Fabrication of metallic double-gate field emitter arrays and their electron beam collimation characteristics

The fabrication of double-gate metallic field emitter arrays with large collimation gate apertures and their field emission beam characteristics are reported. The device fabrication steps, including the molding technique for array fabrication, the electron extraction gate fabrication by the self-aligned resist etch-back method, and the fabrication of the collimation gate electrode using a focused ion beam assisted method are described in detail. The experimental results of 2 × 2 tip arrays with the proposed double-gate structure demonstrate an order of magnitude enhancement in beam brightness with minimal current loss. A similarly high beam brightness enhancement was achieved with a 20 × 20 tip array device, showing the scalability of the proposed structure. The observation of improved current-voltage characteristics with the 20 × 20 tip array is ascribed to the difference in gate aperture shape. The possibility of further improving the beam characteristics of double-gate field emitter arrays and the reduction of the transverse electron velocity spread are discussed.