Ellipsometric investigation of metal–alkali-halide interfaces

Spectroscopic ellipsometry (1.5<h{ν}<5.0 eV) has been used to follow the evolution of the complex optical dielectric function of Al, Cu, and Pt films with increasing coverage on the (100) surfaces of KCl and NaCl cleaved in ultrahigh vacuum. At low coverages, optical absorptions are observed which are not present in the bulk metal or dielectric. The results can be accounted for in terms of an effective-medium mixture of metal particles in a dielectric host. No optical transitions related to either interface states or defects were detected.