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446 results on '"Baehtz, C."'

1. Plasma screening in mid-charged ions observed by K-shell line emission

Author

Šmıd, M., Humphries, O., Baehtz, C., Brambrink, E., Burian, T., Cho, M. S., Cowan, T. E., Gaus, L., Gu, M. F., Hájková, V., Juha, L., Konopkova, Z., Le, H. P., Makita, M., Pan, X., Preston, T., Schropp, A., Scott, H. A., Štefanıková, R., Vorberger, J., Wang, W., Zastrau, U., and Falk, K.

Subjects
Physics - Plasma Physics
Abstract

Dense plasma environment affects the electronic structure of ions via variations of the microscopic electrical fields, also known as plasma screening. This effect can be either estimated by simplified analytical models, or by computationally expensive and to date unverified numerical calculations. We have experimentally quantified plasma screening from the energy shifts of the bound-bound transitions in matter driven by the x-ray free electron laser (XFEL). This was enabled by identification of detailed electronic configurations of the observed K{\alpha}, K\b{eta} and K{\gamma} lines. This work paves the way for improving plasma screening models including connected effects like ionization potential depression and continuum lowering, which will advance the understanding of atomic physics in Warm Dense Matter regime.

Published
2024

2. Letter of Intent: Towards a Vacuum Birefringence Experiment at the Helmholtz International Beamline for Extreme Fields

Author

Ahmadiniaz, N., Bähtz, C., Benediktovitch, A., Bömer, C., Bocklage, L., Cowan, T. E., Edwards, J., Evans, S., Viñas, S. Franchino, Gies, H., Göde, S., Görs, J., Grenzer, J., Acosta, U. Hernandez, Heinzl, T., Hilz, P., Hippler, W., Huang, L. G., Humphries, O., Karbstein, F., Khademi, P., King, B., Kluge, T., Kohlfürst, C., Krebs, D., Laso-García, A., Lötzsch, R., Macleod, A. J., Marx-Glowna, B., Mosman, E. A., Nakatsutsumi, M., Paulus, G. G., Rahul, S. V., Randolph, L., Röhlsberger, R., Rohringer, N., Sävert, A., Sadashivaiah, S., Sauerbrey, R., Schlenvoigt, H. -P., Schmidt, S. M., Schramm, U., Schützhold, R., Schwinkendorf, J. -P., Seipt, D., Šmíd, M., Stöhlker, T., Toncian, T., Valialshchikov, M., Wipf, A., Zastrau, U., and Zepf, M.

Subjects
Physics - Instrumentation and Detectors, High Energy Physics - Experiment, High Energy Physics - Phenomenology, Physics - Optics
Abstract

Quantum field theory predicts a nonlinear response of the vacuum to strong electromagnetic fields of macroscopic extent. This fundamental tenet has remained experimentally challenging and is yet to be tested in the laboratory. A particularly distinct signature of the resulting optical activity of the quantum vacuum is vacuum birefringence. This offers an excellent opportunity for a precision test of nonlinear quantum electrodynamics in an uncharted parameter regime. Recently, the operation of the high-intensity laser ReLaX provided by the Helmholtz International Beamline for Extreme Fields (HIBEF) has been inaugurated at the High Energy Density (HED) scientific instrument of the European XFEL. We make the case that this worldwide unique combination of an x-ray free-electron laser and an ultra-intense near-infrared laser together with recent advances in high-precision x-ray polarimetry, refinements of prospective discovery scenarios, and progress in their accurate theoretical modelling have set the stage for performing an actual discovery experiment of quantum vacuum nonlinearity., Comment: 34 pages, 21 figures

Published
2024

3. Phase transition kinetics of superionic H2O ice phases revealed by Megahertz X-ray free-electron laser-heating experiments

Author

Husband, R. J., Liermann, H. P., McHardy, J. D., McWilliams, R. S., Goncharov, A. F., Prakapenka, V. B., Edmund, E., Chariton, S., Konôpková, Z., Strohm, C., Sanchez-Valle, C., Frost, M., Andriambariarijaona, L., Appel, K., Baehtz, C., Ball, O. B., Briggs, R., Buchen, J., Cerantola, V., Choi, J., Coleman, A. L., Cynn, H., Dwivedi, A., Graafsma, H., Hwang, H., Koemets, E., Laurus, T., Lee, Y., Li, X., Marquardt, H., Mondal, A., Nakatsutsumi, M., Ninet, S., Pace, E., Pepin, C., Prescher, C., Stern, S., Sztuk-Dambietz, J., Zastrau, U., and McMahon, M. I.

Published
2024
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4. Shock compression experiments using the DiPOLE 100-X laser on the high energy density instrument at the European x-ray free electron laser: Quantitative structural analysis of liquid Sn.

Author

Gorman, M. G., McGonegle, D., Smith, R. F., Singh, S., Jenkins, T., McWilliams, R. S., Albertazzi, B., Ali, S. J., Antonelli, L., Armstrong, M. R., Baehtz, C., Ball, O. B., Banerjee, S., Belonoshko, A. B., Benuzzi-Mounaix, A., Bolme, C. A., Bouffetier, V., Briggs, R., Buakor, K., and Butcher, T.

Subjects
FREE electron lasers, LIQUID analysis, ENERGY density, X-ray lasers, LASERS, LIQUID density
Abstract

X-ray free electron laser (XFEL) sources coupled to high-power laser systems offer an avenue to study the structural dynamics of materials at extreme pressures and temperatures. The recent commissioning of the DiPOLE 100-X laser on the high energy density (HED) instrument at the European XFEL represents the state-of-the-art in combining x-ray diffraction with laser compression, allowing for compressed materials to be probed in unprecedented detail. Here, we report quantitative structural measurements of molten Sn compressed to 85(5) GPa and ∼ 3500 K. The capabilities of the HED instrument enable liquid density measurements with an uncertainty of ∼ 1 % at conditions which are extremely challenging to reach via static compression methods. We discuss best practices for conducting liquid diffraction dynamic compression experiments and the necessary intensity corrections which allow for accurate quantitative analysis. We also provide a polyimide ablation pressure vs input laser energy for the DiPOLE 100-X drive laser which will serve future users of the HED instrument. [ABSTRACT FROM AUTHOR]

Published
2024
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5. Novel experimental setup for megahertz X‐ray diffraction in a diamond anvil cell at the High Energy Density (HED) instrument of the European X‐ray Free‐Electron Laser (EuXFEL)

Author

Liermann, HP, Konôpková, Z, Appel, K, Prescher, C, Schropp, A, Cerantola, V, Husband, RJ, McHardy, JD, McMahon, MI, McWilliams, RS, Pépin, CM, Mainberger, J, Roeper, M, Berghäuser, A, Damker, H, Talkovski, P, Foese, M, Kujala, N, Ball, OB, Baron, MA, Briggs, R, Bykov, M, Bykova, E, Chantel, J, Coleman, AL, Cynn, H, Dattelbaum, D, Dresselhaus-Marais, LE, Eggert, JH, Ehm, L, Evans, WJ, Fiquet, G, Frost, M, Glazyrin, K, Goncharov, AF, Hwang, H, Jenei, Zs, Kim, J-Y, Langenhorst, F, Lee, Y, Makita, M, Marquardt, H, McBride, EE, Merkel, S, Morard, G, O'Bannon, EF, Otzen, C, Pace, EJ, Pelka, A, Pigott, JS, Prakapenka, VB, Redmer, R, Sanchez-Valle, C, Schoelmerich, M, Speziale, S, Spiekermann, G, Sturtevant, BT, Toleikis, S, Velisavljevic, N, Wilke, M, Yoo, C-S, Baehtz, C, Zastrau, U, and Strohm, C

Subjects
diamond anvil cells, X-ray free-electron lasers, high-precision X-ray diffraction, finite element modeling, Condensed Matter Physics, Optical Physics, Physical Chemistry (incl. Structural), Biophysics
Abstract

The high-precision X-ray diffraction setup for work with diamond anvil cells (DACs) in interaction chamber 2 (IC2) of the High Energy Density instrument of the European X-ray Free-Electron Laser is described. This includes beamline optics, sample positioning and detector systems located in the multipurpose vacuum chamber. Concepts for pump-probe X-ray diffraction experiments in the DAC are described and their implementation demonstrated during the First User Community Assisted Commissioning experiment. X-ray heating and diffraction of Bi under pressure, obtained using 20 fs X-ray pulses at 17.8 keV and 2.2 MHz repetition, is illustrated through splitting of diffraction peaks, and interpreted employing finite element modeling of the sample chamber in the DAC.

Published
2021

6. Shock compression experiments using the DiPOLE 100-X laser on the high energy density instrument at the European x-ray free electron laser: Quantitative structural analysis of liquid Sn

Author

Gorman, M, Mcgonegle, D, Smith, R, Singh, S, Jenkins, T, Mcwilliams, R, Albertazzi, B, Ali, S, Antonelli, L, Armstrong, M, Baehtz, C, Ball, O, Banerjee, S, Belonoshko, A, Benuzzi-Mounaix, A, Bolme, C, Bouffetier, V, Briggs, R, Buakor, K, Butcher, T, Di Dio Cafiso, S, Cerantola, V, Chantel, J, Di Cicco, A, Clarke, S, Coleman, A, Collier, J, Collins, G, Comley, A, Coppari, F, Cowan, T, Cristoforetti, G, Cynn, H, Descamps, A, Dorchies, F, Duff, M, Dwivedi, A, Edwards, C, Eggert, J, Errandonea, D, Fiquet, G, Galtier, E, Laso Garcia, A, Ginestet, H, Gizzi, L, Gleason, A, Goede, S, Gonzalez, J, Harmand, M, Hartley, N, Heighway, P, Hernandez-Gomez, C, Higginbotham, A, Höppner, H, Husband, R, Hutchinson, T, Hwang, H, Lazicki, A, Keen, D, Kim, J, Koester, P, Konopkova, Z, Kraus, D, Krygier, A, Labate, L, Lee, Y, Liermann, H, Mason, P, Masruri, M, Massani, B, Mcbride, E, Mcguire, C, Mchardy, J, Merkel, S, Morard, G, Nagler, B, Nakatsutsumi, M, Nguyen-Cong, K, Norton, A, Oleynik, I, Otzen, C, Ozaki, N, Pandolfi, S, Peake, D, Pelka, A, Pereira, K, Phillips, J, Prescher, C, Preston, T, Randolph, L, Ranjan, D, Ravasio, A, Redmer, R, Rips, J, Santamaria-Perez, D, Savage, D, Schoelmerich, M, Schwinkendorf, J, Smith, J, Sollier, A, Spear, J, Spindloe, C, Stevenson, M, Strohm, C, Suer, T, Tang, M, Toncian, M, Toncian, T, Tracy, S, Trapananti, A, Tschentscher, T, Tyldesley, M, Vennari, C, Vinci, T, Vogel, S, Volz, T, Vorberger, J, Walsh, J, Wark, J, Willman, J, Wollenweber, L, Zastrau, U, Brambrink, E, Appel, K, Mcmahon, M, Gorman, M. G., McGonegle, D., Smith, R. F., Singh, S., Jenkins, T., McWilliams, R. S., Albertazzi, B., Ali, S. J., Antonelli, L., Armstrong, M. R., Baehtz, C., Ball, O. B., Banerjee, S., Belonoshko, A. B., Benuzzi-Mounaix, A., Bolme, C. A., Bouffetier, V., Briggs, R., Buakor, K., Butcher, T., Di Dio Cafiso, S., Cerantola, V., Chantel, J., Di Cicco, A., Clarke, S., Coleman, A. L., Collier, J., Collins, G. W., Comley, A. J., Coppari, F., Cowan, T. E., Cristoforetti, G., Cynn, H., Descamps, A., Dorchies, F., Duff, M. J., Dwivedi, A., Edwards, C., Eggert, J. H., Errandonea, D., Fiquet, G., Galtier, E., Laso Garcia, A., Ginestet, H., Gizzi, L., Gleason, A., Goede, S., Gonzalez, J. M., Harmand, M., Hartley, N. J., Heighway, P. G., Hernandez-Gomez, C., Higginbotham, A., Höppner, H., Husband, R. J., Hutchinson, T. M., Hwang, H., Lazicki, A. E., Keen, D. A., Kim, J., Koester, P., Konopkova, Z., Kraus, D., Krygier, A., Labate, L., Lee, Y., Liermann, H. -P., Mason, P., Masruri, M., Massani, B., McBride, E. E., McGuire, C., McHardy, J. D., Merkel, S., Morard, G., Nagler, B., Nakatsutsumi, M., Nguyen-Cong, K., Norton, A. -M., Oleynik, I. I., Otzen, C., Ozaki, N., Pandolfi, S., Peake, D. J., Pelka, A., Pereira, K. A., Phillips, J. P., Prescher, C., Preston, T. R., Randolph, L., Ranjan, D., Ravasio, A., Redmer, R., Rips, J., Santamaria-Perez, D., Savage, D. J., Schoelmerich, M., Schwinkendorf, J. -P., Smith, J., Sollier, A., Spear, J., Spindloe, C., Stevenson, M., Strohm, C., Suer, T. -A., Tang, M., Toncian, M., Toncian, T., Tracy, S. J., Trapananti, A., Tschentscher, T., Tyldesley, M., Vennari, C. E., Vinci, T., Vogel, S. C., Volz, T. J., Vorberger, J., Walsh, J. P. S., Wark, J. S., Willman, J. T., Wollenweber, L., Zastrau, U., Brambrink, E., Appel, K., McMahon, M. I., Gorman, M, Mcgonegle, D, Smith, R, Singh, S, Jenkins, T, Mcwilliams, R, Albertazzi, B, Ali, S, Antonelli, L, Armstrong, M, Baehtz, C, Ball, O, Banerjee, S, Belonoshko, A, Benuzzi-Mounaix, A, Bolme, C, Bouffetier, V, Briggs, R, Buakor, K, Butcher, T, Di Dio Cafiso, S, Cerantola, V, Chantel, J, Di Cicco, A, Clarke, S, Coleman, A, Collier, J, Collins, G, Comley, A, Coppari, F, Cowan, T, Cristoforetti, G, Cynn, H, Descamps, A, Dorchies, F, Duff, M, Dwivedi, A, Edwards, C, Eggert, J, Errandonea, D, Fiquet, G, Galtier, E, Laso Garcia, A, Ginestet, H, Gizzi, L, Gleason, A, Goede, S, Gonzalez, J, Harmand, M, Hartley, N, Heighway, P, Hernandez-Gomez, C, Higginbotham, A, Höppner, H, Husband, R, Hutchinson, T, Hwang, H, Lazicki, A, Keen, D, Kim, J, Koester, P, Konopkova, Z, Kraus, D, Krygier, A, Labate, L, Lee, Y, Liermann, H, Mason, P, Masruri, M, Massani, B, Mcbride, E, Mcguire, C, Mchardy, J, Merkel, S, Morard, G, Nagler, B, Nakatsutsumi, M, Nguyen-Cong, K, Norton, A, Oleynik, I, Otzen, C, Ozaki, N, Pandolfi, S, Peake, D, Pelka, A, Pereira, K, Phillips, J, Prescher, C, Preston, T, Randolph, L, Ranjan, D, Ravasio, A, Redmer, R, Rips, J, Santamaria-Perez, D, Savage, D, Schoelmerich, M, Schwinkendorf, J, Smith, J, Sollier, A, Spear, J, Spindloe, C, Stevenson, M, Strohm, C, Suer, T, Tang, M, Toncian, M, Toncian, T, Tracy, S, Trapananti, A, Tschentscher, T, Tyldesley, M, Vennari, C, Vinci, T, Vogel, S, Volz, T, Vorberger, J, Walsh, J, Wark, J, Willman, J, Wollenweber, L, Zastrau, U, Brambrink, E, Appel, K, Mcmahon, M, Gorman, M. G., McGonegle, D., Smith, R. F., Singh, S., Jenkins, T., McWilliams, R. S., Albertazzi, B., Ali, S. J., Antonelli, L., Armstrong, M. R., Baehtz, C., Ball, O. B., Banerjee, S., Belonoshko, A. B., Benuzzi-Mounaix, A., Bolme, C. A., Bouffetier, V., Briggs, R., Buakor, K., Butcher, T., Di Dio Cafiso, S., Cerantola, V., Chantel, J., Di Cicco, A., Clarke, S., Coleman, A. L., Collier, J., Collins, G. W., Comley, A. J., Coppari, F., Cowan, T. E., Cristoforetti, G., Cynn, H., Descamps, A., Dorchies, F., Duff, M. J., Dwivedi, A., Edwards, C., Eggert, J. H., Errandonea, D., Fiquet, G., Galtier, E., Laso Garcia, A., Ginestet, H., Gizzi, L., Gleason, A., Goede, S., Gonzalez, J. M., Harmand, M., Hartley, N. J., Heighway, P. G., Hernandez-Gomez, C., Higginbotham, A., Höppner, H., Husband, R. J., Hutchinson, T. M., Hwang, H., Lazicki, A. E., Keen, D. A., Kim, J., Koester, P., Konopkova, Z., Kraus, D., Krygier, A., Labate, L., Lee, Y., Liermann, H. -P., Mason, P., Masruri, M., Massani, B., McBride, E. E., McGuire, C., McHardy, J. D., Merkel, S., Morard, G., Nagler, B., Nakatsutsumi, M., Nguyen-Cong, K., Norton, A. -M., Oleynik, I. I., Otzen, C., Ozaki, N., Pandolfi, S., Peake, D. J., Pelka, A., Pereira, K. A., Phillips, J. P., Prescher, C., Preston, T. R., Randolph, L., Ranjan, D., Ravasio, A., Redmer, R., Rips, J., Santamaria-Perez, D., Savage, D. J., Schoelmerich, M., Schwinkendorf, J. -P., Smith, J., Sollier, A., Spear, J., Spindloe, C., Stevenson, M., Strohm, C., Suer, T. -A., Tang, M., Toncian, M., Toncian, T., Tracy, S. J., Trapananti, A., Tschentscher, T., Tyldesley, M., Vennari, C. E., Vinci, T., Vogel, S. C., Volz, T. J., Vorberger, J., Walsh, J. P. S., Wark, J. S., Willman, J. T., Wollenweber, L., Zastrau, U., Brambrink, E., Appel, K., and McMahon, M. I.

Abstract

X-ray free electron laser (XFEL) sources coupled to high-power laser systems offer an avenue to study the structural dynamics of materials at extreme pressures and temperatures. The recent commissioning of the DiPOLE 100-X laser on the high energy density (HED) instrument at the European XFEL represents the state-of-the-art in combining x-ray diffraction with laser compression, allowing for compressed materials to be probed in unprecedented detail. Here, we report quantitative structural measurements of molten Sn compressed to 85(5) GPa and ∼ 3500 K. The capabilities of the HED instrument enable liquid density measurements with an uncertainty of ∼ 1 % at conditions which are extremely challenging to reach via static compression methods. We discuss best practices for conducting liquid diffraction dynamic compression experiments and the necessary intensity corrections which allow for accurate quantitative analysis. We also provide a polyimide ablation pressure vs input laser energy for the DiPOLE 100-X drive laser which will serve future users of the HED instrument.

Published
2024

7. Phase transition kinetics of superionic H2O ice phases revealed by Megahertz X-ray free-electron laser-heating experiments.

Author

Husband, R. J., Liermann, H. P., McHardy, J. D., McWilliams, R. S., Goncharov, A. F., Prakapenka, V. B., Edmund, E., Chariton, S., Konôpková, Z., Strohm, C., Sanchez-Valle, C., Frost, M., Andriambariarijaona, L., Appel, K., Baehtz, C., Ball, O. B., Briggs, R., Buchen, J., Cerantola, V., and Choi, J.

Subjects
PHASE transitions, FACE centered cubic structure, ICE sheets, LASER pulses, HIGH temperatures, FREE electron lasers, FEMTOSECOND pulses
Abstract

H2O transforms to two forms of superionic (SI) ice at high pressures and temperatures, which contain highly mobile protons within a solid oxygen sublattice. Yet the stability field of both phases remains debated. Here, we present the results of an ultrafast X-ray heating study utilizing MHz pulse trains produced by the European X-ray Free Electron Laser to create high temperature states of H2O, which were probed using X-ray diffraction during dynamic cooling. We confirm an isostructural transition during heating in the 26-69 GPa range, consistent with the formation of SI-bcc. In contrast to prior work, SI-fcc was observed exclusively above ~50 GPa, despite evidence of melting at lower pressures. The absence of SI-fcc in lower pressure runs is attributed to short heating timescales and the pressure-temperature path induced by the pump-probe heating scheme in which H2O was heated above its melting temperature before the observation of quenched crystalline states, based on the earlier theoretical prediction that SI-bcc nucleates more readily from the fluid than SI-fcc. Our results may have implications for the stability of SI phases in ice-rich planets, for example during dynamic freezing, where the preferential crystallization of SI-bcc may result in distinct physical properties across mantle ice layers. The authors perform heating experiments using femtosecond X-ray free electron laser pulses to explore the phase stability of superionic H2O. The absence of a face-centered cubic phase below 50 GPa, where superionic ice forms from the melt, is attributed to the short heating time and may help understanding the stability of superionic phases in ice-rich planets. [ABSTRACT FROM AUTHOR]

Published
2024
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8. Dynamic optical spectroscopy and pyrometry of static targets under optical and x-ray laser heating at the European XFEL.

Author

Ball, O. B., Prescher, C., Appel, K., Baehtz, C., Baron, M. A., Briggs, R., Cerantola, V., Chantel, J., Chariton, S., Coleman, A. L., Cynn, H., Damker, H., Dattelbaum, D., Dresselhaus-Marais, L. E., Eggert, J. H., Ehm, L., Evans, W. J., Fiquet, G., Frost, M., and Glazyrin, K.

Subjects
DIAMOND anvil cell, OPTICAL spectroscopy, X-ray lasers, OPTICAL measurements, FREE electron lasers, PYROMETRY, BACKGROUND radiation
Abstract

Experiments accessing extreme conditions at x-ray free electron lasers (XFELs) involve rapidly evolving conditions of temperature. Here, we report time-resolved, direct measurements of temperature using spectral streaked optical pyrometry of x-ray and optical laser-heated states at the High Energy Density instrument of the European XFEL. This collection of typical experiments, coupled with numerical models, outlines the reliability, precision, and meaning of time dependent temperature measurements using optical emission at XFEL sources. Dynamic temperatures above 1500 K are measured continuously from spectrally- and temporally-resolved thermal emission at 450–850 nm, with time resolution down to 10–100 ns for 1–200 μ s streak camera windows, using single shot and integrated modes. Targets include zero-pressure foils free-standing in air and in vacuo, and high-pressure samples compressed in diamond anvil cell multi-layer targets. Radiation sources used are 20-fs hard x-ray laser pulses at 17.8 keV, in single pulses or 2.26 MHz pulse trains of up to 30 pulses, and 250-ns infrared laser single pulses. A range of further possibilities for optical measurements of visible light in x-ray laser experiments using streak optical spectroscopy are also explored, including for the study of x-ray induced optical fluorescence, which often appears as background in thermal radiation measurements. We establish several scenarios where combined emissions from multiple sources are observed and discuss their interpretation. Challenges posed by using x-ray lasers as non-invasive probes of the sample state are addressed. [ABSTRACT FROM AUTHOR]

Published
2023
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9. High Curie temperature and perpendicular magnetic anisotropy in homoepitaxial InMnAs films

Author

Yuan, Y., Wang, Y., Gao, K., Khalid, M., Wu, C., Zhang, W., Munnik, F., Weschke, E., Baehtz, C., Skorupa, W., Helm, M., and Zhou, S.

Subjects
Condensed Matter - Materials Science
Abstract

We have prepared the dilute magnetic semiconductor (DMS) InMnAs with different Mn concentrations by ion implantation and pulsed laser melting. The Curie temperature of the In1-xMnxAs epilayer depends on the Mn concentration x, reaching 82 K for x=0.105. The substitution of Mn ions at the Indium sites induces a compressive strain perpendicular to the InMnAs layer and a tensile strain along the in-plane direction. This gives rise to a large perpendicular magnetic anisotropy, which is often needed for the demonstration of electrical control of magnetization and for spin-transfer-torque induced magnetization reversal., Comment: 16 pages, 5 figures

Published
2015
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10. Hyperdoping silicon with selenium: solid vs. liquid phase epitaxy

Author

Zhou, S., Liu, F., Prucnal, S., Gao, K., Khalid, M., Baehtz, C., Posselt, M., Skorupa, W., and Helm, M.

Subjects
Condensed Matter - Materials Science
Abstract

Chalcogen-hyperdoped silicon shows potential applications in silicon-based infrared photodetectors and intermediate band solar cells. Due to the low solid solubility limits of chalcogen elements in silicon, these materials were previously realized by femtosecond or nanosecond laser annealing of implanted silicon or bare silicon in certain background gases. The high energy density deposited on the silicon surface leads to a liquid phase and the fast recrystallization velocity allows trapping of chalcogen into the silicon matrix. However, this method encounters the problem of surface segregation. In this paper, we propose a solid phase processing by flash-lamp annealing in the millisecond range, which is in between the conventional rapid thermal annealing and pulsed laser annealing. Flash lamp annealed selenium-implanted silicon shows a substitutional fraction of around 70% with an implanted concentration up to 2.3%. The resistivity is lower and the carrier mobility is higher than those of nanosecond pulsed laser annealed samples. Our results show that flash-lamp annealing is superior to laser annealing in preventing surface segregation and in allowing scalability., Comment: 19 pages, 7 figures, to be published at Scientific Reports

Published
2015
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11. A comprehensive study of the magnetic, structural and transport properties of the III-V ferromagnetic semiconductor InMnP

Author

Khalid, M., Gao, Kun, Weschke, E., Huebner, R., Baehtz, C., Gordan, O., Salvan, G., Zahn, D. R. T., Skorupa, W., Helm, M., and Zhou, Shengqiang

Subjects
Condensed Matter - Materials Science
Abstract

The manganese induced magnetic, electrical and structural modification in InMnP epilayers, prepared by Mn ion implantation and pulsed laser annealing, are investigated in the following work. All samples exhibit clear hysteresis loops and strong spin polarization at the Fermi level. The degree of magnetization, the Curie temperature and the spin polarization depend on the Mn concentration. The bright-field transmission electron micrographs show that InP samples become almost amorphous after Mn implantation but recrystallize after pulsed laser annealing. We did not observe an insulator-metal transition in InMnP up to a Mn concentration of 5 at./%. Instead all InMnP samples show insulating characteristics up to the lowest measured temperature. Magneotresistance results obtained at low temperatures support the hopping conduction mechanism in InMnP. We find that the Mn impurity band remains detached from the valence band in InMnP up to 5 at./% Mn doping. Our findings indicate that the local environment of Mn ions in InP is similar to GaMnAs, GaMnP and InMnAs, however, the electrical properties of these Mn implanted III-V compounds are different. This is one of the consequences of the different Mn binding energy in these compounds., Comment: 21 pages, 8 figures, to be published at J. Appl. Phys

Published
2015
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12. Imaging x-ray spectrometer at the high energy density instrument of the European x-ray free electron laser

Author

Pan, X, Smid, M, Stefanikova, R, Donat, F, Baehtz, C, Burian, T, Cerantola, V, Gaus, L, Humphries, O, Hajkova, V, Juha, L, Krupka, M, Kozlova, M, Konopkova, Z, Preston, T, Wollenweber, L, Zastrau, U, Falk, K, Pan X., Smid M., Stefanikova R., Donat F., Baehtz C., Burian T., Cerantola V., Gaus L., Humphries O. S., Hajkova V., Juha L., Krupka M., Kozlova M., Konopkova Z., Preston T. R., Wollenweber L., Zastrau U., Falk K., Pan, X, Smid, M, Stefanikova, R, Donat, F, Baehtz, C, Burian, T, Cerantola, V, Gaus, L, Humphries, O, Hajkova, V, Juha, L, Krupka, M, Kozlova, M, Konopkova, Z, Preston, T, Wollenweber, L, Zastrau, U, Falk, K, Pan X., Smid M., Stefanikova R., Donat F., Baehtz C., Burian T., Cerantola V., Gaus L., Humphries O. S., Hajkova V., Juha L., Krupka M., Kozlova M., Konopkova Z., Preston T. R., Wollenweber L., Zastrau U., and Falk K.

Abstract

A multipurpose imaging x-ray crystal spectrometer is developed for the high energy density instrument of the European X-ray Free Electron Laser. The spectrometer is designed to measure x rays in the energy range of 4-10 keV, providing high-resolution, spatially resolved spectral measurements. A toroidally bent germanium (Ge) crystal is used, allowing x-ray diffraction from the crystal to image along a one-dimensional spatial profile while spectrally resolving along the other. A detailed geometrical analysis is performed to determine the curvature of the crystal. The theoretical performance of the spectrometer in various configurations is calculated by ray-tracing simulations. The key properties of the spectrometer, including the spectral and spatial resolution, are demonstrated experimentally on different platforms. Experimental results prove that this Ge spectrometer is a powerful tool for spatially resolved measurements of x-ray emission, scattering, or absorption spectra in high energy density physics.

Published
2023

13. Evidence for charge and orbital order in the doped titanates RE_(1-x)Ca_xTiO_3 (RE=Y, Er, Lu)

Author

Komarek, A. C., Reuther, M., Lorenz, T., Cousson, A., Link, P., Morgenroth, W., Trots, D., Baehtz, C., and Braden, M.

Subjects
Condensed Matter - Strongly Correlated Electrons
Abstract

Combining macroscopic and diffraction methods we have studied the electric, magnetic and struc- tural properties of RE_(1-x)Ca_xTiO_3 (RE=Y, Er, Lu) focusing on the concentration range near the metal-insulator transition. The insulating phase, which is stabilized by a smaller rare-earth ionic ra- dius, exhibits charge order with a predominant occupation of the dxy orbital. The charge and orbital ordering explains the broad stability range of the insulating state in RE_(1-x)Ca_xTiO_3 with smaller rare-earth ions. The strong modulation of the Ti-O bond distances indicates sizeable modulation of the electric charge., Comment: 4 pages 4 figures

Published
2011

15. Imaging x-ray spectrometer at the high energy density instrument of the European x-ray free electron laser

Author

Pan, X., primary, Šmíd, M., additional, Štefaníková, R., additional, Donat, F., additional, Baehtz, C., additional, Burian, T., additional, Cerantola, V., additional, Gaus, L., additional, Humphries, O. S., additional, Hajkova, V., additional, Juha, L., additional, Krupka, M., additional, Kozlová, M., additional, Konopkova, Z., additional, Preston, T. R., additional, Wollenweber, L., additional, Zastrau, U., additional, and Falk, K., additional

Published
2023
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16. MHz free electron laser x-ray diffraction and modeling of pulsed laser heated diamond anvil cell

Author

Jaisle, N, Cebron, D, Konopkova, Z, Husband, R, Prescher, C, Cerantola, V, Dwivedi, A, Kaa, J, Appel, K, Buakor, K, Ball, O, Mcwilliams, R, Strohm, C, Nakatsutsumi, M, Zastrau, U, Baehtz, C, Baron, M, Edmund, E, Biswas, J, Mchardy, J, Sturtevant, B, Ehm, L, Goncharov, A, Mcmahon, M, Buchen, J, Cynn, H, Pace, E, Liermann, H, Sneed, D, Cooper, S, Anae, M, Kim, J, Wu, Z, Lee, Y, Hwang, H, Kim, T, Choi, J, Lee, J, Merkel, S, Chantel, J, Koemets, E, Marquardt, H, Prakapenka, V, Chariton, S, Shevchenko, E, Fiquet, G, Rosa, A, Mezouar, M, Garbarino, G, Morard, G, Husband, RJ, Kaa, JM, Ball, OB, Mcwilliams, RS, Baron, MA, Mchardy, JD, Sturtevant, BT, Goncharov, AF, Mcmahon, MI, Pace, EJ, Liermann, HP, Sneed, DT, Cooper, SC, Wu, ZY, Hwang, HJ, Koemets, EG, Prakapenka, VB, Rosa, AD, Jaisle, N, Cebron, D, Konopkova, Z, Husband, R, Prescher, C, Cerantola, V, Dwivedi, A, Kaa, J, Appel, K, Buakor, K, Ball, O, Mcwilliams, R, Strohm, C, Nakatsutsumi, M, Zastrau, U, Baehtz, C, Baron, M, Edmund, E, Biswas, J, Mchardy, J, Sturtevant, B, Ehm, L, Goncharov, A, Mcmahon, M, Buchen, J, Cynn, H, Pace, E, Liermann, H, Sneed, D, Cooper, S, Anae, M, Kim, J, Wu, Z, Lee, Y, Hwang, H, Kim, T, Choi, J, Lee, J, Merkel, S, Chantel, J, Koemets, E, Marquardt, H, Prakapenka, V, Chariton, S, Shevchenko, E, Fiquet, G, Rosa, A, Mezouar, M, Garbarino, G, Morard, G, Husband, RJ, Kaa, JM, Ball, OB, Mcwilliams, RS, Baron, MA, Mchardy, JD, Sturtevant, BT, Goncharov, AF, Mcmahon, MI, Pace, EJ, Liermann, HP, Sneed, DT, Cooper, SC, Wu, ZY, Hwang, HJ, Koemets, EG, Prakapenka, VB, and Rosa, AD

Abstract

A new diamond anvil cell experimental approach has been implemented at the European x-ray Free Electron Laser, combining pulsed laser heating with MHz x-ray diffraction. Here, we use this setup to determine liquidus temperatures under extreme conditions, based on the determination of time-resolved crystallization. The focus is on a Fe-Si-O ternary system, relevant for planetary cores. This time-resolved diagnostic is complemented by a finite-element model, reproducing temporal temperature profiles measured experimentally using streaked optical pyrometry. This model calculates the temperature and strain fields by including (i) pressure and temperature dependencies of material properties, and (ii) the heat-induced thermal stress, including feedback effect on material parameter variations. Making our model more realistic, these improvements are critical as they give 7000 K temperature differences compared to previous models. Laser intensities are determined by seeking minimal deviation between measured and modeled temperatures. Combining models and streak optical pyrometry data extends temperature determination below detection limit. The presented approach can be used to infer the liquidus temperature by the appearance of SiO 2 diffraction spots. In addition, temperatures obtained by the model agree with crystallization temperatures reported for Fe-Si alloys. Our model reproduces the planetary relevant experimental conditions, providing temperature, pressure, and volume conditions. Those predictions are then used to determine liquidus temperatures at experimental timescales where chemical migration is limited. This synergy of novel time-resolved experiments and finite-element modeling pushes further the interpretation capabilities in diamond anvil cell experiments.

Published
2023

24. Novel experimental setup for megahertz X-ray diffraction in a diamond anvil cell at the High Energy Density (HED) instrument of the European X-ray Free-Electron Laser (EuXFEL)

Author

Liermann, H. P., Konôpková, Z., Appel, K., Prescher, C., Schropp, A., Cerantola, V., Husband, R. J., McHardy, J. D., McMahon, M. I., McWilliams, R. S., Pépin, C. M., Mainberger, J., Roeper, M., Berghäuser, A., Damker, H., Talkovski, P., Foese, M., Kujala, N., Ball, O. B., Baron, M. A., Briggs, R., Bykov, M., Bykova, E., Chantel, J., Coleman, A. L., Cynn, H., Dattelbaum, D., Dresselhaus-Marais, L. E., Eggert, J. H., Ehm, L., Evans, W. J., Fiquet, G., Frost, M., Glazyrin, K., Goncharov, A. F., Hwang, H., Jenei, Z., Kim, J.-Y., Langenhorst, F., Lee, Y., Makita, M., Marquardt, H., McBride, E. E., Merkel, S., Morard, G., Obannon, E. F., Otzen, C., Pace, E. J., Pelka, A., Pigott, J. S., Prakapenka, V. B., Redmer, R., Sanchez-Valle, C., Schölmerich, M., Speziale, S., Spiekermann, G., Sturtevant, B. T., Toleikis, S., Velisavljevic, N., Wilke, M., Yoo, C.-S., Baehtz, C., Zastrau, U., Strohm, C., Liermann, H. P., Konôpková, Z., Appel, K., Prescher, C., Schropp, A., Cerantola, V., Husband, R. J., McHardy, J. D., McMahon, M. I., McWilliams, R. S., Pépin, C. M., Mainberger, J., Roeper, M., Berghäuser, A., Damker, H., Talkovski, P., Foese, M., Kujala, N., Ball, O. B., Baron, M. A., Briggs, R., Bykov, M., Bykova, E., Chantel, J., Coleman, A. L., Cynn, H., Dattelbaum, D., Dresselhaus-Marais, L. E., Eggert, J. H., Ehm, L., Evans, W. J., Fiquet, G., Frost, M., Glazyrin, K., Goncharov, A. F., Hwang, H., Jenei, Z., Kim, J.-Y., Langenhorst, F., Lee, Y., Makita, M., Marquardt, H., McBride, E. E., Merkel, S., Morard, G., Obannon, E. F., Otzen, C., Pace, E. J., Pelka, A., Pigott, J. S., Prakapenka, V. B., Redmer, R., Sanchez-Valle, C., Schölmerich, M., Speziale, S., Spiekermann, G., Sturtevant, B. T., Toleikis, S., Velisavljevic, N., Wilke, M., Yoo, C.-S., Baehtz, C., Zastrau, U., and Strohm, C.

Abstract

The high-precision X-ray diffraction setup for work with diamond anvil cells (DACs) in interaction chamber 2 (IC2) of the High Energy Density instrument of the European X-ray Free-Electron Laser is described. This includes beamline optics, sample positioning and detector systems located in the multipurpose vacuum chamber. Concepts for pump–probe X-ray diffraction experiments in the DAC are described and their implementation demonstrated during the First User Community Assisted Commissioning experiment. X-ray heating and diffraction of Bi under pressure, obtained using 20 fs X-ray pulses at 17.8 keV and 2.2 MHz repetition, is illustrated through splitting of diffraction peaks, and interpreted employing finite element modeling of the sample chamber in the DAC.

Published
2021

25. Novel experimental setup for megahertz X-ray diffraction in a diamond anvil cell at the High Energy Density (HED) instrument of the European X-ray Free-Electron Laser (EuXFEL)

Author

Liermann, H, Konôpková, Z, Appel, K, Prescher, C, Schropp, A, Cerantola, V, Husband, R, Mchardy, J, Mcmahon, M, Mcwilliams, R, Pépin, C, Mainberger, J, Roeper, M, Berghäuser, A, Damker, H, Talkovski, P, Foese, M, Kujala, N, Ball, O, Baron, M, Briggs, R, Bykov, M, Bykova, E, Chantel, J, Coleman, A, Cynn, H, Dattelbaum, D, Dresselhaus-Marais, L, Eggert, J, Ehm, L, Evans, W, Fiquet, G, Frost, M, Glazyrin, K, Goncharov, A, Hwang, H, Jenei, Z, Kim, J, Langenhorst, F, Lee, Y, Makita, M, Marquardt, H, Mcbride, E, Merkel, S, Morard, G, O'Bannon, E, Otzen, C, Pace, E, Pelka, A, Pigott, J, Prakapenka, V, Redmer, R, Sanchez-Valle, C, Schoelmerich, M, Speziale, S, Spiekermann, G, Sturtevant, B, Toleikis, S, Velisavljevic, N, Wilke, M, Yoo, C, Baehtz, C, Zastrau, U, Strohm, C, Liermann, H P, Husband, R J, McHardy, J D, McMahon, M I, McWilliams, R S, Pépin, C M, Ball, O B, Baron, M A, Coleman, A L, Dresselhaus-Marais, L E, Eggert, J H, Evans, W J, Goncharov, A F, Jenei, Zs, Kim, J Y, McBride, E E, O'Bannon, E F, Pace, E J, Pigott, J S, Prakapenka, V B, Sturtevant, B T, Yoo, C S, Liermann, H, Konôpková, Z, Appel, K, Prescher, C, Schropp, A, Cerantola, V, Husband, R, Mchardy, J, Mcmahon, M, Mcwilliams, R, Pépin, C, Mainberger, J, Roeper, M, Berghäuser, A, Damker, H, Talkovski, P, Foese, M, Kujala, N, Ball, O, Baron, M, Briggs, R, Bykov, M, Bykova, E, Chantel, J, Coleman, A, Cynn, H, Dattelbaum, D, Dresselhaus-Marais, L, Eggert, J, Ehm, L, Evans, W, Fiquet, G, Frost, M, Glazyrin, K, Goncharov, A, Hwang, H, Jenei, Z, Kim, J, Langenhorst, F, Lee, Y, Makita, M, Marquardt, H, Mcbride, E, Merkel, S, Morard, G, O'Bannon, E, Otzen, C, Pace, E, Pelka, A, Pigott, J, Prakapenka, V, Redmer, R, Sanchez-Valle, C, Schoelmerich, M, Speziale, S, Spiekermann, G, Sturtevant, B, Toleikis, S, Velisavljevic, N, Wilke, M, Yoo, C, Baehtz, C, Zastrau, U, Strohm, C, Liermann, H P, Husband, R J, McHardy, J D, McMahon, M I, McWilliams, R S, Pépin, C M, Ball, O B, Baron, M A, Coleman, A L, Dresselhaus-Marais, L E, Eggert, J H, Evans, W J, Goncharov, A F, Jenei, Zs, Kim, J Y, McBride, E E, O'Bannon, E F, Pace, E J, Pigott, J S, Prakapenka, V B, Sturtevant, B T, and Yoo, C S

Abstract

The high-precision X-ray diffraction setup for work with diamond anvil cells (DACs) in interaction chamber 2 (IC2) of the High Energy Density instrument of the European X-ray Free-Electron Laser is described. This includes beamline optics, sample positioning and detector systems located in the multipurpose vacuum chamber. Concepts for pump-probe X-ray diffraction experiments in the DAC are described and their implementation demonstrated during the First User Community Assisted Commissioning experiment. X-ray heating and diffraction of Bi under pressure, obtained using 20 fs X-ray pulses at 17.8 keV and 2.2 MHz repetition, is illustrated through splitting of diffraction peaks, and interpreted employing finite element modeling of the sample chamber in the DAC.

Published
2021

26. The High Energy Density Scientific Instrument at the European XFEL

Author

Zastrau, U, Appel, K, Baehtz, C, Baehr, O, Batchelor, L, Berghäuser, A, Banjafar, M, Brambrink, E, Cerantola, V, Cowan, T, Damker, H, Dietrich, S, Di Dio Cafiso, S, Dreyer, J, Engel, H, Feldmann, T, Findeisen, S, Foese, M, Fulla-Marsa, D, Göde, S, Hassan, M, Hauser, J, Herrmannsdörfer, T, Höppner, H, Kaa, J, Kaever, P, Knöfel, K, Konôpková, Z, Laso García, A, Liermann, H, Mainberger, J, Makita, M, Martens, E, Mcbride, E, Möller, D, Nakatsutsumi, M, Pelka, A, Plueckthun, C, Prescher, C, Preston, T, Röper, M, Schmidt, A, Seidel, W, Schwinkendorf, J, Schoelmerich, M, Schramm, U, Schropp, A, Strohm, C, Sukharnikov, K, Talkovski, P, Thorpe, I, Toncian, M, Toncian, T, Wollenweber, L, Yamamoto, S, Tschentscher, T, Zastrau, Ulf, Appel, Karen, Baehtz, Carsten, Baehr, Oliver, Batchelor, Lewis, Berghäuser, Andreas, Banjafar, Mohammadreza, Brambrink, Erik, Cerantola, Valerio, Cowan, Thomas E, Damker, Horst, Dietrich, Steffen, Di Dio Cafiso, Samuele, Dreyer, Jörn, Engel, Hans Olaf, Feldmann, Thomas, Findeisen, Stefan, Foese, Manon, Fulla-Marsa, Daniel, Göde, Sebastian, Hassan, Mohammed, Hauser, Jens, Herrmannsdörfer, Thomas, Höppner, Hauke, Kaa, Johannes, Kaever, Peter, Knöfel, Klaus, Konôpková, Zuzana, Laso García, Alejandro, Liermann, Hanns Peter, Mainberger, Jona, Makita, Mikako, Martens, Eike Christian, McBride, Emma E, Möller, Dominik, Nakatsutsumi, Motoaki, Pelka, Alexander, Plueckthun, Christian, Prescher, Clemens, Preston, Thomas R, Röper, Michael, Schmidt, Andreas, Seidel, Wolfgang, Schwinkendorf, Jan Patrick, Schoelmerich, Markus O, Schramm, Ulrich, Schropp, Andreas, Strohm, Cornelius, Sukharnikov, Konstantin, Talkovski, Peter, Thorpe, Ian, Toncian, Monika, Toncian, Toma, Wollenweber, Lennart, Yamamoto, Shingo, Tschentscher, Thomas, Zastrau, U, Appel, K, Baehtz, C, Baehr, O, Batchelor, L, Berghäuser, A, Banjafar, M, Brambrink, E, Cerantola, V, Cowan, T, Damker, H, Dietrich, S, Di Dio Cafiso, S, Dreyer, J, Engel, H, Feldmann, T, Findeisen, S, Foese, M, Fulla-Marsa, D, Göde, S, Hassan, M, Hauser, J, Herrmannsdörfer, T, Höppner, H, Kaa, J, Kaever, P, Knöfel, K, Konôpková, Z, Laso García, A, Liermann, H, Mainberger, J, Makita, M, Martens, E, Mcbride, E, Möller, D, Nakatsutsumi, M, Pelka, A, Plueckthun, C, Prescher, C, Preston, T, Röper, M, Schmidt, A, Seidel, W, Schwinkendorf, J, Schoelmerich, M, Schramm, U, Schropp, A, Strohm, C, Sukharnikov, K, Talkovski, P, Thorpe, I, Toncian, M, Toncian, T, Wollenweber, L, Yamamoto, S, Tschentscher, T, Zastrau, Ulf, Appel, Karen, Baehtz, Carsten, Baehr, Oliver, Batchelor, Lewis, Berghäuser, Andreas, Banjafar, Mohammadreza, Brambrink, Erik, Cerantola, Valerio, Cowan, Thomas E, Damker, Horst, Dietrich, Steffen, Di Dio Cafiso, Samuele, Dreyer, Jörn, Engel, Hans Olaf, Feldmann, Thomas, Findeisen, Stefan, Foese, Manon, Fulla-Marsa, Daniel, Göde, Sebastian, Hassan, Mohammed, Hauser, Jens, Herrmannsdörfer, Thomas, Höppner, Hauke, Kaa, Johannes, Kaever, Peter, Knöfel, Klaus, Konôpková, Zuzana, Laso García, Alejandro, Liermann, Hanns Peter, Mainberger, Jona, Makita, Mikako, Martens, Eike Christian, McBride, Emma E, Möller, Dominik, Nakatsutsumi, Motoaki, Pelka, Alexander, Plueckthun, Christian, Prescher, Clemens, Preston, Thomas R, Röper, Michael, Schmidt, Andreas, Seidel, Wolfgang, Schwinkendorf, Jan Patrick, Schoelmerich, Markus O, Schramm, Ulrich, Schropp, Andreas, Strohm, Cornelius, Sukharnikov, Konstantin, Talkovski, Peter, Thorpe, Ian, Toncian, Monika, Toncian, Toma, Wollenweber, Lennart, Yamamoto, Shingo, and Tschentscher, Thomas

Abstract

The European XFEL delivers up to 27000 intense (>1012photons) pulses per second, of ultrashort (≤50 fs) and transversely coherent X-ray radiation, at a maximum repetition rate of 4.5MHz. Its unique X-ray beam parameters enable groundbreaking experiments in matter at extreme conditions at the High Energy Density (HED) scientific instrument. The performance of the HED instrument during its first two years of operation, its scientific remit, as well as ongoing installations towards full operation are presented. Scientific goals of HED include the investigation of extreme states of matter created by intense laser pulses, diamond anvil cells, or pulsed magnets, and ultrafast X-ray methods that allow their diagnosis using self-amplified spontaneous emission between 5 and 25keV, coupled with X-ray monochromators and optional seeded beam operation. The HED instrument provides two target chambers, X-ray spectrometers for emission and scattering, X-ray detectors, and a timing tool to correct for residual timing jitter between laser and X-ray pulses.

Published
2021

47. Femtosecond laser-generated high-energydensity states studied by x-ray FELs

Author

Nakatsutsumi, M., Appel, K., Baehtz, C., Chen, B., Cowan, T. E., Göde, S., Konopkova, Z., Pelka, A., Priebe, G., Schmidt, A., Sukharnikov, K., Thorpe, I., Tschentscher, T., and Zastrau, U.

Subjects
x-ray free-electron laser, femtosecond dynamics, high-energydensity state, relativistic plasma
Abstract

The combination of powerful optical lasers and an x-ray free-electron laser (XFEL) provides unique capabilities to study the transient behaviour of matter in extreme conditions. The high energy density science instrument (HED instrument) at the European XFEL will provide the experimental platform on which an unique x-ray source can be combined with various types of high-power optical lasers. In this paper, we highlight selected scientific examples together with the associated x-ray techniques, with particular emphasis on femtosecond (fs)-timescale pump–probe experiments. Subsequently, we present the current design status of the HED instrument, outlining how the experiments could be performed. First user experiments will start at the beginning of 2018, after which various optical lasers will be commissioned and made available to the international scientific community.

Published
2017

48. Use of plasma treatment to grow carbon nanotube forests on TiN substrate.

Author

Esconjauregui, S., Bayer, B. C., Fouquet, M., Wirth, C. T., Yan, F., Xie, R., Ducati, C., Baehtz, C., Castellarin-Cudia, C., Bhardwaj, S., Cepek, C., Hofmann, S., and Robertson, J.

Subjects
CARBON nanotubes, HYDROGEN plasmas, SUBSTRATES (Materials science), NANOPARTICLES, CRYSTALLOGRAPHY
Abstract

Hydrogen plasma pretreatment is used to enforce the growth of vertically-aligned carbon nanotube forests on TiN substrates. The evolution of the substrate, catalyst, and nanotubes are studied by in situ and ex-situ photoemission and X-ray diffraction in order to understand the growth mechanism. We find that TiN retains its crystallographic structure and its conductivity during plasma pretreatment and nanotube growth, which is confirmed by electrical measurements. Plasma pretreatment is found to favor the growth of nanotube forests by root growth, as it binds the catalyst nanoparticles more strongly to the substrate than thermal pretreatment. We find that plasma pretreatment time should be limited, otherwise poor or no growth is found. [ABSTRACT FROM AUTHOR]

Published
2011
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49. In-situ study of growth of carbon nanotube forests on conductive CoSi2 support.

Author

Bayer, B. C., Zhang, C., Blume, R., Yan, F., Fouquet, M., Wirth, C. T., Weatherup, R. S., Lin, L., Baehtz, C., Oliver, R. A., Knop-Gericke, A., Schlögl, R., Hofmann, S., and Robertson, J.

Subjects
CARBON nanotubes, PHOTOEMISSION, COBALT, OXIDATION, CARBIDES
Abstract

The growth of high density vertically aligned carbon nanotube forests on conductive CoSi2 substrate layers is characterized by in situ x-ray photoemission spectroscopy and x-ray diffraction. We use in situ silicidation to transform as loaded, low conductivity CoSi supports to highly conductive CoSi2 during nanotube growth. These cobalt silicide films are found to be stable against oxidation and carbide formation during growth and act as an excellent metallic support for growth of aligned nanotubes, resembling the growth on the insulating Fe/Al2O3 benchmark system. The good catalytic activity is attributed to interfacial reactions of the Fe catalyst particles with the underlying CoSi2 support. We obtain ohmic conduction from the support layer to the carbon nanotube forest. [ABSTRACT FROM AUTHOR]

Published
2011
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50. Multiple ferromagnetic secondary phases in Fe implanted yttria stabilized zirconia.

Author

Shalimov, A., Zhou, Shengqiang, Roshchupkina, O., Jeutter, N., Baehtz, C., Talut, G., Reuther, H., and Potzger, K.

Subjects
ZIRCONIUM oxide, YTTRIUM, IRON, FERROMAGNETISM, RADIATION
Abstract

The formation of secondary phases inside yttria stabilized zirconia (YSZ) crystals implanted with Fe ions was investigated by means of synchrotron radiation x-ray diffraction, conversion electron Mössbauer spectroscopy, and x-ray diffraction reciprocal space mapping. Fe ions have been implanted into single crystals of YSZ(001) at elevated temperatures. As the implanted ion fluence is increased an increase in α-Fe cluster formation was observed, along with the appearance of γ-Fe and secondary phases of Fe oxide(s). The clusters are proposed to consist of a metallic core and an oxide shell. Ferromagnetic hyperfine splitting was detected by Mössbauer spectroscopy and was mainly attributed to the presence of Fe3+ and α-Fe. [ABSTRACT FROM AUTHOR]

Published
2010
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