Chemical effects in the Auger spectrum of lead, deposited on nickel oxide - an indirect characterization of the NiO growth mode on Ni(100)

The interaction of submonolayer lead deposits with oxygen pre-exposed Ni(l 0 0) has been investigated by Auger electron spectroscopy (AES) and low energy electron diffraction (LEED). By comparison with the Auger line shapes of metallic lead and orthorhombic lead oxide, chemical effects have been evidenced in the Ph Auger spectrum, for submonolayer lead deposits performed on the NiO phase (hydroxylated or not). Inversely, it has been shown that no chemical effect occurred for lead deposits performed on an O-adsorbed phase. This difference of chemical state has been used to investigate the growth mode of NiO on Ni(I 0 0). The nucleation and growth of NiO islands among an O-adsorbed phase have been proved through this lead deposit approach, which appeared distinctly more sensitive than LEED to evidence the beginning and the end of the "biphased" domain. Under annealing to T greater than or equal to 500 K, the decomposition of a full oxide thin film, into a mixture of oxide islands and O-adsorbed phase, has also been evidenced through this lead deposit method. (C) 2002 Elsevier Science B.V. All rights reserved.