CONVENTIONAL AND NEGATIVE ELECTRON AFFINITY PHOTOEMITTERS

Abstract
This talk will be divided into three parts. The first will be a brief survey of the "conventional" photocathodes with useful quantum yield in the visible and the near infrared spectral region. These cathodes include those represented by the chemical formulae Ag-O-Cs (S-1), Cs₃Sb (S-11), Bi-Ag-O-Cs (S-10), Na₂KSb, K₂CsSb, and (Cs)Na₂KSb (S-20). Second, the essential features of the negative electron affinity (NEA) concept will be discussed and the basic advantages of NEA materials for photoemission, as well as for secondary electron emission, will be summarized. In the third part, the present status of the practical use of NEA electron emitters will be presented. These include GaP, GaAs, Si, and the ternary III-V compounds. The technological problems encountered in working with these materials will be discussed. A few concluding remarks will deal with the prospects of future developments.