Imaging water on Ag(111):Field induced reorientation and contrast inversion

摘要

Water adsorbed on Ag(l11) at 70 K forms circular clusters that consist of six molecules.In scanning tunneling microscopy,this cyclic hexamer is imaged as a protrusion for voltages below V_(SS)=-93 meV and as a depression for voltages above V_(SS) .The electronic density of states,however,increases around V_(SS).We explain this counterintuitive result with the aid of calculated images by a change from constructive to destructive interference between different tunneling channels due to a field induced reorientation of the molecule under the tunneling tip.