Surface state localization by adatoms
A new type of electronic states at metal surfaces has been identified based on theoretical simulations and scanning tunneling spectroscopy (STS) of single Cu adatoms on the Cu(111) surface. The states, which we call surface state localization (SSL) states, are localized around the adatom, but do not derive from any atomic states of free Cu. Instead, the existence of such states can be understood from the adatom interacting with two-dimensional electronic states (Shockley surface states) that exist on many metal surfaces, such as Cu(111). First predicted by theory, the existence of these states has been proven by STS experiments. In addition to the surface state localization, our spectroscopic measurements reveal an unoccupied adatom resonance which derives from quasi-atomic s and p orbitals; this resonance gives rise to intriguing behavior when assembling compact nanostructures atom by atom.
Figure:
STM image of single Cu adatoms on the Cu(111) surface (left), plot of the calculated resonant wave function associated with the SSL state (center) and STS spectra for different lateral distances, R, revealing the adatom-localized resonance below the surface state band (right); The STM image on the right indicates the positions where spectra were taken.
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