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Specimen PreparationThere are preparation facilities for both transmission and scanning electron microscope specimens on both sides of campus. The picture below shows the preparation laboratory located in SES (Science and Engineering South). ![[picture of preparation laboratory]](EMS-EPrep.320x240.jpg)
There are many ways of preparing specimens for electron microscopy. The EMS staff are available to help investigators determine the best way of getting the information they need from their specimens. The following is intended only as a general guideline. The size of the SEM specimen depends on which instrument you need for your analysis. The Hitachi S-3000N is able to accept specimens up to 150mm in diameter (although parts of the specimen cannot be accessed). The JEOL JSM-6320F can accept specimens up to 30mm in diameter and 10mm high. The JEOL JXA-733 can accept specimens up to 100mm in diameter and 20mm high. In general, however, the amount of material should be kept as small as possible, especially if it is non-conducting. Conducting specimens can be imaged in all three SEMs without any further specimen preparation. Non-conducting specimens may need coating with a conducting film in order to reduce charging at high vacuum in all microscopes. The EMS is able to coat with either carbon, platinum/gold, platinum/palladium or, for high resolution imaging, chromium. In low vacuum mode (S-3000N only) it is not necessary to coat any specimen and some non-conducting specimens can be imaged without charging at low voltage (S-3000N, JSM-6320F). For X-ray microprobe analysis (JEOL JXA-733) specimens should be polished flat for better accuracy. All EMS TEMs take standard size specimens (3mm in diameter). The maximum thickness of the specimen depends on the density of the material, the accelerating voltage of the microscope and the resolution of the analysis to be carried out. The EMS has extensive specimen preparation facilities to convert bulk material into transmission thin samples of the correct diameter. Specimens can be either self supporting (i.e. the whole specimen consists of one material) or supported on a grid or a slotted 3mm washer. Biological specimens are typically prepared using an ultra-microtome to cut slices less than 100nm thick which can then be supported on a grid. Self supporting Material Science specimens typically are polished down to 100-200 micrometer, a 3mm disc is cut from the material, then the central region is pre-thinned to a few micrometers before final thinning, to perforation, is carried out by Ion Beam Thinning, Electropolishing or Chemical Thinning. Another approach is to slice and mount on a grid before polishing down and then final thinning to perforation. Brittle materials specimens can often be crushed, dispersed in alcohol and a drop of liquid placed onto a grid supporting an amorphous carbon film. The EMS has the following equipment available in the MSB laboratory:
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