D-band quantum well states in Ag(111) monolayer films; substrate-induced shifts

Abstract

We report a study of 4d electronic states in monolayer silver films grown on Pd(111),Ni(111), Mo(110) and Cu(100) surfaces studied by means of high-resolution angle-resolvedphotoemission spectroscopy (ARPES). The Ag-4d states, when measured in the surfaceBrillouin zone centre (SBZ), show substrate-dependent shifts. Density functional theory(DFT) calculations for a free-standing silver monolayer provide evidence that theobserved shifts are not induced by lateral expansion, compression or distortion of thesilver unit cell. Using the phase accumulation model we show that 4d-derivedelectronic states in silver monolayers can be described in terms of quantum well statesand that the matching of the electron wavefunctions at the interface with thesubstrate is one of the important mechanisms that generates the Ag-4d energy shifts.The dispersion of the states around the SBZ centre is measured and discussed.