Planotech scintillator discs are made of carefully selected P47 phosphor and coated very uniformly and recommended for routine use. They have a high signal output and good working life. They should not normally be coated with aluminum, unless cathodoluminescence studies are envisaged. An aluminum coating reduces the efficiency by some 20%. Discs are available for all principal types of microscope. Please refer to the ordering table below. Special sizes are available upon request.
YAG (Yttrium Aluminum Garnet) single crystal scintillators are chosen by many scanning electron microscopists because they have a very fast response time of 50 - 60ns and (unlike plastic or most phosphor scintillators) they do not degrade when bombarded by electrons or ions. They are therefore particularly suited for high current operations. Light emission peaks at about 560nm which means that S20 photo cathodes are most suitable for detecting the emission. The response is better than for the Plano P47 discs below 5kV and again at higher accelerating voltages, where the performance of powder scintillators falls off while the response of the YAG continues to increase linearly. The crystal should be coated with 50 nm of aluminum before use. If the layer becomes damaged, it can be removed with sodium hydroxide without damage to the crystal. The crystals are mounted with the matt surface in contact with the light pipe as this has been shown to increase the efficiency. Uncoated YAG scintillators may be baked at temperatures up to 1000° C. Sizes are listed in the ordering table.
YAP (Yttrium Aluminum Provskite) crystals are more efficient in terms of light output than YAG crystals (see graphs). Also, the emission spectrum peaks at about 378nm, and this corresponds fairly closely with the maximum sensitivity of the S11 photo cathode which is in general use in most electron microscopes. In such microscopes there would, therefore, be a significant improvement in signal by using a YAP crystal rather than a YAG. The decay time is faster than YAG (40ns compared with 80ns ) so its overall performance is markedly superior to YAG, while it shares the advantage of insensitivity to radiation damage. It is available in the same formats, see listing in the ordering table .
As an economical choice for Cambridge/Leo SEMs, we offer plastic light pipes with the excellent Planotech P47 scintillator discs. The replaceable 12mm diameter discs are not coated with aluminum. This is a very economical way of obtaining a high performance pick up system with an easily replaced scintillator disc.
Efficient operation of the SEM demands regular replacement of the scintillator. Rather than purchasing replacement tips for light pipes, it is preferable to use a quartz light type and to coat its tip with scintillator material in suspension. This can be washed off and the light pipe recoated when necessary
P47 phosphor powder highly recommended for scintillator discs for those who wish to prepare their own. For normal applications the resulting disc should not be aluminum coated