Publications de Christian Felix

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The aim of this research project is to study the deposition of thermal atoms and small ionised clusters on well defined surfaces. For this, an installation has been developed at the Institut de Physique Expérimentale to produce mass selected ionic metal clusters using a sputtering source and to deposit them on well defined metallic surfaces. The chosen investigation method is Thermal Energy Atom Scattering (TEAS), a specularly reflected helium beam probes the surface and offers a very high sensitivity to th

The emerging field of spintronics explores the many possibilities offered by the prospect of using the spin of the electrons for fast, nanosized electronic devices. The effect of magnetization acting on a current is the essence of giant or tunnel magnetore ...

Thermal helium scattering is used to characterize the deposition of silver atoms on Pd (100) in the coverage range 0 to 10% of a monolayer, at surface temperature between 80 and 160 K, the latter being the threshold of adatom mobility. The attenuation of t ...

We have investigated the deposition at zero impact kinetic energy of the Ag atom and clusters (Ag/sub 7/,Ag/sub 19/) on the (100) and (111) surfaces of Pd by molecular dynamics simulations performed within the embedded atom-method scheme. Our results elucidate the role played by the adsorption energy in determining the final morphology of the cluster/substrate system when ideal nondestructive deposition conditions are implemented. While implantation of the atom is not observed, we find a finite probability

We report for the first time the absorption and fluorescence spectra of gold dimers in a neon matrix. The dimer absorption spectra show the A←X transition predicted from measurements in the gas phase and not observed so far in a matrix, as well as the so-c ...

We report absorption spectra for Ag7, Ag9, and Ag11 in an argon matrix grown at a temperature of 28 K and compare them with previous spectra of the same species measured in matrices of argon grown at lower temperatures as well as in neon matrices. We discu ...

Thermal energy helium scattering is used to measure the isothermal desorption of NO from Pt(111) in the temperature range 343-383 K. Taking into account the vibrational degrees of freedom to calculate the residence time of the molecules, the energy of adso ...

We present a new method to determine surface diffusion constants using specular reflected thermal helium scattering. The specular reflected helium intensity is recorded in real time as a function of surface coverage of the adsorbate and surface temperature ...

We present a new experiment to monitor ionized atom and mass selected cluster depositions in real time using specular reflected thermal helium scattering. Monomer Ag ions with an incident kinetic energy of E/sub dep/=20 eV and E/sub dep/=95 eV create surfa ...

Mass selected Ag/sub n/ clusters (n=1,7,19) from a secondary ion source have been deposited onto a Pt(111) substrate at low temperature. The surface and resulting cluster morphology have subsequently been characterized within the same UHV chamber by variable temperature STM as a function of cluster size, kinetic impact energy, and substrate temperature. The kinetic energy per cluster atom was found to be the decisive parameter for a controlled deposition. Noble gas buffer layers ( approximately=10 ML Ar), w

The room temperature stability of nanometer-sized silver clusters in silica matrices has been investigated by following the temporal evolution of their surface plasmon absorption. Ag clusters in SiO2 were prepared by either annealing silica samples doped w ...

Clusters of metal atoms at a fixed size can assume different structural arrangements, known as isomers, which may have nearly the same energy. Therefore at given experimental conditions distribution of these isomers can be present. While the size selection is a relatively common technique, the isomer selection is not; it is therefore more difficult to obtain information about a single isomer. We report here on isomer specific spectroscopy of Ag9 clusters together with ab initio calculations allowing to iden

We present a new experiment which is able to monitor mass-selected cluster depositions in red time using specular reflected thermal helium scattering. Ag/sub 7//sup +/ with an incident energy of 2.86 and of 13.6 eV/atom is deposited on Pd(100) at different ...

A new method to measure the diffusion of adsorbed molecules over macroscopic distance on single crystal surfaces is presented and demonstrated with the system CO on Pt(111). A controlled coverage of molecules, typically of the order of 0.01 monolayer, is d ...

Light emission during the collision of ions and cluster ions on a metal surface covered by rare gas matrices of variable thickness is reported. The light intensity as a function of distance from the metal surface follows the classical image dipole theory. ...

We use molecular dynamics to analyze the dependence on the impact angle of the distribution of defects originated by the deposition of a Ag/sub 19/ cluster on Pd(100) at initial kinetic energies 0.1, 2, 20 and 95 eV. For increasing energy the cluster undergoes a transition from a multi-layered adsorbed structure to a two-dimensional one. Implantation of Ag atoms and promotion of Pd substrate atoms is common to all energies and angles and, for a given initial total kinetic energy, it increases with decreasin

Spin-dependent transport in granular metallic nanostructures has been investigated by means of a thermoelectric measurement. Cobalt clusters of well-defined size ( = 15 and 600), embedded in copper and silver matrices, show magnetic field responses of u ...

We study the deposition and the very first steps of nucleation and growth of Ag on Pd(100) with thermal energy atom scattering. This technique is a very sensitive and nonperturbing probe to surface point defects, which permits an in situ and in-time monitoring of the deposition. The intention of this paper is to give a detailed description of the approach used in our work. The form of the specularly reflected helium signal as a function of coverage and surface temperature is compared to a theoretical curve,

Molecular dynamics simulations of the impact of Ag atoms at low energies (20 eV and 95 eV in the direction perpendicular to the surface) on Pd(100) are performed using embedded atom (EAM) potentials. The results are compared with recent helium scattering data relative to the impact of Ag/sub 1//sup +/ ions on a Pd(100) surface. Overall, the simulation results are in favorable agreement with the experiments and allow the outcome of the collision to be described in terms of a defect population consisting of t

Christian Felix

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Déposition d'atomes et d'agrégats d'argent triés en taille sur le palladium (100) : une étude par diffusion d'hélium

Enhanced magnetic field sensitivity of spin-dependent transport in cluster-assembled metallic nanostructures

Neighbor driven mobility of silver adatoms on Pd(100) measured by thermal helium scattering

Deposition of metallic clusters on a metallic surface at zero initial kinetic energy: evidence for implantation and site exchanges

Gold dimer in neon: an absorption and fluorescence study

Matrix effects on the optical response of silver nanoclusters

Chemisorption and macroscopic diffusion of NO on Pt(111)

Surface diffusion of Ag on Pd(100) measured with specular helium scattering

The fate of mass selected silver clusters deposited on Pd(100)

Hard and soft landing of mass selected Ag clusters on Pt(111)

Instability of Ag nanoparticles in SiO2 at ambient conditions

Isomer specific spectroscopy of metal clusters trapped in a matrix: Ag9

Mass-selected deposition of Ag 7 on Pd(100). Evidence for implantation and strong fragmentation

Measurement of macroscopic diffusion of CO on Pt(111) by thermal helium scattering

Collision-induced luminescence from the impact of ions and cluster ions on solid rare gases

Angle dependence and defect production in metal-on-metal cluster deposition on surfaces

Spin-dependent transport in cluster-assembled nanostructures: influence of cluster size and matrix material

Monodispersed metal clusters in solid matrices: A new experimental setup

Surface mobility of Ag on Pd(100) measured by specular helium scattering

Low energy impact of silver atoms on Pd(100): comparison between helium scattering and microscopic scale simulation results