INTERACTION OF ALKALI METALS WITH SOLID SURFACES STUDIED BY LOW-ENERGY D+ SCATTERING

Abstract

The study of alkali-metal adsorption on metal and semiconductor surfaces has been a favored topic of surface science. This is motivated by a number of interesting physical effects, such as charge transfer, work function changes, and alteration of surface reactivity. Despite considerable research efforts, however, there has still been significant controversies about most of these properties. In this paper, a review is presented concerning alkali–metal adsorption on well-defined transition-metal and semiconductor surfaces, with particular emphasis on the bond-nature analysis using low-energy D + scattering. The analysis based on resonance neutralization of the D + ions associated with the 1s hole diffusion into the band reveals that Na, K, and Cs adatoms have significant covalency on the transition metal surfaces while those except for Na are ionically adsorbed on the semiconductor surfaces in a small coverage regime (< 1.7 × 1014 adatoms/cm 2). The charge state of Na is rather critical because of the larger ionization energy than the others. The other examples are concerned with the analyses of the interaction of these alkali–metal adatoms with electronegative species such as oxygen and halogens on the metal and semiconductor surfaces.