An emitter is configured to emit charged particles. The emitter comprises a body, a metal layer and a charged particle source layer. The body has a point. The metal layer is of a first metal on at least the point. The charged particle source layer is on the metal layer. The point comprises a second metal other than the first metal.

A thermionic cathode, an electron emission apparatus, and a method of fabricating the thermionic cathode are provided. The thermionic cathode includes an emitter. The emitter includes a lanthanum hexaboride (LaB.sub.6) crystal having a crystallographic orientation of (310). The operating temperature of the thermionic cathode is greater than 1800 K.