Aberration corrected TEM: current status and future prospects

Aberration correction leads to a substantial improvement in the interpretable resolution of Transmission Electron Microscopes. Electron optical correctors based on two strong hexapole elements linked through a round lens transfer doublet enables direct correction of all axial aberrations to third order. Subsequent, indirect computational analysis of a focal or tilt series of images offers the possibility of further compensation of the axial aberrations to fifth order. This paper describes 1st and 2nd generation aberration corrected instrumentation installed in Oxford and also the use of combinations of direct and indirect correction / compensation in a variety of different geometries to achieve specimen exit plane wavefunctions containing directly interpretable structural information significantly below 0.1 nm.