LOW-WORK-FUNCTION SURFACES FOR NEGATIVE-ELECTRON-AFFINITY PHOTOEMITTERS

Abstract

The photoemission threshold of GaAs–Cs–O is explained on the basis of a heterojunction model composed of GaAs and Cs2O. The concepts involved in this model are generalized to an arbitrary heterojunction, leading to the result that it is, in principle, possible to obtain surfaces with work function lower than 0.5 eV. If deposited on an appropriate substrate, these surfaces offer the exciting possibility of highly efficient photoemission well into the infrared. A possible practical negative-electron-affinity photoemitter with efficient response to 1.4 μ is suggested.