Dipole moments associated with edge atoms; A comparative study on stepped Pt,Au and W surfaces

Work function measurements have been performed on stepped Pt and Au surfaces with (111) terraces and on W surfaces with (110) terraces. In each case the work function decreases linearly with increasing step density and depends on the step orientation. The work function changes are attributed to dipole moments associated with the step edges. The dipole moments per unit step length are larger for open edge structures than for densely packed ones. The dipole moments for Pt are about twice as large as for Au and W.