1. Transmission and Reflection Holography at Low Energies
- Author
-
Bernhard G. Frost and David C. Joy
- Subjects
Physics ,Diffraction ,Microscope ,Reflection high-energy electron diffraction ,business.industry ,Holography ,Bioengineering ,Surfaces and Interfaces ,Condensed Matter Physics ,Surfaces, Coatings and Films ,law.invention ,Low-energy electron microscopy ,Optics ,Mechanics of Materials ,law ,Scanning transmission electron microscopy ,Reflection (physics) ,business ,Field ion microscope ,Biotechnology - Abstract
We have designed a low voltage point source microscope operated with a nanotip field emitter and without any electron optical lenses such that it can be operated in the transmission mode as well as in a reflection mode. An electron gun needed in the reflection mode is the most important difference between the two modes of operation. The magnification of the object wave is achieved by placing the specimen in the divergent electron beam of a nanotip field emitter and observing the object wave using a micro channel plate (MCP) at a great distance from the sample. As no lenses are present a procedure for scaling the magnification has been developed. Since electrons from a point source are highly coherent the out of focus images of the sample are interferograms and contain true three dimensional information of the sample. The transmission mode gives us the following results: (1) Electrons diffracted at an edge of the specimen cause Fresnel fringes in the image plane. (2) An electrically charged holey carbon foil can act in the same way on the electrons as the Young's double slit experiment and results in an interference pattern consisting of parallel fringes. The reflection mode shows us: (1) The image depends on the angle of reflection. (2) An arrangement similar to a field ion microscope resolves single atoms of the specimen. [DOI: 10.1380/ejssnt.2004.81]
- Published
- 2004