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NaxC60 thin films with Na concentration 0 ⩽ x ⩽ 3 were investigated using angle-dependent photoelectron spectroscopy. For low doping we observed two distinct fulleride phases coexisting with regions of pristine C60. One of these fulleride phase is predominantly formed close to the surface and disappears after annealing and further addition of Na. At higher doping a phase with stoichiometry of x = 3 is formed.

The adsorption of a benzylic amide [2]catenane on a Au(1 1 1) single crystal has been studied using infrared reflection absorption spectroscopy. The evolution of the infrared spectra during catenane deposition at different temperatures of the gold substrate (300 and 90 K) has been compared. Evidence of the catenane deformation upon chemisorption have been found at 300 K only. At 90 K the catenane is weakly adsorbed without any deformation. (c) 2005 Elsevier B.V. All rights reserved.

Often metal nitrides posses unique properties for applications, such as great hardness, high melting points, chemical stability, novel electrical and magnetic properties. One route to the formation of metal nitride films is through ion irradiation of metal surfaces. In this report, the results of irradiation of Au(1 1 0) surfaces by nitrogen ions with kinetic energies of 0.5 and 2 keV are studied with high resolution X-ray photoemission spectroscopy. N1s core level spectra show clear evidence for the formation of a gold nitride at, or in close vicinity to, the surface––the first direct observation of nitride formation by this element. Subsurface molecular nitrogen is also observed, the relative concentration of which increases with irradiation energy. We suggest that the subsurface molecular nitrogen is most likely present in the form of trapped bubbles.

In this paper we report a photoelectron spectroscopy (XPS and UPS) study of films of a benzylic amide [2]catenane on Au(1 1 1). We show that this molecule retains its molecular integrity during sublimation and that it chemisorbs on the metal surface. Potassium intercalation modifies the electronic structure of the films. We have observed a reduction of its amide functions and a modification of the charge density of the aromatic rings. The creation of polaron-like states in the gap of the neutral catenane and a decrease in the catenane work function of 0.8 eV have been demonstrated.

The adsorption from the gas phase of a macrocyclic molecule composed of benzylic amide (–CONH–CH 2 –C 6 H 4 –) groups on Au(1 1 1) at 300 K has been studied using high resolution electron energy loss spectroscopy. The film order and vibrational properties were explored as a function of coverage, method of adlayer deposition and annealing. Beyond a critical coverage, a template effect strongly influences the macrocycle’s orientation with respect to the substrate. In the case of ordered films (domain size>80 A), the intensity of the out-of-plane C–H deformation mode relative to the in-plane C–H stretch indicates that an adsorption geometry with the plane of the phenyl rings largely parallel to the Au(1 1 1) surface is favoured in the submonolayer to monolayer coverage regime. Upon consideration of solid state X-ray diffraction data, this flat-lying molecular orientation, which is accompanied by chemisorption via the carbonyl function, must involve considerable distortion of the adsorbed macrocycle from its crystal structure.

Thiol-functionalised catenane and rotaxane thin films were investigated in order to understand the self-assembly of such complex molecules on Au(111). Adsorption from the liquid phase at 300 K leads to the formation of overlayers without long-range order, as evidenced by high-resolution electron energy-loss spectroscopy (HREELS). As expected for thiol adsorption, the sulfur 2p binding energies determined by X-ray photoelectron spectroscopy (XPS) are consistent with the formation of thiolate surface intermediates. The properties of these films are explored as a function of annealing. Changes in vibrational spectra such as the emergence of a AuO band and variations in core-level binding energies and intensities reveal molecular rearrangement due to partial desorption. In addition, based on coherent domain sizes estimated by the angular width of the elastic beam intensity, annealing promotes long-range order within the adlayers.

C60 was deposited on Ni(110), Pt(111) and Ag(111) and annealed at different temperatures. The structural properties of the overlayer were investigated by low-energy electron diffraction, the changes induced by adsorption on its electronic properties were studied by valence band and core-level photoemission spectroscopy and inverse photoemission spectroscopy. On all surfaces C60 is chemisorbed and a clear signature for charge transfer is found for C60 on Ni(110) and Ag(111). Decomposition of C60 takes place on Ni(110) and Pt(111) above 690 K and 560 K respectively. The decomposition is a kinetically limited reaction on both surfaces and on Pt(111) we find a very strongly chemisorbed precursor state for decomposition.

Adsorbate dynamics has received increasing interest over the last years, as it has been realized that the electron dynamics of the substrate can be profoundly affected by adsorbates due to couplings between vibrational and electronic states. Persson has developed a model where the scattering of the conduction electrons by the adsorbate results in a friction force between the adsorbate and the metallic substrate. The model predicts that the dipole-forbidden low-frequency adsorbate modes exhibit anti-absorption peaks, and that the broadband infrared (IR) reflectance change displays a characteristic frequency dependence in the anomalous skin-effect region, with an asymptotic limit in the mid-IR. The friction coefficient, which can be extracted from the asymptotic change of the reflectance, equals the inverse of the electronic contribution to the lifetime of the frustrated parallel translation. This model has been verified by recording simultaneously the direct-current (DC) resistance change, the broadband IR reflectance change and the IR features for various adsorbates on Cu(111) thin films epitaxially grown on TiO 2 (110) substrates. The friction coefficients obtained from the DC resistance change and from the IR reflectance change show good agreement. Coadsorption experiments reveal the marked dependence of the friction coefficient on the adsorbate-induced density of states at the Fermi level ( E F ). Using the Newns–Anderson model for chemisorption, the IR reflectance change of C 60 adsorbed on the following noble metal surfaces: Ag(111), Au(110) and Cu(100), indicates a high density of induced states at E F .

We have studied the coadsorption of oxygen with a (2 × 2) monolayer of K on graphite. At least three different adsorption phases for oxygen have been found. Different spectroscopic techniques have been used in order to identify the different oxygen species adsorbed on the surface. For low oxygen coverage, the molecules dissociate and form a K2O species. At higher oxygen doses, K2O2 and KO2 are present on the surface up to saturation coverage. XAS yields an O2 bond length of about 1.39 Å for the KO2 in this phase. This species is found to form an ionic complex which is weakly bound to the graphite.

We have studied the vibrational properties of thin C60 overlayers deposited on ideally H-terminated Si(111) surfaces, by multiple infrared reflection and high-resolution electron energy-loss spectroscopies. We find that the SiH interface remains intact upon C60 deposition: the SiH stretching mode frequency, initially at 2083.8 cm−1, shifts downward to 2062 cm−1, and broadens while keeping the same integrated intensity. Due to the symmetry-breaking effect at the surface on the adsorbed C60 molecules, a new IR band is observed at 1445 cm−1 which is mainly s-polarised. No evidence for chemical interaction between C60 and HSi(111)-(1 × 1) is found, pointing to van der Waals-type bonding. From the relative intensities of the dipole-active and -inactive modes in HREELS in the specular direction, and from the angular width of the scattered elastic peak, the growth of an ordered film is inferred.