Quantisation of valence states observed in small Ag islands on the GaAs(110) surface

The morphology of Ag on the cleaved (110) surface of GaAs has been modified by control of the growth conditions. Deposition at 300 K results in a partially ordered, rough surface, while at 100 K a disordered but uniform film results. High resolution core and valence level photoemission has been applied to monitor the annealing of the film deposited at low temperature. This results in the formation of uniform, crystalline Ag islands. The sp valence band of Ag appears as a sequence of separate peaks in the photoelectron emission spectrum. The number and separation of the peaks depend on the amount of metal deposited; a consequence of quantum confinement in these islands. The photon energy and emission angle dependence of the peak positions and intensities are related to the real space structure of the crystallites and to the position of the probed states in the extended bulk Ag Brillouin zone.