Quantum-well states in ultrathin aluminium films on Si(1 1 1)

Investigations of the thickness dependent electronic structure of ultrathin aluminium films deposited on Si(1 1 1) 7×7 using angle resolved photoelectron spectroscopy show the first experimental observation of quantum-well states in this system. Deposition at 100 K favours an abrupt and homogeneous interface and the growth of an epitaxial, quasi two-dimensional Al(1 1 1) overlayer of good crystalline quality, making possible the observation of overlayer states for thicknesses up to 30 Al monolayers. We obtain the decay length of the Al(1 1 1) surface state as well as the energy-dependent phase shift of the electron waves at the Al/Si interface.