Surface-state depopulation on small Ag(111) terraces

The dependence of the local density of states near the Fermi energy E-F on the width of terraces T is investigated by tunneling scanning spectroscopy on Ag(111) at 7 K. With decreasing T, the electronic density in the occupied surface state shifts monotonically towards E-F, leading to a depopulation at T=3.2 nm in quantitative agreement with a Fabry-Perot model. Depopulation coincides with a switch from confinement by terrace modulation to step modulation.