VALENCE-BAND DENSITY-OF-STATES OF SMALL COBALT PARTICLES ON SI(111) SUBSTRATE

Small Co particles were prepared by sputter etching of a 4-5 nm thick ''island-like'' Co film deposited on Si(111) substrate. The density of states (DOS) of the valence band was measured by means of ultraviolet photoemission (UPS) during the sputter etching to monitor the formati on of small Co particles. It was found that at a given thickness of th e Co island the Fermi level was shifted by 1.8-1.9 eV toward higher bi nding energy and the DOS decreased or no states were detectable at the Fermi level. This effect was explained by the formation of small Co p articles with electronic structure which is significantly different fr om that of the bulk Co.