Selective emission of electrons from patterned negative electron affinity cathodes

We have observed electron emission into vacuum from the exposed areas of a patterned p/sup ++/-GaAs substrate which was coated with cesium and oxygen. The emission barrier is a double layer of titanium-tungsten/silicon nitride. The exposed areas of the cathode were activated to the negative electron affinity (NEA) condition. It has been an open question whether it would be possible to activate the exposed areas of a patterned GaAs cathode. This result opens the possibility of utilizing NEA cathode technology for projection electron beam lithography tools, NEA-based vacuum microelectronics devices, and a combination of bulk devices with NEA emitters. A picture of an emission pattern projected onto a phosphor screen is presented. Auger depth profile was used to determine the stability of the TiW/GaAs interface through the activation procedure. Short and long term current stability were measured. A technique for cathode recovery and reactivation has been developed.>