Electrical and optical characterization of field emitter tips with integrated vertically stacked focus

A revised version of the authors´ BPM that includes quantitatively accurate closed-form expressions for the Fowler-Nordheim coefficients is summarized. For field emitter arrays with integrated focus with the gate and focus biased at the same potential (V_G, = V_F) the emission current was 100 nA/tip at 42 V, with about 50% intercepted by the focus. It was deduced that the tip radius of curvature is 2.4-3.6 nm. Analytical model, numerical simulation, and transmission electron microscopy micrographs all gave tip ROC values in this range. We studied electron beam collimation with lowering the focus voltage VF at different values of the gate voltage V_G, and observed that the optimal VF is about 0.25 V_G, confirming earlier predictions by the authors. From the measurements of beam collimation as a function of cathode-anode separation, we deduced the horizontal velocity of electrons. Under optimal collimation the estimated horizontal velocity was practically zero, and diameter of the spot size produced by a 5 × 5 array with a 40 × 40 μm footprint on the phosphor screen biased at 5 kV and located 15 mm away was at most 50 μm.