IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Surface Science Thursday Sessions
       Session SS2-ThM

Paper SS2-ThM3
Ultrathin Epitaxial Mg Films on Si(111): Quantum Size Effects

Thursday, November 1, 2001, 9:00 am, Room 122

Session: Electronic Structure II
Presenter: C. Rogero, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Germany
Authors: L. Aballe, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Germany
C. Rogero, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Germany
K. Horn, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Germany
Correspondent: Click to Email
We demonstrate, using angle-resolved photoelectron spectroscopy and LEED, that highly perfect ultrathin epitaxial Mg(0001) films can be grown on Si(111) using low temperature deposition and annealing. This is in contrast to films grown at room temperature which present an interfacial silicide and subsequent growth of a disordered Mg metallic film. The wave-vector dependent electronic structure of the well-ordered films is investigated in detail with photoelectron spectroscopy, as a function of overlayer thickness. The spectra exhibit a number of thickness-dependent discrete peaks in the region of the magnesium s-p band for films up to 40 monolayers thick. These are caused by electron confinement within the Mg overlayer, and can be identified as quantum well resonances derived from the magnesium s-p band. These quantum well resonances (QWR) are interpreted in terms of the phase-accumulation model, and the Mg band structure is found to account for all the main features in the spectra. An estimation of the decay length of the Mg(0001) surface state wave function is obtained from its dependence of binding energy on film thickness. The in-plane dispersion of the QWR for films of different thicknesses is measured and analyzed along the surface Brillouin zone. The data point to a strain-driven thickness-dependent structural transition at a critical thickness of about 20 Mg monolayers. The dependence of spectral intensity on photon energy in the range of the Mg bulk and multipole plasmon energies demonstrates the effect of field enhancement in the Mg film.