Auger characteristics of BaO layers on various substrates

• Published in: Applied surface science 1988-02, Vol.31 (2), p.239-252
• Main Authors: Haas, G.A., Shih, A.
• Format: Article
• Language: English
• Subjects: Applied sciences; Chemistry; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; General and physical chemistry; Materials science; Metals, semimetals and alloys; Metals. Metallurgy; Physics; Solid-gas interface; Specific materials; Surface physical chemistry
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/0169-4332(88)90064-5

The charge transfer interactions between a BaO monolayer adsorbate and various substrates were determined from interatomic Auger transitions (Ba 4d, Ba 5p, valence) in the 65 to 75 V energy range as well as from the changes in the O KLL lines in the 480 to 520 V region. The results showed that a greater charge transfer existed between O and oxide-forming metals such as W and Nb than on “noble” metals such as Ir and Rh. (For the purpose of this paper, these metals were designated here as “interactive” and “noninteractive” respectively.) For the interactive case, the majority of the contribution to the negative charge on the O seemed to come from the substrate rather than the Ba and these electrons also appeared to be bound more tightly. For the noninteractive substrates, there were fewer and more loosely bound electrons on the O and these were obtained mostly from the Ba rather than from the substrate. However, the smaller charge transfer noted between the O and these substrates was compensated here by a sizeable charge transfer interaction between the Ba and the substrate, i.e. the Ba giving 6s electrons to the substrate, thus becoming more positively charged. Variations were noted in the intensity of the interactions between the BaO adsorbate and different substrates of the same type (i.e. either interactive or noninteractive types), and these are discussed as are also the effects of BaO-BaO interactions.