Glossary of Terms:

Scanning Electron Microscopy (SEM): An SEM operates like an optical microscope except that it uses an electron beam instead of light to image a sample. The electrons have energies of 1 - 30 keV and are focussed into a small spot (<10 nanometers) and then scanned over the sample. They penetrate into the surface region of the sample and knock out electrons that are then detected to form the image. Since the electron beam has a smaller wavelength than visible light an SEM can "see" smaller features in the sample (< 10 nanometers). Since electrons are scattered quickly in air the electron beam in an SEM and the sample must be in a vacuum. And since the electrons peneatrate into the sample it must be electrically conductive or a thin layer of C or Au must be deposited before imaging.

Scanning Transmission Electron Microscopy (STEM): A STEM exploits the very short wavelengths of accelerated electrons to resolve materials down to the nanometer range. Compared to an SEM the electrons are accelerated to higher energies (80-200 keV) in order that they penetrate through the sample. This means that bulk properties, including crystallinity, defects, and microstructure, can be investigated in thin samples. The beam can be rastered in a focussed spot as in the SEM or expanded in a large area parallel beam. High resolution compositional analysis of the sample is carried out via techniques including x-ray emission analysis, electron energy loss spectroscopy, high angle annular dark field, and energy filtered imaging. Images are viewed on a fluorescent screen or through a digital interface.

Lorentz Microscopy: A electromagnetic lens situated below the sample in a TEM such that the sample can be imaged without a magnetic field being applied.

EELS: Electron energy loss spectroscopy: The energy of the electron beam after passing through the sample is analysed by a magnetic field (Lorentz force) which curves the electrons through slits. EELS spectra are used to identify atomic compositions and bonding particularly in the case of low mass elements. The electrons of a certain energy range can be used to form an energy filtered TEM image (EFTEM).