The Electron Microscopy Center

Just another College of Engineering site

Transmission Electron Microscopy (TEM/STEM)

High resolution HAADF STEM image of Pt particle on CeO2. Image recorded by Alan Dozier on our JEOL 2010F. Project funded via grants of Uschi Graham and Burt Davis

Description

Our TEM’s operate at 200KeV. Electrons are transmitted through the sample in either a spread out imaging mode or in a focused probe used for convergent beam diffraction (CBD) or scanning transmission electron microscopy (STEM). Usually spectroscopy, either EDS or EELS, is done in STEM mode, with the beam being under computer control. This allows for the profiling and mapping of elements or other properties.

Sample requirements

Generally a sample must be thinner than 2 microns to obtain any kind of image at all. One micron is preferred for most work. For high resolution STEM and EELS work .5 micron is near the optimum. There are a variety of preparation techniques to thin bulk samples. Standard methods can be used in many cases, but frequently for new materials some experimentation and optimization of prepration parameters is required to get the best sample and eliminate artifacts. The thickness requirments of particles, nanotubes, nanowires follow similar rules. Typically these samples can simply be placed on a carbon film or lacey carbon grid.

Technique Advantages

  • High magnification and resolution for both TEM and STEM
  • Compositional profiling and mapping
  • Structural analysis is possible using different combinations of techniques and computational analysis
  • Diffraction analysis from large scale down to less than 1nm

Limitations

The main limitation here is sample preparation. For EELS work this is critical, especially for near edge structure analysis. In EELS the sample should be 500 angstrom thick or less. 100nm can be tolerated for simple edge identification.

EMC TEM’s

JEOL 2000FX

  • LaB6 Filament
  • ASID Unit with SED
  • += 26 degree tilt range
  • single, double, and straining holders available
  • Equipped with Oxford Inca EDS system
  • Equipped with GATAN TV with digital image capture

This TEM is mostly used for training. This is where a new user will get their first experience on a TEM. This microscope is also frequently used for diffraction work and for checking samples.

JEOL 2010F

  • Field Emission Gun
  • Ultra High Resolution Pole Piece
  • +- 12 degree tilt
  • JEOL single, double low background, and GATAN cryo double tilt holders available
  • Fischione HAADF detector
  • Oxford EDS detector
  • EmiSpec EsVision
  • GATAN GIF 2000