Basic Studies of High Performance Multialkali Photocathodes
Final rept. 1 Sep 1974-31 Aug 1978
STANFORD UNIV CA DEPT OF MATERIALS SCIENCE AND ENGINEERING
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X-ray photoemission studies XPS of Cs3Sb, Na2KSb, and Na2KSbCs alkali antimonide photocathodes prepared in ultrahigh vacuum on pyrex, suprasil quartz, and stainless steel substrates have been made. The results for these surfaces are the same. Employing the concept of the Auger Parameter we demonstrate that the most photosensitive alkali-antimonide photoemitters are ionic semiconductors with a direct correlation between degree of ionicity and photosensitivity. We further show the dependence of photoemission threshold on lattice constant and ionicity. It is concluded from these studies that the structure of the most photosensitive s-20 consists of a surface layer of K2CsSb upon a base layer of Na2KSb and not a monolayer of CS upon Na2KSb as we commonly thought.
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