Effect of overlayer thickness on electron emission from Si:Cs-O NEA surfaces

Experimental and theoretical studies of the variation in photoresponse of the Si:Cs-O negative electron affinity (NEA) photocathode with thickness of the Cs-O overlayer and acceptor concentration in the Si bulk, are reported. Resonance transmission peaks in the variation of photoyield with increasing overlayer thickness are predicted and observed. From a comparison of theoretical and experimental curves, the electron attenuation length in the overlayer is estimated to be about 50 AA. The theoretical analysis indicates that the optimum overlayer is metallic with a carrier concentration of about 2*1021 cm-3, varying slightly with bulk acceptor concentration.