Aperture-collimated double-gated silicon field emitter arrays

We report the fabrication and characterization of aperture-collimated double-gated silicon field emitter arrays (FEAs) with conical tips below the gate aperture. Electrical measurements show that the anode current is relatively independent of the focus voltage consistent with numerical simulation of the structure using finite-element modeling. Optical measurements show that the device produces a small beam spot, which is roughly the same size as the silicon FEA footprint with an estimated beam divergence between 0.1 degrees and 0.4 degrees that is independent of the focus voltage. The experimental results are consistent with numerical simulation of the double-gated field emitter structure with the tip below the gate. Both experimental and numerical simulation results show that the focus field factor OF is much smaller than the gate field factor beta(G). Numerical simulation of other structures with the tip above the gate and the tip in-plane with the gate show that beta(F) is much higher than beta(G) or has a comparable value to beta(G).