NUMERICAL CORRECTION OF LENS ABERRATIONS IN PHASE-RETRIEVAL HRTEM

Phase-retrieval methods in high-resolution transmission electron micro scopy allow one to determine the wave function at the exit-plane of th e object (the exit-plane wave function). Viable methods for the retrie val of the exit-plane wave function are off-axis electron holography a nd focal-series reconstruction. In the framework of these methods, att ention has been directed so far mostly at the correction of the wave f unction with respect to the ''main'' contributions to the aberration f unction, which are caused by the spherical aberration and by the defoc using of the objective lens. We describe a procedure which allows to m easure and correct routinely for all relevant residual aberrations whi ch may be present due to possible beam misalignment, 2-fold or 3-fold astigmatism. Using focal-series reconstruction it is demonstrated that a substantial gain in interpretable resolution can be observed in the retrieved wave function by taking into account these additional aberr ation effects.