W. Pilz

Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Saxony, Germany

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Publications (23)26.97 Total impact

  • physica status solidi (RRL) - Rapid Research Letters 07/2013; 7(7):501-505. · 2.39 Impact Factor
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    ABSTRACT: We have carried out a series of measurements demonstrating the feasibility of using the Dresden electron beam ion source (EBIS)-A, a table-top sized, permanent magnet technology based electron beam ion source, as a charge breeder. Low charged gold ions from an AuGe liquid metal alloy ion source were injected into the EBIS and re-extracted as highly charged ions, thereby producing charge states as high as Au(60 +). The setup, the charge breeding technique, breeding efficiencies as well as acceptance and emittance studies are presented.
    The Review of scientific instruments 02/2012; 83(2):02A511. · 1.52 Impact Factor
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    ABSTRACT: The self-organisation of periodic pattern on (001) Ge by bombardment with different heavy ion species (Bi+, Bi++, Bi2+, Bi3+, Bi3++) obtained from a liquid metal ion source in a mass separating 30kV FIB system was studied. Aspect ratios exceeding values reported so far for elemental semiconductors substantially were found after cluster irradiation. An excellent regular self-ordering of dots (40nm in height, interdistance of ∼50nm) and ripple pattern were achieved. Despite of high ion fluence, Raman measurements prove a crystalline surface layer. This result deviates drastically from monomer irradiation, where similar to former ion irradiation of Ge a spongy amorphous surface layer is formed. For the transition from the usual behaviour to the unexpected pronounced pattern formation a threshold of the energy density deposited by the collision cascade was identified: If the deposited energy density exceeds the melting threshold, dot or ripple pattern appear. In our model we assume that the ion-impact-induced deposition of energy per volume (estimated by SRIM) must exceed the energy needed for melting. Thus, Bi segregation during resolidification of the melted pool and the 5% volume difference between molten and solid Ge can cause the observed Bi separation and Ge patterning, respectively. A consistent, qualitative model will be discussed.
    Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms 02/2012; · 1.27 Impact Factor
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    ABSTRACT: Ge surfaces of up to 780 K temperature have been irradiated at normal incidence with up to 1017 Bi+ ions cm-2 having kinetic energies from 10 to 30 keV. The resulting surface morphologies have been studied by scanning electron microscopy. While at room temperature the impacts of high-energy Bi+ ions result in porous networks, at elevated irradiation temperatures hexagonally ordered dot arrays are formed, whereas after a further temperature increase the surface becomes smooth. The comprehensive experimental studies have been summarized in a phase diagram of surface morphologies in the ion energy versus substrate temperature plane. In this phase diagram, the onset of dot formation with increasing substrate temperature has been consistently modeled by nanomelting of the collision cascade volume of ion impacts, thereby taking into account the thermodynamic parameters of amorphous Ge (melt temperature, heat of fusion, and heat capacity) as well as the energy density deposited in the cascade volume as predicted by established simulation programs.
    Journal of Vacuum Science & Technology B Microelectronics and Nanometer Structures 01/2012; 30(6). · 1.36 Impact Factor
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    ABSTRACT: Ge (100) surfaces were irradiated by heavy Bi+ and Bi++ ions extracted from a Bi-liquid metal ion source in a mass separated focused ion beam system with energies of 30 and 60keV, respectively. Networks of different nanoporous (or sponge like) structures were found depending on ion energy, fluence, angle of incidence, and irradiation temperature. The porous and amorphous surface structures are explained in terms of high concentration vacancies close to the surface. The surface modification was investigated using SEM and AFM imaging and FIB for cross section preparation.
    Applied Physics A 01/2011; 104(4):1153-1158. · 1.69 Impact Factor
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    ABSTRACT: This paper summarizes the results of studies to enhance the performance of Dresden Electron Beam Ion Traps regarding aspects which are important for charge breeding, i.e. the injection of externally produced low charged ions and their conversion to highly charged ions. The properties of the electron beam of this compact room-temperature operated EBIT were investigated via position sensitive X-ray detection. A detailed analysis of the spatial distribution as well as the energy of the X-ray photons emitted from the electron beam region allowed for the determination of the source parameters needed to guarantee optimal ion trapping conditions and ionization rates. The parameters found in this investigation were applied for the successful realization of charge breeding with the Dresden EBIT.
    Journal of Instrumentation 09/2010; 5(09):C09006. · 1.66 Impact Factor
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    ABSTRACT: Four different liquid metal ion sources (LMIS), working with pure Bi as well as with Bi containing alloys (Au13Bi87, Ga38Bi62, Ga35Bi60Li5) were investigated with respect to the emission behavior as a function of current and temperature, the mass spectra and the energy distribution of the individual ion species. Additionally, for the pure Bi-LMIS the sputtering rates for Bi ions and clusters on Si, SiO2 and Ge substrates were compared with that of Ga projectile ions using a mass separating focused ion beam system.
    Applied Physics A 01/2010; 99(1):145-150. · 1.69 Impact Factor
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    ABSTRACT: A carbon-cerium alloy liquid metal ion source �LMIS� with unintentional aluminum content is presented for generating focused ion beams of carbon ions, as well as ionized clusters with sizes of 2, 4, and 8 atoms. Emission-current-dependent measurements were carried out for the mass spectra and energy spread of all species, but focused on the carbon monomer ions and clusters. The full width at half maximum of the energy distribution was determined to be 6.5 eV for the monomer carbon ion and 14 eV for the light clusters at an emission current of 5 �A. The source showed good beam performance when used with a mass-separated focused ion beam column. Applications to graphene structures, organic matter, and other carbon-containing materials are promising tasks for the new carbon-containing alloy LMIS.
    Journal of vacuum science & technology. B, Microelectronics and nanometer structures: processing, measurement, and phenomena: an official journal of the American Vacuum Society 11/2009; 27(6):L47. · 1.36 Impact Factor
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    ABSTRACT: A GaBi alloy liquid metal ion source has been studied. From an analysis of the source mass spectra as a function of emission current, a mechanism is suggested for the production of single- and double-charged ions. There is good agreement with the results of Swanson's investigations of a pure Bi source.
    Ultramicroscopy 09/2007; 107(9):865-8. · 2.47 Impact Factor
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    ABSTRACT: Focused ion beam systems employing liquid metal ion sources have become of increasing importance in the microelectronics industry. Maskless ion implantation as a modern patterning technique is one of the most attractive application of Focused Ion Beams. In spite of the fact that a great deal of research has been carried out on liquid metal ion sources, surprisingly few results exist on the temperature dependence of their emission characteristics. In this article we study a AuGe liquid metal alloy ion source. The unusual results are explained in terms of the abnormal behavior of the surface tension of the alloy with temperature.
    AIP Conference Proceedings. 04/2007; 899(1).
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    ABSTRACT: In this work a Ga38Bi62 alloy liquid metal ion source has been studied, which allows to implant in the case of a silicon substrate shallow donor ions (Bi) as well as acceptors (Ga) in the sub micron range without changing the source. A detailed analysis of the mass spectra as a function of emission current, obtained from this source, was used to investigate the mechanism for the production of single and double-charged ions. Moreover, the intensity of cluster ions extracted by the source, as a function of emission current is represented. Theoretical modeling supports the experimental results
    01/2006;
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    ABSTRACT: This reports on an extensive study of the characteristics of AuGe and AuGeSi liquid metal alloy ion sources as a model system for new semiconductor compatible FIB sources. Such characteristics include ion beam mass spectra. A careful investigation has been undertaken where the emitter temperature is the main variable parameter. This work concerns the temperature dependence of the mass spectra of two needle-type liquid metal alloy ion sources (LMAISs), namely Au77Ge14Si9 (Tm = 364°C) and Au73Ge27 (Tm = 365°C). The sources are important for producing SiGe implanted layers. The experimental results, in conjunction with existing theories, strongly points towards the co-existence of two mechanisms for the emission of doubly-charged monomer ions: direct filed-evaporation and post-ionisation.
    Journal of Physics Conference Series 07/2005; 10(1):214.
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    ABSTRACT: Detritiation by heat treatment of graphite or carbon fibre composite (CFC) tiles retrieved from the Tokamak Fusion Test Reactor (TFTR) was assessed using the standard and well proved technique of full combustion combined with liquid scintillation analysis. Complete carbon tiles were heated in a oven to 500 °C in air for one hour at Princeton Plasma Physics Laboratory (PPPL) and sent to Tritium Laboratory Karlsruhe (TLK) for surface and depth profile analysis. Coring/full combustion technique performed on the treated and untreated tiles, both graphite and CFC, has shown that only the tritium held close to the surface (few tens μm) is efficiently released by baking in air while the bulk tritium is almost unaffected. Therefore, baking the tile under air, even at 500 °C, does not detritiate the bulk.
    Journal of Nuclear Materials. 01/2004;
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    ABSTRACT: Depth profiling measurements of tritium in carbon samples have been performed during the past seven years at the AMS facility installed at the Rossendorf 3 MV Tandetron. The samples have been cut from the inner walls of the fusion experiments ASDEX-upgrade/Garching and JET/Culham. The tritium content of the samples from JET required a dedicated AMS facility to prevent any contamination of the versatile 3 MV Tandetron. On the basis of an air-insulated 100 kV tandem accelerator equipped with a gas stripper an AMS facility exclusively devoted to tritium depth profiling was installed, tested and used for routine measurements. After additional successful tests employing diamond-like carbon (DLC) stripper foils at this accelerator, another small and compact 100 kV tandem accelerator with SF6 insulation and a DLC stripper has been installed at the AMS facility. Results obtained with the different tandem accelerators are presented.
    Pramana 01/2004; 59(6):1053-1059. · 0.56 Impact Factor
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    ABSTRACT: Depth profiling measurements of light elements have been performed at the Forschungszentrum Rossendorf using an AMS facility at the 3 MV Tandetron. This facility is equipped with a simple arrangement for mechanical scanning of the sample inside a commercial sputter source and with a conventional detection system. After measurements of depth profiles of tritium in carbon samples from fusion experiments this AMS facility has been applied to depth profiling of humidity penetrated into as-implanted SiO2 layers. For this aim, Ge+ and Si+ ion implanted SiO2 layers (1014–1016 cm−2) were exposed to an artificial atmosphere with H218O humidity. AMS allows the discrimination of isobar atomic and molecular ions, thus depth profiles of 18O− and (18OH)− molecular ions could be investigated. By measuring 18O4+ or H+ species of these ions, the process of humidity penetration in as-implanted SiO2 has been studied.
    Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms 01/2004; 219:459-462. · 1.27 Impact Factor
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    ABSTRACT: Tritium depth profiling measurements by accelerator mass spectrometry have been performed at a facility installed at the Rossendorf 3 MV Tandetron. In order to achieve an uniform erosion at the target surface inside of a commercial Cs ion sputtering source and to avoid edge effects, the samples were mechanically scanned inside of a commercial Cs sputter ion source. The sputtered negative ions were mass analysed by the injection magnet of the Tandetron. The tritium ions are counted after the acceleration with semiconductor detectors. Depth profiles have been measured for carbon samples which had been exposed to the plasma at the first wall of the Garching fusion experiment ASDEX-Upgrade and from the European fusion experiment JET, Culham/UK. A dedicated AMS facility with an air-insulated 100 kV tandem accelerator for depth profiling measurements at samples with high tritium concentration is under construction. First results of test operation are presented.
    Physica Scripta - PHYS SCR. 01/2001; 94(1):98-101.
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    ABSTRACT: Recent results on measurements of tritium and other hydrogen isotopes in first wall materials of large tokamaks are discussed and evaluated. Data on the in situ and ex situ release of tritium from plasma facing components under different conditions are assessed.
    Fusion Engineering and Design. 01/2001;
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    ABSTRACT: Tritium depth profiling by accelerator mass spectrometry has been performed at the Rossendorf 3 MV Tandetron. Tritium particles are counted after the accelerator using a semiconductor detector, while deuterium and other light elements are simultaneously measured with the Faraday cup between the injection magnet and the accelerator. Depth profiles have been measured in carbon samples cut from the first wall tiles of the Garching fusion experiment ASDEX-Upgrade and of the European fusion experiment JET, Culham/UK. Tritium contents in the JET samples were up to six orders higher than in samples from ASDEX-Upgrade. Tritium beam currents from samples with high tritium content were measured partly in the Faraday cup before the accelerator. A dedicated tritium AMS facility with an air-insulated 100 kV tandem accelerator is under construction.
    Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms 01/2000; 172:655-658. · 1.27 Impact Factor
  • Physical Review B 06/1999; 60(1). · 3.66 Impact Factor
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    ABSTRACT: Stopping powers and equilibrium charge-state distributions for 0.2-1.2 MeV/u 7Li, 11B, 12C, 14N, 16O, 31P, and 35Cl ions, measured in transmission of a 780 nm crystalline silicon foil, are reported. Using a high-resolution electrostatic analyzer, ion energy loss was determined within +/-3%. The thickness of the Si foil was measured independently by Rutherford backscattering and SEM with an uncertainty of about 3-4 %. The random and channeling stopping powers were estimated within approximately +/-5%, fitted using an empirical expression, and compared with the TRIM95 database. Resulting differences between the fitted and the empirical stopping powers were in the range of 5-15%, depending on ion species and incident beam energy. The equilibrium charge fractions were determined within about +/-4% for most cases. At small angles to the \{110\} plane, the energy-loss spectra exhibit a multiple peak structure, primarily due to trajectory selection.
    Physical Review B 01/1999; 59(1):226-234. · 3.66 Impact Factor