Aberration Corrected Lattice Imaging With Sub Ångstrom Resolution

Abstract In 1999 NCEM's One Ångstrom Microscope (OAM) became fully operational. The OAM is a Philips CM300 FEG/UT field emission microscope with holographic capabilities that is equipped with a Gatan Image Filter (GIF) and operates at 300 kV. It was designed to reach a resolution close to the “magic barrier” around one Ångstrom (100 pm) by combining mid voltage technology with advanced computer processing [1,2]. Ahardware correction of the three-fold astigmatism allows for aberration free imaging down to sub Ångstrom values [3]. In this contribution it will be shown that the instrument's performance exceeded expectations because sub Ångstrom resolution can be achieved by reconstructing electron exit waves from focal series [4]. Figure la depicts a simulated [110] lattice image of a 90° partial dislocation in silicon. Tersoff potentials were used to calculate the exact atomic positions around dislocations with different core structures [5].