Tunnelling spectroscopy of surface state scattering and confinement

Using low-temperature scanning tunnelling microscopy we have investigated confinement of electronic surface states to hexagonal islands and other nanoscale structures on Ag(111). Local spectroscopy and spatial maps of the differential conductance are analysed using simple models of the electronic structure. We find that the concept of confinement of a two-dimensional surface state applies down to very small structures, and observe in real space how proximity to defects affects surface state lifetimes.