Different quantization behaviors of electrons confined in nanostructures at surfaces

Abstract

We show that two confinement modes exist for electronic states localized on a nanostructured surface. Image potential states confined on Ar islands on Cu(100) and on vacancy islands on 1 ML $\mathrm{Ar}∕\mathrm{Cu}(100)$ surface are studied. Whereas the Ar islands lead to the expected ``particle-in-a-box'' quantization, the vacancy islands are shown to exhibit a very different behavior, characterized by a much lower quantization energy. The two situations correspond to the confinement of two-dimensional surface-localized states on repulsive or attractive areas of the surface, and one should thus be as common as the other.