We have investigated the molecular orientation and electronic structures of nonplanar vanadyl phthalocyanine (VOPc) on the Si( 111)-(7 × 7) and Ag(111) surfaces by X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, and X-ray magnetic circular dichroism. The VOPc molecule adsorbs on Ag(111) in a parallel orientation to the surface with an oxygen-up configuration. A strong interaction between the N and C atoms of VOPc and surface Ag atoms is observed at the interface, although no marked change in the electronic state is observed for the V atom, similarly to the case for VOPc in a multilayer. On the other hand, the chemical interaction of the O atom of VOPc with the surface Si atoms favors the oxygen-down configuration. This chemical interaction causes the cleavage of the VO π bond and facilitates electron charge transfer to the V−N−C molecular orbitals. Such intermediation of the oxygen atom between the V atom and Si surface suppresses the direct interaction between them, and the spin magnetic moment of V remains the same as that of bulk VOPc molecules.

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Vanadium phthalocyanine (VPc) monolayers and multilayers were synthesized on Ag(111), and the electronic and magnetic states of an unachieved VPc with a divalent state of V were investigated. The VPc monolayer was fabricated by directly depositing the V atoms on a metal-free phthalocyanine (H 2 Pc) monolayer under ultrahigh-vacuum conditions. The VPc multilayer was synthesized by repeated VPc monolayer deposition and subsequent sample annealing at approximately 450 K. The N 1s X-ray photoelectron spectra (XPS) of these samples showed a remarkable reduction in the peak assigned to H-bonded N atoms, concomitant with the appearance of a new peak attributed to V-bonded N atoms close to the peak of iminic N. Additionally, the oxidation state of V estimated from the V 2p XPS peak position corresponded to 1.6 and 2.4 in the monolayer and multilayer samples, respectively. These results clearly imply that VPc monolayers and multilayers were successfully obtained. The main ground-state electronic configuration of the V center was found to be 2 E g by angle-dependent V L-edge X-ray absorption spectroscopy. Furthermore, X-ray magnetic circular dichroism (XMCD) measurements suggest that this 2 E g state was mixed with the 2 A 1g state by spin−orbit coupling in the ground state. Data revealed that VPc shows a paramagnetic state on the Ag surface and in an H 2 Pc film but an antiferromagnetic state in the multilayer. Partial electron charge transfer was also observed from the Ag surface to the V center at the VPc/Ag(111) interface, leading to a significant decrease in XMCD signals in the monolayer.

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Peierls-type instability and structural phase transition are shown to occur on the surface of a normal metal. An In overlayer on Cu(001) undergoes a reversible transition at approximately 350 K. Scanning tunneling microscopy of the low-temperature, reduced-symmetry phase indicates a strong periodic lattice distortion (PLD). Angle-resolved photoemission of the high-temperature phase reveals that the In-derived surface resonance constitutes a square-shaped, quasi-two-dimensional Fermi surface within the projected bulk Cu bands. The Fermi surface exhibits one-dimensional nesting upon the transition, which is in agreement with the PLD periodicity.

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The structural and magnetic properties of iron nitride thin films on a Cu͑001͒ surface were investigated by low-energy electron diffraction ͑LEED͒, scanning tunneling microscopy ͑STM͒, x-ray absorption spectroscopy, and x-ray magnetic circular dichroism ͑XMCD͒. In the STM and LEED observations of 1 and 2 monolayer ͑ML͒ films, the nitride films exhibit p4gm͑2 ϫ 2͒ reconstructed smooth surfaces without significant amounts of dislocations or islands. The stoichiometry of the 1 ML film was found to be Fe 2 N, while that of 2 ML was Fe 4 N, consisting of a topmost layer with the Fe 2 N composition and a second layer containing Fe atoms only. The XMCD measurements were performed for nitride films up to 4 ML. The angle-dependent XMCD spectra indicate that the films are ferromagnetic, with easy axes along the surface parallel direction. In addition, according to the results of the sum-rule analysis, strong magnetic anisotropy appears in the 1 ML film, where the orbital magnetic moment perpendicular to the surface is almost zero. The total magnetic moment, which is a combination of the spin and orbital magnetic moments, increases with the increase in film thickness up to 3 ML. The magnetic moment for more than 2 ML is ϳ2.1 B , which is nearly equal to that of bulk ␥Ј-Fe 4 N of 2.2 B .