Electron Holography with aCs-Corrected Transmission Electron Microscope

Abstract

C_scorrectors have revolutionized transmission electron microscopy (TEM) in that they substantially improve point resolution and information limit. The object information is found sharply localized within 0.1 nm, and the intensity image can therefore be interpreted reliably on an atomic scale. However, for a conventional intensity image, the object exit wave can still not be detected completely in that the phase, and hence indispensable object information is missing. Therefore, for example, atomic electric-field distributions or magnetic domain structures cannot be accessed. Off-axis electron holography offers unique possibilities to recover completely the aberration-corrected object wave with uncorrected microscopes and hence we would not need aC_s-corrected microscope for improved lateral resolution. However, the performance of holography is affected by aberrations of the recording TEM in that the signal/noise properties (“phase detection limit”) of the reconstructed wave are degraded. Therefore, we have realized off-axis electron holography with aC_s-corrected TEM. The phase detection limit improves by a factor of four. A further advantage is the possibility of fine-tuning the residual aberrations bya posterioricorrection. Therefore, a combination of both methods, that is,C_scorrection and off-axis electron holography, opens new perspectives for complete TEM analysis on an atomic scale.