- A medium-energy ion scattering investigation of the structure and surface vibrations of two-dimensional YSi2 grown on Si(1 1 1)
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Medium-energy ion scattering has been used to determine the atomic structure of two-dimensional yttrium silicide on silicon (1 1 1). A full quantitative analysis of the atomic positions of the Si atoms in the top bilayer yields a model similar to that previously suggested in the literature with a Si1-Si2 vertical spacing of 0.80 ± 0.03 A?, but with the Si bilayer relaxed slightly further away from the Y layer (Si2-Y vertical spacing of 1.89 ± 0.02 A?). Observing the effects of the top bilayer vibrations yields a model with significant enhancements.
- Wood,Bonet,Noakes,Bailey,Tear
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- Structure of YSi2 nanowires from scanning tunneling spectroscopy and first principles
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Exceptionally long and uniform YSi2 nanowires are formed via self-assembly on Si(001). The in-plane width of the thinnest wires is known to be quantized in odd multiples of the silicon lattice constant. Here, we identify a class of nanowires th
- Iancu,Kent,Zeng,Weitering
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- Thermoelectric Properties of Bulk Yttrium Silicide (YSi2) Fabricated by Arc Melting and Spark Plasma Sintering
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Yttrium silicide (YSi2) nanoparticles in SiGe are reported to enhance the thermoelectric figure-of-merit (ZT) to the recorded value (≈1.81). However, the thermoelectric properties of bulk YSi2 has never been reported. In this work, the thermoelectric properties of YSi2 is studied for the first time. The bulk YSi2 is fabricated by arc melting highly pure Si and Y raw materials. The ingot is crushed to powder and compacted to form a highly dense pellet by spark plasma sintering. By optimizing the processing parameters, the single phase with the AlB2-type structure (P6/mmm) is formed. The Hall measurements show that YSi2 exhibit a metallic-like behavior with a very high electron concentration. This result in the thermoelectric properties with a very large electrical conductivity (≈18 × 105 Ω?1 m?1) but a small Seebeck coefficient (?26 μV K?1) at room temperature, and decrease with temperature. The thermal conductivity is around 14–19 W m?1 K?1 for all temperature range. The maximum ZT value is 0.026 at 423 K.
- Wongprakarn, Suphagrid,Pinitsoontorn, Supree,Tanusilp, Sora-At,Kurosaki, Ken
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- Use of angle-resolved photoemission and density functional theory for surface structural analysis of YSi2
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The atomic structure of two-dimensional yttrium silicide epitaxially grown on Si(1 1 1) was investigated by means of density functional theory calculations and angle-resolved photoemission experiments. The obtained accuracy of the calculations allowed to discriminate different surface arrangements in a quantitative way via comparing their theoretical band structure to the experimental result. Theoretically we find significant changes in the dispersion of a surface localized band upon varying the thickness of the topmost silicon bilayer. For a thickness of 0.4 ? of the topmost silicon bilayer a strong asymmetry of the surface localized band with respect to Γ is found, while a thickness of 0.8 ? yields a more symmetric dispersion of the band. By comparison with the experimental photoemission results, which show a rather symmetric band around Γ, we can conclude that the topmost bilayer has a thickness of 0.8 ?.
- Koitzsch,Bovet,Garnier,Aebi,Rogero,Martín-Gago
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- Dumbbells of five-connected silicon atoms and superconductivity in the binary silicides MSi3 (M = Ca, Y, Lu)
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The new metastable binary silicides MSi3 (M = Ca, Y, Lu) have been synthesized by high-pressure, high-temperature reactions at pressures between 12(2) and 15(2) GPa and temperatures from 900(100) to 1400(150) K. The atomic patterns comprise int
- Schwarz, Ulrich,Wosylus, Aron,Rosner, Helge,Schnelle, Walter,Ormeci, Alim,Meier, Katrin,Baranov, Alexey,Nicklas, Michael,Leipe, Susann,Mueller, Carola J.,Grin, Yuri
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p. 13558 - 13561
(2012/10/08)
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- The ternary RE-Si-B systems (RE = Dy, Ho, Er and Y) at 1270 K: Solid state phase equilibria and magnetic properties of the solid solution REB2-xSix (RE = Dy and Ho)
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The solid state phase equilibria in the ternary RE-Si-B diagrams (RE = Dy, Ho, Er and Y) were determined at 1270 K using experimental techniques such as X-ray diffraction, scanning electron microscopy and electron probe microanalysis. In general, three ternary phases were obtained for each diagram: the line compound RE5Si2B8 with tetragonal symmetry, the boron-inserted Nowotny phase RE5Si3Bx of Mn5Si3-type and the solid solution REB2-xSix of AlB2-type. Prior to this work, the binary systems RE-Si and RE-B, which form the boundary of each diagram, were also re-investigated. In addition to the structures of RE5Si3 (Mn5Si3-type, RE = Dy, Ho and Y) and Dy3Si4 (Ho3Si4-type) which were previously reported or will be presented in a forthcoming paper, the X-ray single crystal structures of RE5Si4 (Sm5Ge4-type, RE = Dy and Ho), DySi (CrB-type) and HoSi in both polymorphic modifications, i.e. the FeB- (high temperature) and CrB- (low temperature) types, were determined and are described herein. Structural relationships between members of the same series on one side, and between both forms of HoSi on the other side, are also discussed in terms of coordination polyhedra and interatomic distances. Finally, magnetic measurements were performed on the alloys REB2-xSix, which in case of RE = Dy exhibit a marked increase of the magneto-crystalline anisotropy, whereas for RE = Ho a change from ferromagnetic to antiferromagnetic behaviour with increasing silicon content is encountered.
- Roger, Jérome,Babizhetskyy, Volodymyr,Guizouarn, Thierry,Hiebl, Kurt,Guérin, Roland,Halet, Jean-Fran?ois
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- SYNTHESIS OF METAL SILICIDE POWDERS BY THERMOLYSIS OF METAL CHLORIDESI WITH MAGNESIUM SILICIDE
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Thermolysis (850 deg C) of a mixture of Mg2Si and MCln (M= Y,Gd,Dy,Ho,Ti,Zr,Hf,Nb,Ta, Mo,W,Fe,Pt; n=3,4,5) produces metal silicides MxSiy, as microcrystalline powders.The reactions give a useful insight into mechanisms working in this type of reaction. Key words: Metal silicide, metal chlorides, magnesium silicide, powder diffraction, thermolysis.
- Fitzmaurice, Jonathan C.,Hector, Andrew L.,Parkin, Ivan P.,Rowley , Adrian T.
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