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 0.1deg and 0.4deg 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 beta _F 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