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The
research activity focuses on the one hand on the study of the interaction
of atomic and molecular species with various types of surfaces and nanoparticles
and on the other hand on the growth of nanostructures and thin films.
The interaction of atoms and molecules with surfaces is a subject of
considerable interest in various applied fields such as heterogeneous catalysis,
plasma surface interactions, materials processing, astrophysics etc. In
recent years the objective of our work has been the understanding
of the physics of the basic phenomena involved in surface chemistry and surface
analysis by low energy ion scattering on surfaces (LEIS) and secondary ion
emission of interest in secondary ion mass spectroscopy (SIMS). In this
respect our work focused on electron transfer phenomena and inelastic
ion surface collisions leading to various processes of ionisation, excitation
of both projectile and solid and secondary electron or atom/ion emission.
Some experiments dealt with a study of energy losses phenomena or stopping
of low energy ions a subject of interest in e.g. doping by implantation
of semiconductors. On a more applied side we investigated low energy ion
induced production of lesions in DNA - a subject of interest in heavy ion
cancer therapy.
Recent projects focus on a study of interactions
with supported metal nanoparticles and ultrathin films with a focus on quantum size effects, as well as studies
of interactions with organic self assembled monolayers. An investigation
of growth of metal nanoparticles and ultrathin films on various inorganic
substrates and organic structures is being conducted, the latter in relation
with molecular electronics applications.
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Pages under reconstruction....sorry
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Electron
transfer processes
in gas-surface interactions.
Get a report
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The primary interest of this
work is the study of electron transfer processes, which are of much importance
in adsorption and reactions at surfaces. Usual surface science experiments
deal with the study of either the kinetics of adsorption/desorption (e.g.
in TPD) or with characterisation of adsorbates or products of reactions
in situ (e.g. in AES, UPS, XPS, LEED, STM etc..). The manner in which the
electronic states of a gas phase particle (atom or molecule) approaching
the surface are affected by the interaction with it and the time dependent
dynamics of the electron transfer process of this moving particle with the
solid is however usually not studied. Information on these fundamental aspects
of gas surface interactions, can be obtained using atom or ion beam scattering
in which the energy and charge state of particles are monitored. These
experiments allow one to obtain quantitative information in controlled
temporal and spatial conditions. This quantitative data can serve as a rigorous
test of theoretical predictions concerning the energy positions and widths
of atomic or molecular states near a surface and of the time dependent dynamics
of electron transfer. Our studies, have on the one hand focussed on negative
ion formation. This process presents a simple case of resonant electron
capture involving electrons near the Fermi level also involved in many reactions
at surfaces. We have also investigated positive ion neutralisation by Auger
type processes and quasi resonant electron transfer involving inner shell
electrons. Our work has involved clean metals, semiconductors, as well as
surfaces exposed to reactive gasses (oxygen, chlorine). These cases are
also of special interest in relation with oxidation and chloridation problems
and allow a progressive study of changes as one goes from metal to dielectric.
This gives an opprtunity to investigate adsorbate induced electronic effects
in promotion and poisoning of reactions at surfaces. This work was extended
to the case of some oxides like MgO and TiO2 surfaces. The most
recent developments involve study of nanostructured surfaces :
metal clusters grown on oxides and other substrates.
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| The objective of this work is
the understanding of the physics of the basic phenomena involved in low
energy ion scattering on surfaces (LEIS) and secondary ion emission of
interest in SIMS. Backscattering of ions relies on the survival of the
particles in the ionic state in the incoming and outgoing trajectories.
It has been realised that in some cases neutralised projectiles can be
reionised in the violent binary collision with surface atoms, leading to
much higher backscattering yield than expected. One of our main objectives
was to understand the basic mechanism involved in ionisation and excited
state production in the binary collisions and delineate similarities and
differences with gas phase atom-atom collisions involving similar projectile-target
pairs in view of establishing the extent of applicability of models used to
describe the gas phase case. An important issue is the effect of electron
exchange between the outgoing excited or ionised species and in particular
the effect of the chemical environement or surface composition on the outcome
of the scattering event. LEIS (ISS) is extensively used in surface science
to analyse the elemental composition of the surface layer. A thorough understanding
of all these phenomena is essential for the use of LEIS as a quantitative
analysis tool. Our work in past years has concentrated on the study of ionisation
and excited state production in collisions of inert gas and some reactive
(O, F, Cl) atom/ion collisions with various metal (Na, Mg, Al, Ag, Pd) and
semiconductor (Si) surfaces. A major effort is being made at understanding
the effect of the chemical environement :changes induced by the presence of
adsorbates from submonolayer chemisorption to dielectric layer formation |
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| Ion interaction
with biomolecules |
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| Biological effects of heavy ions
have attracted considerable attention in relation to space missions,
and medical applications. In medicine this interest stems from the specific
characteristics of the energy transfer of heavy ions in matter, where
it attains a maximum in a relatively small region at the end of the ion
trajectory resulting in the Bragg peak. Thus as opposed to X rays or neutrons
the main biological effects are found to be concentrated in a fairly well
defined region of space at the end of the particle’s track. Furthermore
it has been noted that some cells have exhibited greater sensitivity to
heavy ion irradiation than to X-rays. These aspects have motivated an increasing
use of heavy ions in cancer therapy. In relation with this work our group
has recently started a study of low keV heavy ion induced lesions in DNA. |
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Openings
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Post-doc positions are available through
the University & ministry of education. Current deadline is mid
march..
Interested candidates having an M.Sc equivalent can compete for Ph.D scholarships
along with local students.
Interested persons should contact us.
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Conferences
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