Field Emission Electron and its Applications

Concepts of highly bright electron source for beam systems such as electron microscopes and electron exposure systems are given. Recent progress in developing thermal field electron source is reviewed. It is shown that work function of W(100) surface is selectively reduced by modifying the surface with yttrium and with oxygen. The reduced work function is 2.1 eV, which is about 0.6 eV smaller compared with ZrO/W(100) thermal field emitter. It is also shown that the work function of Molybdenum is also reduced on (100) surface selectively by modifying the surface with zirconium and with oxygen. The reduced work function is 2.0eV. Potential abilities of field emission arrays and carbon nano-tubes for electron sources are critically shown.