Development of coherent electron emission source of Pd-atom nanotips

We have fabricated nano-scaled Pd atom clusters to apply to a field electron source, and the electron emission characteristics were investigated. Owing to the formation of the Pd nanotips, field electron beams were drastically converged within a cone angle of approximately 5 degree. This collimation of the electron beams was quite relevant to the case of previously-studied W nanoemitters. Analysis based on Fowler-Nordheim formalism, where work function of W(111) was assumed, to be available for each specimen, predicts that the effective tip radius ranged from 150 and 200 nm for the conventional W emitter and from 20 to 30 nm for the Pd nanotip. Noticeably, the Pd nanotips were found to regenerate and to exhibit equivalent emission characteristics repeatedly. This unlimited revival function is significant for the practical use, and not possessed by the previously studied W nanotips.