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This brief review describes the understanding of the surface chemistry of metals that was gained in the first ten years of the use of surface analytical techniques: the period 1968-1978. The work undertaken during this period established what we still recognise as a basic description of the technological surface with which the coating and adhesive industry has to deal. Since that time the same analytical techniques have been developed greatly, giving more information in shorter times and having a much greater sensitivity. This has enabled subsequent studies of bonding types and their relation to good adhesion. Nevertheless, it is hoped that this review of the early work and its systematic study of the hierarchy of layers that form on metallic surfaces will be of use for students and researchers entering the field of adhesion science. [ABSTRACT FROM AUTHOR]

In an earlier paper we proposed a new method for interpretation of background structure in X-ray photoelectron (XP) spectra and showed that this could be used to study bonding states in intermetallic compounds using, as an example, a particular Ti-Al alloy. In this paper we have applied this method to study a set of aluminides: Me-Al alloys, where Me represents a transition metal: Ti, V, Fe, Ni or Nb. The method for background interpretation is based on a peak-shape parameter κ, which links the intrinsic energy loss structure, associated with a given line in the XP spectrum, to the atomic number. This parameter is thus related to the number of final state configurations available to the photo-excited atom or ion and we show, now, how the value for aluminium varies across a series of compounds with the transition metals. The results for κ are accompanied by measurement of the Auger parameters which may be indicative of the charge transfer occurring between Al and Me and thus are also influenced by the final state configuration. The approximate proportionality found between these two parameters gives confirmation that κ may be a sensitive probe of the final state and bonding effects and confirms the extent to which aluminium orbitals interact with the 3d transition metal structure of vanadium, iron and nickel, and the 4d of Nb. This is in full accord with the results obtained from the TiAl alloy. Complementary information was obtained by comparing the values of κ for the pure metals with those for the vanadium, iron, nickel, niobium and aluminium peaks in the intermetallic compound. XP spectra have been obtained from the alloys and these are also presented in the paper. As a result of this work it is concluded that the final state features of the spectra result from charge transfer between sp and sd valence bands. [ABSTRACT FROM AUTHOR]

Most atomic force microscopy (AFM) images of highly ordered pyrolytic graphite (HOPG) yield only every other atom with a lattice constant 2.46 Å. However, its full honeycomb structure, revealing all six carbon atoms of each hexagon, can only be obtained under certain conditions. A particular problem is the large meniscus force generated by a thin condensed layer of water when imaging under ambient conditions. We show that this can be reduced within an enclosure box by self-heating by the piezoelectric scanner and optical system. This was confirmed by obtaining a sequence of consecutive capillary force-distance loops. We have found all six carbon atoms in simultaneous imaging of trace and retrace scan direction although the contrast of the image is inverted according to the direction of the scan. The atomic corrugations at various contact forces were also examined. We observed giant corrugation amplitudes of graphite by AFM, which were as large as 5 Å. This anomalous effect, together with the inversion of contrast, was attributed to a combination of the elastic deformation of normal movement and the 'stick-slip' process from the harder lateral lattice of graphite. The honeycomb structures generated at high forces show clearly a warped structure with high (B site) and low (A site) carbon atoms. We have interpreted this as evidence of a surface diamond-like structure of HOPG induced by the probing tip. [ABSTRACT FROM AUTHOR]

This paper reports an investigation of a set of Ti-Al-based alloys by X-ray photoelectron spectroscopy. A new method for interpretation of the X-ray photoelectron spectrum allows a peak-shape parameter kappa to be defined, which links the intrinsic energy loss structure associated with a given line in the spectrum to atomic number. This parameter enables quantitative interpretation of steps in background intensity which are related to the number of final state configurations available to the photoexcited atom or ion. We have investigated the extent to which aluminium orbitals interact with the 3d transition metal structure of titanium by comparing the values of kappa for the pure metals with those for the titanium and aluminium peaks in the intermetallic compound. We conclude that this gives direct evidence for bond overlap in these alloys. The results on kappa were then compared with the Auger parameters which are also related to the relaxation process following the photoemission and therefore indicative of the charge transfer mechanism occurring between Al and Ti. In undertaking this study, which required the preparation of the intermetallic compounds for spectroscopic analysis, we have had to investigate various means of sample preparation. In particular we have developed a means by which the bulk metal structure can be exposed and transferred with minimal oxidation using an insitu milling device. [ABSTRACT FROM AUTHOR]