The scanning electron microscope, the most common type of electron microscope, is best suited for viewing the surface topography of an object. For experiments in which it is necessary to see the interior structure of an object, however, a transmission electron microscope is more appropriate. An HVEM is best suited for studying biological structures, but an IVEM is needed to get an accurate picture of the atomic structure of inert materials. Such experiments require a very thin sample of material. Some materials can be as thick as several microns, but for a dense material like gold, the sample can be no thicker than about 0.1 micron.
Many experiments require that the test material be irradiated with ions.
Typically, a separate piece of equipment does the irradiation and an IVEM is used to view the material. Observing the structure as the irradiation takes place has its benefits, however. The IVEM at Argonne is directly connected to an ion-beam accelerator and an ion implanter, which fire charged atoms of varying energies into material samples to show the microscopic changes produced by ion radiation. The microscope was booked solid for experiments before it was even installed late last year. A German research organization, for example, is implanting irradiated germanium atoms into silica to test the photoluminescence of the atomic matrix.