Iridium single atom tips fabricated by field assisted reactive gas etching

•Iridium single atom tips (SATs) were prepared.•SATs were be regenerated by field assisted chemical etching using oxygen as an etchant gas.•Oxygen is corrosive to Iridium at room temperature under high field conditions.•Oxygen corrosion rate of Iridium at reduced temperature is slowed.•SATs are stable at room temperature for high field ionization gases such as neon. We present a simple, reliable method to fabricate Ir single atom tips (SATs) from polycrystalline wire. An electrochemical etch in CaCl2 solution is followed by a field assisted reactive gas etch in vacuum at room temperature using oxygen as an etching gas and neon as an imaging gas. Once formed, SATs are cooled to liquid nitrogen temperatures and their underlying structure is examined through evaporation of the apex atoms. Furthermore, a method is developed to repair Ir SATs at liquid nitrogen temperatures when apex atoms evaporate. This method may be used to fabricate Ir SAT ion sources.