Resolving the stacking fault structure of silver nanoplates.

Abstract

The stacking fault structure (SFT) is the key to understanding the symmetry breaking of fcc nanocrystals and the origin of two-dimensional (2D) anisotropic growth of nanoplates. After resolving the SFT in Ag nanoplates under aberration-corrected transmission electron microscope (TEM) observations, it is found that there are three basic stacking faults, namely, twinned stacking fault (SF-t), a layer missed stacking fault (SF-m) and a layer inserted stacking fault (SF-i). The SFT is composed of one or a combination of two or all of the three kinds of stacking faults with a total number varying from 4 to 9. It has been demonstrated that the SFT could generate concave faces, step faces and (100) faces in the lateral directions, which provides sites for adding-atoms with a higher coordination number than on the top and bottom flat (111) faces, and results in the anisotropic growth along the 2D direction. Additionally, Ag nanoplates fall into either center symmetry or mirror symmetry when the corresponding number is even or odd. The center symmetry and mirror symmetry with different side face arrangements in turn manipulate the shape evolution to cubes and bipyramids, respectively. Our study provides a comprehensive understanding of the formation and growth of 2D metal nanomaterials.