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1. IntroductionSeveral methods of phase retrieval from HRTEM image intensity distributions have been proposed but no standard method has emerged. We report on the results achieved using a technique based on a development of the “focus variation method”. The dependence of the retrieved wavefunction on various experimental parameters is investigated and the method tested using computer simulated images. The method is shown to be useful in finding the complex wavefield at the exit surface of the specimen, but the relationship of this to the specimen structure is left as a seperate problem.

SummaryA methodology for obtaining high-resolution crystal structure potential distributions from electron microscope images of defects is examined using image simulation methods. The technique is based on the inversion of the multislice procedure when extended to nonperiodic potentials. The sensitivity of the method to the defect model and position in the crystal is examined briefly with the preliminary conclusion that this should not severely limit the applicability of the method. The major impediment for the successful experimental application of the method to the detection and structure determination of single, isolated self-interstitial defects in silicon is likely to be the preparation and fixation of the surfaces of the specimen.