Beam profile measurement of volcano-structured double-gate Spindt-type field emitter arrays

Double-gated Spindt-type field emitter arrays with volcano structures were fabricated using a double-layered photoresist as a lift-off layer for image sensor application. The gate aperture height and emitter tip angle were varied to optimize the device structure, wherein the gate aperture height was changed by controlling the etch-back time during the gate opening process and the emitter tip angle was changed by selecting the emitter material. The Ni emitter had a narrow tip angle while the Mo emitter had wider tip angle. For the formation of the Mo emitter, a thick Ni buffer layer was necessary to prevent delamination. Electron beam focusing characteristics were evaluated using the scanning slit method, and it was found that both a higher gate aperture and a wider tip angle facilitated better beam focusing. A wider tip angle, however, increased the operating voltage of the field emitter arrays. Additionally, a higher gate aperture did not affect the operational voltage. Therefore, a narrow tip angle with...