Abstract
Noble-metal covered W(111) single-atom pyramidal tips (SATs) are artificially created, highly stable atom perfect nanostructures with broad scientific and technological interests. Using first-principles calculations, the binding energy of the topmost atom is found to be nearly identical to the cohesive energy of the metal despite its greatly reduced coordination. This explains the extraordinary high stability of the SATs. In addition, the tip states below Ef that localize not only in the real space but also in the energy domain is a genetic property of the reduced dimension of the apex of the pyramidal tip structure. The calculated spectral features may also provide a foundation for future scanning tunneling spectroscopy measurements as well as an elemental analysis of surface atoms using SATs in scanning tunneling spectroscopy. © 2010 The American Physical Society.