Towards sub-0.5 إ electron beams

In the 4 years since the previous meeting in the SALSA series, aberration correction has progressed from a promising concept to a powerful research tool. We summarize the factors that have enabled 100–120 kV scanning transmission electron microscopes to achieve sub-Å resolution, and to increase the current available in an atom-sized probe by a factor of 10 and more. s is corrected, fifth-order spherical aberration (C5) and chromatic aberration (Cc) pose new limits on resolution. We describe a quadrupole/octupole corrector of a new design, which will correct all fifth-order aberrations while introducing less than 0.2 mm of additional Cc. Coupled to an optimized STEM column, the new corrector promises to lead to routine sub-Å electron probes at 100 kV, and to sub-0.5 Å probes at higher operating voltages.