Growth, structure and properties of ultra-thin copper films on a V(110) surface

Abstract

In this work we study the evolution and electronic properties of copper ultra-thin films grown at room temperature on a V(110) single crystal surface using angle-resolved ultraviolet photoemission spectroscopy (ARUPS), X-ray photoemission spectroscopy (XPS), Auger electron spectroscopy (AES) and low-energy electron diffraction (LEED). Up to 5 monolayers (5 ML) the films grow in an imperfect layer-by-layer mode; this being more pronounced at coverages above 2 ML. The LEED studies show that films up to 2 ML coverage grow pseudomorphically, forming thus a body-centered cubic (bcc)-copper film. The 5 ML film shows no clear LEED pattern, although the appearance of quantum well states (QWS) at 1.1 and 1.9 eV binding energy in the ARUPS spectrum suggests that the film as a whole is rather well ordered. Dispersion of the Cu 3d bands of the 5 ML film follows the calculated dispersion of the bcc copper along the ΓN high symmetry axis. The 2 ML film also shows a QWS (at 1.8 eV) of very high intensity. Annealing affects significantly only the films of coverages higher than 2 ML: clusters are formed on the 2 ML thick copper overlayer. These findings contribute also to a better understanding of the results obtained by thermal treatment of ultra-thin vanadium films grown on a Cu(100) surface, in which case a segregated copper film is formed on top of the bcc-vanadium film. The work function of the clean and ordered V(110) surface is found to be 4.65±0.08 eV.