Electronic Structure of an Ordered Monolayer of Cu on Zn(0001)

We have measured the energy distribution curves of photoelectrons (hν=21.2 eV) from a Zn single-crystal (0001) face covered by an ordered Cu monolayer and from bulk Cu. We have found a narrow (2.3-eV total width) Cu d-state peak 1.20 eV below the position of the peak of bulk Cu $3d$ structure. We have also calculated the density of states for both a Cu monolayer on Zn and an unsupported Cu monolayer. Theory is in good agreement with experiments. The overlayer density of states is shown to be very similar to that of the unsupported atomic layer.