Field Emission from Polycrystalline Silicon Surfaces

Polysilicon field emitters were micromachined on current limiting polysilicon resistors. Field emission data of the diode structures revealed a significant difference between phosphorous doped and intrinsic polysilicon tips, or surface emitters. Phosphorus doped polysilicon tip and surface emitters emit at similar fields, regardless of the degree of their sharpness. Similarly, intrinsic polysilicon tip and surface emitters emit at similar applied fields, regardless of the degree of their sharpness. This behavior is attributed to the surface morphology of the polysilicon after oxidation and plasma etch. Materials analysis suggest the formation of sharp ridges, possibly along the grain boundaries, on the emission surfaces that contributes to similar magnitude of field enhancement from the nano-scale structures on both the surface and sharp tip emitters.