructed crystal.