Reinhard Weyl

Improvements in electron microscopy by application of superconductivity

Resolution tests on amorphous carbon foils were carried out in an electron microscope with a superconducting system containing 4 lenses including a shielding lens at 200 kV beam voltage. Due to the mechanical and electrical stability of the system and the absence of contamination of the specimen the highest space frequencies transferred at vertically incident beam were 6 nm-1 corresponding to a resolution of 0.17 nm, a value which approaches the theoretical resolving power of the electron optical system. It should also be feasible to apply such a lens system for microprobe analysis without strongly reducing the theoretical resolution limit, if the construction of the shielding lens is slightly changed.

Radiation damage due to knock-on processes on carbon foils cooled to liquid helium temperature

Radiation damage on a holey carbon foil was investigated in an electron microscope with a superconducting lens system, where the temperature of the specimen and its environment initially was 4 K. Due to an electron dose of 2 X 10(4) As/cm2 the diameter of a hole increased 5 nm. Rough calculations show that this increase can be ascribed to knock-on processes. Estimates of the rise in specimen temperature during the irradiation are given.

Superconducting lenses in electron microscopy

Abstract Various types of superconducting electron microscope lenses and lens-systems have been designed and tested in the last ten years. A resolution of 0.4 nm was achieved at several laboratories. Future potentialities for the application of superconducting lenses including microwave lenses, for example, in high voltage electron microscopy are discussed.

Reduction of Radiation Damage by Imaging with a Superconducting Lens System

Radiation damage is enemy number one for electron microscopical investigations of organic specimens at high resolution. Many different methods have been developed to obtain more information with a resolution better than 1 nm in spite of this handicap. In this paper we restrict ourselves to the application of low specimen-temperatures for fighting beam damage.