Presentation Information
[10p-E311-5]Optimization of geometrical structures of W field emitters with a nano-protrusion forconfinement of electron beam divergence
〇Shigekazu Nagai1, Junki Shima1, Tatsuo Iwata1 (1.Mie Univ.)
Keywords:
Field emitter,Electron optics
High-brightness electron sources are indispensable for high-resolution electron microscopy and related spectroscopies. A nano-protrusion formed on a tungsten emitter apex by field-assisted oxygen etching reduces the effective source size and suppresses beam divergence through a local electrostatic lens effect, but quantitative design guidelines relating the emitter geometry to the divergence have not been established. Here, the dependence of the beam divergence angle on the protrusion height and the shank angle was systematically studied by electron-optical simulation (SIMION) and field emission microscopy (FEM). Nano-protrusions were fabricated on W tips by field-assisted oxygen etching, and their heights were determined by the ring-counting method of field ion microscopy. Simulation and experiment showed that the divergence half-angle decreases with lower protrusion height and larger shank angle, reaching 4.4 deg at a shank angle of 22 deg, in good agreement with the simulation.