Spherical-aberration correction in tandem with the restoration of the exit-plane wavefunction: synergetic tools for the imaging of lattice imperfections in crystalline solids at atomic resolution
by Karsten Tillmann, Lothar Houben, Andreas Thust, and Knut Urban
With the availability of resolution-boosting and delocalization-minimizing techniques, aberration-corrected high-resolution transmission electron microscopy is currently enjoying great popularity with respect to the atomic scale imaging of lattice imperfections in crystalline solidstate materials. In the present review, the most striking practical benefits arising from the synergetic combination of two sophisticated state-of-the-art techniques, i.e. spherical- aberration-corrected imaging as well as the numerical restoration of the exit-plane wavefunction from a focal series of high-resolution micrographs, are illustrated by highlighting their combined use for the atomic-scale characterization of misfit dislocations, stacking faults and grain boundaries in common semiconductor materials and metastable metal phases.
For these purposes recent progress is reviewed in the atomic-scale characterization of (i) Lomer-type misfit dislocations at InxGa1-xAs/GaAs heterointerfaces and extrinsic stacking fault ribbons in GaAs together with the associated lattice displacements, (ii) the core structure of chromium implantation-induced Frank partial dislocations in GaN as well as (iii) tilt boundaries between b-phase Ta crystallites in thin metallization layers. In addition, practical advantages are demonstrated of the retrieval of he exit-plane wavefunction not only for the measurement and subsequent elimination of residual lens aberrations still present in aberration-corrected microscopy, but also for the proper alignment of specimens during operation of the electron microscope.
Further reading: Journal of Materials Science 41 (2006) 4420-4433