ON THE ELECTRON AND METALLIC ION EMISSION FROM NANOTIPS FABRICATED BY FIELD-SURFACE-MELTING TECHNIQUE - EXPERIMENTS ON W AND AU TIPS

In this work we present a study of the metallic ion and electron emissions from protrusions of approximately 2 nm size formed on top electric field to a tip of approximately 70 to 100 nm radius, at temperatures of approximately one third of the bulk melting point. By using field emission and field ion microscopies it is possible to characterize the emitting sources. They are found to be pyramids ending in one atom. By controlling the applied voltage (field) and temperature, the sources can emit either metallic ions for positive polarity, or electrons for negative polarity. Since they emit from one ending atom the produced beams are coherent, and they are also self-collimated with an opening angle of approximately 2-degrees and approximately 4-degrees for ions and electrons, respectively. The experiments are performed with single crystal W[111] and non-oriented Au tips. The determined fields for ion emission are substantially lower than for usual field ion microscopy tips.