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432 results on '"Hofsäss, H."'

7. Formation of magnetic nanoclusters in Fe implanted amorphous and crystalline SiO2.

Author

Bharuth-Ram, K., Ronning, C., and Hofsäss, H.

Subjects
ELECTRON spectroscopy, MOSSBAUER spectroscopy, MAGNETIC moments, MAGNETIC fields, IRON clusters, ION implantation, HYPERFINE interactions
Abstract

Conversion electron Mössbauer Spectroscopy (CEMS) studies have been conducted on Fe implanted amorphous and crystalline SiO2 which were annealed in air up to a temperature of 1000oC. For both samples, dramatic changes set in after the 1000oC anneal and the CEM spectra are dominated by strong ferromagnetic sextets. In the amorphous sample, the sextet is characterized by magnetic hyperfine fields of 33T, 31T and 29 T, consistent with the formation α-Fe nanoclusters. In the crystalline sample the ferromagnetic sextet has spectral parameters of δ = 0.38(3) mm/s and Bhf = 52.3T, consistent with formation of α-Fe2O3 clusters, reflecting the precipitation of the implanted Fe into such clusters. The line ratios of lines 1, 2 and 3 (and 6, 5 and 4) of the sextet are 3:4:1, reflecting alignment of the magnetic moment of the precipitates normal to the c-axis of the sample surface. [ABSTRACT FROM AUTHOR]

Published
2024
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12. First PAC experiments in MAX-phases

Author

Jürgens, D., Uhrmacher, M., Hofsäss, H., Röder, J., Wodniecki, P., Kulinska, A., Barsoum, M., Pasquevich, A., editor, Rentería, M., editor, Saitovitch, E. Baggio, editor, and Petrilli, H., editor

Published
2008
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15. Low-energy Se ion implantation in MoS₂ monolayers

Author

Bui, M. N., Rost, S., Auge, M., Tu, J.-S., Zhou, L., Aguilera, I., Blügel, S., Ghorbani Asl, M., Krasheninnikov, A., Hashemi, A., Komsa, H.-P., Jin, L., Kibkalo, L., O’Connell, E. N., Ramasse, Q. M., Bangert, U., Hofsäss, H. C., Grützmacher, D., and Kardynal, B. E.

Subjects
defect healing, Raman spectroscopy, dry viscoelasic transfer, transition metal dichalcogenide monolayer, photoluminescence, ultralow energy ion implantation, MoS₂
Abstract

In this work, we study ultra-low energy implantation into MoS₂ monolayers to evaluate the potential of the technique in two-dimensional materials technology. We use 80 Se⁺ ions at the energy of 20 eV and with fluences up to 5.0 · 10¹⁴ cm⁻². Raman spectra of the implanted films show that the implanted ions are predominantly incorporated at the sulfur sites and MoS₂₋₂ₓ Se₂ₓ alloys are formed, indicating high ion retention rates, in agreement with the predictions of molecular dynamics simulations of Se ion irradiation on MoS₂ monolayers. We found that the ion retention rate is improved when implantation is performed at an elevated temperature of the target monolayers. Photoluminescence spectra reveal the presence of defects, which are mostly removed by post-implantation annealing at 200 ˚C, suggesting that, in addition to the Se atoms in the substitutional positions, weakly bound Se adatoms are the most common defects introduced by implantation at this ion energy.

Published
2022

21. High-current caesium sputter ion source with planar ionizer for accelerator mass spectrometry

Author

Yordanov, D., Hofsäss, H., Rugel, G., Akhmadaliev, S., Borany, J., Facsko, S., and Feige, J.

Subjects
New Mass Spectrometric Methods and Technical Developments
Abstract

A new caesium sputter negative ion source with planar ionizer for Accelerator Mass Spectrometry (AMS) is being built, regarding quantifying the ratios of long-lived cosmogenic radionuclides in micrometeorites. The focus of the ion source is on an optimal ion-optics design, together with a realization of new concepts for the construction and function of the ionizer, with the possibility of the precise in-situ adjustment of the ion-optical components, and optimization of the caesium ion beam and ion transport. In addition, the source is designed for operation with higher cathode voltage (up to 20 kV), which aims to increase the sputter rate of the sample, and in turn to increase the extracted negative current. Higher ion currents and better ion yields mean shorter measuring times, higher precision due to higher counting statistics and/or higher throughput of samples in an AMS runs. The authors would like to thank the Federal Ministry of Education and Research of Germany for its financial support (project 05K2016), and the HZDR’s Ion Beam Center for its essential contribution to the realization of this project.

Published
2020

37. Argon ion beam induced surface pattern formation on Si.

Author

Hofsäss, H., Bobes, O., and Zhang, K.

Subjects
*ION beams, *PATTERN formation (Physical sciences), *ARGON, *SILICON, *IRRADIATION
Abstract

The development of self-organized surface patterns on Si due to noble gas ion irradiation has been studied extensively in the past. In particular, Ar ions are commonly used and the pattern formation was analyzed as function of ion incidence angle, ion fluence, and ion energies between 250 eV and 140 keV. Very few results exist for the energy regime between 1.5 keV and 10keV and it appears that pattern formation is completely absent for these ion energies. In this work, we present experimental data on pattern formation for Ar ion irradiation between 1 keV and 10 keV and ion incidence angles between 50° and 75°. We confirm the absence of patterns at least for ion fluences up to 1018 ions/cm². Using the crater function formalism and Monte Carlo simulations, we calculate curvature coefficients of linear continuum models of pattern formation, taking into account contribution due to ion erosion and recoil redistribution. The calculations consider the recently introduced curvature dependence of the erosion crater function as well as the dynamic behavior of the thickness of the ion irradiated layer. Only when taking into account these additional contributions to the linear theory, our simulations clearly show that that pattern formation is strongly suppressed between about 1.5 keV and 10 keV, most pronounced at 3 keV. Furthermore, our simulations are now able to predict whether or not parallel oriented ripple patterns are formed, and in case of ripple formation the corresponding critical angles for the whole experimentally studied energies range between 250eV and 140keV. [ABSTRACT FROM AUTHOR]

Published
2016
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41. α-Emission channeling studies of the lattice site of oversized atoms implanted in Fe and Ni single crystals

Author

Wachter, J. De, primary, Blässer, S., additional, Hofsäss, H., additional, Jahn, S., additional, Lindroos, M., additional, Moons, R., additional, Pattyn, H., additional, Restle, M., additional, Vantomme, A., additional, Wahl, U., additional, Duppen, P. Van, additional, Collaboration, the ISOLDE, additional, and Langouche, G., additional

Published
1996
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42. Lattice sites of Li in CdTe

Author

Restle, M., primary, Bharuth-Ram, K., additional, Quintel, H., additional, Ronning, C., additional, Hofsäss, H., additional, Wahl, U., additional, and Jahn, S.G., additional

Published
1996
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46. Development of an efficient high-current ion source for Accelerator Mass Spectrometry

Author

Hofsäss, H., Bregolin, F., Yordanov, D., Rugel, G., Akhmadaliev, S., Merchel, S., and Feige, J.

Subjects
AMS, micrometeorite
Abstract

A new efficient negative ion source for Accelerator Mass Spectrometry (AMS) is being built to quantify the ratios of long-lived cosmogenic radionuclides in micrometeorites. Measuring these extremely small ratios is at the technological limits of present AMS systems. The new source is designed specifically to provide a higher AMS detection sensitivity by having an optimal ion-optics design, incorporating new concepts for the construction and operation of the Cs ionizer, optimized Cs ion beam currents and Cs vapor transport, as well as the operation with higher cathode voltages than usual. Moreover, its design is modular providing ease of access and simplifying maintenance while providing better mechanical stability. Several source parameters can be controlled and measured during operation to achieve a better source performance. The new source will consist of a auto-aligning modular ionizer, a Cesium supply with active temperature control of the supply tubes, a novel shroud for the Cs supply and a cathode operated at up to -20 kV cathode bias. The design is optimized using COMSOL ion optics simulations, including space charge effects, thermal transport simulations as well as detailed sputter simulations. The authors would like to thank the Federal Ministry of Education and Research of Germany for its financial support (project 05K2016), and the HZDR's Ion Beam Center for its essential contribution to the realization of this project.

Published
2018

47. Development of an efficient high-current ion source for Accelerator Mass Spectrometry

Author

Bregolin, F. L., Hofsäss, H., Rugel, G., Akhmadaliev, S., Merchel, S., and Feige, J.

Subjects
micrometeorites, AMS, ion source
Abstract

A new high-current negative ion source for Accelerator Mass Spectrometry (AMS) is being built to quantify the ratios of long-lived cosmogenic radionuclides in micrometeorites, which are of great astrophysical interest. Measuring these extremely small ratios is at the technological limits of present AMS systems. The new source is designed specifically to provide a higher AMS detection sensitivity by having an optimal ion-optics design, incorporating new concepts for the construction and operation of the Cs ionizer, optimized Cs ion beam currents and Cs vapor transport. The operation with higher cathode, extraction and pre-acceleration voltages than usual is possible. Moreover, its design is modular providing ease of access and simplifying maintenance while having better mechanical stability at the same time. Several operational parameters can be controlled and measured during operation to achieve a higher ion source performance. Detailed ion-optics simulations of the ion source are compared with test measurements, and the design optimized based on its results. The authors would like to thank the Federal Ministry of Education and Research of Germany for its financial support (project 05K2016), and the HZDR’s Ion Beam Center for its essential contribution to the realization of this project.

Published
2018

49. List of contributors

Author

Accomo, R., primary, Achtziger, N., additional, Adams, S.J.A., additional, Akasaki, I., additional, Albert, J.P., additional, Amano, H., additional, André, R., additional, Antonelli, A., additional, Asif Khan, M., additional, Aulombard, R.L., additional, Austin, R.F., additional, Balestrino, G., additional, Baltramiejūnas, R., additional, Bechstedt, F., additional, Bécourt, N., additional, Bergman, L., additional, Bernholc, J., additional, Bertho, D., additional, Bertoni, CM., additional, Billat, S., additional, Boćkowski, M., additional, Bodin, C., additional, Bodin-Deshayes, C., additional, Boiko, E.B., additional, Boring, P., additional, Bouhelal, A., additional, Bratina, G., additional, Brennan, K.F., additional, Briddon, P.R., additional, Briot, O., additional, Broser, I., additional, Bsiesy, A., additional, Bucher, E., additional, Burchard, A., additional, Cantwell, G., additional, Carter, C.H., additional, Castro, T., additional, Cavenett, B.C., additional, Chadi, D.J., additional, Chen, K.M., additional, Chen, X., additional, Cheng, H., additional, Choyke, W.J., additional, Christensen, N.E., additional, Cibert, J., additional, Cingolani, R., additional, Cloitre, T., additional, Cohen, P.I., additional, Collins, A.T., additional, Cotal, H.L., additional, Cricenti, A., additional, Dabbicco, M., additional, Dang, L.S., additional, Davis, R.F., additional, Deicher, M., additional, DePuydt, J.M., additional, Dischler, B., additional, Dmitriev, V.A., additional, Donegan, J.F., additional, Doran, J.P., additional, Dubowski, J.J., additional, Eckey, L., additional, Edmond, J.A., additional, Efros, A.L., additional, Egan, R.J., additional, Engelbrecht, F., additional, Evstropov, W., additional, Fanciulli, M., additional, Feldman, R.D., additional, Felici, A.C., additional, Ferrara, M., additional, Ferrari, L., additional, Ferry, D.K., additional, Feuillet, G., additional, Fiedler, M., additional, Finocchi, F., additional, Fischer, R., additional, Fishman, G., additional, Franciosi, A., additional, Fricke, Ch., additional, Frolov, S.I., additional, Fuchs, D., additional, Galli, G., additional, Gaponenko, S.V., additional, Gaspard, F., additional, Gavrilenko, V.I., additional, Gavryushin, V., additional, Gebhardt, W., additional, Germanenko, I.N., additional, Geurts, J., additional, Geyzers, K.P., additional, Gil, B., additional, Gladfelter, W., additional, Gleitsman, G., additional, Göbel, E.O., additional, Godet, C., additional, Goede, O., additional, Gorczyca, I., additional, Gribkovskii, V.P., additional, Grzegory, I., additional, Gumlich, H.-E., additional, Gunshor, R.L., additional, Gurskii, A.L., additional, Gutowski, J., additional, Gygi, F., additional, Haase, M.A., additional, Haberstroh, C, additional, Harsch, W.C., additional, Hauksson, I., additional, Hayashi, S., additional, Hegarty, J., additional, Heimbrodt, W., additional, Heime, K., additional, Heine, V., additional, Heitz, R., additional, Helbig, R., additional, Henderson, B., additional, Henneberger, F., additional, Hérino, R., additional, Hermans, J., additional, Heuken, M., additional, Hoffmann, A., additional, Hoffmann, H., additional, Hoffmann, N., additional, Hofsäss, H., additional, Humphreys, T.P., additional, Hunt, R.W., additional, Iarlori, S., additional, Iida, S., additional, Ikoma, K., additional, Itie, J.P., additional, Jacobs, K., additional, Jahn, S.G., additional, Jancu, J.M., additional, Jaussaud, C., additional, Jentzsch, T., additional, Johnson, R.L., additional, Jones, R., additional, Jouanin, C., additional, Jouneau, P.H., additional, Jun, J., additional, Jungnickel, V., additional, Juodžbalis, D., additional, Kajihara, S.A., additional, Kanicki, J., additional, Karmann, S., additional, Katayama-Yoshida, H., additional, Kawakami, Y., additional, Kazlauskas, A., additional, Kean, A., additional, Khan, M.R.H., additional, King-Smith, R.D., additional, Kinto, H., additional, Kißmann, U., additional, Klimakow, A., additional, Klyui, N.I., additional, Koide, N., additional, Koidl, P., additional, Kong, H.-S., additional, Kong, H.S., additional, König, Th., additional, Kono, J., additional, Kononenko, V.K., additional, Kotaki, M., additional, Kreß, C., additional, Krings, T., additional, Krukowski, St., additional, Kubertavicius, V., additional, Kudlek, G.H., additional, Kuhn, W., additional, Kunc, K., additional, Kuroda, Y., additional, Kuznia, J.N., additional, Kwak, K.W., additional, Labrunie, G., additional, Laks, D.B., additional, Lambrecht, W.R.L., additional, Lankes, S., additional, Lebed, V. Yu., additional, Lei, T., additional, Leibenzeder, S., additional, Lepore, M., additional, Licht, T., additional, Ligeon, M., additional, Linkov, I. Yu., additional, Litwin-Staszewska, E., additional, Logothetidis, S., additional, Luce, G., additional, Lutsenko, E.V., additional, Lux-Steiner, M. Ch., additional, Madéore, F., additional, Magerle, R., additional, Mahnke, H.-E., additional, Maier, K., additional, Malinovskii, I.E., additional, Manabe, K., additional, Marinelli, M., additional, Markey, B.G., additional, Markwitz, A., additional, Marshall, T., additional, Mathieu, H., additional, Matsunami, H., additional, McCaldin, J.O., additional, McGill, T.C., additional, McKeever, S.W.S., additional, Meier, J., additional, Mihalcescu, I., additional, Milani, E., additional, Mitcovets, A.I., additional, Mitsuyu, T., additional, Miura, N., additional, Molnar, R.J., additional, Molva, E., additional, Morohashi, M., additional, Morozenko, Ya.V., additional, Moustakas, T.D., additional, Mujica, A., additional, Mula, G., additional, Muller, F., additional, Müller-Sebert, W., additional, Muñoz, A., additional, Mura, A., additional, Naumov, A., additional, Needs, R.J., additional, Nemanich, R.J., additional, Nicolini, R., additional, Nurmikko, A.V, additional, O'Donnell, K.P., additional, Oguchi, T., additional, Ohkawa, K., additional, Okamoto, S., additional, Okazaki, N., additional, Okumura, H., additional, Osman, M.A., additional, Palmour, J.W., additional, Paloura, E.C., additional, Palummo, M., additional, Paoletti, A., additional, Papon, A.M., additional, Paroli, P., additional, Parrinello, M., additional, Pensl, G., additional, Pereira, E., additional, Perlin, P., additional, Petalas, J., additional, Pfeiffer, W., additional, Phillips, M.C., additional, Pikus, F.G, additional, Pinter, I., additional, Pirzer, M., additional, Pohl, U., additional, Pohl, U.W., additional, Polatoglou, H.M., additional, Polian, A., additional, Polini, R., additional, Ponga, B.E., additional, Ponthenier, J.L., additional, Porowski, S., additional, Prins, J.F., additional, Prior, K.A., additional, Puls, J., additional, Qiu, J., additional, Qteish, A., additional, Raciukaitis, G., additional, Reining, L., additional, Reisinger, T., additional, Restle, M., additional, Righini, M., additional, Rodríguez-Hernández, P., additional, Rolfe, S.J., additional, Romestain, R., additional, Ryzhikov, VD., additional, Sailer, B., additional, Sander, D., additional, Santos, L., additional, Sasaki, T., additional, Sawada, M., additional, Scamarcio, G., additional, Scarselli, M.A., additional, Schadt, M., additional, Schneider, A., additional, Schneider, J., additional, Schöner, A., additional, Schülzgen, A., additional, Selci, S., additional, Shinohara, M., additional, Simpson, J., additional, Sorba, L., additional, Spellmeyer, B., additional, Stanley, R.P., additional, Stanzl, H., additional, Stein, R.A., additional, Stewart, H., additional, Suemune, I., additional, Sulzer, G., additional, Suski, T., additional, Suttrop, W., additional, Swenberg, J.F., additional, Taghizadeh, M.R., additional, Takeyama, S., additional, Tansley, T.L., additional, Tebano, A., additional, Thurian, P., additional, Tosatti, E., additional, Trager-Cowan, C., additional, Troullier, N., additional, Tschentscher, I., additional, Tsuboi, N., additional, Tsujimura, A., additional, Tsukioka, K., additional, Tupenevich, P.A., additional, Turner, K.F., additional, Uchiki, H., additional, Uhrmacher, M., additional, Ullrich, B., additional, Uttamchandani, D., additional, Van de Walle, C.G., additional, van der Weide, J., additional, Van Hove, J.M., additional, Vanderbilt, D., additional, Vanzetti, L., additional, Vasileska, D., additional, Vial, J.C., additional, Wagner, H.P., additional, Wahl, U., additional, Waldmann, H., additional, Walker, CT., additional, Wang, E.G., additional, Wang, M.W., additional, Wang, S.Y., additional, Wang, Y., additional, Weinhold, V., additional, Wiehert, T., additional, Wild, C., additional, Witthuhn, W., additional, Wolf, H., additional, Wolf, K., additional, Wörz, M., additional, Yablonskii, G.P., additional, Yagi, M., additional, Yamaga, S., additional, Yamanaka, M., additional, Yang, F., additional, Yoshii, S., additional, Yoshikawa, A., additional, Yu, X., additional, Zeitz, W., additional, and Zimin, L.G., additional

Published
1993
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