Variation of the local work function at steps on metal surfaces studied with STM

With a scanning tunneling microscope we have measured the apparent barrier height (ABH) on large terraces of the clean Cu(111) surface and large Au(111) terraces of the Au/Cu(111) surface, and the results are in good agreement with the correspondent surface work function. From the ABH images of these surfaces low-value-valleys along steps are clearly visible, as expected from "Smoluchowki smoothing." A simple simulation of the valley makes us to be able to determine that the smoothing-induced dipole moment for Au and Cu steps is 0.16+/-0.05 and 0.5+/-0.15 D/step atom, respectively. [S0163-1829(98)00528-1].