An electro-optical emission layer of an alkali metal-Sb cpd. (I), at which electrons are detached by light and which is applied to a surface with almost) th same crystal structure contains =2, esp. ca 1 mu g Sb/cm2. The matl. pref. consists of a CsI support and a SbCs3 emission layer. The CsI pref. is applied to a stable support in a thickness such that it forms an interference cathode with the SbCs3 layer. The matl. is used in an X-ray image intensifier with an input screen of a Na-activated CaI phosphor layer combined with a photocathode layer, sepd. by a Na-free layer of an alkali metal, esp. Cs. The thickness of the emission layer can be reduced to 10nm and it gives a higher quantum yield than the usual Sb layers of 3 mu g/cm2. Five times as many photoelectrons are emitted per incident amt. of radiation and surface area of the element.
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