Seeing is Not Always Believing: Reduction of Artefacts by an Improved Point Resolution With a Spherical Aberration Corrected 200 Kv Transmission Electron Microscope

Abstract The most interesting structures in materials science are non-periodic areas where the crystalline structure is disturbed such as interfaces, defects or dislocations. These non-periodic structures can be hidden by artefacts, caused by aberrations, and therefore they can be easier analysed if an aberration free imaging system can be used. Therefore, in order to improve the point resolution and to obtain easier access to the hidden information, a spherical aberration corrected 200 kV TEM, following a proposal by Rose, was set up. Phase contrast in a transmission electron microscope (TEM) is obtained, as it was shown by Scherzer, due to the phase shifting power of the wave aberrations as there are: the defocus and the spherical aberration. The defocus can be optimised in terms of the well transferred bandwidth of spatial frequencies (Scherzer defocus) Δfsch = (Cs*λ.)1/2. The upper limit of the spatial frequency without a contrast reversal when choosing a Scherzer defocus is called the point resolution d ≈ 0.71 (Cs λ3)1/4.