Experimental investigation of GaAs-Cs photocathode stability

The recent discovery that a GaAs-Cs emitter surface is one of the most efficient photoemitters throughout the visible and near infrared region has stimulated hopes that this system might form the cathode of improved phototubes. A number of problems stand in the way of realizing this hope, one of which is investigated here. It has been reported that the infrared response, and to a lesser degree the visible response of the GaAs-Cs system, decays in time. An investigation into the origin and the nature of this instability is reported here, with the conclusion that the decay in sensitivity is due to an excess accumulation of Cs on the GaAs surface. The experimental investigation also includes age studies, methods of resensitization of the cathode, and the effects of an argon atmosphere.