Electron
Microscope Facility
In electron microscopy a beam of electrons are focused upon a sample. The interaction of the beam with the sample produces a number of measurable effects, most commonly:
- Secondary electrons - these produce an image of the surface morphology of a sample. This is perhaps the most common form of electron microscope image used in the media (as well as scientific journals of course !). As well as producing superior magnifications than conventional light microscopy the technique also offers a far greater depth of field (focusing range). image
- Backscatter electrons - these electron images identify materials of differing atomic density (atomic number contrast). image
- Cathodoluminescence - some materials produce light in the visible spectrum when exited by an electron beam. Differences in the trace element concentrations in these materials may then be imaged. image
- X-rays - these are also produced with interaction of an electron beam and a sample. By measuring the wavelength of the x-rays it is possible to determine qualitatively which elements are present. If a flat, polished sample is used the x-rays measured may be compared to standards to produce quatitative analysis.
Most conventional electron microscopes operate under vacuum and sample size is restricted to the size of the sample chamber and stage. Samples are normally coated (with a precious metal such as gold or with carbon) in order to produce an electrically conductive surface layer necessary for this work.
Instruments
JEOL JSM-5410LV Scanning Electron Microscope
The JEOL JSM-5410LV scanning electron microscope (SEM) allows high resolution photography of samples. Magnification ranges from 35 to 200,000. In addition, this instrument allows samples to be analysed in low vacuum without coating. Thus archaeological artefacts, semi-viscous liquids (molasses), type samples, crystals, waxes and more can be examined.The different photographic modes are
- Surface topology. - Microstructural characteristics of solid samples - morphology of insects,plants,marine specimens and biological crystals image
- Atomic Number Contrast mode - Differentiates between materials of different density - grains in sand - cartilage in animals - heavy metals in plants or tissue image
- Cathodoluminescence - certain impurities in minerals cause visible light to be emitted. Click here to find out more about cathodoluminescence .
JEOL JXA-8200 Superprobe
The JEOL JXA-8200 superprobe combines the features of high magnification, high resolution imaging with elemental analysis. It allows for the non-destructive analysis of very small amounts of solid materials. This is a state-of-the-art instrument. A full description may be found at the following link: JEOL SUPERPROBE
JEOL 840A Electron Microprobe 
The JEOL 840A electron microprobe (EMPA) is a high resolution SEM and a WD/ED Combined Electron Probe Microanalyzer (EPMA). It has 3 wavelength dispersive X-ray spectrometers (WDS) and an energy dispersive X-ray spectrometer (EDS). The analytical components are controlled by Moran Scientific hardware and software.
The applications for the electron microprobe include analysis of a wide range of sample types inclluding geological, biological, archaeological and metalurgical materials. Chemical analyses may be obtained to provide
- Qualitative elemental analysis of individual features (particularly for identification of small, accessory phases)
- Quantitative element analysis of individual features (requires a flat, polished sample)
- X-ray line profiles and maps, (provides qualitative digital images showing the elemental distribution and quantitative data).
| For all general enquiries contact - Dr Kevin Blake |
| Email: kevin.blake@jcu.edu.au |
| Phone: (07) 47 81 4864 |
| Fax: (07) 47 81 5550 |
