GROWTH OF COPPER, NICKEL, AND PALLADIUM FILMS ON GRAPHITE AND AMORPHOUS-CARBON

The growth of films of Pd, Ni, and Cu on amorphous carbon has been studied under ultrahigh vacuum from the lowest coverages detectable to films many atomic layers thick. Since surface diffusion of these metals does not occur on amorphous carbon at room temperature, these metals are present as isolated adatoms at the lowest coverages (110 monolayer). The electronic states of the metal adatoms are found by photoemission and Auger spectroscopies to be markedly different from those of the bulk metal. All states have a larger binding energy and the valence band is narrower than in the bulk. At increasing coverages (14-34 monolayer) additional metal atoms fill the gaps between adatoms, and a discontinuous film develops. As a result the electronic states become more like those in the bulk. As coverages increase into the range of several atomic layers, the films are almost continuous, and the electronic states are those of the bulk metal. In contrast to this, ultraviolet photoelectron spectra show that even at the threshold of detectability, Pd, Ni, and Cu atoms deposited on the basal plane of cleaved graphite nucleate into clusters sufficiently large to exhibit valence-band and core-binding energies characteristic of bulk metals. © 1979 The American Physical Society.