Electron dynamics in vacancy islands: Scanning tunneling spectroscopy on Ag(111)

The dynamics of Ag(111) surface state electrons confined to nanoscale hexagonal and triangular vacancy islands are investigated using scanning tunneling spectroscopy. The lifetimes of quantized states with significant amplitude near the centers of the vacancies are weakly affected by the geometry of the confining cavity. A model that includes the dependence of the lifetime on electron energy, vacancy size, step reflectivity, and the phase coherence length describes the results well. For vacancy islands with areas in the range of ≈40--2200.3em0exnm² lossy scattering is the dominant lifetime-limiting process. This result and a corrected analysis of published experimental data improve the consistency of experimental and calculated surface-state lifetimes.