Visualization of individual emission sites on flat broad-area field emission cathodes.

We introduce a novel scanning projection field emission microscope (SPFEM) designed to study flat broad-area field emission cathodes. The instrument merges capabilities of measuring the electron field emission current from an individual emitting site and genuine projection of electrons onto a luminescent screen. This is achieved by an optimized shape of the anode probe having a 0.04 mm aperture which generates an uniform macroscopic electric field across the investigated area of the cathode. This fact also enables presentation of the relation between the current density and the applied electric field. The magnification of the electron-optical system alone was calculated by computational modeling for some cathode-probe distances and for some voltages. The unique SPFEM performance is demonstrated on smooth sulfur-doped nanodiamond films synthesized on molybdenum substrates.