Optimum geometry and space-charge effects in vacuum microelectronics devices

A numerical method is presented for the simulation of electrical characteristics of microemitter devices. The method, a combination of the boundary integral method and the finite difference method, is capable of dealing with arbitrary microemitter shapes and calculating space-charge effects. A spherical mesh structure has been used, which allows calculations with high resolution in the vicinity of a microemitter apex. Seven different microemitter shapes have been simulated for the comparison of their field-enhancement factors. The optimum geometry of a microemitter is found to be a cusp-like shape. The space charge has an effect on field emission current only for current densities above 10/sup 8/ A/cm/sup 2/.<
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