Effort was directed toward the fabrication of a micron-spaced thermionic converter diode. This technique demonstrated that interelectrode spacings down to 1.5 ..mu..m could be obtained. Several methods of duplicating the emitter and collector surfaces were also investigated. Two new techniques are proposed; both stem from an earlier idea of using evaporation, photolithography, and etching techniques. These two fabrication methods yielded a one-piece diode structure with a thick-film copper collector, eliminating the need to physically duplicate the electrode surfaces and realign the electrodes. Effort has also been directed toward a more detailed theoretical analysis of micron-spaced thermionic converter performance. Taking into account heat losses through the interelectrode support structure, it is likely that the maximum energy conversion efficiency may be greatest at a spacing somewhat larger than 1 micron (..mu..m), but less than 10 ..mu..m.