BOOK OF ABSTRACTS - fis.unam.mxtrujillo/rem06/BookofAbstracts.pdfbook of abstracts first...
Transcript of BOOK OF ABSTRACTS - fis.unam.mxtrujillo/rem06/BookofAbstracts.pdfbook of abstracts first...
BOOK OF ABSTRACTS
FIRST INTERNATIONAL MEETING
ON RECENT DEVELOPMENTS IN
THE STUDY OF RADIATION
EFFECTS IN MATTER.
5th - 8th December, 2006
PLAYA DEL CARMEN QUINTANA ROO, MEXICO.
In recent years we have seen a rapidly increasing research activity towards the development
and understanding of novel synthetic materials with particular emphasis on their properties at
the nano-metric level. The quest for synthesis, analysis and modification of modern materials
has come from a variety of approaches amongst which are very promising perspectives using
radiation- laser, gammas, electrons, ions
The rapid pace at which international research is driving towards new classes of materials
makes it timely to establish forums of discussion to review both the state -of- the art and
future directions of radiation.
The Meeting will be held in the quiet and picturesque region of Playa del Carmen, Q. Roo,
on the Mexican Caribbean during December 5th – 8th, 2006, being the first of a series of
meetings aimed at gathering specialists in the field of radiation effects and related areas of
expertise. Our wish is that these inspiring surroundings will provide the framework for intense
scientific exchange in formal and informal discussions on recent advances in theoretical and
experimental aspects of the effects of radiation in matter.
A FESTSCHRIFT DEDICATED TO LEWIS T. CHADDERTON FOR HIS FIFTY YEARS IN
PHYSICS
The Organizing Committee also wishes this meeting to be a
Festschrift to recognize Lewis T. Chadderton of the Australian
National University, on the occasion of his 68th birthday and
his fifty years of scientific contributions in a wide number of
areas in physics - including those listed as topics at this
meeting. Lew Chadderton has been a decisive contributor to the knowledge inter alia of radiation effects and damage in
solids, crystal lattice defects, amorphous solids, fission
damage and fission tracks, electron channeling, geo- and
thermo-chronology, transmission electron microscopy and total
current spectroscopy.
His attitude towards new problems in physics has been always inspiring for many colleagues
and with a restless spirit he continues opening new arenas internationally in the area of
modern materials research. The breadth of topics in this meeting and their timely relevance
do indeed, in themselves, also provide laudable grounds for this special Festschrift
International Organizing Committee:
S. A. Cruz ( Physics Department, Universidad Autónoma Metropolitana, México)
L. C. Feldman (Dept. of Physics and Astronomy, Vanderbilt University, USA )
D. Fink ( Hahn-Meitner-Institut, Berlin, Germany)
A.P. Pathak (School of Physics, University of Hyderabad, India)
M. C. Ridgway (RSPhysSE, Australian National University, Australia)
Local Organizing Committee:
R. Cabrera-Trujillo (Centro de Ciencias Físicas, UNAM-Cuernavaca, México)
C. Cisneros (Centro de Ciencias Físicas, UNAM-Cuernavaca, México)
G. Espinosa ( Instituto de Física, UNAM, México)
E. Haro-Poniatowski ( Physics Department, Universidad Autónoma Metropolitana, México)
J. L. Hernández-Pozos (Physics Department, Universidad Autónoma Metropolitana, México)
A. I. Oliva (Centro de Investigacion y de Estudios Avanzados, IPN-Mérida, México) )
SPONSORS
The Organizing Committee wishes to thank the following institutions for their valuable support for
making this Meeting possible:
Universidad Autónoma Metropolitana
Universidad Nacional Autónoma de México Centro de Ciencias Físicas-Cuernavaca
Instituto de Ciencias Nucleares Instituto de Física
Instituto de Investigaciones en Materiales
Sociedad Mexicana de Física División de Física de Radiaciones
Centro de Investigación y de Estudios Avanzados, IPN Unidad Mérida
Secretaria de Educación Pública.
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FIRST INTERNATIONAL MEETING ON RECENT DEVELOPMENTS IN
THE STUDY OF RADIATION EFFECTS IN MATTER.
Playa del Carmen, Quintana Roo.
Dec 5th – 8th, 2006.
TUESDAY, DECEMBER 5TH, 2006.
8:30 – 9:00 WELCOME AND OPENING.
SESSION I.
CHAIRMAN: R. A. BARAGIOLA.
9:00-9:30 (TUE-01)
"SI IMPLANTATION IN SI, RADIATION DAMAGE AND POINT DEFECT
ENGINEERING"
WEI-KAN CHU UNIVERSITY OF HUSTON, USA
9:30-10:00 (TUE-02)
“VIBRATIONAL DYNAMICS AND BOND BREAKING OF H-SILICON”
LEONARD C FELDMAN VANDERBILT UNIVERSITY, USA
10:00-10:30 (TUE-03)
“ION BEAMS FOR NANO-SCALE SYNTHESIS”
DARYUSH ILA ALABAMA A & M UNIVERSITY, USA
---------- COFFEE ----------
SESSION II
CHAIRMAN: G. MARLETTA 10:45 -11:15
(TUE-04) “SCALING LAWS FOR GUIDING HIGHLY
CHARGED IONS THROUGH NANOCAPILLARIES IN INSULATING PET
POLYMERS”
NIKOLAUS STOLTERFOHT HAHN-MEITNER-INSTITUT BERLIN,
GERMANY
11:15 – 11 45 (TUE-05)
CREATION OF SUFACE NANOSTRUCTURES BY IRRADIATION WITH SLOW HIGLY
CHARGED IONS
FRIEDRICH AUMAYR TECHNICAL UNIVERSITY, WIEN,
AUSTRIA
11:45-12:15 (TUE-06)
SPATIAL AND ELECTRONIC CHARACTERIZATION OF NANO-FEATURES
CREATED BY HIGHLY CHARGED IONS
JOSHUA M POMEROY NATIONAL INSTITUTE OF STANDARDS
AND TECHNOLOGY GAITHERSBURG, USA
---------- COFFEE ----------
SESSION III
CHAIRMAN: J. AIZPURUA
12:30 – 13:00 (TUE-07)
SURFACE MODIFICATION OF PLOYMERS
GIOVANNI MARLETTA UNIVERSITA DEGLI STUDI DI CATANIA
ITALY
13:00 – 13:30 (TUE-08)
COLLECTIVE ELECTRONIC EXCITATIONS AT METAL SURFACES
VYACHESLAV M SILKIN DONOSTIA INTERNATIONAL PHYSICS
CENTRE, SAN SEBASTIAN, SPAIN
---------- LUNCH ----------
SESSION IV
CHAIRMAN: Z. L. MISKOVIC
16:15-16:45 (TUE-09)
NANOSCALE OPTICAL MICROSCOPY AND SPECTROSCOPY: NANOPARTICLE
PLASMONICS
JAVIER AIZPURUA DONOSTIA INTERNATIONAL PHYSICS
CENTRE, SAN SEBASTIAN, SPAIN
16:45 -17:15 (TUE-10)
IRRADIATION EFFECTS ON METAL NANOCRYSTALS
PATRICK KLUTH THE AUSTRALIAN NATIONAL
UNIVERSITY, CANBERRA, AUSTRALIA.
17:15 - 17:45 (TUE-11)
UV-LASER AND ELECTRON IRRADIATION EFFECTS ON SILVER NANOSTRUCTURES
E HARO-PONIATOWSKI UNIVERSIDAD AUTÓNOMA
METROPOLITANA, MEXICO CITY, MEXICO
19:30 HRS, RECEPTION COCKTAIL
WEDNESDAY, DECEMBER 6TH, 2006.
SESSION I
CHAIRMAN: A. DUNLOP
8:30-9:00 (WED-01)
SHINY QUARTZ: CATHODOLUMINESCENCE AFTER ION-IRRADIATION
KLAUS PETER LIEB UNIVERSITÄT GÖTTINGEN,
GERMANY
9:00-9:30 (WED-02)
EFFECT OF ION IRRADIATION AND POST-ANNEALING ATMOSPHERE ON THE
PHOTOLUMINESCENCE INDUCED BY SI NANOCRYSTALS PRODUCED BY HOT
IMPLANTATION IN SIO2
MONI BEHAR UNIVERSIDADE FEDERALE RIO GRANDE SUL, PORTO ALEGRE,
BRASIL
9:30-10:00 (WED-03)
STRUCTURAL CHARACTERISTICS OF NANOCRYSTALLINE ZRO2 POWDER SOL-
GEL DERIVED FOR LUMINESCENCE APPLICATIONS
TEODORO RIVERA INSTITUTO POLITÉCNICO NACIONAL,
MEXICO CITY, MEXICO
10:00-10:30 (WED-04)
DOSE RATES EFFECTS ON THE THERMOLUMINESCENT PROPERTIES OF
MWCVD DIAMOND FILM
MARCELINO BARBOZA-FLORES UNIVERSIDAD DE SONORA,
SONORA, MEXICO
---------- COFFEE ----------
SESSION II
CHAIRMAN: R. TENNE
10:45 -11:15
(WED-05) ION BEAM SYNTHESIS OF QUANTUM DOTS
IN INSULATORS HARRY BERNAS
UNIVERSITÉ PARIS SUD PARIS, FRANCE
11:15 – 11:45
(WED-06) NONLINEAR OPTICAL SUSCEPTIBILITIES IN
THIN METAL-DIELECTRIC MULTILAYERS GROWN BY PULSED LASER DEPOSITION
LUIS HERNANDEZ-POZOS UNIVERSIDAD AUTÓNOMA
METROPOLITANA, MEXICO CITY, MEXICO
11:45-12:15
(WED-07) COLOR CENTERS ENVISIONED AS
CONFINED QUANTUM SYSTEMS: THE CASE OF F, F´AND F2
+ CENTERS
JOSE LUIS MARIN UNIVERSIDAD DE SONORA,
SONORA, MEXICO
---------- COFFEE ----------
SESSION III
CHAIRMAN: F. AUMAYR
12:30 – 13:00 (WED-08)
CHIRIAL THIN FILMS: FABRICATION AND PROPERTIES
EVA SCHUBERT UNIVERSITY OF NEBRASKA-LINCOLN,
USA
13:00 – 13:30 (WED-09)
THERMALIZED NON-EQUILIBRATED MATTER: FROM MICROSCOPIC SYSTEMS
TO NANOSTRUCTURES
SERGEY Y KUN UAEM-CUERNAVACA, MEXICO &
AUSTRALIAN NATIONAL UNVERSITY, AUSTRALIA
---------- LUNCH ----------
SESSION IV
CHAIRMAN: R. P. WEBB
16:15-16:45 (WED-10)
INORGANIC NANOTUBES AND FULLERENE-LIKE STRUCTURES (IF): A PROGRESS
REPORT
RESHEF TENNE WEIZMANN INSTITUTE
ISRAEL
16:45-17:15 (WED-11)
NANO-ISLANDS AND NANOWIRES PRODUCED VIA ION IMPLANTATION
FERNANDO ZAWISLAK UNIVERSIDADE FEDERALE RIO
GRANDE SUL, PORTO ALEGRE, BRASIL
17:15 – 17:45 (WED-12)
PROSPECTS OF ION CHANNELING THROUGH CARBON NANOTUBES
ZORAN MISKOVIC UNIVERSITY OF WATERLOO
ONTARIO, CANADA
THURSDAY, DECEMBER 7TH, 2006.
SESSION I
CHAIRMAN: W. K. CHU
8:30 – 9:00 (THU-01)
STRUCTURAL MODIFICATIONS INDUCED IN VARIOUS TYPES OF TARGETS IRRADIATED
WITH ENERGETIC CLUSTER IONS
ANNIE DUNLOP ECOLE POLYTECHNIQUE
FRANCE
9:00 – 9:30 (THU-02)
THE COMPUTER SIMULATION OF ENERGETIC CLUSTERS SOLID
INTERACTIONS
ROGER WEBB UNIVERSITY OF SURREY,
UNITED KINGDOM
9:30 – 10:00 (THU-03)
FRAGMENTATION OF FULLERENES FRANK HARRIS UNIVERSITY OF FLORIDA
USA
10:00 – 10:30 (THU-04)
CLASSICAL-TRAJECTORY MONTE CARLO SIMULATIONS OF THE ELECTRONIC
STOPPING CROSS-SECTION FOR PROTON, ANTIPROTON AND HYDROGEN
PROJECTILES IMPINGING ON HYDROGEN ATOMS
MARIO JAKAS UNIVERSIDAD DE LA LAGUNA
TENERIFE, SPAIN
---------- COFFEE ----------
SESSION II
CHAIRMAN: T. WANG
10:45 -11:15 (THU-05)
THEORETICAL INVESTIGATION OF FRAGMENTATION AND ENERGY
DEPOSITION CROSS-SECTIONS FOR SWIFT ION IMPACT ON SMALL, MODEL
BIOMOLECULES
JOHN SABIN UNIVERSITY OF FLORIDA
USA
11:15 – 11 45 (THU-06)
FRAGMENTATION OF POLYATOMIC MOLECULES IN COLLISIONS WITH ATOMIC
IONS
YNGVE ÖHRN UNIVERSITY OF FLORIDA
USA
AFTERNOON:
VISIT TO TULUM & TANKA
EVENING ( 20:00:HRS )
METTING BANQUET & FESTSCHRIFT ADDRESS.
FRIDAY, DECEMBER 8TH, 2006.
SESSION I
CHAIRMAN: P. KLUTH
9:00-9:30 (FRI-01)
FAST IONS TRACKS IN DIELECTRIC: FROM THE GALACTIC TO THE ATOMIC SCALE
RAUL BARAGIOLA UNIVERSITY OF VIRGINIA
USA.
9:30-10:00 (FRI-02)
SWIFT HEAVY IONS IRRADIATION AS A TOOL FOR CREATING NOVEL
NANOELECTRONIC STRUCTURES
DIETMAR FINK HAHN-MEITNER.INSTITUTE, BERLIN
GERMANY
10:00-10:30 (FRI-03)
MEASUREMENT OF GEOLOGICAL TIME AND TEMPERATURE BASED ON PARTICLE
TRACKS IN NATURAL MINERALS
RAYMOND JOCKHEERE TECHNISCHE UNIVERSITÄT
BERGAKADEMIE FREIBERG, GERMANY
---------- COFFEE ----------
SESSION II
CHAIRMAN: N. STOLTERFOHT
10:45 -11:15 (FRI-04)
TEMPERATURE DISTRIBUTION IN A SWIFT ION INDUCED SPIKE: AN EXPERIMENTAL
APPROACH
G SZENES EOTVOS UNIVERSITY BUDAPEST, HUNGARY
11:15 – 11 45 (FRI-05)
AFM STUDY OF SOME RADIATION EFFECTS ON MATERIALS
C. VAZQUEZ-LOPEZ CENTRO DE INVESTIGACIÓN Y
ESTUDIOS AVANZADOS (INSTITUTO POLITÉCNICO NACIONAL), MÉXICO CITY, MEXICO.
---------- COFFEE ----------
SESSION III
CHAIRMAN: Y. ÖHRN
12:30 – 13:00 (FRI-06)
ELECTRONIC STRUCTURE OF TRANSITION METAL FLUORIDES AND OXIDES
DETERMINED BY RESONANT X-RAY ABSORPTION AND X-RAY EMISSION
SPECTROSCOPIES
JOSÉ JIMÉNEZ-MIER INSTITUTO DE CIENCIAS NUCLEARES,
UNAM, MEXICO CITY, MEXICO
13:00 – 13:30 (FRI-07)
EXPERIMENTAL STUDY OF HIGHLY CHARGED IONS IMPACT ON SOLID
SURFACES
TIESHAN WANG LANZHOU UNIVERSITY,
P.R. CHINA
13:00 HRS. MEETING CLOSING REMARKS
TUE- 01 "SI IMPLANTATION IN SI, RADIATION DAMAGE AND POINT DEFECT ENGINEERING"
Wei-Kan Chu
Department of Physics, and Texas Center for Superconductivity and Advanced Materials University of Houston, Houston, TX 77004-5002, USA
High energy Si self-implantation in Si is a topic with great potential for applications, because
collision, and collision cascade will always produce interstitial and vacancy pairs without any
chemical effect. Due to the forward momentum transfer during collision, the distribution of
interstitials is always deeper then that of the vacancies. After annulations of vacancies and
interstitials in the near vicinity, a vacancy enriched surface region and an interstitial enriched
region near the projected range are developed. The separation of the two regions could be
microns, if MeV implantation were used.
We have developed a point defect engineering (PDE) approach using high-energy ion
bombardments producing vacancies near the surface region of Si where ultra shallow devices
are made. Excessive interstitials near the end of projected range are buried deep inside the
substrate away from the device region. With ever shrinking feature size, it requires a continued
reduction of diffusion lengths of dopants in Si. Normally, one uses very low energy ion
implantation and ultra fast annealing to reduce the dopant diffusion in Si. However, boron ion
implantation undergoes an "anomalous" fast diffusion upon any annealing, which is detrimental
to the ultra-shallow junction formation. Boron diffusion in Silicon is mediated via a interstitial
process. Manipulation of point defects can retard boron diffusion near surface region and
enhance the activation of boron in Si. This non-equilibrium method tailors the diffusivity (not just
diffusion) of boron in silicon and enables the formation of p-type junction as shallow as 10 to 20
nm.
TUE-02 “VIBRATIONAL DYNAMICS AND BOND BREAKING OF H-SILICON”
S.V.S. Nageswara Rao1, S.K. Dixit2,3, G. Lüpke4, N.H. Tolk1 and L.C. Feldman1,2,3
1Department of Physics and Astronomy, 2Interdisciplinary Materials Science Program, 3Vanderbilt Institute of Nano-scale Science and Engineering, Vanderbilt University, Nashville, TN 37235, USA
4Department of Applied Science, College of William and Mary, Williamsburg, VA 23187, USA
Light impurities implanted into or adsorbed onto crystalline solids give rise to localized vibrational
modes, directly observed in infrared absorption. The spectra reveal detailed configurations of the
impurity-substrate bonding configuration. Using intense, time-resolved, infra-red radiation we
have carried out direct measurements of the lifetime of a vibrationally excited state of hydrogen
implanted into silicon. The lifetime, for hydrogen in silicon, is shown to vary over two orders of
magnitude, (10psec-500psec), depending on the defect configuration of hydrogen within the
silicon lattice. We have also measured the stability of these different configurations under ion
bombardment. Surprisingly the stability is a sensitive to relatively subtle differences in structure.
The lifetime and stability is critical in describing a range of solid state phenomena: 1) longevity of
silicon (CMOS) transistors, 2) intensity limitations in solid-state lasers, 3) the non-linear
absorption in IR desorbed (bio) materials, and 4) the interaction of defects with implanted ions.
TUE-03 “ION BEAMS FOR NANO-SCALE SYNTHESIS”*
Daryush ILA
Center for Irradiation Materials,
Department of Physics, Alabama A & M University, 4900 Meridian Street
Normal, AL 35762-1447, USA
We have used ion beam to form nanolayers of nanoscale materials within various host materials.
One system consists of nano-layers (Quantum Well) of Nano-Crystals (Quantum Dots) to
generate optical filters (OF) with variable window as well as to produce highly efficient
thermoelectric generators (TEG). To generate highly efficient TEG, we had to enhance the
electrically conductive, the thermal insulation and increase the Seebeck Coefficient. Some of the
materials selected we had to dope the nano-layers by keV implantation of selected species
followed by MeV bombardment. In some selected materials systems we formed nano-layered
structures by co-deposition followed by MeV bombardment to form nanocrystals. The interaction
of QWs as well as the interaction of QDs results in generation of phonon mini-bands reducing
the thermal conductivity, while increasing the electrical conductivity. We will present our finding
on the dependence of the thermal conductivity (using 3ω technique), electrical conductivity
(using Hall effects), and the Seebeck coefficient as a function of ion bombardment fluence for
several selected materials systems produced in house.
* Support in part by NSF, NASA, and AAMU Research Institute.
TUE-04. “SCALING LAWS FOR GUIDING HIGHLY CHARGED IONS THROUGH NANOCAPILLARIES
IN INSULATING PET POLYMERS”
N. Stolterfoht, R. Hellhammer, D. Fink, and J. Bundesmann.
Hahn-Meitner-Institut Berlin, Glienickerstr. 100, D-14109 Berlin, Germany
Experiments in our laboratory have shown that highly charged ions are guided through
nanocapillaries in insulating PET polymers without changing their initial charge state [1-3]. The
ion guiding was found to be significant when the capillary axis was tilted by an angle up to 20°.
This finding was interpreted as a deflection of the ions near the entrance region of a capillary,
where a significant charge patch is produced in a self-organizing manner [1,4]. The patch is
characterized by the potential U which, in turn, governs the guiding power of the capillaries.
In our previous work [1-3] the capillaries in PET were manufactured by etching ion tracks
produced with fast ions of a few hundred MeV. We used high-Z xenon ions for which the effects
of Rutherford scattering are considerable, resulting in a noticeable angular spread of the
capillary inclination. Recently, we fabricated capillaries with 250 MeV krypton ions for which the
angular spread of the ion tracks was significantly reduced to ~0.4°. With the parallel capillaries
new features can be observed in comparison with our previous measurements.
In this work, we present experiments with the parallel PET capillaries of 200 nm diameter
and 10 µ length. We performed measurements using projectiles with different energies and
charge states, i. e., Ne7+ and Ne9+ at 3-10 keV, Ar13+ at 7-13 keV, and Xe25+ at 25-40 keV. Using
scaling procedures, the results can be summarized to fit one universal curve, which support
previous model assumptions [2,3]. In addition, the data show that the fraction of transmitted ions
remains nearly constant when the current of the incident ions varies by more than an order of
magnitude. This finding indicates that the potential U is nearly constant and is primarily a
quantity characteristic for the geometry and material of the capillary entrance region only.
[1] N. Stolterfoht et al., Phys. Rev. Lett. 88 (2002) 133201 [2] N. Stolterfoht et al., Vacuum 73 (2004) 31 [3] R. Hellhammer et al., Nucl. Instr. Methods B 232 (2005) 235 [4] K. Schiessl, et al. NIM B 232 (2005) 228 and Phys. Rev. A 72 (2005) 62902
TUE-05 “CREATION OF SURFACE NANOSTRUCTURES BY IRRADIATION WITH SLOW HIGHLY
CHARGED IONS”
A.S. El-Said1, W. Meissl1, M.C. Simon1, J.R. Crespo López-Urrutia2, C. Lemell3,
I.C. Gebeshuber1, HP. Winter1, J. Ullrich2, C. Trautmann4, M. Toulemonde5, and F. Aumayr1*
1 Institut für Allgemeine Physik, TU Wien, 1040 Vienna, Austria 2 Max-Planck Institut für Kernphysik, 69029 Heidelberg, Germany 3 Institut für Theoretische Physik, TU Wien, 1040 Vienna, Austria
4 Gesellschaft für Schwerionenforschung (GSI) 64291 Darmstadt, Germany 5 Centre Interdisciplinaire de Recherches Ions Laser (CIRIL), 14070 Caen Cedex 5, France
Upon interaction of highly charged ions (HCI) with solid surfaces a large amount of potential energy is deposited within a very short time (a few femtoseconds) within a nanometer size volume close to the surface [1]. This unique ability of HCI offers a promising way for surface nanostructuring of different materials [2,3]. We present first results on the generation of surface nanostructures by HCI on CaF2 (111) cleaved surfaces.
The CaF2 (111) single crystals were irradiated with slow (E/m < 5 keV/amu) HCI from the Heidelberg-EBIT (electron beam ion trap). As for other ionic fluoride single crystals, ion-induced surface structures in CaF2 are known to be stable in atmosphere at room temperature [4,5]. After irradiation, the crystals were investigated by scanning force microscopy in ambient air. Fig. 1 shows typical AFM topographic images of CaF2(111) after irradiation with 4.4 keV/amu Xe46+ ions. Hillock-like nanostructures protruding from the surface are observed. The AFM images were evaluated with respect to hillock height and width distributions. The number of hillocks per unit area is in good agreement with the applied ion fluence. By using slow HCI in different charge states we find clear evidence that the hillock formation requires a critical potential energy of 14 keV. With increasing potential energy, both the basal diameter and the height of the hillocks become larger. Estimations of the energy density deposited on the atoms indicate that the threshold is linked to a solid-liquid phase transition.
Figure 1: AFM topographic image of a CaF2 single crystal surface after irradiation with 4.4 keV/amu Xe46+ ions. This work has been supported by Austrian Science Foundation FWF and was carried out within Association EURATOM-ÖAW. The experiments were performed at the distributed LEIF-Infrastructure at MPI Heidelberg Germany, supported by Transnational Access granted by the European Project HPRI-CT-2005-026015. [1] F. Aumayr, HP. Winter, Phil. Trans. R. Soc. Lond. A 362 (2004) 77. [2] Y. Baba, et al., Surf. Sci. 599 (2005) 248. [3] F. Aumayr and HP. Winter, e-J. Surf. Sci. Nano-techn. 1 (2003) 171 [4] A.S. El-Said, et al. Nucl. Instr. Meth. B 218, 492 (2004). [5] C. Muller, et al., Nucl. Instr. and Meth. B 191, 246 (2002). * presenting author: e-mail [email protected]
TUE-06 “SPATIAL AND ELECTRONIC CHARACTERIZATION OF NANO-FEATURES CREATED BY HIGHLY CHARGED IONS”
J.M. Pomeroy1, H. Grube1, A.C. Perrella2
1National Institute of Standards and Technology (NIST), Gaithersburg, MD, USA 2US Army Research Laboratory, Adelphi, MD, USA
Atomic scale imaging of a diverse range of surfaces irradiated with highly charged ions (HCIs)
have revealed nanometer size features whose synthesis and structure are poorly understood.
HCIs can carry a significant amount of neutralization energy (51 keV per ion for Xe 44+, used in
most of the results presented) in addition to their kinetic energy. This potential energy amplifies
the violence of the HCI's interaction with the surface by generating massive secondary electron
and sputtered atom yields, etc. This talk will present STM images of surface features observed
on metals with emphasis on the Au(111) surface and the features of the physical structure.
Further, results will be presented from electronic measurements of multilayer systems that
include tunnel junctions that have been irradiated with HCIs. The total conductance of the
junction is observed to increase linearly with the HCI dose, but the rate of increase is
substantially less than a single conduction quantum per ion per spin. Results of electronic
measurements that provide insight into the electronic properties of the HCI modified tunnel
barrier will be emphasized. Cumulative results from spatial and electronic measurements will be
presented and their implications discussed.
TUE-07 “SURFACE MODIFICATIONS OF POLYMERS BY ION BEAMS FOR BIOLOGICAL
APPLICATIONS”
Giovanni Marletta
Laboratory for Molecular Surfaces and Nanotechnology (LAMSUN) – Dipartimento di Scienze Chimiche – Università degli Studi di Catania
Viale A.Doria 6 – 95125 Catania (Italy) Web page: www.unict.it/lamsun/
The need for having a breakthrough in fields relevant to health and safety-like
biocompatible materials, bioelectronics devices, biosensors etc., is the driving force to develop
new performant methods for the controlled modification of surfaces of materials. In particular,
polymers represent the material of choice for most of the desired biological applications, due to
their highly specific properties, including the dynamical behaviour in presence of external stimuli
and the biomimetic mechanical properties.
A welt of competing methods is currently used to modify variable materials thicknesses at
the surfaces of inorganic or polymeric materials. Roughly, we can distinguish three basic areas,
respectively consisting in “wet chemistry” approach to attach specific functional group onto
materials surfaces, deposition of thin and ultrathin films at the materials surfaces and radiation-
based methods to intrinsically modify the chemical and physical structure of the materials of
interest.
Among the irradiation-based techniques, ion beams have been shown to have a number
of intrinsic advantages with respect to other methods, while having an intrinsic complexity. In the
present talk it will be shown that the physics and chemistry of ion beam-polymer interaction
involve different hierarchical levels of surface modification, going from the modification of the
polymer backbone, to the modification of functional groups density at the surfaces and their
distribution at the nanometric scale, the formation of new phases, the formation of nanofeatures
on the surfaces, the modification of the electrical properties, etc...
In recent years it has been shown that ion beams are extremely effective in inducing
controlled modification of the biological response at surfaces, involving not only the modification
of adsorption/adhesion processes of aminoacids, oligopeptides, DNA strands and proteins, but
also affecting in a peculiar way the biochemical mechanism of the cells-surface interaction. In
particular, it can be shown that the biological response of cellular systems critically depends
upon few critical features of the irradiated surfaces as, for instance, the relative weight of the
various components of the surface free energy of the modified polymers and the electrical
properties of the surfaces. Examples will be given on the modified interaction processes of
simple aminoacids as L-lysine, of oligopeptide sequences, of proteins as Human Serum Albumin
and Fibronectin and cellular systems including fibroblasts, osteoblasts and perycites with
irradiated surfaces. Finally, the possibility of achieving the direct patterning of biological systems
by ion beams will be demonstrated.
TUE-08 “COLLECTIVE ELECTRONIC EXCITATIONS AT METAL SURFACES”
V.M.Silkin1, E.V.Chulkov1,2, P.M.Echenique1,2
1Donostia International Physics Center (DIPC), 20018 San Sebastián, Basque Country, Spain. 2Departamento de Física de Materiales, Facultad de Ciencias Químicas, UPV/EHU and Centro Mixto
CSIC-UPV/EHU, 20080 San Sebastián, Basque Country, Spain
The termination of a bulk metal by a surface gives rise to surface-localized collective excitations of the electrons, the so-called surface plasmons [1] During several decades of intensive investigations remarkable progress has been achieved in the understanding of these excitations at metal surfaces [2]. These excitations play an important role in such areas as surface dynamics, surface plasmon (SP) microscopy, SP resonance technology as well as in photonic applications. Despite the progress in the study of these excitations, the quantitative level of agreement between experiment and theory in the description of energy dispersion and lifetime of SP has not been achieved until recently [3] mainly because of difficulties in the incorporation of band structure effect in the evaluation of SP properties [2].
In this contribution we report on the results of parameter-free ab initio calculations of the SP energy and linewidth for some metal surfaces. We investigate the relative impact of band structure and dynamical exchange-correlations on the SP. For comparison we also calculate the SP characteristics by using the jellium model. The results obtained show that even for such nearly-free electron metals good agreement with the experimental SP energy and linewidth in a large range of 2D momenta is found only if both the bulk and surface band structure on the same footing together with dynamical exchange-correlations are taken into account. In particular, three dimensional band structure effects are crucial for the description of the SP linewidth, whereas jellium model fails to reproduce the experimental linewidth for both small and large momenta
Whereas SPs show an optical dispersion, i.e. they always have a finite energy, in general a few eV, they can neither be excited thermally nor do they contribute to the decay of low-energy electrons or phonons.
Recently it was demonstrated theoretically that a new type of collective electron mode on metal surfaces is possible [4]. In contrast to the usual surface plasmon, it has an acoustic dispersion, i.e., has a acoustic linear dispersion at low values of parallel momentum transfer. This low-energy excitation mode was very recently detected on the (0001) surface of beryllium using electron energy loss spectroscopy [5]. Here we report on our detailed ab initio calculations showing that this novel mode is caused by the coexistence at the metal surface of a partially occupied quasi two-dimensional one-particle surface-state band with the underlying three-dimensional bulk electron continuum. The possibility to excite this collective electron mode can lead to new situations at metal surfaces, where many phenomena, such as electron, phonon, and adsorbate dynamics can be significantly influenced by opening of this new low-energy decay channel.
References
[1] R.H.Ritchie, Phys. Rev. 106, 874 (1957). [2] P.J.Feibelman, Prog. Surf. Sci. 12, 287 (1982); M.Rocca, Surf. Sci. Rep. 22, 1 (1995); A.Liebsch, Electronic Excitations at Metal Surfaces (Plenum Press, New York, 1997). [3] V.M.Silkin et al., Phys. Rev. Lett. 93, 176801 (2004). [4] V.M.Silkin et al., Europhys. Lett. 66, 260 (2004). [5] B.Diaconescu et al., submitted
TUE-09 “NANOSCALE OPTICAL MICROSCOPY AND SPECTROSCOPY: NANOPARTICLE
PLASMONICS”
Javier Aizpurua
Donostia International Physics Center, Paseo Manuel Lardizabal 4, Donostia-San Sebastián 20018, Spain
Collective oscillations of valence electrons in metallic materials, also known as plasmons,
determine the optical response of these materials. The energy and strength of these surface
oscillations are a function of the shape, size and coupling of the nanoparticles. With the use of
the boundary element method (BEM), we solve Maxwell's equations to calculate light scattering
and surface modes in nanostructures that are commonly used as hosts and/or samples in
different field-enhanced scanning probe microscopies and spectroscopies. The light scattering
and near field distribution of particles such as nanorings [1], nanorods [2], nanospheres, or
nanodisks are calculated and interpreted in terms of the plasmon modes supported by the
nanosystems. The results are related for each case with different spectroscopic experiments
and connected with the capabilities of these structures to host biomolecules and perform the
corresponding spectroscopy. Special emphasis is placed on the near-touching limit for pairs of
spherical particles to understand recent experiments in the literature. We also study the
electromagnetic response of gold particles when they are coupled to a metallic tip in scattering-
type near field optical microscopy (s-SNOM) [3,4]. We present the analysis of the backscattered
signal and the near field distribution obtained with different tips for gold particles. We obtain
different optical and infrared contrast for different particle size and substrate material. We
associate these differences in contrast to the properties of the tip-particle-substrate coupling.
The understanding of the coupling of the modes in these systems and the consequences for the
local field enhancement are crucial to engineer and design plasmonic devices for detection and
effective optical response.
[1] J. Aizpurua et al. Phys. Rev. Lett. 90, 057401 (2003).
[2] J. Aizpurua et al. Phys. Rev. B. 71, 235420 (2005).
[3] R. Hillenbrand et al. App. Phys. Lett. 83, 368 (2003).
[4] A. Cvitkovic et al. Phys. Rev. Lett. 97, 060801 (2006).
TUE-10 “IRRADIATION EFFECTS ON METALLIC NANOCRYSTALS”
P. Kluth1, B. Johannessen1, R. Giulian1, D. J. Sprouster1, C. S. Schnohr1, L. L. Araujo1,
A. P. Byrne2, G.J. Foran3, D. J. Cookson4, and M. C. Ridgway1
1Department of Electronic Materials Engineering, The Australian National University, Canberra ACT 0200 2 Department of Nuclear Physics/Faculty of Physics, Australian National University, Canberra, Australia
3Australian Nuclear Science and Technology Organization, Menai, Australia 4Advanced Photon Source, Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, Illinois 60439,
USA
Ion irradiation of metallic nanocrystals (NCs) embedded in SiO2 can lead to a number of different
effects depending on the irradiation conditions. At energies where nuclear stopping is
predominant, structural disorder/amorphisation followed by inverse Ostwald ripening/dissolution
due to ion beam mixing were observed with increasing irradiation fluence. At very high irradiation
energies (swift heavy ion irradiation), where the energy loss is nearly entirely due to electronic
stopping, a shape transformation of the NCs from spherical shapes to elongated rods is
apparent. We will present an overview of our results on these effects on a number of different
materials systems including Au, Cu, and Pt NCs. Structural and morphological characterization
has been performed by transmission electron microscopy (TEM) in combination with advanced
synchrotron based analytical techniques, in particular x-ray absorption spectroscopy (XAS) and
small-angle x-ray scattering. We present evidence for ion irradiation induced amorphisation of
elemental metal NCs attributed to their initially higher energy structural state as compared to
bulk material and possibly preferential nucleation of the amorphous phase at the NC/SiO2
interface. In contrast, bulk elemental metals cannot be rendered amorphous by ion irradiation. At
higher irradiation fluences, ion beam mixing is dominant, resulting in a significant alteration of the
NC size distribution consistent with inverse Ostwald ripening and dispersion of a significant
fraction of the metal atoms in the SiO2. The observed shape transformation in the NCs during
swift heavy ion irradiation is governed by the formation of molten tracks in the SiO2 as the ion
passes through the material. It is clearly characterized as a cumulative process and necessitates
a minimum NC size to occur. Potential mechanisms governing the shape change will be
discussed.
TUE-11 “UV-LASER AND ELECTRON IRRADIATION EFFECTS ON SILVER NANOSTRUCTURES”
E. Haro-Poniatowski1*, N. Batina2, M. C. Acosta-García2, M. A. Pohl-Alfaro3, P. Castillo-Ocampo4, C. Ricolleau5, E. Fort5
1) Departamento de Física, 2) Departamento de Química, 3) Departamento de Ingeniería Eléctrica, 4) Laboratorio de Microscopía Electrónica
Universidad Autónoma Metropolitana Iztapalapa, Av. San Rafael Atlixco No. 186 Col. Vicentina, C. P. 09340 México D. F.
5) Laboratoire Matériaux et Phénomènes Quantiques and Laboratoire de Physique du Solide, UMR 7162, CNRS/Université Paris 7 - Denis Diderot, ESPCI, 10 rue Vauquelin, 75005 Paris Cedex, France
The induced changes on silver nanostructures are investigated using a special experimental
procedure consisting in depositing by pulsed laser deposition and subsequently inducing the
changes directly on transmission electron microscopy grids. The nanostructures have different
morphologies, from isolated spherical-like particles to quasi percolated films. The changes can
be induced either by UV laser in air or by electron beam irradiation in situ in the transmission
electron microscope. The induced modifications were investigated using transmission electron
microscopy and atomic force microscopy. Striking effects are observed on quasi percolated films
which are transformed in assemblies of silver nanoparticles. Upon further irradiation the
nanoparticles grow in size. Furthermore the arrangement of these silver nanoparticles
assemblies can be controlled by irradiating the grids through masks, razor edges (1) and
gratings, taking advantage of their respective diffractive properties. A detailed account and
analysis of the observed effects is given in the present work.
(1) Patterning of nanostructured thin films by structured light illumination E. Haro-Poniatowski, J. P. Lacharme, E. Fort, C. Ricolleau Appl. Phys. Lett. 87, 143103, 2005
*email address: [email protected]
WED-01 “SHINY QUARTZ: CATHODOLUMINESCENCE AFTER ION-IRRADIATION”
K. P. Lieb, P. K. Sahoo1, S. Gasiorek, and J. Keinonen2.
II. Physikalisches Institut, Universität Göttingen, Friedrich-Hund-Platz 1, D-37077 Göttingen, Germany
Ion implantation is a promising route for doping quartz with luminescent impurity atoms and
growing photoactive nanoparticles of them. The present work focuses on cathodoluminescence
(CL) and epitaxy during or after Na, Rb, Cs, Ge, and Ba ion implantation [1-6] as well as Rb/Ge
double implan-tation [7] in crystalline α-quartz, under the conditions of dynamic, chemical or
laser-induced epitaxy [8]. In addition to the known intrinsic CL bands, which have been
associated with specific defects in the silica matrix, very intense blue or violet bands were found.
They are correlated with the implanted ion species and follow their thermal behaviour. The
quantum efficiency and possible origins of the blue/violet CL emission for various ions and
processing treatments will be discussed [9,10]. Technologically, the case of double Rb/Ge
implantation [8] appears to be very promising since it offers a high CL output and full chemical
epitaxy.
1 Present address: Instituut voor Kern- en Stralingsfysica, KU Leuven, B-3001 Heverlee, Belgium 2 Permanent address: Accelerator Laboratory, University of Helsinki, FI-00014 Helsinki, Finland [1] S. Dhar, et al., Appl. Phys. Lett. 85 (2004) 1341.
J. Appl. Phys. 97 (2004) 014910 [2] P. K. Sahoo, et al., J. Appl. Phys. 96 (2004) 1392 [3] S. Gąsiorek, et al., J. Appl. Phys. 95 (2004) 4705;
Appl. Phys. B84 (2006) 357 [4] J. Keinonen, et al., Appl. Phys. Lett 88 (2006) 261102 [5] S. Gąsiorek, et al., J. Non-Cryst. Solids 352 (2006) 2986 [6] P. K. Sahoo, et al., Appl. Surf. Sci. 252 (2006) 4477 [7] F. Roccaforte, W. Bolse, K. P. Lieb, J. Appl. Phys. 89 (2001) 3611;
K. P. Lieb, in Encyclopedia of Nanoscience and Nanotechnology, vol. 3, H. S. Nalwa, Ed. (2004) 233-251
[8] P. K. Sahoo, et al., Appl. Phys. Lett. 87 (2005) 021105 [9] P. K. Sahoo, S. Gasiorek, S. Dhar, K. P Lieb,
Nucl. Instr. Meth. B249 (2006) 109 [10] K. P. Lieb and J. Keinonen, Contemp. Phys., in press
WED-02 “EFFECT OF ION IRRADIATION AND POST-ANNEALING ATMOSPHERE ON THE
PHOTOLUMINESCENCE INDUCED BY SI NANOCRYSTALS PRODUCED BY HOT IMPLANTATION IN
SIO2”
U.S.Siasa,b, M.Behara, H.Boudinova, E.C.Moreirac
aInstituto de Física, UFRGS, Caixa Postal 15051, 91501-970 Porto Alegre, RS, Brasil
bCentro Federal de Educação Tecnológica de Pelotas, 96015-360, Pelotas, RS, Brasil cInstituto de Física Universidade Federal Unipampa, Bage, RS, Brasil
In the present contribution the photoluminescence (PL) behavior of Si nanocrystals (NCs)
produced by 600 °C Si implantation into SiO2 matrix has been investigated after ion irradiation
and subsequent annealing in Ar or N2 atmosphere.
With this aim we have implanted Si+ ions at 170 keV at a fluence of 1.0 × 1017 Si/cm2.
After annealing at 1100 oC we have observed two PL bands; one centered at 780 and the other
with much higher intensity at 1000 nm. Afterwards we irradiated the samples with 2 MeV Si+ ions
at a fluence of 2.0 × 1013 Si/cm2. Consequently, we have observed a complete PL quenching
due to the Si NCs amorphization as shown by transmission electron microscopy measurements
(TEM). Furthermore we performed a pos-annealing at 900 oC in N2 or Ar atmosphere. As a
consequence the PL signal was recovered, but with strong PL shape modifications.
When the 4 hours annealing in N2 atmosphere was performed the band centered at 1000
nm recovered its original PL intensity, while the shorter wavelength band recovered only 50% of
its original PL value. Additional annealing up to 7.5 hours induces on the low energy band (1000
nm) an increase of its intensity by a factor of two, while the high energy one (780 nm) does not
show any change. Only after 15 h of annealing this PL band recovered the original intensity,
while the one centered at 1000 nm increased 5 times its original PL value.
On the other hand, the 900 oC annealing performed in an Ar atmosphere has induced a
different behavior. The long wavelength band recovered its PL intensity after 4 hours annealing
time, while the one corresponding to the low energy band remains at half of its original value.
After 7.5 hours of annealing the long wavelength band duplicate its intensity, while the short
wavelength band remains at the same value. Further annealing performed for 15 hours have not
induced further changes in the whole PL spectrum.
In the case of Ar, the above described effects can be tentatively explained on the basis of
simple thermal relaxation process produced in the Si/SiO2 interface. On the other hand,
annealing in N2 induces a process of thermal relaxation that is compounded by exchange of
nitrogen with the oxide network.
WED 03 “ STRUCTURAL CHARACTERISTICS OF NANOCRISTALLINE ZRO2 POWDER SOL-
GEL DERIVED FOR LUMINESCENCE APPLICATIONS“
T. Rivera1*, L. Olvera2, J. Azorín2, M. Barrera2, A.M. Soto2, R. Sosa2, J.A.I Díaz1 and C. Furetta1
1Centro de Investigación en Ciencia Aplicada y TecnologíaAvanzada-Legaria, IPN, 11500, México D.F.
México 2Universidad autónoma Metropolitana-Iztapalapa, 11500 México D.F., México,.
Nanocrystalline ceramics are attracting and increasing interest nowadays. Sol gel is a low
temperature method using chemical precursors that produces ceramics and glasses with better
purity and homogeneity than high temperature conventional processes. This new method of
preparation of nanophosphors was recently strongly developed for high efficiency luminescent
devices needs applying still smaller and smaller particles of luminescent materials. There it is
important to retain a high degree of crystallization of ZrO2 and correlated possible concentration
of defects in nanosized particles of nanophosphors. The XRD patterns show that the calcined
material has a strongly monoclinic structure. Thermoluminescent glow curve of ZrO2 show a
glow curve with two peaks. Photoluminescence (PL) spectra of ZrO2 also were obtained.
* Corresponding author: [email protected]
WED 04 “DOSE RATE EFFECTS ON THE THERMOLUMINESCENT PROPERTIES OF MWCVD DIAMOND FILM”
S. Gastelum†, E. Cruz-Zaragoza‡, V. Chernov†, R. Melendez†, M. Pederoza-Montero†, and
M. BARBOZA-FLORES*†
†Centro de Investigación en Física, Universidad de Sonora, A. P. 5-088, 83190 Hermosillo Sonora, México
‡Instituto de Ciencias Nucleares UNAM, A. P. 70-543, 04510 México D. F., México
Synthetic CVD diamond, being non toxic and tissue equivalent, has been proposed as a ionizing
radiation passive dosimeter with relevant applications in radiotherapy and clinical dosimetry. In
the present work, the thermoluminescence (TL) properties of microwave assisted chemical
vapor deposition (MWCVD) diamond, 6 µm thick film grown on (100) silicon substrates, were
studied after room temperature γ-irradiation for 2.4, 5.94, 13.1, 20.67, 43.4 and 81.11 Gy/min
dose rates in the range of 0.05 – 10 kGy. At fixed irradiation dose, the TL glow curve shape
changes and the TL efficiency increases as the dose rate increases. However, a TL efficiency
decrease is observed at a 90 Gy dose for dose rate greater than 43.4 Gy/min. A temperature
shift of the maximum intensity of about 10 K is observed for higher dose rate. As the dose
increases, at any dose rate, the peak temperature at the maximum intensity of the TL glow curve
shifted a few degrees K toward the lower temperature side. A computer deconvolution program
allowed us indistinctly to identify the existence of first order kinetics TL peaks at low doses, and
two first order kinetics TL glow peaks at dose higher than 300 Gy. Supralinear and sublinear
dose behavior were found for low and higher dose; respectively, with a significant dependence
on the dose rate. Due to the dose rate dependence of the TL properties of the CVD diamond
sample, it should be taken into consideration for dosimetric applications involving synthetic
diamond.
*Corresponding author: Tel.: +52 662 259 2156; fax: +52 662 212 6649.
E-mail: [email protected]
WED-05 “ION BEAM SYNTHESIS OF QUANTUM DOTS IN INSULATORS” *
H. Bernas
CSNSM-CNRS, Université Paris Sud, 91405 Orsay Campus, France Fabricating metallic or semiconducting nanocrystal arrays in insulators is of interest for their
optical (e.g., plasmonics) or magnetic (e.g., high-density recording media) properties. Ion beam
synthesis has certainly played a role in this area, but basic questions remain. What are the
microscopic mechanisms that control nanocluster growth, determine their density and size
distributions? Can we control these processes in order to tailor the properties? Confronting
irradiation experiments with very different deposited energy densities (photons versus ions), we
demonstrate major analogies with the photographic process and emphasize the role of
chemistry in nanocluster nucleation and growth processes in glasses. Examples are given for
Ag and PbS nanocluster synthesis. In the former, redox modification by irradiation-induced
electron and hole formation affects nucleation. In the latter, charge state differences affect
diffusion and growth. We devised a strategy to produce PbS quantum dots emitting intense
photoluminescence at 1.5 microns. Finally, we show that the log-normal shape of cluster size
distributions signals a loss of information as to the formation process, hence loss of property
control.
* This work was carried out with R. Espiau de Lamaestre (CSNSM-CNRS and Corning Research Center,
Avon, France)
WED-06 “NON-LINEAR OPTICAL SUSCEPTIBILITIES IN THIN METAL-DIELECTRIC MULTILAYERS
GROWN BY PULSED LASER DEPOSITION “
J L Hernández-Pozos.
Laboratorio de Óptica Cuántica, Departamento de Física Universidad Autónoma Metropolitana-Iztapalapa.
Av. San Rafael Atlixco No. 186 Col. Vicentina, C. P. 09340 México D. F MEXICO.
Thin multilayers with metal-dielectric structure have proven to posses higher optical nonlinarities
compared with purely dielectric materials. We present multilayer structures made of
TiO2/Cu/TiO2 grown by pulsed laser ablation. TiO2 layers are growth under an oxygen
atmosphere; otherwise the film stoichiometry is not preserved and shows oxygen deficiency. Cu
layers are grown under pressures of 10—4 mbar.
Because of the periodic modulation in the refractive index and the metallic component,
dielectric/metal/dielectric ( D/M/D ) structures might present high optical nonlinearities that may
be tuned, In preliminary measurements we have observed optical nonlinearities at two different
timescales.
WED-07 “COLOR CENTERS ENVISIONED AS CONFINED QUANTUM SYSTEMS: THE CASE OF F,
F' AND +2F CENTERS*”
J.L. Marín, R. Aceves, R. A. Rosas, S. Grijalva**
Departamento de Investigación en Física, Universidad de Sonora, Apdo. Postal 5-088, 83190 Hermosillo,
Son. and Departamento de Física, Universidad de Sonora, Apdo. Postal 1626 83000, Hermosillo, Son. México.
The connection between what nowadays are known as confined quantum systems, i.e., systems
whose dimensions are of the order of a few nanometers and some defects in alkali halides
crystals, known as color centers, is explored in this work within a semicontinuum model, that is,
this peculiar quantum system of nanometric dimensions, is assumed as a cavity of a given
shape in which one or two electrons are trapped, the surrounding material is considered as a
continuum polarizable medium. In this context, for the sake of solving, approximately or exactly,
Schrödinger's equation, the potential felt by the trapped electron(s) can be simply modeled.
Once the potential is specified, the solution of the equation can be found and some physical
magnitudes of interest can be obtained and compared with their respective experimental
measurements. In doing so, we show that this approach constitutes an interesting alternative in
the study of some properties of these kind of defects.
*One of the authors (JLM) dedicate this work to the memory of Professor Carlos Ruiz-Mejía his former
teacher and very close friend and colleague.
**Graduated student at MS program of Departamento de Investigación en Física, Universidad de Sonora.
WED-08 “CHIRAL THIN FILMS: FABRICATION AND PROPERTIES”
Eva Schubert Department of Electrical Engineering, University of Nebraska-Lincoln, U.S.A.
Nanostructures with complex geometries promise a high application potential for instance as optical and photonic materials, magnetic storage devices or sensors. Glancing angle deposition (GLAD) in combination with a computer controlled substrate rotation is a sophisticated method to customize manifold nanostructure varieties. In our work the particle flux is provided by ion beam sputtering and reaches the substrate under an extremely oblique angle-of-incidence (typically 85 deg respective to the normal). This deposition configuration supports a competitive growth mechanism, yielding to highly porous sculptured thin films (STF) consisting of slanted amorphous silicon needles with a diameter from 20 nm to 50 nm. By applying an appropriate substrate rotation during growth, the nanostructure geometry can be tailored. Chevrons and square screws (Fig. 2b and Fig. 2c) are created with a symmetric stepwise substrate rotation of 180 deg and 90 deg, respectively. The fabrication of circular screws (Fig. 2a) and vertical posts is realised by a constant substrate rotation, and the nanostructure geometry depends on the ratio from deposition rate to substrate rotation speed.
Figure 1 Principle of GLAD
Figure 2. Chirial Nanostructures from Si grown by GLAD, (a)
screws, (b) chevrons, (c) sq screws
Sculptured thin film growth on unseeded substrates is determined by self-ordering phenomena yielding to periodic arrangements of ensembles from nanostructures across the substrate, and Periodic sculptured thin films can be also achieved by using prepatterend substrate templates.
Figure 3. STF growth on substrate templates.
This talk will give a survey about the basic experimentally determined structural and physical (mainly optical) properties obtained on sculptured thin films with different chiral geometries (posts, screws, and chevrons). Additionally, examples for the technical use of chiral solid state materials are demonstrated and discussed.
100
a b c
100 nm
surface diffusion
substrate
particle flux
structure shade
+ substrate rotation
WED-09 “THERMALIZED NON-EQUILIBRATED MATTER: FROM MICROSCOPIC SYSTEMS TO
NANOSTRUCTURES”
L. Benet1, M. Bienert1, J. Flores1, S.Yu. Kun2,3, T.H. Seligman1
1Centro de Ciencias FÍsicas, UNAM, Cuernavaca, Morelos, Mexico 2 Facultad de Ciencias, UAEM, Cuernavaca, Morelos, Mexico
3 Nonlinear Physics Center and Department of Theoretical Physics, RSPhysSE, ANU, Canberra, Australia
Thermalization in highly excited quantum many-body systems does not necessarily mean a
complete memory loss of the way the system was formed. One of the manifestations of such a
thermalized nonequilibrated matter is revealed by (i) a strong asymmetry around 900 c.m. of
evaporating yields in nuclear and photonuclear reactions [1,2], and (ii) highly stable rotational
wave packets in heavy-ion collisions [3,4,5] and bimolecular chemical reactions [5,6]. The effect
is described in terms of anomalously slow phase relaxation in highly excited quantum many-
body systems. This effect may pave the way for quantum computing, with a large number of
qubits n ~ 100 - 1000, far beyond the quantum chaos boarder [1,2]. We shall propose and
discuss experimental tests of a formation of the thermalized non-equilibrated matter in
nanostructures, e.g. in atomic clusters and many-electron quantum dots.
[1] J. Flores, S.Yu. Kun, T.H. Seligman, Phys. Rev. E 72, 017201 (2005); quant-ph/0502050.
[2] M. Bienert, J. Flores, S.Yu. Kun, T.H. Seligman, Symmetry, Integrability and Geometry:
Methods and Applications (SIGMA) 2, paper 027 (2006); quant-ph/0602224; and references therein.
[3] S.Yu. Kun, B.A. Robson, A.V. Vagov, Phys. Rev. Lett. 83, 504 (1999).
[4] S.Yu. Kun, L. Benet, L.T. Chadderton, W. Greiner, F. Haas, Phys. Rev. C 67, 011604(R)
(2003); quant-ph/0205036.
[5] L. Benet, S.Yu. Kun, Wang Qi, Phys. Rev. C 73, 064602 (2006); quant-ph/0503046.
[6] L. Benet, L.T. Chadderton, S.Yu. Kun, O.K. Vorov, Wang Qi, \Quantum-classical transition
for an analog of double-slit experiment in complex collisions", to be submitted.
WED-10 “INORGANIC NANOTUBES AND FULLERENE-LIKE STRUCTURES (IF): A PROGRESS
REPORT”
R. Tenne
Department of Materials and Interfaces, Weizmann Institute, Rehovot 76100, Israel
In this presentation a progress report, focused mainly on the results obtained in our lab will be
presented. While the synthesis and study of IF materials from layered metal dichalcogenides, like
WS2 and MoS2 remain a major challenge, some progress with the synthesis of IF structures from
other compounds, like metal oxides and metal halides have been realized. The synthesis of some
new IF materials, like Cs2O, NiBr2 and others will be described.
The study of the mechanical properties of individual WS2 nanotubes will be discussed in some
detail. The agreement between theory and experiment suggests that the nanotubes are of high
crystalline order and their mechanical properties are predictable.
The study of MoS2 nanooctahedra 3-6 nm in size, which can be considered to be the true
inorganic fullerenes of these and many other layered structures, will be discussed. The
agreement between the calculated and experimentally observed structures indicate that the
nanooctahedra are indeed the stable structures in this size range, beyond this size the quasi-
spherical nested MoS2 structures become stable.
Some new potential applications for these and related materials will be discussed in the fields
of friction reduction of various objects; catalysis; rechargeable batteries, coatings, etc. will be
discussed as well. To capitalize on these opportunities, a production facility for up to 100 kg/day
of IF-WS2 is about to start operating soon.
WED-11 “NANO-ISLANDS AND NANOWIRES PRODUCED VIA ION IMPLANTATION”
F. Kremer1, D.L. Baptista1, P.F.P. Fichtner2 and F.C. Zawislak1
1Instituto de Física, UFRGS, Porto Alegre, Brasil
2Departamento de Metalurgia, Escola de Engenharia, UFRGS, Porto Alegre, Brasil
In the first part of this contribution we report results on the formation of Sn and Pb nanoislands at
the SiO2/Si interface. Ions of Sn and Pb are implanted in the SiO2 film, and post-implantation
thermal treatments at the temperature of 1100°C produce a dense array of nanoislands at the
SiO2/Si interface. Our results show that the implantation parameters, the annealing temperature,
atmosphere and time can be used to control the size, the shape, the composition and probably
the uniformity of the created discreet system of nanoislands. The formed nanoclusters and
nanoislands are investigated using a combination of Rutherford backscattering spectroscopy,
transmission electron microscopy (TEM) and high resolution TEM.
The second part reports the formation of self-assembled Ni nanoparticles by ion implantation
and their application as catalytic seeds for the growth of vertically aligned carbon nanotube
(CNT) arrays. By implanting Ni ions at 100-130 keV at doses of 5×1015 and 1×1016 Ni.cm−2
respectively, Ni nanoparticles were formed inside a 450 nm SiO2 film on Si substrates.
Post-annealing treatments at 700, 900 and 1100°C in a N2 atmosphere were performed,
resulting in the formation of self-assembled Ni nanoparticles with mean diameter of 4, 10 and
40 nm respectively. Diluted HF solution was used to etch the SiO2 layer until the nanoparticles
were exposed to the surface. Finally, vertically aligned carbon nanotubes arrays were grown by
PECVD using C2H2 and NH3 gases under controlled conditions. The samples were characterized
via scanning electron microscopy (SEM), high-resolution TEM and atomic force microscopy
(AFM). The spatial distribution as well the diameter and crystallinity of the Ni nanoparticles are
analyzed for each annealing temperature. The CNTs arrays are analyzed in terms of their
density as well as the diameter of the tubes.
WED-12 “PROSPECTS OF ION CHANNELING THROUGH CARBON NANOTUBES”
Zoran L. Miskovic
Department of Applied Mathematics, University of Waterloo,
Waterloo, Ontario, Canada N2L 3G1
Investigation into the properties of carbon nanotubes (CNTs) has been growing at a relentless
rate over the past fifteen years owing to a boundless range of prospective applications of these
unique carbon molecules in nanotechnology. According to some authors, CNTs are nowadays
considered the hottest topic in physics (http://physicsweb.org/articles/news/10/5/4/1). Important
part of this research endeavor includes interactions with energetic particle beams for the purpose
of both analyzing and modifying the atomic structure and electronic properties of CNTs.
In particular, the past decade has witnessed a spur of theoretical activity in modeling and
simulations of ion channeling through either individual CNTs or bundles, or ropes of CNTs in a
wide range of energies, going from ultra-relativistic down to hyper-thermal. It is expected that the
unique mechanical and electronic properties of CNTs, combined with their high aspect ratio and
the nanometer wide channels can offer potentially great advantages for ion channeling in
comparison to crystal channels, such as wider acceptance angles, lower required minimum ion
energies, 3D control of beam deflection, and weaker dechanneling. However, ion channeling
through CNTs has not yet been realized experimentally, and question remains as to whether
such process is feasible for the purpose of anticipated applications.
In addition to reviewing the status of theoretical modeling of ion channeling through CNTs, a
critical assessment of the conclusions coming from theory will be presented and discussed in the
context of planning possible experiments on this process.
THU-01 „STRUCTURAL MODIFICATIONS INDUCED IN VARIOUS TYPES OF TARGETS IRRADIATED
WITH ENERGETIC CLUSTER IONS”
Annie Dunlop
Laboratoire des Solides Irradiés, Ecole Polytechnique, CEA-DRECAM-CNRS,91128 Plaiseau Cedex,
France.
The talk will concentrate on the structural modifications induced around the path of energetic
projectiles. In the high energy range, energy deposition by the projectile occurs mainly via
electronic excitation and ionisation of target atoms. We will show that this energy deposited in
the electronic system can efficiently be converted into atomic movements leading to structural
modifications in all types of targets.
The use of energetic heavy cluster ions allows to increase the density of energy deposited
in electronic processes by orders of magnitude compared to that resulting from GeV heavy ion
slowing down. This allows to create latent tracks in many materials that were considered as
resistant to electronic excitations and to induce a wide variety of phase changes. The talk will
give an overview of such effects.
THU-02 “THE COMPUTER SIMULATION OF ENERGETIC CLUSTER SOLID INTERACTIONS”
Roger Webb.
Surrey Ion Beam Centre, Advanced Technology Institute, University of Surrey, GU12 5LY, UK
There is a growing interest in the application of accelerated clusters and molecular species as
both implantation and analysis tools. Large clusters have been in use for the deposition of films
and the soft landing of bio materials for a number of years now.
More recently the use of fullerene as a sputtering ion in SIMS has lead to a revitalisation of
academic interest in the technique – as witnessed by the recent SIMS XV conference – and a
host of new potential applications in the identification of molecular species and molecular
imaging. The use of even larger clusters employed with electro-spraying techniques has also
been developed as a new analysis technique (DESI) created. The application of giant gas
clusters combining a component of “active” ingredient in a large inert cluster is making a large
impact in the semiconductor world to provide a new method (“infusion doping”) for shallow
junction formation in silicon and for providing a tool for surface smoothing.
It is clear that there are an increasing number of applications of energetic clusters in the
materials world. In this paper computer simulation techniques are employed to investigate why
clusters are of such interest. In particular the role of cluster impacts on molecular desorption will
be investigated and the effects of variable energy deposition for large gas clusters in infusion
doping will be highlighted.
THU-03 “FRAGMENTATION OF FULLERENES”
R. T. Chancey, J. Oddershede, J. R. Sabin, and Frank E. Harris
University or Florida, Niels Bohr Institute, and University of Utah
We have performed classical molecular dynamics simulations of the fragmentation collisions of
neutral fullerenes (C_24, C_60, C_100, and C_240) with a hard wall. We wrote a highly efficient
special-purpose molecular dynamics code to facilitate the study of tens of thousands of collision
trajectories with a broad range of initial orientations and energies. These simulations indicate
the importance of studying a sufficient ensemble of collision events, and enable statistical
analyses of the fragment size distributions. The results are compared with surface-impact
experimental studies of fullerenes and with the fragmentation patterns observed in systems
ranging from meteorites to atomic nuclei.
THU-04 “CLASSICAL-TRAJECTORY MONTE-CARLO CALCULATIONS OF THE ELECTRONIC
STOPPING CROSS-SECTION FOR PROTON, ANTIPROTON AND HYDROGEN PROJECTILES
IMPINGING ON HYDROGEN ATOMS”
Mario M. Jakas1
Departamento de Física Fundamental y Experimental, Electrónica y Sistemas. Universidad de La Laguna. 38205 La Laguna, Tenerife.
Spain
Although Classical Mechanics cannot account for the electronic structure of atoms and
molecules, the present study shows that the stopping cross-section can be calculated, to a high
degree of accuracy, by assuming that electrons are classical particles. In fact, using such an
approach, the electronic stopping cross-section (Se) for protons, anti-protons and hydrogen
projectiles bombarding hydrogen atoms has been calculated and the results are found to
compare remarkably well with both experiments and previous quantum-mechanics calculations.
The dependence of Se upon the initial state of the electron is analyzed. It turned out that Se is
particularly sensitive to the initial eccentricity of the electron orbit. Similarly, an analysis of the
electron trajectory during projectile-target scattering reveals interesting aspects of the stopping
process which may help one to understand the way electrons absorb energy from the incoming
projectile
1 E-mail address: [email protected]
THU-05 “THEORETICAL INVESTIGATION OF FRAGMENTATION AND ENERGY DEPOSITION CROSS
SECTIONS FOR SWIFT ION IMPACT ON SMALL, MODEL BIOMOLECULES”
John R. Sabin,1 Remigio Cabrera-Trujillo,2 Erik Deumens,1 and Yngve Öhrn1
1. University of Florida, 2. UNAM-Cuernavaca
The subject of the theoretical and computational work presented in this talk is related to damage
of cellular matter caused by energetic, charged particle radiation such as electrons, protons, and
alpha particles. The direct damage to DNA by swift ions is less important than the damage
caused to DNA by intermediate species produced by interaction of the radiation with other
components of the cellular medium such as water and small bio-organic molecules. These
intermediate species include ions, radicals, and electrons, which, by a variety of mechanisms,
can be involved in reactive processes that result in serious damage to DNA and other larger
biomolecules. Here we investigate the interaction of radiation with some small, model
biomolecules using a theoretical scheme known as Electron Nuclear Dynamics (END), which is
time dependant, direct, and non-adiabatic. As no potential surfaces are required in this
approach, the instantaneous coulomb forces among the participating electrons and nuclei steer
the dynamics of the process. The coupling among all electrons and electrons is explicit. The
major advantage of this method is that all possible product channels are considered together,
and all at the same level of approximation, thus increasing the reliability of prediction of product
distributions. The studies reported here involve 3He2+ colliding with small model biomolecules,
such as formaldehyde and glycine, and we discuss the associated fragmentation and energy
deposition cross sections.
Formaldehyde (CH2O) Glycine (H2NCH2COOH)
THU-06 “FRAGMENTATION OF POLYATOMIC MOLECULES IN COLLISIONS WITH ATOMIC IONS”
Yngve Öhrn.
Quantum Theory Project
University of Florida
P.O Box 118431, Gainesville, FL 3211, USA
Reactive encounters of atomic ions with polyatomic molecules at energies in the keV range
commonly falls outside the scope of adiabatic theory. Such processes involves a large number
of sationary electronic states and associated many-dimensional potential energy surfaces
making apparoaches that employ such quantities prohibitively di_cult. Electron Nuclear
Dynamics1 (END)2 o_ers a time-dependent and nonadiabatic approach to molecular processes
that works via instantaneous Coulombic interactions among particpating electrons and atomic
nuclei. A brief presentation of recent advances in this approach to dynamical processes will be
followed by a discussion of results with comparisons to experiment for proton collisions with
hydrocarbon molecules and for proton collisions with water dimers. Calculated and experimental
cross sections and fragmentation patterns for He2+ and He+ collisions with water molecules 3
will also be presented.
This work was supported by NSF grant 0513386. References.
1) Y. Ohrn et.al., in Time-Dependent Quantum Molecular Dynamics, edited by J. Broeckhove and
L. Lathouwers (Plenum, New York, 1992),pp279-292
2) E. Deumens, A. Diz, R. Longo, and Y. Ohrn, Rev. Mod. Phys. 66, 917 (1994)
3) N. Stolterfoht, R. Cabrera-Trujillo, R. Hellhammer, Z. Pesic, E. Deumens, Y. Ohrn, and J. R.
Sabin, Adv. Quantum Chemistry (in press) (2006)
FRI-01 “FAST ION TRACKS IN DIELECTRICS: FROM THE GALACTIC TO THE ATOMIC SCALE”
Raúl A. Baragiola
Laboratory for Atomic and Surface Physics University of Virginia
In a recent commentary§ I addressed the question of what strategy to use when choosing a
research problem, given our finite lives, if we are to have the largest impact. There I recalled
Poincaré advice to look for extreme or limiting situations, going to the infinitely large and the
infinitesimally small. Bridging the extremes, the theme of this talk will be a problem in
astrophysics - the amorphous / crystalline ratio of interstellar dust and their icy mantles,
discussing its necessary cause, high-density ionization tracks, a subject that counted Lew
Chadderton among its pioneers. I will emphasize the incomplete understanding of the so-called
velocity effect in track formation where, for the same stopping power, ions with v < vm, the
velocity of the stopping power maximum, produce more effects (damage, sputtering) that ions
with v > vm. The discussion will be centered in the atomistic aspects of the physical stage of the
energy deposition and will be illustrated with our recent measurements of the velocity effect in
the sputtering of solid oxygen[1].
§ R. A. Baragiola, Some Challenging Unsolved Problems in Atomic Collisions In Solids. Nucl. Instr. Meth.
Phys. Res. B 237 (2005) 520-524
[1] M. Fama, D. A. Bahr, and R. A. Baragiola, to be submitted.
FRI-02 “SWIFT HEAVY ION IRRADIATION AS A TOOL FOR CREATING NOVEL NANOELECTRONIC
STRUCTURES”
D.Fink1, L.T.Chadderton2, W.R.Fahrner3, K.Hoppe4, A. Kiv5, A.Sad5
1Hahn-Meitner-Institute Berlin, Glienicker Str. 100, D-14109 Berlin, Germany 2 Inst. of Advanced Studies, ANU Canberra, GPO Box 4, ACT, Australia
3Chair of Electronic Devices, Inst.of Electrotechnique, Fernuniversität, Hagen, Germany 4South Westfalia University of Applied Sciences, Hagen, Germany
5Ben-Gurion University of the Negev, Israel, P.O.B. 653, Beer-Sheva, 84105, Israel 5 Al-Balqa University- P.O.Box 2041- Amman-11953-Jordan
An overview is given about the strategies to create a novel “Swift-heavy Ion Track Electronics
(SITE)” and an “Electrolytic Electronics with Etched Tracks (E3T)”, by combining swift heavy ion
tracks in thin membranes with conventional semiconductor-based electronic skills and eventually
also with nanoparticles on the one hand, and with electrolytes on the other hand. In this way,
multiparametric and multilevel ambient-sensing and decision-making electronic elements can be
constructed which offer a range of unusual properties.
The most interesting feature in both types of ion track electronics is the frequent occurrence of
two different working states, eventually leading to negative differential resistances (NDRs). NDRs
can show up as well within individual track structures, as via track-to-track interaction; in the latter
case the NDRs are tunable. An interesting consequence of NDRs are self-pulsating tracks. It is
suggested to use structures with NDRs as primary active electronic elements. It is now our aim to
improve the reproducibility of these ion track structures, for reliable technological applications.
FRI-03 “MEASUREMENT OF GEOLOGICAL TIME AND TEMPERATURE BASED ON PARTICLE TRACKS
IN NATURAL MINERALS“
Raymond Jonckheere.
Geologisches Institut, Technische Universität Bergakademie Freiberg, Bernhard-von-Cotta-straße 2, D-09599 Freiberg
Several natural minerals contain trace amounts of uranium. Spontaneous nuclear fission of the isotope 238U leads to the formation of particle (fission) tracks along the trajectories of the ejected nuclear fragments. The lattice damage along a fission track is repaired at elevated temperatures, leading to a gradual reduction of its etchable length, which depends in the first place on the highest temperature that the track has experienced. Thus fission tracks can be thought of as maximum-reading thermometers that are generated throughout geological time. Geological processes that produce temperature variations in a rock, such as magma intrusion, meteorite impact, sediment burial, uplift of mountain ranges due to the collision of tectonic plates or climatic factors, the erosion of plate margins, etc., are so registered in the length distribution of fission tracks. A fission-track length distribution thus provides a geological time and temperature record that is accessible to measurement. Apatite occurs in low concentrations in most rocks and is the mineral whose potential has been most exploited. The apatite grains are mounted in resin, polished and etched. The etchant attacks the damage along the fission tracks at a faster rate than the exposed undamaged apatite surface. This produces etch figures, visible under an optical microscope, whose etchable length reflects the maximum temperature that each track has experienced. Tracks intersecting the polished surface are of little use since their lengths are truncated and thus not a measure of the "true" track length. Track length measurements are for this reason performed on fission tracks confined within the interior of the mineral grains and accidentally etched via a surface-intersecting fission track or a crack. Fission-track T(t)-modelling has supplied valuable information in a string of geological studies but some matters of principle are debated that prevent from placing too literal an interpretation on the palaeo-temperature estimates. During the two decades since its development in the late eighties, T(t)-modelling has been improved through the incorporation of chemical parameters and procedures to account for anisotropic length reduction and through the development of better modelling software. It is nevertheless remarkable that, during all this time and despite ambivalent results, its basic principles have almost never been challenged and that the critical observations that have been expressed in print have met with immediate reprisals. It is no exaggeration to call the present consensus unscientific, and, for this reason, to predict its imminent end and to expect that a detailed and extensive re-examination of the fundamental principles of fission-track T(t)-modelling will dominate research in the coming decade. Several fundamental issues must be re-examined. (1) The resolution of T(t)-modelling, i.e. the limits of palaeo-temperature information contained in the fission-track length distribution, separate from limits implicit in the user-entered modelling constraints. It can be shown that there can exist no pure "data-driven" solution although it is sometimes advocated as the certain outcome of "correct" modelling procedure. (2) The calibration of the annealing equations describing the extent of track-length reduction at fixed (T,t)-conditions. The existing equations have been fitted to data from high-temperature, short-duration experiments on induced tracks in pre-annealed samples. The alternative is to estimate the annealing parameters from length measurements of fossil tracks in borehole samples exposed to (T,t)-conditions inferred from independent evidence. This approach not straightforward and less attractive from a methodological standpoint but it is intolerable that attempts at an independent calibration continue to be opposed, given the questions raised about the extrapolation of lab data to geological timescales. (3) Fission-track counts and length measurements are performed on etched grain mounts with the aid of a high-magnification optical microscope. The biases inherent in the track counts affect the fission-track age and have in part been circumvented by the introduction of age standards but their causes are to a large extent still unclear. The sampling biases associated with track-length measurements have been the subject of recent research but are also still obscure. It is no exaggeration to state that we neither understand what we count nor what we measure. It is important that the principal biases are separated. The "length bias" correction is an essential element of all T(t)-modelling. However, it plots the apparent track densities versus the apparent mean track lengths for different degrees of annealing and it is used to correct both the measured lengths and the measured track densities despite the fact that counts of surface-intersecting tracks and measurements of confined tracks are affected by different biases. (4) T(t)-modelling rests on axioms such as that annealing involves a single process and that a track has no properties other than its mean length (principle of equivalent time) that are to some extent contradicted by the evidence. All these issues must be re-examined. The involvement of track physicists and an understanding of the fundamental processes involved in track formation and repair are of crucial importance in this undertaking.
FRI-04 “TEMPERATURE DISTRIBUTION IN A SWIFT ION INDUCED SPIKE: AN EXPERIMENTAL
APPROACH”
G. Szenes
Department of Materials Physics, Eotvos University, Budapest, Hungary H-1518 Budapest P.O.B. 32, Hungary
The peak temperature and the width of the temperature distribution are key parameters for thermal spike effects. A thorough analysis of existing experimental data on ion-induced latent tracks in insulators allows the unambiguous derivation of the temperature distribution in the spike.
It has been reported in numerous publications that track diameter 2R is controlled by the electronic stopping power Se and tracks are formed only above a threshold value Seo. Earlier, Seo=αc(Tm-Tir) has been found, where c is the specific heat calculated by the Neumann-Kopp’s rule, α is the same constant for all track forming insulators and Tm and Tir are the melting and irradiation temperatures [1]. This is strong evidence that tracks are formed by fast cooling of the ion-induced melt. On the other hand, the track radii satisfy the equation R2=m2ln(Se/Seo), where the peculiarity is, that m is the same constant for any track forming insulator whatever is the energy of the bombarding ions [1]. Combining these two equations leads to a simple expression (Tm-Tir)=(<se>/3αk)exp{- R2/m2} where <se> is the average stopping power per atom and k is the Boltzmann constant.
It can be shown that when the peak temperature of the spike attains its maximum value Tp=<se>/3αk, the melt has the maximum diameter 2r and the width of the distribution is 2r=2R at T=Tm, where T is the local temperature. Thus, when the track radii R are measured in various insulators, the widths of the distributions are obtained at a single Tm temperature in each solid. However, these independent Ti=Tmi, ri=Ri (i=1..n) data pairs satisfy the same Gaussian function with identical parameters at given values of <se> and Tir . This is more than an indication that there must be a close relationship between the temperature distributions in these solids.
We speak about Tm and do not about e.g. the Curie temperatures because Tm has a preferred role for the experimental method which is applied. The temperature distribution is formed in the spike as a result of the interaction of excited electrons with lattice atoms. It is highly important that Tm has no preferred physical meaning in this process. Consequently, if the above Gaussian distribution is valid for Ti=Tmi, ri=Ri (i=1..n) data pairs in various insulators, it must be valid at various other temperatures T Tm, as well. This is possible only if the ion-induced local temperature
distribution is independent of material parameters at the moment when Tp=maximum and it has the form
)1(m
rexp
k3
sTT
2
2e
ir⎪⎭
⎪⎬⎫
⎪⎩
⎪⎨⎧−
α><
+=
in any track forming insulator. There is a velocity effect in the formation of tracks: Seo is reduced for low velocity ions and they form larger tracks than high velocity ions at equal values of Se [2]. Thus, α=αL and α=αH at low and high ion velocities and αL<αH in Eq.(1). Accordingly, when the ion velocity is reduced keeping Se=constant, Tp is increased, however, the variance of the distribution remains constant. This is the physical origin of the velocity effect. The importance of the correct temperature distribution cannot be overemphasized. A typical example is the electronic sputtering in an oxide when thermal spike analyses based on different temperature distributions deduce activation energies differing by an order of magnitude [3]. Finally, the physical consequences of Eq.(1) and the temperature range of its validity are discussed. References [1] G. Szenes, Phys. Rev. B 51, 8026 (1995), J. Nucl. Mat. 336, 81(2005). [2] A. Meftah, et al., Phys. Rev. B 48, 920(1993). [3] G. Szenes, Nucl. Instr. and Meth. B 233, 70 (2005).
FRI-05 “AFM STUDY OF SOME RADIATION EFFECTS ON MATERIALS”
G. Espinosa1., J. I. Golzarri1, C. Vázquez-Lopez2.
1Instituto de Física, UNAM, Apdo. Postal 20-364, México, D.F 2Departamento de Física, CINVESTAV, Apdo. Postal 14-740, México 07000, D.F.
In this work, we show that Atomic Force Microscopy (AFM) is very reliable to study nuclear
tracks on solids. The materials were irradiated with 252Cf fission fragments, with average
energies of 79 and 104 MeV. The results show that each material present quite different effects.
For example, in diamond and quartz it was observed pits and ejected material deposited on
ordered sites. In amorphous silica the ejected material was deposited randomly.
The main aim of this study is to help the understanding of the interaction of the radiation with
insulating materials.
FRI-06 “ELECTRONIC STRUCTURE OF TRANSITION METAL FLUORIDES AND OXIDES
DETERMINED BY RESONANT X-RAY ABSORPTION AND X-RAY EMISSION SPECTROSCOPIES.”
José Jiménez-Mier1, Guillermo M. Herrera-Pérez1, Paul Olalde-Velasco1,. Elizabeth Chavira2,
Ioscani Jiménez3, david L Ederer4, T.A. Schuler4.
1.Instituto de Ciencias Nucleares, UNAM, 2.Instituto de Investigaciones en Materiales, UNAM,
3.Facultad de Química, UNAM, 4.Department of Physics, Tulane University.
We present results of soft x-ray absorption and emission experiments at the transition metal L2,3
edge of TiF4, TiO2, V2O5, VF4, MnF2, MnO, and CoF2. The experiments were carried out at beam
line 8.0.1 of The Advanced Light Source in Berkeley. Incoming photons from an udulator are
monochromatized and then fall into the sample. Total electron yield (TEY) measurements are
used to determine the x-ray absorption spectrum of each sample. At selected values of the
excitation energy we then record x-ray emission spectra. The processes studied are the excitation of a 2p electron into an unoccupied 3d state in the transition metal and its subsequent
decay by x-ray emission. These are therefore studies in which the transition metal ion does not
change its charge, and thus one obtains information about electronic states involved in the
excitation and the decay. This photon-in-photon-out technique allows the determination of the
energy position of the transition metal excited states in the compound. For all compounds we
found an elastic emission peak, one or several inelastic peaks that correspond to decay into d-
excited terms, and broad features that occur because of transitions into charge transfer states.
TiF4, TiO2 and V2O5 are very good examples of ionic compounds in which the transition metal
occurs in a d0 ground configuration. For these compounds we found elastic emission and a
broad valence emission feature. We also found a low energy loss emission feature that
corresponds to production of a charge transfer state. VF4 is a good example of a d1 compound.
For resonant emission of this compound we found the elastic peak, charge transfer peaks and
an inelastic emission peak with an energy loss that corresponds to the excitation energy of the
3d electron from the t2g to the eg orbital. MnO and MnF2 both have a half-filled 3d5 subshell. The
ground state is a high-spin 6A1 term, and the d excitations give an indication of the energy
required to flip a spin in these systems. We find states at energy losses of 3.5 and 5.1 eV in
these compounds. We also obtained emission into charge transfer excited states that are at energy losses of about 13 eV in MnF2 and 9 eV in MnO. Finally, CoF2 is an example of a d7
compound in a high-spin quartet term. The emission spectra show an elastic peak, several
inelastic peaks that correspond to production of spin-flip states, but also to production of higher
quartet terms. The absorption data are compared with the results of ligand-field atomic multiplet
calculations, and the emission data are compared with free-ion Hartree-Fock calculations. The
comparison shows very good agreement between experiment and theory for the d5 and d7
compounds, but it is necessary to explicitly include charge transfer in the calculation to
reproduce the TEY spectra of the d0 and d1 compounds.
FRI-07 “EXPERIMENTAL STUDY OF HIGHLY CHARGED IONS IMPACT ON SOLID SURFACE”*
Tieshan Wang, He Xu, Haibo Peng, Rui Cheng, Jia Yang and Dajie Ding
School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000, China e-mail: [email protected]
Recent experimental studies on the impact of highly charged ion (HCI) on solid surface have
been briefly reviewed in this paper. Some new experimental results about the HCI impact on
metals, Si, SiO2, mica and HOPG are reported. The relative sputtering yields induced by Pbq+
and Arq+ projectiles have been studied correlated to the projectile’s charge state, kinetic energy,
incident angle and target materials. Significantly dependences on the projectiles’ charge state
and incident angle are derived out from the measurement, but the phenomena are different on
various target materials. A dependence on projectile’s velocity is also found, but the trend is
different in case of Pbq+ and Arq+ projectiles. Metals, semiconductor and isolators have shown
different sputtering yield versus projectiles’ parameters. Nano-dots on HOPG samples created
by the impact of Arq+ have been investigated correlated to the charge state from 8+ to 14+,
kinetic energy from 20qev to 20 qkeV, respectively. The diameter and height of nano-dots have
been measured. Both parameters have a wide distribution, while same projectile ion has been
used. The main size of dots depends to the charge state and projectile’s kinetic energy. The
form of nano-dots is mostly unsymmetrical. Some dots double-, tri- and multi-peaks have been
also observed. The further study of the nano-dots created by impact of other projectile ions and
on other material is under going.
* This work has been supported by the Nature Science Foundation of China and the Cuiying talent program of Lanzhou University.