Theoretical and experimental studies of photoemission from Al quantum wells on Si(1 1 1)

Recently, it has become possible to grow extremely high quality metallic quantum wells on semiconductor substrates showing coherent coupling across the interface. In the present work, a simple tight-binding model of such structures is applied to Al/Si(1 1 1). The model is compared to synchrotron radiation photoemission spectra recorded for this system. Experimentally, the influence of the substrate on quantum well energy levels is revealed as a change of slope of the thickness dependence of these levels as the Fermi edge is approached. This signature of coupling across the interface is partly reproduced by the model. When calculations for free-standing films and films on a substrate are compared, the latter show significantly improved agreement with experiment.