Magellan Scanning Electron Microscope (SEM) Laboratory
The instrument is an FEI Magellan 400 XHR Scanning Electron Microscope located in the basement of Spilker, room 008 A.
Principles of operation:
In a scanning electron microscope (SEM), a fine beam of electrons is scanned across the surface of a specimen in synchronism with a spot on the display screen. A detector monitors the intensity of a chosen secondary signal from the specimen (for example, secondary electrons) and the brightness of the display spots controlled by an amplified version of the detected signal. If, for any reason, the intensity of the emitted secondary signal changes across the specimen then contrast will be seen in the image on the display screen. The resulting image is strikingly similar to what would be seen through an optical microscope; the illumination and shadowing show a natural-seeming topography.
It is important to remember that the image formed in an SEM is not necessarily that of the surface. As the electron beam penetrates the sample, the interaction causes excitation of secondary, backscatter, and Auger electrons; characteristic and Bremsstrahlung x-rays; and photons. It is possible, by choosing the electron energy, to control the depth to which the electrons penetrate and the type of emitted signal used to form the image. While this gives the microscopist a great deal of control over the nature of the final image, an understanding of how the image is formed is required to interpret it sensibly.
Electron beam resolution:
|At optimum working distance (SE mode)|
|15 kV||0.8 nm|
|2 kV||0.8 nm|
|1 kV||0.9 nm|
|200 V||1.5 nm|
Restrictions on samples:
The sample material must be able to withstand a high vacuum environment without outgassing. It must be clean. It may be attached to the sample holder using a suitable SEM vacuum-quality adhesive (please check with us first). Insulating samples will be more difficult to analyze, although we do have several strategies to work with them. Please check with us as to what may work best with your sample.
Training and Service:
Before being considered for training on the FEI Magellan SEM, you must first be a fully qualified user of the FEI Sirion SEM or the FEI DB235 Dual-Beam FIB/SEM. Further information is on the training info page.
Service requests will be considered on a case-by basis. However, our normal mode of operation is to train users to perform the characterization experiments themselves.