Oxo-centered carboxylate-bridged trinuclear complexes deposited on Au(111) by a mass-selective electrospray.

We developed an apparatus for nondestructive in vacuum deposition of mass-selected fragile Cr based metal trinuclear complexes, by modifying a commercial Mass Spectrometer containing an electrospray ionization source. Starting from a solution, this system creates a beam of ionized molecules which is then transferred into an evacuated region where the molecules can be mass selected before deposition. To verify the system efficiency, we deposited sub monolayers of oxo-centered carboxylate-bridged trinuclear complexes (Cr3 and Cr2Ni) on Au(111) surface. By XPS and STM we determined the deposited molecule stoichiometry and the surface coverage. The results show that this apparatus is works well for the in vacuum deposition of molecular nanomagnets and, thanks to its reduced dimensions, it is portable

Grafting molecular Cr7Ni rings on a gold surface

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Addressing the magnetic properties of sub-monolayers of single-molecule magnets by X-ray magnetic circular dichroism

We report on a comparative study of electronic and magnetic properties of Mn6 single-molecule magnets (SMMs) grafted on gold surface. Two derivatives with spin-ground states S ¼ 4 andhave been functionalized with 3-tp-CO2 (3-thiophene carboxylate, tpc) ligands and characterized thick films (TFs) as well as sub-monolayers (sMLs) by synchrotron based techniques. X-ray absorption spectroscopy at the Mn L2,3 edges shows the modification of the spectral lineshape in the sMLs respect to the TFs suggesting that the local symmetry at the Mn sites changes once the molecules deposited on gold surface. In spite of this, the expected MnIII oxidation state is preserved. X-ray magnetic circular dichroism (XMCD) spectra show that the total magnetic moment is only spin part because of the quenched orbital moment. Moreover, variable temperature and variable XMCD spectra reveal an effective decrease of the Mn spin moment for both derivatives

Magnetic interplay between two different lanthanides in a tris-phthalocyaninato complex: a viable synthetic route and detailed investigation in the bulk and on the surface

Future applications of molecular units in quantum information technologies require a fine control at the single molecule level. This includes the choice of each functional element, the intramolecular interaction and the robustness of molecules when dispersed on a substrate. Keeping these goals in mind, we designed and synthesized a heterometallic phthalocyaninato-complex including two different lanthanides in each moiety, namely [PcDyPcTbPc*] (Pc being phthalocyanines; and Pc* being 2,3,9,10,16,17,23,24- octahexyl-substituted phthalocyanines). Full magnetic characterization was performed down to the mK temperature range on bulk microcrystals by means of AC susceptibility, DC magnetization (including microSQUID) and specific heat measurements. A weak, yet sizeable, interaction between the two lanthanides is clearly detected by different techniques, altering the magnetic behavior of the single lanthanide as observed in the parent [LnPc2] complexes. Isolated [PcDyPcTbPc*] molecules dispersed on HOPG and the Au surface by liquid phase deposition are proven to maintain their main chemical and magnetic features by combined XPS, XAS and XMCD analysis and to lie with one Pc ligand flat to the surface. Opening of a small but sizable hysteresis loop at 1.8 K is directly observed on both Tb and Dy sites proving the retention of magnetization at the single molecule level

Antiferromagnetic coupling of TbPc2 molecules to ultrathin Ni and Co films

The magnetic and electronic properties of single-molecule magnets are studied by X-ray absorption spectroscopy and X-ray magnetic circular dichroism. We study the magnetic coupling of ultrathin Co and Ni films that are epitaxially grown onto a Cu(100) substrate, to an in situ deposited submonolayer of TbPc2 molecules. Because of the element specificity of the X-ray absorption spectroscopy we are able to individually determine the field dependence of the magnetization of the Tb ions and the Ni or Co film. On both substrates the TbPc2 moleculescouple antiferromagnetically to the ferromagnetic films, which is possibly due to a superexchange interaction via the phthalocyanine ligand that contacts the magnetic surface

Self-Assembled Monolayer of Cr7Ni Molecular Nanomagnets by Sublimation

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Auto-organisation de nanofils de Césium sur la surface (110) d'InAs et densité d'états d'un gaz d'électrons bidimensionnel à la surface de semiconducteurs

PARIS-BIUSJ-Thèses (751052125) / SudocCentre Technique Livre Ens. Sup. (774682301) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Atomic topography and self-assembly of one-dimensional potassium chains on the InAs(110) surface

One-dimensional (1D) potassium chains, obtained on the InAs(110) surface, are studied by scanning tunneling microscopy (STM). The (2xn) symmetry in the low energy electron diffraction pattern, becoming a c(2x6) structure at the completion of the first layer, is explained by the various spacing D between alkali chains in the [001] direction. The distribution of D as a function of the chain density suggests the presence of a repulsive interaction among the chains, which drives the self-assembling of the 1D structures. The origin of the interaction is discussed in comparison with the model proposed for the Cs/InAs(110) interface, showing the general validity of the model for this class of chain structures. The atomic structure of an isolated chain is investigated by high-resolution STM images, revealing the asymmetry in the charge density induced by K adatoms and a modification of the As-related charge density of the topmost substrate layer

Single particle and collective excitations of a two-dimensional electron gas at the Cs/InAs(110) Surface

The accumulation space-charge region at a semiconductor surface has been studied by a joint investigationof the plasmon excitation and the spectral density of the quasi-two-dimensional electron gas ~Q2DEG!. Theanalysis has been performed by means of high-resolution electron-energy-loss spectroscopy and highresolutionultraviolet photoemission, respectively. The accumulation layer was produced by depositing tinyamounts of Cs on the InAs~110! surface. By using a semiclassical dielectric model, the formation of theQ2DEG in the subsurface region was unambiguously proved by a satisfactory description of the coverage andprimary energy dependence of the collective excitations. The characteristic parameters of the Q2DEG, i.e.,charge density and width of the space-charge region, are determined. These results are in very good agreementwith the values deduced by self-consistently solving the Poisson and Schro¨dinger coupled equations, whichalso give the eigenvalue spectrum and spectral density as measured by photoemission

CuPc molecules adsorbed on Au(110)-(1 x 2): Growth morphology and evolution of valence band states

We present the growth morphology, the long-range ordering, and the evolution of the valence band electronic states of ultrathin films of copper phthalocyanine (CuPc) deposited on the Au(110)-(1 x 2) reconstructed surface, as a function of the organic molecule coverage. The low energy electron diffraction patterns present a (5 x 3) reconstruction from the early adsorption stages. High-resolution UV photoelectron spectroscopy data show the disappearance of the Au surface states related to the (1 x 2) reconstruction, and the presence of new electronic features related to the molecule-substrate interaction and to the CuPc molecular states. The CuPc highest occupied molecular orbital gradually emerges in the valence band, while the interface electronic states are quenched, upon increasing the coverage. (C) 2003 Published by Elsevier Science B.V