Backscattered electron detection in environmental SEM.

An examination of the backscattered electron imaging status in environmental scanning electron microscopy is presented with particular attention to the testing and use of cerium doped yttrium aluminium garnet and yttrium aluminium perovskite scintillation detectors. A comparison is made with plastic scintillating backscattered electron detectors used previously (Nuclear Enterprises type NE102A scintillator). Semi-disk, strip and wedge shapes of these materials have been tested in conjunction with various light-guide geometries. These systems have been combined with two different types of photomultipliers, which also play a critical role in the total detector efficiency. The advantage of increased light output from the monocrystal materials is gained only if matched with suitable light-guides and photomultipliers. The associated problems are discussed and proposals for further work are made for the construction of most efficient backscattered electron detectors in the environmental scanning electron microscope.