Low-energy electron and ion projection microscopy

Interactions of sulfur with nickel surfaces: Adsorption, diffusion and desorption

The low energy electron point source microscope (kendroscope) is used to acquire in-line holograms of rodlike macromolecules of phthalocyaninato polysiloxane (PcPS). The molecules were placed on a new class of substrates, thin microstructured silicon membranes that have slits about 100 nm wide which can be “bridged” by the molecular chains. The resulting in-line holograms of PcPS were recorded digitally and reconstructed numerically via a Kirchoff–Helmholtz transform. The mechanisms of image formation and uncertainties relating to the interpretation of the holograms are discussed.

Holographic imaging of macromolecules

Low energy electron point source (LEEPS) microscopy has the capability to record in-line holograms at very high magnifications with a fairly simple set-up. After the holograms are numerically reconstructed, structural features with the size of about 2 nm can be resolved. The achievement of an even higher resolution has been predicted. However, a number of obstacles are known to impede the realization of this goal, for example the presence of electric fields around the imaged object, electrostatic charging or radiation induced processes. This topical review gives an overview of the achievements as well as the difficulties in the efforts to shift the resolution limit of LEEPS microscopy towards the atomic level. A special emphasis is laid on the high sensitivity of low energy electrons to electrical fields, which limits the structural determination of the imaged objects. On the other hand, the investigation of the electrical field around objects of known structure is very useful for other tasks and LEEPS microscopy can be extended beyond the task of imaging. The determination of the electrical resistance of individual nanowires can be achieved by a proper analysis of the corresponding LEEPS micrographs. This conductivity imaging may be a very useful application for LEEPS microscopes.

http://iopscience.iop.org/article/10.1088/0953-8984/22/34/343001/pdf

Low energy electron point source microscopy: beyond imaging.

This paper shows that by using nanotips as nanosources of electrons, Fresnel diffraction by nano‐objects is observed in a low‐energy‐electron projection microscope without any magnetic field shielding. The results shown are consistent with the Aharonov‐Bohm effect and Lorentz force deviation due to the magnetic stray fields.

Low‐energy‐electron diffraction by nano‐objects in projection microscopy without magnetic shielding

An electron field emitter is used as an approximate point source of electrons to produce magnified shadows, or profile images, of small electrically conducting objects in ultrahigh vacuum. Some electrical and electron optical properties of this type of microscopy are described.

Allan J. Melmed

Papers

Field emission shadow microscopy