Local work function changes determined by field emission resonances: $\mathrm{Na}\mathrm{Cl}∕\mathrm{Ag}(100)$

Local work function changes determined by field emission resonances: $Na Cl ∕ Ag (100)$

Hans-Christoph Ploigt, Christophe Brun, Marina Pivetta, François Patthey, and Wolf-Dieter Schneider

Phys. Rev. B 76, 195404 – Published 6 November 2007

Abstract

Electrons trapped in field emission resonances (FERs) in front of a Ag(100) surface covered with ultrathin NaCl islands are probed by scanning tunneling spectroscopy. The eigenstates in the potential well formed between the tip and the sample are calculated within a one-dimensional model. This approach permits to locally determine a work function reduction of $1.3 eV$ in going from the bare substrate to NaCl islands of up to 3 ML. Spatial mapping of the FERs across a NaCl island edge at typical distances of $1 nm$ from the surface yields a lateral resolution for the surface potential changes of $1 nm$ .