Cesium photocathode material

The photocathode material used in most commercial phototubes is a compound of cesium and antimony (Cs-Sb). The material used to coat the dynodes is either Cs-Sb or silver-magnesium (Ag-Mg). The secondary emission rate of the dynodes depends not only on the type of surface but also on the voltage applied. 

Many different types of photocathodes are used in photomultipliers. With a selection of various cathodes, it is possible to cover the range of response from the soft x-ray region (approximately 5 to 500 A) to the near infrared (approximately 12,000 A). Materials and combinations used include cesium-oxygen-silver cesium-antimony cesium-antimony-bismuth sodium-potassium antimony sodium-potassinm-cesinm-antimony copper-iodine and cesium-iodine. The thermal emission at 25°C of copper iodide and cesium iodide tends to run less than the other materials. 

Devices with negative electron affinity (NEA) Material with negative electron affinity is used for photocathode, e.g., strongly doped semiconductor coated with cesium... 

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