Novel flat MIS electron emitter

The flat metal-insulator-semiconductor (MIS) electron emitter is a simple design allowing easy manufacture, and is relatively insensitive to environment conditions making operation possible in poor vacuum conditions. A stack of 5000 Å polysilicon/150 Å silicon oxide/50 Å gold deposited on n++ doped silicon showed the best performance. We have observed emission current densities as high as 2-10 A/cm² at efficiencies from 3-10%. The polysilicon serves a dual role. Bumps on the poly surface act as field-enhanced emission sites while the bulk of the film behaves as a ballast resistor that prevents run away emission from any one emission site. The thin gold layer self-assembles into a nano-mesh with >100 pores/μm² through which electrons escape. Emission theory, including energy distribution and angular divergence of the emitted beams, are discussed.