HREM image of a vacancy in copper

Abstract

The possibility of identification of vacancies in copper with high resolution electron microscopy is demonstrated. Dynamical calculations taking into account lattice relaxation and the size of an extended unit cell are performed for computing images, in which the effects of defocus, beam divergence, and chromatic aberration as well as spherical aberration are considered. The following results are obtained. (i) Under the optimum condition, the instrumental parameters such as a defocus, spherical aberration, chromatic aberration, and beam divergence make it possible to identify vacancies. (ii) The image of the vacancy is only weakly influenced by lattice relaxation. (iii) It is possible to determine the vacancy position with a small extended unit cell such as 2 × 2. (iv) The image of the vacancy largely depends on the specimen thickness.