A double detector system for BSE and SE imaging

The double detector system described here is a simple device suitable for any SEM. It permits efficient imaging of specimen surfaces in either the secondary electron (SE) or backscattered electron (BSE) mode. The BSE detector is an annular single‐crystal scintillator made of yttrium aluminium garnet (YAG) and the SE detector has a scintillator of the same material. Both detectors have their own light guides which are connected to a single photomultiplier. The choice of signal is made with a mechanical diaphragm mounted on a flange between the light guide and the photomultiplier. The SE detector may be replaced by a second BSE detector to allow the detection of “low” take‐off angle BSEs to provide information which differs from that given by the annular BSE detector which operates to detect BSEs with a “high” take‐off angle. In this way it is possible to image either material or topographic contrast with high resolution and to take advantage of the choice of detected electrons.