An electron emitter assembly for use in an x-ray emitting device or other electron emitter-containing device is disclosed. In one embodiment, an x-ray tube is disclosed, including a vacuum enclosure that houses both an anode having a target surface, and a cathode positioned with respect to the anode. The cathode includes an electron emitter assembly for emitting a beam of electrons during tube operation. The electron emitter assembly comprises a refractory metal foil with a plurality of shaped rung structures for emitting an electron beam that maximizes flux while simultaneously focusing the electron beam in two dimensions. Focusing occurs primarily through an electrical field shaped by the electron emitter assembly and through balancing current density, electrical resistance, and heat loss through thermal conduction to control the regions that emit electrons. Furthermore, the refractory metal foil can be configured with a modified work function for preferential electron emission.