Ion Beam Physics Group

ION BEAM PHYSICS GROUP

of

Institute for Particle and Nuclear Physics

Wigner Research Centre for Physics

Topics of Research

The Ion Beam Physics Group is devoted to the ion beam modification and analysis of solid surfaces. Its activities include research in biology, environmental and material science, archeology and art. Members of laboratory participate in the education of physics in collaboration with Eötvös Loránd University (ELTE) and Budapest University of Technology and Economics (BME). We offer practical training and diploma thesis for undergraduate (BSc) and PhP programs for graduate (MSc) students.

In 2013 the former Nuclear Analysis Group of the Department of Biophysics joint in the Ion Beam Physics Group.

The Ion Beam Laboratory is member of the Hungarian Ion-beam Physics Platform (HIPP).

Scientific staff

    Szilágyi, Edit                     Head of the departmen, head of the group
    Bányász, István                   Senior research fellow
    Kótai, Endre                     Senior research fellow, associate fellow
    Kostka, Pál                       Senior engineer, associate fellow
    Kovács, Imre                     Senior research fellow
    Németh, Attila                   Senior research fellow
    Szőkefalvi-Nagy, Zoltán        Professor emeritus

PhD students

    Technical staff
    Balázs, Tamás
    Kiss, László
    Seres, Csaba
    Vad, Gábor
    Zwikl, Zoltán

    Former members

    The accelerator complex consists of a homemade 5-MV single-ended VdG accelerator and a 450-kV heavy-ion cascade implanter connected to each other via a joint scattering chamber. Three other beam lines (RBS/channelling, proton microprobe and PIXE, the latter allowing for performing external analysis) are devoted to ion-beam analysis. Information are provided for users here.

    Research Activity
    Some of the most frequently used methods in depth profiling of different elements in solids are based on Ion Beam Analysis (IBA) using ions of a few MeV energy. In these methods, for example Rutherford Backscattering Spectrometry (RBS), Elastic Recoil Detection Analysis (ERDA), Nuclear Reaction Analysis (NRA), Particle induced Xray spectroscopy (PIXE) and X-ray fluorescence(XRF), the element to be analyzed is identified by the energy and type of the emitted particles coming from a specific reaction between the incident ion and the given target element. Although these methods are well established, many problems still arise when new applications are considered.
    The subject of our activities may be divided in three categories:
      In the field of IBA methodology:
    • Detection of light impurity in heavy substrate is one of the main problems of Rutherford backscattering spectroscopy. We developed a new method for O detection, based on the O16 (α,α) O16 elastic resonance. The sensitivity of O detection is increased by a factor of 10.
    • Using glancing incidence, the detection limit increased an additional factor of 3.5,
      and the depth resolution has been improved by a factor of 5.
    • Elastic recoil detection (ERDA) is a fast, nondestructive method for depth profiling of hydrogen isotopes. We joined to the development of ERDA. We measured the cross-section of the H1(He4, He4)H1 elastic recoil reaction and developed a method to select the measuring parameters for optimal depth resolution.
    • The ion beam channeling method is used in the study of impurity distributions and implantation damage in crystalline materials. E. Kótai developed a new method for measuring the stopping power of channel ions using resonance backscattering method. This method does not require any special target preparation.
    • E. Kótai developed a computer code (RBX) for data analysis and spectrum simulation in Rutherford backscattering spectrometry. RBX is only code, which can evaluate and simulate channeling spectra using analytical formulas. The program has been used in 17 laboratories in the world.
    • In the field of solid state physics and material science:

    • Ion implantation
    • Thin films
    • Nano particles
    • Radiation damage
    • Interdisciplination research:

    • Archelogy
    • Cultural heritage
    • Biology

    Selected publications


    Full list

    Software developement

    Members of Ion Beam Physics Section developed some software for analysis, simulation of IBA spectra, which are open for IBA community.

    RBX

    RBX is a computer program to synthesize and analyze RBS, BS, ERDA, NRA spectra.

    Features:

    • Simulation of RBS, ERDA, Forward scattering, NRA spectra
    • Simulation of RBS/c channeling spectra
    • Evaluation of RBS, RBS/c, ERDA, NRA spectra
    • Stopping power databases: ZBL 62, SRIM 2003, channeling
    • Cross section library: editable, import: Sigmabase, R33 files
    • Scattering geometry: IBM, Cornell
    • Isotope calculation: specific isotopes and/or natural abundance
    • Screening calculation: L’Ecuyer or H.H.Andersen
    • Straggling model: Bohr, Chu, Yang, Tschalär
    • Multiple scattering: same as DEPTH code
    • Geometric scattering
    • Pileup correction
    • Stopper foils: simulated (homogeneous foils only)
    • Energy calibration: linear
    • Operation system : MS Windows XP, Vista, 7

    Contact: Endre Kótai (kotai at rmki.kfki.hu)

    DEPTH

    DEPTH code has now been developed further to calculate the energy and depth resolution of ion beam analysis methods as Rutherford backscattering spectrometry, Elastic recoil detection analysis and Nuclear Reaction Analysis for targets containing multilayers. The reflection and transmission geometries are considered as well.

    Features:

    • Calculation of depth resolution for ERD and RBS spectra
    • Calculation of optimal depth resolution
    • Calculation of cross-section of a given reaction and a given line using the thick target method
    • Calculation of the energy loss of the incident ion (at the incident energy) going through the absorber foil and its Bohr straggling
    • Calculation of the Tschalar effect without and with a given inhomogenity
    • Operation system : MS Windows XP, Vista, 7

    Contact: Edit Szilágyi(szilagyi at rmki.kfki.hu)

    Download: from Sigmabase or from IBIS

    RBS-MAST

    RBS-MAST is a Monte-Carlo simulation program for simulating RBS spectra taken on inhomogeneous or 3D structured samples (e.g., porous materials, non-continuous layers, composites, etc).

    Features:

    • Simulation of RBS and BS spectra
    • Scattering geometry: IBM, Cornell
    • Both periodic and randomly distributed structures are treated
    • Embedded objects (brick, ball, ellipsoid, cylinder, cone, etc.)
    • Operation system : MS Windows XP, Vista, 7

    Contact: Endre Kótai (kotai at rmki.kfki.hu)

    Latest results

    Real-time in situ spectroscopic ellipsometry studies of ion bombardment effects on single crystalline germanium

    In situ real time spectroscopic ellipsometry was applied to follow the the evolution of disorder and morphology change induced by ion bombardment in single crystalline germanium. Earlier studies show peculiar cellular structure caused by ion bombardment.
    The M-88 spectroscopic ellipsometer (J.A. Woollam Co. Inc.) with rotating analyzer was mounted on the chamber of Heavy Ion Cascade Implanter. The vacuum chamber is equipped with high-quality entrance and exit windows to minimize deviation caused by birefringence. Angle of incidence was 75 degree. Ge wafer from Umicore (Orientation (100), resistivity approx. 0.4 Ohmcm was cleaned in diluted HF and rinsed in deionized DI) water. After cutting into small rectangles the samples were rinsed again in DI and dried in nitrogen gas. The sample was implanted by 200 keV Sb+ ions.
    Based on the paper written by Kaiser et al., the critical dose for Sb implantation into Ge (the onset of void formation due to ion implantation) is equal about from 3 to 5 x 1014 cm-2. In our experiment the implantation was completed in 79 minutes (corresponding to a total fluence of 1 x 1016 cm-2), it means that the formation of voids began around 5 minutes after starting the bombardment. So we guess that the wave-like part in the figure showing the measured Ψ angles in function of time is in connection of the void formation.


    Time evolution of the measured ellipsometric Ψ parameter at three different wavelength values (382 nm, 418.4 nm and 450 nm). The ion beam was switched on at about 1 min and it was switched off at around 80 min



    The ion beam was switched on at about 1 min and after that the Ψ parameter showed a sudden increase. We interpret it as the change of the refractive index caused by ion-implantation induced amorphization

    Energy and depth resolution in elastic recoil coincidence spectrometry

    Elastic recoil coincidence spectrometry was implemented into the analytical ion beam simulation program DEPTH. The energy spread contributions are reconsidered for elastic recoil coincidence spectrometry. The correlations between FSS and ERDA are taken into account.

    Spectra based on the
    • individual detector signal and
    • containing the energy sum of the detected scattered and recoiled (ESDSR) particles originating from the same scattering events can be calculated.

    In the calculations the following effects are considered:
    • the dependency of the energy spread contributions,
    • the effective detector geometry,
    • the yield loss due to angular spread,
    • Mott’s cross section for the identical, spin zero particles is included.

    The first results achieved on simulation of 12C-12C scattering were presented at the 19th International Conference on Ion Beam Analysis, (Cambridge, UK, 7-11 September, 2009). In Figure 1 the measured and simulated ESDSR spectra of a carbon implanted Al foil are shown.


    Fig. 1. Measured and simulated ESDSR spectra of 12C–12C scattering at normal incidence of 12 MeV 12C ions and in 45o– -45o geometry taken on an implanted Al foil of a thickness of 2 µm. The implantation was carried out with 1 MeV 12C ions with a fluence of 1.3 x 1016 12C/cm2. The experimental spectrum and parameters were taken from ref. [1]: beam energy spread 0.1 %, the detector distance and diaphragm were set to 80 and 5 mm respectively, which results a solid angle of 3 msr and an angular distribution of 45+-2o and detector resolution 150 keV. The following layer structure was used (from front side): 16 nm CH / 1080 nm Al / 160 nm Al1C0.003 / 250 nm Al1C0.006 / 160 nm Al1C0.003 / 670 nm Al / 12 nm CH. The density of hydrocarbon deposit was 11.4 x1022 at/cm3.

    Read the paper

    [1] I. B. Radović, M. Jakšić, F. Schiettekatte, J. Anal. At. Spectrom. 24 (2009) 194.

    Concentration dependence of helium retention in lithium silicates

    The retention of gaseous impurities and diffusion-accumulation mechanisms in solids may have a major impact on the macroscopic properties of the solids, e.g., hardness and rigidity, which may rise concerns in applications where materials are exposed to high dose ion-irradiation. For example, structural and functional materials of fission and fusion reactor vessels are inevitably – sometimes necessarily – exposed to constant irradiation of α, p and other particles originating from fission/fusion reactions. Therefore a better understanding of the trapping mechanisms and the quantitative knowledge of the retention scales are necessary for developing future fission and fusion reactor materials.

    In this work lithium orthosilicate (Li4SiO4) is investigated, which is one of the candidates for tritium breeding material in fusion reactor blankets. Hence it is a subject of hydrogen/helium retention and radiation damage experiments. Previously it was shown through helium implantation-retention experiments that in substoichiometric silicon-oxide (SiOx) a threshold level can be observed at x=1.3, i.e., the implanted helium escapes from the oxides if x exceeds 1.3. Li-silicates can also be considered as a mixture of SiO2 and Li2O. In this work we investigate whether a similar threshold level exists for helium retention in Li-containing silicate ceramics as it does in case of substoichiometric silicon oxides.


    Helium retention of lithium silicates and SiOx. The compositions are expressed in SiO2 volume percentages, for better comparison. In this representation both materials show a similar trend.

    Read the paper

    Characterisation of annealed Fe/Ag bilayers by RBS and XRD

    The sharpness of the Fe–Ag interfaces is very important for the magnetic coupling processes. To study the stability of the Fe–Ag interfaces very long time experiments are necessary at room temperature. To enhance the processes which take place at interfaces, high temperature annealing can be used.
    A detailed annealing experiment was carried out on Si-covered Fe/Ag (Ag grown on Fe) and Ag/Fe (Fe grown on Ag) polycrystalline bilayers, which were deposited on Si(111) substrates by MBE method. Heat treatments of various duration and temperature were applied in UHV conditions. Rutherford backscattering spectrometry and X-ray diffractometry were used to determine the effects of the heat treatments. In case of Fe/Ag samples, formation of iron-silicide phases was observed between the Fe layer and Si substrate, and the silver and the silicon capping layer were also completely mixed with each other. In case of the Ag/Fe samples the silver moved to the sample surface through the iron layers, while iron shifted to the substrate and mixed with silicon.


    RBS-spectra of as-prepared and annealed Si(111)/Ag/Fe/Si sample at various annealing temperatures (symbols measured, lines: simulated spectra).

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    Radiation induced deformation and masking properties of ordered colloidal nanoparticle masks

    A promising fast and cheap technique to create arrays of small objects on a substrate surface or embedded in the substrate material is nanosphere lithography (NSL). In NSL, a self-organized layer of colloidal spheres is used as a mask for a lithographic step such as illumination, ion implantation, deposition, or etching. When NSL is used an array of nanostructures, arranged in closely packed hexagonal symmetry, is left on the substrate surface (deposition) or embedded in the substrate (implantation). However, ion implantation through a mask which consists of colloidal nanoparticles leads not only to the patterning of the substrate but also to the deformation of the nanomask itself due to ion–nanoparticle interactions. The nature and the intensity of this deformation process strongly depend on the size of the nanospheres and the implantation parameters (ion energy, ion mass, ion fluence, substrate temperature). The nanomask deformation effect also has influence on the masking/patterning properties.
    The 500 keV Xe2+ irradiation-induced anisotropic deformation of ordered colloidal silica nanoparticulate masks is followed using 2 MeV 4He+ Rutherford Backscattering Spectrometry (RBS) with different measurement geometries and the improved data analysis capabilities of the RBS-MAST spectrum simulation code. The three-dimensional (3D) geometrical transformation from spherical to oblate ellipsoidal and polygonal shape and the decrease of the mask’s hole size was observed. We also show the capability of the conventional RBS technique to characterize laterally ordered submicron-sized three-dimensional structures.
    Read the paper

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