Prerequisites for a Cc/Cs-corrected ultrahigh-resolution TEM.

After the introduction of a corrector to compensate for the spherical aberration of a TEM and the acceptance of this new instrumentation for high-resolution CTEM (conventional transmission electron microscope) and STEM (scanning transmission electron microscope) by the electron microscopy community, a demand for even higher resolution far below 1A has emerged. As a consequence several projects around the world have been launched to make these new instruments available and to further push the resolution limits down toward fractions of 1A. For this purpose the so-called TEAM (transmission electron aberration-corrected microscope) has been initiated and is currently under development. With the present paper we give a detailed assessment of the stability required for the base instrument and the electric stability, the manufacturing precision, and feasible semi-automatic alignment procedures for a novel C(c)/C(s)-corrector in order to achieve aberration-free imaging with an information limit of 0.5A at an acceleration voltage of 200 kV according to the goals for the first TEAM instrument. This new aberration corrector, a so-called Achroplanat, in combination with a very stable high-resolution TEM leads to an imaging device with unprecedented resolving power and imaging properties.