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The oxidation of Cu0.7Zn0.3(111) exposed to O2 at low pressure (7.0 × 10− 7 mbar) and higher pressure (1 mbar) both at 400 K has been investigated by photoelectron spectroscopy. The results evidenced a preferential oxidation of Zn at the surface in agreement with the literature and Zn segregation to the surface. Moreover, a systematic fitting procedure of high-resolution spectra enabled us to decompose the Zn 2p core-level peak into metallic and oxide components in order to follow the growth of the oxide. By combining these results with careful analysis of the Zn L3M45M45 Auger transition, we evidenced the formation of a discontinuous ZnO layer (3D ZnO islands) in both pressure conditions. Measurements of the O 1s peak for two photon energies using synchrotron radiation allowed us to identify interface and bulk components. Changes in the Zn 3d level and valence band during the initial steps of oxidation were also followed. We show that not only thermodynamics but also kinetic effects have to be considered to describe this complex oxidation process. The importance of the role played by the structural quality of the sample on the composition, growth kinetic and structure of the surface oxide layer is evidenced.

International audience; IGF tri-peptide adsorption on Au(110)-(1 × 2) under Ultra High Vacuum (UHV) conditions has been investigated using surface science techniques such as synchrotron based Angle Resolved X-ray Photoemission Spectroscopy (AR-PES or AR-XPS), Low Energy Electron Diffraction (LEED) and Scanning Tunnelling Microscopy (STM). The behaviour of IGF molecules has been revealed to be coverage dependent; at low coverage, there is formation of islands presenting a chiral self-organised molecular network with a (4 2, − 3 2) symmetry as shown by Low Energy Electron Diffraction (LEED) and Scanning Tunnelling Microscopy (STM) on the unaltered Au(110)-(1 × 2) reconstruction, suggesting significant intermolecular interactions. When the coverage is increased, the islands grow bigger, and one can observe the disappearance of the self-organised network, along with a remarkable destruction of the (1 × 2) substrate reconstruction, as shown by STM. The effect of IGF on the surface gold atoms has been further confirmed by angle-resolved photoemission measurements which suggest a modification of the electronic states with the (1 × 2) symmetry. The resulting molecular organisation, and overall the gold surface disorganisation, prove a strong surface-molecule interaction, which may be probably be explained by a covalent bonding.

The thermal stability of the Co/ β -Si 3 N 4 /Si(111) interface has been studied by high-resolution photoemission spectroscopy in a temperature range extending from room temperature to 650 °C. It is demonstrated the ability of a very thin crystalline buffer layer of silicon nitride to prevent the interfacial reaction between cobalt and silicon at room temperature. The behaviour of the interface at higher temperature shows the formation of cobalt silicides already at 300 °C. Moreover, the presence of new components in the decomposition of the photoemission spectra is discussed in the light of the existing literature.

We have studied the development of Schottky barrier heights during the initial formation of Pb,Bi/Si interfaces. In the sub-monolayer regime we have followed the band bending changes using synchrotron radiation core-level spectroscopy. In addition to a bulk-sensitive mode used to determine the band bending changes ( h ν = 108 eV), we recorded spectra in a surface-sensitive mode ( h ν = 130 eV) to better follow the surface peak changes associated with the different atomic arrangements. We compare the Schottky barrier heights obtained in the monolayer regime with recent measurements on in situ prepared Pb/Si(111) diodes.

The interaction between thermally grown SiO 2 surfaces and hexafluoroazomethane was studied by means of soft X-ray photoemission. No interactions were observed for dark exposures, however, large exposures with simultaneous UV irradiation produced a surface layer consisting largely of trifluoromethyl radicals, the primary photolysis products of hexafluoroazomethane. The evolution of the surface as a function of annealing temperature is also discussed.

The Fe/MoS2(0001) interface has been studied by high-resolution photoelectron spectroscopy using synchrotron radiation. The evolution of the Mo3d, Fe3p, and S2p core levels and of the valence band spectra (hν = 152 eV) during growth of vapor-deposited Fe films (1–10 A) indicates the production of sulfur vacancy defects in the MoS2(0001) surface. Several submonolayer sulfur surface species were formed, including sulfur adsorbed on the Fe surface and a reacted Fe-S species. The MoS2 surface was found to be covered for Fe film thicknesses of ~10 A. Annealing a 10 A film to 600 K resulted in the Fe film beginning to agglomerate, while annealing to 700–900 K resulted in further agglomeration of the Fe film. Annealing to 700–900 K also resulted in reformation of a partially disordered MoS2(0001)-1 × 1 surface with ~5% defects, as determined from photoelectron spectroscopy and low-energy electron diffraction. The overlayer film remained primarily in the form of metallic Fe, before and after annealing to temperatures ≲ 900 K, which was shown by the behavior of the Fe3p core level spectra and valence band spectra. Annealing the sample to 1200 K resulted in decomposition of the MoS2(0001) surface. The results indicate that the Fe/MoS2(0001) system exhibits some interfacial reactivity but does not form bulk Fe-S compounds. The results have been compared to those of previous studies of the Fe/MoS2(0001) system.

Sb adsorption on Si(111)2×1 surfaces in ultrahigh vacuum is studied by LEED, Auger and photoemission yield spectroscopies. The results are compared to the adsorption of lower valency elements In and Sn. A Volmer-Weber growth process with no ordered structure at low coverage is observed, different from the In and Sn cases. Ionization energy, band bending and surface state density show also somewhat different behaviour from those of In and Sn but consistent with the growth process and the formation of covalent bonds at the abrupt interface. High initial surface mobility of Sb has been observed.

The initial steps of ultrahigh vacuum deposition of Sn on clean cleaved Si(111) surfaces kept at room temperature were studied using low energy electron diffraction (LEED), Auger electron spectroscopy (AES) and photoemission yield spectroscopy (PYS). AES shows the formation of a seemingly uniform Sn overlayer up to 2 ML followed by the growth of metallic islands. During the adsorption stage, up to 2 ML, the initial 2 × 1 reconstructed surface is first replaced by a √3 × √3 R30° pattern in the 13ML range and then by a 1 × 1 diagram beyond 0.5 ML. Size and valency effects are observed in the very first interaction process up to 13ML. The electronic properties deduced from PYS reveal a monotonous decrease of the ionization energy up to 1 ML, a slight displacement of the Fermi level position towards the top of the valence band at that coverage, and the replacement of the double-structured dangling bond peak of Si(111) 2 × 1 by an apparently unique peak of Sn-induced dangling bond states. A remarkable situation occurs at 1 ML coverage with a very well ordered overlayer and the possible opening of a gap in the induced surface states.