A single-atom sharp iridium tip as an emitter of gas field ion sources

Abstract

We report a reliable method for preparing a pure Ir single-atom tip by thermal treatment in oxygen. The atomic structure of the tip apex and its ion emission characteristics are investigated with field ion microscopy. We have shown that the Ir single-atom tip can be a good field ion emitter, capable of emitting a variety of gas ion beams, such as He+, H2+, N2+, and O2+, with high brightness and stability. In addition, this tip can easily be maintained and regenerated in vacuum, ensuring it has sufficient lifetime for practical applications.

Fabrication of nano ion–electron sources and nano-probes by local electron bombardment

“…Therefore, several methods have been developed to fabricate such ultra-sharp tips [1][2][3][4][5][6]. These methods can produce nanotips with a very sharp end that terminates with a single atom, as can be observed in the field ion microscope (FIM).…”

“…For instance; (1) these methods are restricted to the very end of the tip, which results in a small nanotip aspect ratio, (2) with the exception of the nitrogen field assisted etching method [6], most of these techniques apply only to certain metal tips with a particular crystal orientation, e.g. W(1 1 1) or Ir(2 1 0) [1][2][3][4][5], (3) although the nitrogen etching method has shown outstanding performance compared to the other previous ones, it is restricted to metal tips with a field evaporation threshold reasonably higher than the ionization field of the imaging gas (mostly He) and the ionization field of the etchant gas (like nitrogen).…”

Fabrication of Gas Field Ion Emitter by Field Induced Oxygen Etching Method

“…Recently, various methods for preparing emitter tip with a nanoprotrusion which has a triangular pyramidal shape terminated by a single-atom or a trimer have been investigated [2,3]. However, if the field strength goes over the threshold of ionization field, the emission of ion beam occurs not only from the tip apex but also from the ridges around the apex.…”

Hydrogen Ion Beams from Nanostructured Gas Field Ion Sources

“…Hydrogen ion beams have been reported from various nanotips including pure iridium tips and noble metal covered tungsten tips. [1,2] However, hydrogen ion beams are known to occur as mixtures of H + , H2 + and H3 + depending on the electric field strength. [3] There is some evidence that various tip orientations contribute differently to the ratios of the ions and also that site specific regions also affect the gas species but it has not been clearly determined.…”