Imaging and modeling of nanocrystalline Xe in Al containing defects

Morphological and crystallographic structures of a Xe nanocrystal embedded in Al were determined with off-Bragg high-resolution transmission electron microscopy (OB-HRTEM). The nanocrystals have a size in a range from 1 to 10 nm and precipitate with a FCC structure, mesotactically aligned with Al matrix. OB-HRTEM revealed Xe cuboctahedron crystals with faces parallel to eight Al {111} planes truncated by six {100} planes. Atomic resolution microscopy indicates that the nanocrystals often contain lattice defects, which consist of a stacking fault. Simulated images for a nanocrystal containing a stacking fault agreed well with experimental images. The process of a defect introduction into a nanocrystal was successfully recorded on videotape. A frame by frame analysis shows the introduction of a Shockely partial dislocation to form the fault. This introduction requires the motion of atoms in several layers in one side of the fault, to relax the strain caused by the change in stacking sequence.