Scanning Electron Microscopes

PHILIPS XL20 Scanning Electron Microscope

PHILIPS XL30 Field Emission Gun Scanning Electron Microscope

E3 Electroscan Environmental Scanning Electron Microscope

The scanning electron microscope (SEM) is used to image the surface of a sample. Like the transmission electron microscope (TEM), a SEM has an electron gun at the top of an electron optical column. The beam is focused into a small spot, which is scanned over the specimen in a raster pattern. The specimen is mounted in a vacuum chamber, which is very much larger than that in the TEM. Secondary (specimen) electrons are produced by the interaction of the beam with the sample; a positively biased detector collects these secondary electrons.

This signal is electronically converted into an image produced on a television screen, as the electron beam scans at the same scan rate of a cathode ray tube. The magnification is determined by the area of the sample scanned by the beam. The sample does not have to be thin like those for TEM, because the secondary electrons are emitted from the surface layer. Backscattered electrons, which are reflected (elastically scattered) electrons, whose contrast function is dependent on the mean atomic number of the surface atoms, produce images which give information about elemental distribution in the sample. Characteristic X-rays are also produced by the beam/specimen interaction, and these can produce elemental spectra and maps of the surface.

Adelaide Microscopy offers the use of three Scanning Electron Microscopes with varying and complimentary capabilities (click images for larger versions).

Specifications

Field Emission Scanning Electron Microscope (Philips XL30):

• Field emission electron source offers high-resolution special imaging.
• Low kV imaging for non-coated or insulating materials.
  
• Equipped with Oxford Cryo-transfer and fracture stage, allowing biological and plant samples to be prepared for the vacuum chamber whilst restoring their integrity.
  
• Solid state backscattered electron detector for mean atomic no. imaging
  
• X-ray analysis with thin film EDS detector allowing light element detection.
  
• Electron Backscattered Diffraction Pattern imaging with HKL EBSP camera and control.

Tungsten filament Scanning Electron Microscope (Philips XL20):

• Easy to use via PC control
• Tungsten filament providing high beam currents for x-ray analysis
• Solid state backscattered electron imaging.
• Energy dispersive X-ray analysis

ElectroScan E3 Environmental Scanning Electron Microscope:

• Energy dispersive X-ray analysis
• Capability of viewing wet or moist specimens in their natural states eg biological tissues, textiles, wet or oil-bearing geological samples, adhesives, foodstuffs etc. The environmental SEM can be used to observe some in situ processes, eg dissolution crystallization and dehydration.
• Capability of charge compensation imaging