Thermal stability of single-atom termination at a pyramidal apex of an Ir-W Tip∗

Abstract

A single-atom termination (SAT) tip of Ir-W is one of the most promising candidates among various gas-field-ionization ion sources (GFIS) and field emission (FE) tips. In this work, we investigated thermal stability of the SAT tip with increasing the tip temperature. Above 1300 K, the SAT tip was destroyed, which was consistent with the surface phase transition of the monolayer Ir covered W(111) surface [J. J. Kolodziej, T. E. Madey, J. W. Keister, and J. E. Rowe, Phys. Rev. B 65, 075413 (2002)]. The SAT tip is thermodynamically stable only under negative electric bias in the temperature rang below 1300 K. If the SAT tip was broken accidentally, it was repaired for many times only by heating at the negative bias. The demountable character of the SAT tip was also confirmed.