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 V-F at different values of the gate voltage V-G and observed that the optimal V-F 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 x 5 array with a 40 x 40 mum footprint on the phosphor screen biased at 5 kV and located 15 mm away was at most 50 mum.