Internal Polarization of Oxygen Adatoms on Polycrystalline Ta Investigated by Na-Ion Scattering

Abstract

The neutralization of scattered low-energy alkali-metal ions is used to investigate the internal polarization of oxygen adatoms on a Ta surface. The neutral fraction of 3 keV Na scattered from Ta is 50% from the clean surface and 15% in the presence of oxygen, while the work function is unchanged. These observations can be reconciled if the adatoms were internally polarized, leading to multiple dipoles that each contribute to the work function.