ELECTRONIC-PROPERTIES OF THE LEAKY QUANTUM-WELL SYSTEM AG(111) AU/AG/

Angle-resolved photoemission has been employed to examine the electron ic properties of a lattice-matched, epitaxial system prepared by depos iting first a thin Au(111) if layer on a Ag(111) substrate, and then a Ag(111) overlayer. The Au layer acts as a potential barrier for elect ron motion in the system. The Ag overlayer can be regarded as a quantu m well, but in our experiment, the Au barrier is rather thin, and ther e is substantial coupling between the valence electrons in the Ag over layer and the continuum states in the substrate. Nevertheless, well-de fined quantum-well resonances are observed for Au barriers as thin as two atomic layers. These resonances can be understood as a result of p artial trapping of valence electrons in the Ag overlayer. A calculatio n which takes into account the band structure and surface properties i s carried out. and the results are in good agreement with the experime nt. Initial- and final-state features in the spectra are identified by comparison with theoretical models. The effects of lattice match or m ismatch at the interface will be discussed.