The Experts below are selected from a list of 207 Experts worldwide ranked by ideXlab platform
Mark N. Obrovac - One of the best experts on this subject based on the ideXlab platform.
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Si–Tin alloy Li-ion battery anode materials prepared by reactive N2 gas milling
Journal of Power Sources, 2019Co-Authors: Simeng Cao, J. Craig Bennett, Yukun Wang, Shayne Gracious, Min Zhu, Mark N. ObrovacAbstract:Abstract Si–Tin Alloys were prepared by reactive gas mechanical milling of Si and Ti powders in N2(g) for use as anode materials in Li-ion cells. This is a low-cost and simple method to prepare Si–Tin anode materials. As a comparison, Si–Tin Alloys were also synthesized more conventionally by ball milling Si and Tin powders in Ar. Both Si–Tin Alloys have similar phase compositions, however the Si–Tin Alloys prepared by N2 reactive gas milling have a more homogenous Tin distribution at the nanometer-scale. As a consequence, Si–Tin Alloys prepared by N2 reactive gas milling where much more resistant to Li15Si4 formation during cycling in Li-cells, resulTing in improved cell performance.
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Si-Tin alloy Li-ion battery negative electrode materials made by N 2 gas milling
MRS Communications, 2018Co-Authors: Wang Yukun, Simeng Cao, Min Zhu, Hui Liu, Mark N. ObrovacAbstract:Si-Tin Alloys are attractive for use as negative electrodes in Li-ion cells because of the high conductivity, low electrolyte reactivity, and thermal stability of Tin. Here it is shown that Si-Tin Alloys with high Si content can surprisingly be made by simply ball milling Si and Ti powders in N 2 (g); a reaction not predicted by thermodynamics. This offers a low-cost and simple method of synthesizing these attractive materials. The resulTing Alloys have smaller grain sizes than Si-Tin made by ball milling Si and Tin directly, giving them high thermal stability and improved cycling characteristics in Li cells.
S Mantl - One of the best experts on this subject based on the ideXlab platform.
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silicon germanium Tin Alloys formed by pulsed laser induced epitaxy
Applied Physics Letters, 2012Co-Authors: Stefan Stefanov, J H Werner, M Oehme, Jorg Schulze, J C Conde, Alessandro Benedetti, Christophe A Serra, D Buca, B Hollander, S MantlAbstract:Pulsed lased induced epitaxy is used to obtain heteroepitaxial Ge1−xSnx and Si1−x−yGexSny Alloys with graded composition on Si(001) substrates. The transition from Ge1−xSnx to Si1−x−yGexSny was achieved by varying the number of laser pulses accordingly with the level of intermixing between Si, Ge, and Sn. Melt duration, predicted by numerical methods, is experimentally confirmed by "in-situ" reflectivity measurements and relates, like the end reflectivity value, to the level of intermixing. The possibility to adjust concentration profiles through laser processing of Sn films on virtual germanium buffer layers for lattice engineering of Ge1−xSnx and Si1−x−yGexSny Alloys on silicon substrates is demonstrated.
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laser synthesis of germanium Tin Alloys on virtual germanium
Applied Physics Letters, 2012Co-Authors: Stefan Stefanov, J H Werner, M Oehme, Jorg Schulze, J C Conde, Alessandro Benedetti, Christophe A Serra, D Buca, B Hollander, S MantlAbstract:Synthesis of heteroepitaxial germanium Tin (GeSn) Alloys using excimer laser processing of a thin 4 nm Sn layer on Ge has been demonstrated and studied. Laser induced rapid heaTing, subsequent melTing, and re-solidification processes at extremely high cooling rates have been experimentally achieved and also simulated numerically to optimize the processing parameters. “In situ” measured sample reflectivity with nanosecond time resolution was used as feedback for the simulations and directly correlated to alloy composition. Detailed characterization of the GeSn Alloys after the optimization of the processing conditions indicated substitutional Sn concentration of up to 1% in the Ge matrix.
F. Pezzoli - One of the best experts on this subject based on the ideXlab platform.
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Spin-coherent dynamics and carrier lifetime in strained Ge 1 − x Sn x semiconductors on silicon
Physical Review B: Condensed Matter and Materials Physics (1998-2015), 2019Co-Authors: S. De Cesari, Andrea Balocchi, E. Vitiello, P. Jahandar, E. Grilli, Thierry Amand, Xavier Marie, M. Myronov, F. PezzoliAbstract:We demonstrate an effective epitaxial route for the manipulation and further enrichment of the intriguing spin-dependent phenomena boasted by germanium. We show optical initialization and readout of spins in Ge-rich germanium-Tin Alloys and report on spin quantum beats between Zeeman-split levels under an external magnetic field. While heavy Sn atoms can be readily utilized to strengthen the spin-orbit coupling, our experiments reveal robust spin orientation in a wide temperature range and a persistent spin lifetime that noticeably approaches the nanosecond regime at room temperature. In addition, time decay photoluminescence experiments evidence a temperature-induced monotonic decrease of the carrier lifetime, eventually providing crucial insights also into nonradiative recombination mechanisms.
Simeng Cao - One of the best experts on this subject based on the ideXlab platform.
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Si–Tin alloy Li-ion battery anode materials prepared by reactive N2 gas milling
Journal of Power Sources, 2019Co-Authors: Simeng Cao, J. Craig Bennett, Yukun Wang, Shayne Gracious, Min Zhu, Mark N. ObrovacAbstract:Abstract Si–Tin Alloys were prepared by reactive gas mechanical milling of Si and Ti powders in N2(g) for use as anode materials in Li-ion cells. This is a low-cost and simple method to prepare Si–Tin anode materials. As a comparison, Si–Tin Alloys were also synthesized more conventionally by ball milling Si and Tin powders in Ar. Both Si–Tin Alloys have similar phase compositions, however the Si–Tin Alloys prepared by N2 reactive gas milling have a more homogenous Tin distribution at the nanometer-scale. As a consequence, Si–Tin Alloys prepared by N2 reactive gas milling where much more resistant to Li15Si4 formation during cycling in Li-cells, resulTing in improved cell performance.
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Si-Tin alloy Li-ion battery negative electrode materials made by N 2 gas milling
MRS Communications, 2018Co-Authors: Wang Yukun, Simeng Cao, Min Zhu, Hui Liu, Mark N. ObrovacAbstract:Si-Tin Alloys are attractive for use as negative electrodes in Li-ion cells because of the high conductivity, low electrolyte reactivity, and thermal stability of Tin. Here it is shown that Si-Tin Alloys with high Si content can surprisingly be made by simply ball milling Si and Ti powders in N 2 (g); a reaction not predicted by thermodynamics. This offers a low-cost and simple method of synthesizing these attractive materials. The resulTing Alloys have smaller grain sizes than Si-Tin made by ball milling Si and Tin directly, giving them high thermal stability and improved cycling characteristics in Li cells.
James Kolodzey - One of the best experts on this subject based on the ideXlab platform.
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Thermal Stability of Annealed Germanium-Tin Alloys Grown by Molecular Beam Epitaxy
Journal of Electronic Materials, 2017Co-Authors: N. Bhargava, Leszek Wieluński, Nikolai Faleev, Jay Prakash Gupta, James KolodzeyAbstract:The thermal stability of undoped and boron-doped germanium Tin (Ge1−xSnx) Alloys grown by molecular beam epitaxy with varying composition and layer thickness was investigated. The Alloys were annealed in forming gas at various temperatures up to 800°C for 1 min using rapid thermal processing, and were characterized using high-resolution x-ray diffraction and Rutherford backscattering spectrometry. It was found that the Ge1−xSnx Alloys were stable to well above the growth temperature, but the stability decreased with increasing thickness, Sn content, and doping. Ge1−xSnx Alloys with low Sn composition (x ∼ 0.025) were stable up to 700°C, and for a given Sn composition, the undoped Alloys were more thermally stable than the doped Alloys. As the thickness of the Ge0.975Sn0.025 Alloys increased to about 950 nm, the temperature of thermal stability dropped to 500°C. As the Sn composition of the 90 nm-Ge1−xSnx Alloys increased up to x = 0.08, the temperature of thermal stability dropped to 300°C. At higher annealing temperatures, the Ge1−xSnx alloy degraded with lower crystal quality, and a gradient in the Sn composition appeared, which may be due to Sn diffusion or segregation.
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Photoconductivity of germanium Tin Alloys grown by molecular beam epitaxy
Applied Physics Letters, 2013Co-Authors: Matthew Coppinger, Nupur Bhargava, Sangcheol Kim, John Hart, James KolodzeyAbstract:Photocurrent spectroscopy was used to measure the infrared absorption of germanium-Tin Alloys grown by molecular beam epitaxy. To study dependence on Sn composition, the photocurrent was measured at 100 K on Alloys of Ge1−xSnx with atomic percentages of Sn up to 9.8%. The optical absorption coefficient was calculated from the photocurrent, and it was found that the absorption edge and extracted bandgap energy decreased with increasing Sn content. For all Ge1−xSnx samples, a fundamental bandgap below that of bulk Ge was observed, and a bandgap energy as low as 0.624 eV was found for a Sn percentage of 9.8% at 100 K.
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The properties of germanium-Tin Alloys for infrared device applications
2011 International Semiconductor Device Research Symposium (ISDRS), 2011Co-Authors: James Kolodzey, Matt Coppinger, Sangcheol Kim, Nupur Bhargava, Jay Gupta, Yung Kee YeoAbstract:Germanium-Tin Alloys are attracTing renewed interest for applications including the strain control of CMOS active channels in integrated circuits, and mid-infrared optical devices for medical imaging, chemical spectroscopy, and military counter-measures. With sufficient Sn content above about 10 %, there is the particularly interesTing possibility of an energy bandgap that is direct in reciprocal space, which may lead to efficient light emitters and detectors.