HRTEM analysis of solid precipitates in Xe-implanted aluminum

摘要

High-resolution TEM was carried out to determine shape and atomic arrangement of solid Xe precipitates in Al. Polycrystalline Al TEM specimens were implanted with 30 keV Xe(sup +) at RT to a dose of 3x10(sup 20) ions/m(sup 2) and then annealed at 523 K. Below a size 4 nm dia, the Xe precipitates are solid with an fcc crystal structure mesotacticly aligned with the Al lattice. In HRTEM along (011) projection, the difference in the lattice parameters of solid Xe and Al produces a precipitate image dominated by a 2-D Moire pattern that repeats in both the <001> and <111> directions every 3 Al (or 2 Xe) lattice spacings. Multi-slice image simulations, using a 3-D atomic model, demonstrates that the precipitates are tetradecahedra with faces parallel to the dense (l brace)111(r brace) planes and the (l brace)100(r brace) planes. Off-Bragg illumination of the precipitates minimizes Al lattice fringes and generates precipitate images which are in good agreement with the model.