QUANTUM WELL STATES IN METALLIC THIN LAYERS

Abstract

When going from the bulk solid to a thin film of nanometer dimensions, the electronic structure becomes discretized in the perpendicular direction. These discrete states, also called thin film states and quantum well states, are clearly distinguished in photoemission experiments as two-dimensional and thickness-dependent modulations of the bulk spectra, although their observation is limited to highly perfect epitaxial systems. The photoemission data are well explained in the framework of a simple model for the electron wave function in a quantum well state. Thin film states become spin-polarized when growing on ferromagnetic substrates. Furthermore, spin-polarized, thickness-dependent modulations at a given energy lead to spin-dependent periodic oscillations of the density of states as a function of thickness, which are found to be responsible for the oscillatory coupling observed in magnetic multilayers.