Fabrication of a trimer/single atom tip for gas field ion sources by means of field evaporation without tip heating

•A trimer or single atom tip fabrication method is proposed.•The method relies on field evaporation mechanism with insulating layers which are including tungsten oxide.•The insulating layer was remained owing to the absence of tip heating process.•The results of proposed method are similar to an oxygen assisted etching process. A gas field ion source (GFIS) has many advantages that are suitable for ion microscope sources, such as high brightness and a small virtual source size, among others. In order to apply a tip-based GFIS to an ion microscope, it is better to create a trimer/single atom tip (TSAT), where the ion beam must be generated in several atoms of the tip apex. Here, unlike the conventional method which uses tip heating or a reactive gas, we show that the tip surface can be cleaned using only the field evaporation phenomenon and that the TSAT can also be fabricated using an insulating layer containing tungsten oxide, which remains after electrochemical etching. Using this method, we could get TSAT over 90% of yield.