Microscope
JEOL JEM-2010F
Field Emission Gun
Compared to the standard tungsten and LaB6 filament guns, the field emission gun has several advantages. Namely, small probes (as small as <0.5nm diameter) can be formed for analysis of very small areas of a specimen. The energy spread in the beam is around 1eV or less and this leads to enhancement in the quality of electron energy loss spectra. The coherence of the beam pushes the information limit for high resolution images down to around 1 Angstrom. It also makes electron holography possible - useful for measuring the phase of the electron wave.
Gatan Imaging Filter
The microscope is equiped with a Gatan Imaging Filter (GIF). This device is attached under the camera chamber and gives the user the capability to carry out Electron Spectroscopic Imaging (ESI) and Electron Energy Loss Spectroscopy (EELS). The GIF incorporates sophisticated electron optics and an energy selecting 'slit' which allows the beam to be filtered to reveal additional information in the form of energy filtered images, diffraction patterns or spectra.
A TV rate CCD and a 'Slow Scan' CCD camera are used for image aquisition in real-time, with storage provided by a Macintosh computer.
X Ray Detector
An Oxford Instruments ultrathin window Energy Dispersive X-ray (EDX) detector is also attached to the microscope. The Oxford ISIS software package enables the user to carry out X-ray analysis to determine the elemental composition of the sample. Using a fine electron probe, elements with Z between Berylium and Uranium can be detected down to concentrations as low as 0.1%.
Also, as well as the quantitative and qualitative X-ray analysis already mentioned, using the 'ASID' we can generate X-ray maps (X-ray imaging) showing the way in which the elements are distributed within the specimen.
Piezo Stage
The traditional sample stage is moved by hand or by electric motors, and the smallest movement is rather coarse when seen at the highest magnifications. The piezo-stage employs piezo crystals that expand or contract by minute amounts on the application of a voltage. This enables the specimen to be moved by distances of the order of the interatomic spacing. The full range of the piezo movement is around one micron. We can thus compensate for drift of the specimen, an effect commonly seen especially in cooling or heating holders.
Bright field/Dark field Detector
We can scan the beam across an area of the specimen while recording the X-ray emissions and build up a map of the elements in the specimen. A detector placed below the camera allows us to record the bright field intensity (i.e. the intensity of the unscattered beam) or the dark field intensity (ie the intensity of a scattered beam) and simultaneously build up a corresponding image of the same area as an X-ray map.
Biprism
Holography is performed by overlapping a reference wave with the object wave. With visible light, one can achieve three-dimensional effects. In the electron microscope, holography allows the phase of the electron wave to be measured (not just the intensity as in normal electron microscopy) and this is useful, for example, for measuring magnetic and electric fields in the specimen. The required overlap is achieved by the biprism which deflects a portion of the beam that has passed through the specimen onto a portion of the beam that passed through a hole in the specimen.
Specimen Holders
Jeol
- Jeol Berylium double tilt (x2)
- Jeol Standard double tilt
- Jeol single tilt
Gatan
- Gatan Liquid nitrogen holder/controller (for any temperature within the range 20C to -190C)
Oxford Instruments
- Oxford Instruments Liquid helium holder (for temperatures down to <10K)
Vibration Isolation and Field Cancellation
The microscope is housed in a purpose-built room which is situated in the basement of the building. A large concrete block was cast directly onto bedrock and this was isolated from the rest of the room floor by a 5 mm air gap. The microscope sits directly on this vibration isolated concrete block. Acoustic isolation is enhanced by heavy, ceiling to floor curtaining on all 4 walls.
Advanced Scanning Imaging Device (ASID)
The JEM-2010F was designed to be used in STEM (Scanning Transmission Electron Microscopy) mode with the appropriate hardware. The ASID unit controls the beam parameters and probe sizes down to less than 0.2nm can be generated. Magnifications of 5 million times are easily attainable in this mode.
High Angle Annular Dark Field (HAADF) Detector
The insertion of a HAADF detector, in STEM mode, enables high quality Z contrast images to be aquired either direct to film (Polaroid or roll film) or in digital form, via Oxford ISIS, onto a PC.
Gatan Digiscan
Clean Vacuum System
The vacuum is dragged by a scroll pump backed turbo system for completely oil-free pumping