electron microscopy



Scheme of a Transmission Electron Microscope


Electron gun: The electrons are generated and accelerated to the required high energy.

Condenser system: A set-up of different magnetic lenses and apertures makes it possible to get either a parallel beam (micro probe for TEM) or a convergent beam with selected convergence angles (nano probe for STEM and CBED). Furthermore, the beam can be scanned (STEM) or tilted (DF-TEM).

Objective lens: Most important lens in the microscope since it generates the first intermediate image, the quality of which determines the resolution of the final image.

Diffraction/intermediate lens: Switching between imaging and diffraction mode.

Projective lenses: Further magnification of second intermediate image (image or diffraction pattern, respectively).

Image observation: Images and diffraction pattern can directly be observed on the viewing screen in the projection chamber or via a TV camera mounted below the microscope column. Images can be recorded on negative films, on slow-scan CCD cameras or on imaging plates.

Vacuum system: Because of strong interactions of electron with matter, gas particles must be absent in the column. The required high vacuum is maintained by a vacuum system typically comprising a rotary pump (pre-vacuum pump), a diffusion pump and one or more ion getter pumps.



Schematic representation of a CM30 TEM (FEI) showing the position of the lenses and apertures.
ETH Zürich | ETH chemistry department | ETH inorganic chemistry | Nesper group | EMEZ

modified: 14 May, 2012 by F. Krumeich | © ETH Zürich and the authors