Measurements of vacuum field emission from bio-molecular and semiconductor-metal eutectic composite microstructures

Designs, calculations, and initial data are presented from a program investigating the use of biomolecular and eutectic composite microstructures as vacuum field-emission cathodes. Calculations, supported by the initial data, indicate that these electron sources should be capable of macroscopic beam current densities, J>or=100 A/cm/sup 2/, without the formation of a surface plasma. The absence of a plasma allows these cathodes to operate as a long-pulse to DC electron sources. The designs avoid the formation of surface plasma by forcing the current emitted from the tips to transit a thin layer of silicon. The natural high-field current-limiting nature of the silicon serves to prevent the ablation of tip structures and the subsequent formation of cathode plasma. Initial data obtained with these microstructures has demonstrated Fowler-Nordheim characteristic emission. Coated bio-molecular composite cathodes have demonstrated stable DC current densities of approximately 100 mA/cm/sup 2/, and the eutectic composite cathodes have demonstrated similarly stable DC current densities of approximately 1 A/cm/sup 2/.<
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