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A multi-state magnetic memory dependent on the permeability of Metglas (2015)

J. R. Petrie, K. A. Wieland, J. M. Timmerwilke, S. C. Barron, R. A. Burke, G. A. Newburgh, J. E. Burnette, G. A. Fischer and A. S. Edelstein

American Institute of Physics (AIP)

In: Applied Physics Letters

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Publication Date: 2015-04-09

Description: A three-state magnetic memory was developed based on differences in the magnetic permeability of a soft ferromagnetic media, Metglas 2826MB (Fe 40 Ni 38 Mo 4 B 18 ). By heating bits of a 250 nm thick Metglas film with 70–100 mW of laser power, we were able to tune the local microstructure, and hence, the permeability. Ternary memory states were created by using lower laser power to enhance the initial permeability through localized atomic rearrangement and higher power to reduce the permeability through crystallization. The permeability of the bits was read by detecting variations in an external 32 Oe probe field within 10 μ m of the media via a magnetic tunnel junction read head. Compared to data based on remanent magnetization, these multi-permeability bits have enhanced insensitivity to unexpected field and temperature changes. We found that data was not corrupted after exposure to fields of 1 T or temperatures of 423 K, indicating the effectiveness of this multi-state approach for safely storing large amounts of data.

Print ISSN: 0003-6951

Electronic ISSN: 1077-3118

Topics: Physics

Published by American Institute of Physics (AIP)

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Fabrication of GeSn-multiple quantum wells by overgrowth of Sn on Ge by using molecular beam epitaxy (2015)

F. Oliveira, I. A. Fischer, A. Benedetti, P. Zaumseil, M. F. Cerqueira, M. I. Vasilevskiy, S. Stefanov, S. Chiussi and J. Schulze

American Institute of Physics (AIP)

In: Applied Physics Letters

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Publication Date: 2015-12-29

Description: We report on the fabrication and structural characterization of epitaxially grown ultra-thin layers of Sn on Ge virtual substrates (Si buffer layer overgrown by a 50 nm thick Ge epilayer followed by an annealing step). Samples with 1 to 5 monolayers of Sn on Ge virtual substrates were grown using solid source molecular beam epitaxy and characterized by atomic force microscopy. We determined the critical thickness at which the transition from two-dimensional to three-dimensional growth occurs. This transition is due to the large lattice mismatch between Ge and Sn (≈14.7%). By depositing Ge on top of Sn layers, which have thicknesses at or just below the critical thickness, we were able to fabricate ultra-narrow GeSn multi-quantum-well structures that are fully embedded in Ge. We report results on samples with one and ten GeSn wells separated by 5 and 10 nm thick Ge spacer layers that were characterized by high resolution transmission electron microscopy and X-ray diffraction. We discuss the structure and material intermixing observed in the samples.

Print ISSN: 0003-6951

Electronic ISSN: 1077-3118

Topics: Physics

Published by American Institute of Physics (AIP)

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Ge-on-Si PIN-photodetectors with Al nanoantennas: The effect of nanoantenna size on light scattering into waveguide modes (2016)

Inga A. Fischer, Lion Augel, Timo Kropp, Songchai Jitpakdeebodin, Nuno Franz, Filipe Oliveira, Erlend Rolseth, Tobias Maß, Thomas Taubner and Jörg Schulze

American Institute of Physics (AIP)

In: Applied Physics Letters

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Publication Date: 2016-02-20

Description: Metallic nanoantennas can be used to enhance the efficiency of optical device operation by re-distributing electromagnetic energy. Here, we investigate the effect of a random distribution of disc-shaped Al nanoantennas of different diameters deposited on Ge-on-Si PIN-photodetectors on the wavelength-dependent responsivity. We compare our experimental results to simulations and find that the largest responsivity enhancement is obtained for wavelengths that correspond to energies at or below the bandgap energy of Ge. We argue that this is the result of antenna-mediated scattering of light into waveguide modes within the Ge-on-Si PIN-photodetectors, which is effectively influenced by nanoantenna size, and we discuss a possible application of the concept for integrated biosensing.

Print ISSN: 0003-6951

Electronic ISSN: 1077-3118

Topics: Physics

Published by American Institute of Physics (AIP)

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Compositional dependence of the band-gap of Ge1−x−ySixSny alloys (2016)

Torsten Wendav, Inga A. Fischer, Michele Montanari, Marvin Hartwig Zoellner, Wolfgang Klesse, Giovanni Capellini, Nils von den Driesch, Michael Oehme, Dan Buca, Kurt Busch and Jörg Schulze

American Institute of Physics (AIP)

In: Applied Physics Letters

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Publication Date: 2016-06-15

Description: The group-IV semiconductor alloy Ge 1− x − y Si x Sn y has recently attracted great interest due to its prospective potential for use in optoelectronics, electronics, and photovoltaics. Here, we investigate molecular beam epitaxy grown Ge 1− x − y Si x Sn y alloys lattice-matched to Ge with large Si and Sn concentrations of up to 42% and 10%, respectively. The samples were characterized in detail by Rutherford backscattering/channeling spectroscopy for composition and crystal quality, x-ray diffraction for strain determination, and photoluminescence spectroscopy for the assessment of band-gap energies. Moreover, the experimentally extracted material parameters were used to determine the SiSn bowing and to make predictions about the optical transition energy.

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Electronic ISSN: 1077-3118

Topics: Physics

Published by American Institute of Physics (AIP)

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AK2 deficiency compromises the mitochondrial energy metabolism required for differentiation of human neutrophil and lymphoid lineages (2015)

E Six; C Lagresle-Peyrou; S Susini; C De Chappedelaine; N Sigrist; H Sadek; M Chouteau; N Cagnard; M Fontenay; O Hermine; C Chomienne; P Reynier; A Fischer; I André-Schmutz; N Gueguen; M Cavazzana

Nature Publishing Group (NPG)

In: Cell Death & Disease

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Publication Date: 2015-08-14

Description: AK2 deficiency compromises the mitochondrial energy metabolism required for differentiation of human neutrophil and lymphoid lineages Cell Death and Disease 6, e1856 (August 2015). doi:10.1038/cddis.2015.211 Authors: E Six, C Lagresle-Peyrou, S Susini, C De Chappedelaine, N Sigrist, H Sadek, M Chouteau, N Cagnard, M Fontenay, O Hermine, C Chomienne, P Reynier, A Fischer, I André-Schmutz, N Gueguen & M Cavazzana

Electronic ISSN: 2041-4889

Topics: Biology , Medicine

Published by Nature Publishing Group (NPG)

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High-resolution X-ray emission spectroscopy with transition-edge sensors: present performance and future potential (2015)

J. Uhlig, W. B. Doriese, J. W. Fowler, D. S. Swetz, C. Jaye, D. A. Fischer, C. D. Reintsema, D. A. Bennett, L. R. Vale, U. Mandal, G. C. O'Neil, L. Miaja-Avila, Y. I. Joe, A. El Nahhas, W. Fullagar, F. Parnefjord Gustafsson, V. Sundström, D. Kurunthu, G. C. Hilton, D. R. Schmidt, J. N. Ullom

Wiley-Blackwell

In: Journal of Synchrotron Radiation [Synchrotron Radiation Online]

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Publication Date: 2015-04-21

Description: X-ray emission spectroscopy (XES) is a powerful element-selective tool to analyze the oxidation states of atoms in complex compounds, determine their electronic configuration, and identify unknown compounds in challenging environments. Until now the low efficiency of wavelength-dispersive X-ray spectrometer technology has limited the use of XES, especially in combination with weaker laboratory X-ray sources. More efficient energy-dispersive detectors have either insufficient energy resolution because of the statistical limits described by Fano or too low counting rates to be of practical use. This paper updates an approach to high-resolution X-ray emission spectroscopy that uses a microcalorimeter detector array of superconducting transition-edge sensors (TESs). TES arrays are discussed and compared with conventional methods, and shown under which circumstances they are superior. It is also shown that a TES array can be integrated into a table-top time-resolved X-ray source and a soft X-ray synchrotron beamline to perform emission spectroscopy with good chemical sensitivity over a very wide range of energies.

Print ISSN: 0909-0495

Electronic ISSN: 1600-5775

Topics: Geosciences , Physics

Published by Wiley-Blackwell on behalf of International Union of Crystallography (IUCr).

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Performance of a four-element Si drift detector for X-ray absorption fine-structure spectroscopy: resolution, maximum count rate, and dead-time correction with incorporation into the ATHENA data analysis software (2015)

J. C. Woicik, B. Ravel, D. A. Fischer, W. J. Newburgh

Wiley-Blackwell

In: Journal of Synchrotron Radiation [Synchrotron Radiation Online]

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Publication Date: 2015-12-08

Description: The performance of a four-element Si drift detector for energy-dispersive fluorescence-yield X-ray absorption fine-structure measurements is reported, operating at the National Institute of Standards and Technology beamline X23A2 at the National Synchrotron Light Source. The detector can acquire X-ray absorption fine-structure spectra with a throughput exceeding 4 × 10 5 counts per second per detector element (〉1.6 × 10 6 total counts per second summed over all four channels). At this count rate the resolution at 6 keV is approximately 220 eV, which adequately resolves the Mn K α and K β fluorescence lines. Accurate dead-time correction is demonstrated, and it has been incorporated into the ATHENA data analysis program. To maintain counting efficiency and high signal to background, it is suggested that the incoming count rate should not exceed ∼70% of the maximum throughput.

Print ISSN: 0909-0495

Electronic ISSN: 1600-5775

Topics: Geosciences , Physics

Published by Wiley-Blackwell on behalf of International Union of Crystallography (IUCr).

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