FOCAL-SERIES RECONSTRUCTION IN HRTEM - SIMULATION STUDIES ON NONPERIODIC OBJECTS

The reliability of focal-series reconstruction algorithms for the retr ieval of the wavefunction at the exit plane of the object (exit-plane wavefunction) is investigated for the case of non-periodic object feat ures. Simulated high-resolution electron microscope images of an abrup t GaAs/AlAs interface and of an edge dislocation in GaAs are chosen as test cases. The reconstruction schemes employed for the retrieval of the exit-plane wavefunction are the so-called ''paraboloid method'' (P AM) and the ''maximum likelihood'' method (MAL) which have been develo ped to application stage within the framework of the BRITE-EURAM proje ct No. 3322. Special attention is given to the convergence behavior of the algorithms in the presence of noise and under highly non-linear i maging conditions.