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Sample records for germanides

  1. Ternary scandium and transition metals germanides

    International Nuclear Information System (INIS)

    Kotur, B.Ya.

    1992-01-01

    Brief review of data on phase diagram of ternary Sc-Me-Ge systems (Me-d - , f-transition element) is given. Isothermal sections at 870 and 1070 K of 17 ternary systems are plotted. Compositions and their structural characteristics are presented. Variability of crystal structure is typical for ternary scandium germanides: 70 compounds with the studied structure belong to 23 structural types. Ternary germanides isostructural to types of Sm 4 Ge 4 , ZrCrSi 2 , ZrNiAl, ScCeSi, TiNiSi U 4 Re 7 Si 6 145 compounds from 70 under investigation are mostly formed in studied systems

  2. Superconductors made of niobium germanide

    International Nuclear Information System (INIS)

    Newkirk, L.R.; Valencia, F.A.

    1976-01-01

    This invention concerns the superconductors and particularly the mass coatings of niobium germanide (Nb 3 Ge) exhibiting superconductor properties, as well as the compositions enabling them to be obtained, having transition temperatures of around 20 0 K or more. The invention proposes a composition of a material of the general formula Nb 3 Ge, containing from around 1 to around 10 at. % oxygen. Preferably, the material contains around 5 at. % of oxygen. The invention also proposes fabricated articles in which the compositions described above are associated with and joined to a metallic substrate. Hence, for instance, the present studies involving a superconducting power transmission line for direct current make it possible to envisage the use of conductors placed in a double envelope, enabling the superconducting element transmitting the current to be carried, whilst containing the cryogenic coolant. In this type of design, the coat of superconducting material surrounds a tube containing liquid helium or possibly liquid hydrogen if a sufficiently high superconduction transition temperature can be reached. The tube must be a good heat and electricity conductor in order to achieve good stability of the superconducting coating [fr

  3. Texture in thin film silicides and germanides: A review

    Energy Technology Data Exchange (ETDEWEB)

    De Schutter, B., E-mail: bob.deschutter@ugent.be; De Keyser, K.; Detavernier, C. [Department of Solid State Sciences, Ghent University, Ghent (Belgium); Lavoie, C. [IBM Research Division, T.J. Watson Research Center, P.O. Box 218, Yorktown Heights, New York 10598 (United States)

    2016-09-15

    Silicides and germanides are compounds consisting of a metal and silicon or germanium. In the microelectronics industry, silicides are the material of choice for contacting silicon based devices (over the years, CoSi{sub 2}, C54-TiSi{sub 2}, and NiSi have been adopted), while germanides are considered as a top candidate for contacting future germanium based electronics. Since also strain engineering through the use of Si{sub 1−x}Ge{sub x} in the source/drain/gate regions of MOSFET devices is an important technique for improving device characteristics in modern Si-based microelectronics industry, a profound understanding of the formation of silicide/germanide contacts to silicon and germanium is of utmost importance. The crystallographic texture of these films, which is defined as the statistical distribution of the orientation of the grains in the film, has been the subject of scientific studies since the 1970s. Different types of texture like epitaxy, axiotaxy, fiber, or combinations thereof have been observed in such films. In recent years, it has become increasingly clear that film texture can have a profound influence on the formation and stability of silicide/germanide contacts, as it controls the type and orientation of grain boundaries (affecting diffusion and agglomeration) and the interface energy (affecting nucleation during the solid-state reaction). Furthermore, the texture also has an impact on the electrical characteristics of the contact, as the orientation and size of individual grains influences functional properties such as contact resistance and sheet resistance and will induce local variations in strain and Schottky barrier height. This review aims to give a comprehensive overview of the scientific work that has been published in the field of texture studies on thin film silicide/germanide contacts.

  4. Texture in thin film silicides and germanides: A review

    International Nuclear Information System (INIS)

    De Schutter, B.; De Keyser, K.; Detavernier, C.; Lavoie, C.

    2016-01-01

    Silicides and germanides are compounds consisting of a metal and silicon or germanium. In the microelectronics industry, silicides are the material of choice for contacting silicon based devices (over the years, CoSi_2, C54-TiSi_2, and NiSi have been adopted), while germanides are considered as a top candidate for contacting future germanium based electronics. Since also strain engineering through the use of Si_1_−_xGe_x in the source/drain/gate regions of MOSFET devices is an important technique for improving device characteristics in modern Si-based microelectronics industry, a profound understanding of the formation of silicide/germanide contacts to silicon and germanium is of utmost importance. The crystallographic texture of these films, which is defined as the statistical distribution of the orientation of the grains in the film, has been the subject of scientific studies since the 1970s. Different types of texture like epitaxy, axiotaxy, fiber, or combinations thereof have been observed in such films. In recent years, it has become increasingly clear that film texture can have a profound influence on the formation and stability of silicide/germanide contacts, as it controls the type and orientation of grain boundaries (affecting diffusion and agglomeration) and the interface energy (affecting nucleation during the solid-state reaction). Furthermore, the texture also has an impact on the electrical characteristics of the contact, as the orientation and size of individual grains influences functional properties such as contact resistance and sheet resistance and will induce local variations in strain and Schottky barrier height. This review aims to give a comprehensive overview of the scientific work that has been published in the field of texture studies on thin film silicide/germanide contacts.

  5. Texture in thin film silicides and germanides: A review

    Science.gov (United States)

    De Schutter, B.; De Keyser, K.; Lavoie, C.; Detavernier, C.

    2016-09-01

    Silicides and germanides are compounds consisting of a metal and silicon or germanium. In the microelectronics industry, silicides are the material of choice for contacting silicon based devices (over the years, CoSi2, C54-TiSi2, and NiSi have been adopted), while germanides are considered as a top candidate for contacting future germanium based electronics. Since also strain engineering through the use of Si1-xGex in the source/drain/gate regions of MOSFET devices is an important technique for improving device characteristics in modern Si-based microelectronics industry, a profound understanding of the formation of silicide/germanide contacts to silicon and germanium is of utmost importance. The crystallographic texture of these films, which is defined as the statistical distribution of the orientation of the grains in the film, has been the subject of scientific studies since the 1970s. Different types of texture like epitaxy, axiotaxy, fiber, or combinations thereof have been observed in such films. In recent years, it has become increasingly clear that film texture can have a profound influence on the formation and stability of silicide/germanide contacts, as it controls the type and orientation of grain boundaries (affecting diffusion and agglomeration) and the interface energy (affecting nucleation during the solid-state reaction). Furthermore, the texture also has an impact on the electrical characteristics of the contact, as the orientation and size of individual grains influences functional properties such as contact resistance and sheet resistance and will induce local variations in strain and Schottky barrier height. This review aims to give a comprehensive overview of the scientific work that has been published in the field of texture studies on thin film silicide/germanide contacts.

  6. Growth and evolution of nickel germanide nanostructures on Ge(001).

    Science.gov (United States)

    Grzela, T; Capellini, G; Koczorowski, W; Schubert, M A; Czajka, R; Curson, N J; Heidmann, I; Schmidt, Th; Falta, J; Schroeder, T

    2015-09-25

    Nickel germanide is deemed an excellent material system for low resistance contact formation for future Ge device modules integrated into mainstream, Si-based integrated circuit technologies. In this study, we present a multi-technique experimental study on the formation processes of nickel germanides on Ge(001). We demonstrate that room temperature deposition of ∼1 nm of Ni on Ge(001) is realized in the Volmer-Weber growth mode. Subsequent thermal annealing results first in the formation of a continuous NixGey wetting layer featuring well-defined terrace morphology. Upon increasing the annealing temperature to 300 °C, we observed the onset of a de-wetting process, characterized by the appearance of voids on the NixGey terraces. Annealing above 300 °C enhances this de-wetting process and the surface evolves gradually towards the formation of well-ordered, rectangular NixGey 3D nanostructures. Annealing up to 500 °C induces an Ostwald ripening phenomenon, with smaller nanoislands disappearing and larger ones increasing their size. Subsequent annealing to higher temperatures drives the Ni-germanide diffusion into the bulk and the consequent formation of highly ordered, {111} faceted Ni-Ge nanocrystals featuring an epitaxial relationship with the substrate Ni-Ge (101); (010) || Ge(001); (110).

  7. Growth and evolution of nickel germanide nanostructures on Ge(001)

    International Nuclear Information System (INIS)

    Grzela, T; Capellini, G; Schubert, M A; Schroeder, T; Koczorowski, W; Czajka, R; Curson, N J; Heidmann, I; Schmidt, Th; Falta, J

    2015-01-01

    Nickel germanide is deemed an excellent material system for low resistance contact formation for future Ge device modules integrated into mainstream, Si-based integrated circuit technologies. In this study, we present a multi-technique experimental study on the formation processes of nickel germanides on Ge(001). We demonstrate that room temperature deposition of ∼1 nm of Ni on Ge(001) is realized in the Volmer–Weber growth mode. Subsequent thermal annealing results first in the formation of a continuous Ni_xGe_y wetting layer featuring well-defined terrace morphology. Upon increasing the annealing temperature to 300 °C, we observed the onset of a de-wetting process, characterized by the appearance of voids on the Ni_xGe_y terraces. Annealing above 300 °C enhances this de-wetting process and the surface evolves gradually towards the formation of well-ordered, rectangular Ni_xGe_y 3D nanostructures. Annealing up to 500 °C induces an Ostwald ripening phenomenon, with smaller nanoislands disappearing and larger ones increasing their size. Subsequent annealing to higher temperatures drives the Ni-germanide diffusion into the bulk and the consequent formation of highly ordered, {111} faceted Ni-Ge nanocrystals featuring an epitaxial relationship with the substrate Ni-Ge (101); (010) || Ge(001); (110). (paper)

  8. Incommensurate and commensurate magnetic structures of the ternary germanide CeNiGe3

    International Nuclear Information System (INIS)

    Durivault, L; Bouree, F; Chevalier, B; Andre, G; Weill, F; Etourneau, J; Martinez-Samper, P; Rodrigo, J G; Suderow, H; Vieira, S

    2003-01-01

    The structural properties of CeNiGe 3 have been investigated via electron diffraction and neutron powder diffraction (NPD). This ternary germanide crystallizes in the orthorhombic SmNiGe 3 -type structure (Cmmm space group). Electrical resistivity, ac- and dc-magnetization measurements show that CeNiGe 3 orders antiferromagnetically below T N = 5.5(2) K and exclude the occurrence at low temperatures of a spin-glass state for CeNiGe 3 as previously reported. Specific heat measurements and NPD both reveal two magnetic transitions, observed at T N1 = 5.9(2) K and T N2 = 5.0(2) K. Between T N1 and T N2 , the Ce magnetic moments in CeNiGe 3 are ordered in a collinear antiferromagnetic structure associated with the k 1 = (100) wavevector and showing a relationship with the magnetic structure of the Ce 3 Ni 2 Ge 7 ternary germanide. Below T N2 , this k 1 = (100) commensurate magnetic structure coexists with an incommensurate helicoidal magnetic structure associated with k 2 = (00.409(1)1/2). This last magnetic structure is highly preponderant below T N2 (93(5)% in volume). At 1.5 K, the Ce atoms in CeNiGe 3 carry a reduced ordered magnetic moment (0.8(2) μ B ). This value, smaller than that obtained in Ce 3 Ni 2 Ge 7 , results from an important hybridization of the 4f(Ce) orbitals with those of the Ni and Ge ligands

  9. Transport Measurements and Synchrotron-Based X-Ray Absorption Spectroscopy of Iron Silicon Germanide Grown by Molecular Beam Epitaxy

    Science.gov (United States)

    Elmarhoumi, Nader; Cottier, Ryan; Merchan, Greg; Roy, Amitava; Lohn, Chris; Geisler, Heike; Ventrice, Carl, Jr.; Golding, Terry

    2009-03-01

    Some of the iron-based metal silicide and germanide phases have been predicted to be direct band gap semiconductors. Therefore, they show promise for use as optoelectronic materials. We have used synchrotron-based x-ray absorption spectroscopy to study the structure of iron silicon germanide films grown by molecular beam epitaxy. A series of Fe(Si1-xGex)2 thin films (2000 -- 8000å) with a nominal Ge concentration of up to x = 0.04 have been grown. X-ray absorption near edge structure (XANES) and extended x-ray absorption fine structure (EXAFS) measurements have been performed on the films. The nearest neighbor co-ordination corresponding to the β-FeSi2 phase of iron silicide provides the best fit with the EXAFS data. Temperature dependent (20 coefficient was calculated. Results suggest semiconducting behavior of the films which is consistent with the EXAFS results.

  10. Phase formation and texture of thin nickel germanides on Ge(001) and Ge(111)

    Energy Technology Data Exchange (ETDEWEB)

    De Schutter, B., E-mail: deschutter.bob@ugent.be; Detavernier, C. [Department of Solid-State Sciences, Ghent University, Krijgslaan 281/S1, 9000 Ghent (Belgium); Van Stiphout, K.; Santos, N. M.; Vantomme, A. [Instituut voor Kern- en Stralingsfysica, KU Leuven, Celestijnenlaan 200 D, B-3001 Leuven (Belgium); Bladt, E.; Bals, S. [Electron Microscopy for Materials Research (EMAT), University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp (Belgium); Jordan-Sweet, J.; Lavoie, C. [IBM T.J. Watson Research Center, Yorktown Heights, New York 10598 (United States); Comrie, C. M. [Department of Physics, University of Cape Town, Rondebosch 7700 (South Africa)

    2016-04-07

    We studied the solid-phase reaction between a thin Ni film and a single crystal Ge(001) or Ge(111) substrate during a ramp anneal. The phase formation sequence was determined using in situ X-ray diffraction and in situ Rutherford backscattering spectrometry (RBS), while the nature and the texture of the phases were studied using X-ray pole figures and transmission electron microscopy. The phase sequence is characterized by the formation of a single transient phase before NiGe forms as the final and stable phase. X-ray pole figures were used to unambiguously identify the transient phase as the ϵ-phase, a non-stoichiometric Ni-rich germanide with a hexagonal crystal structure that can exist for Ge concentrations between 34% and 48% and which forms with a different epitaxial texture on both substrate orientations. The complementary information gained from both RBS and X-ray pole figure measurements revealed a simultaneous growth of both the ϵ-phase and NiGe over a small temperature window on both substrate orientations.

  11. Morphology and chemical composition of cobalt germanide islands on Ge(001).

    Science.gov (United States)

    Ewert, M; Schmidt, Th; Flege, J I; Heidmann, I; Grzela, T; Klesse, W M; Foerster, M; Aballe, L; Schroeder, T; Falta, J

    2016-08-12

    The reactive growth of cobalt germanide on Ge(001) was investigated by means of in situ x-ray absorption spectroscopy photoemission electron microscopy (XAS-PEEM), micro-illumination low-energy electron diffraction (μ-LEED), and ex situ atomic force microscopy (AFM). At a Co deposition temperature of 670 °C, a rich morphology with different island shapes and dimensions is observed, and a correlation between island morphology and stoichiometry is found. By combining XAS-PEEM and μ-LEED, we were able to identify a large part of the islands to consist of CoGe2, with many of them having an unusual epitaxial relationship: CoGe2 [Formula: see text] [Formula: see text] Ge [Formula: see text]. Side facets with (112) and (113) orientation have been found for such islands. However, two additional phases were observed, most likely Co5Ge7 and CoGe. Comparing growth on Ge(001) single crystals and on Ge(001)/Si(001) epilayer substrates, the occurrence of these intermediate phases seems to be promoted by defects or residual strain.

  12. The Ho–Ni–Ge system: Isothermal section and new rare-earth nickel germanides

    Energy Technology Data Exchange (ETDEWEB)

    Morozkin, A.V., E-mail: morozkin@tech.chem.msu.ru [Department of Chemistry, Moscow State University, Leninskie Gory, House 1, Building 3, GSP-2, Moscow 119992 (Russian Federation); Knotko, A.V. [Department of Chemistry, Moscow State University, Leninskie Gory, House 1, Building 3, GSP-2, Moscow 119992 (Russian Federation); Yapaskurt, V.O. [Department of Petrology, Faculty of Geology, Moscow State University, Leninskie Gory, Moscow 119992 (Russian Federation); Yuan, Fang; Mozharivskyj, Y. [Department of Chemistry and Chemical Biology, McMaster University, 1280 Main Street West, Hamilton, Ontario L8S 4M1 (Canada); Pani, M.; Provino, A.; Manfrinetti, P. [Institute SPIN-CNR and Dipartimento di Chimica e Chimica Industriale, Università di Genova, Via Dodecaneso 31, 16146 Genova (Italy)

    2015-05-15

    }CuGe{sub 6}-type), HoNiGe{sub 3} (SmNiGe{sub 3}-type), HoNi{sub 0.2÷0.6}Ge{sub 2} (CeNiSi{sub 2}-type), Ho{sub 37÷34}Ni{sub 6÷24}Ge{sub 57÷42} (AlB{sub 2}-type), HoNiGe (TiNiSi-type), Ho{sub 3}NiGe{sub 2} (La{sub 3}NiGe{sub 2}-type), the ternary system contains four new compounds: Ho{sub 3}Ni{sub 11}Ge{sub 4} (Sc{sub 3}Ni{sub 11}Ge{sub 4}-type), HoNi{sub 3}Ge{sub 2} (ErNi{sub 3}Ge{sub 2}-type), Ho{sub 3}Ni{sub 2}Ge{sub 3} (Hf{sub 3}Ni{sub 2}Si{sub 3}-type) and ~Ho{sub 5}Ni{sub 2}Ge{sub 3} (unknown structure). Quasi-binary solid solutions were found to form at 1070 K from the binary Ho{sub 2}Ni{sub 17}, HoNi{sub 5}, HoNi{sub 7}, HoNi{sub 3}, HoNi{sub 2}, HoNi and Ho{sub 2}Ge{sub 3} compounds, while no detectable solubility was observed for the other binary compounds in the Ho–Ni–Ge system. Based on the magnetization measurements, the HoNi{sub 5}Ge{sub 3}, HoNi{sub 3}Ge{sub 2} and Ho{sub 3}Ni{sub 11}Ge{sub 4} (and isostructural (Tb, Dy){sub 3}Ni{sub 11}Ge{sub 4}) compounds have been found to show paramagnetic behavior down to 5 K, whereas Ho{sub 3}Ni{sub 2}Ge{sub 3} exhibits an antiferromagnetic transition at ~7 K. Additionally, the crystal structure of the new isostructural phases (Y, Yb)Ni{sub 3}Ge{sub 2} (ErNi{sub 3}Ge{sub 2}-type), Er{sub 3}Ni{sub 11}Ge{sub 4} (Sc{sub 3}Ni{sub 11}Ge{sub 4}-type) and (Y, Tb, Dy, Er, Tm){sub 3}Ni{sub 2}Ge{sub 3} (Hf{sub 3}Ni{sub 2}Si{sub 3}-type) has been also investigated. - Highlights: • Ho–Ni–Ge system has been investigated at 1070 K and up to ~60 at% Ho. • Eight known ternary holmium nickel germanides were confirmed in Ho–Ni–Ge. • Four new holmium nickel germanides were detected in Ho–Ni–Ge. • Eight new rare earth nickel germanides were detected in (Y, Tb, Dy, Er–Yb)–Ni–Ge. • HoNi{sub 5}Ge{sub 3}, HoNi{sub 3}Ge{sub 2},(Tb, Dy, Ho){sub 3}Ni{sub 11}Ge{sub 4} and Ho{sub 3}Ni{sub 2}Ge{sub 3} are paramagnet down to 5–7 K.

  13. Micro-structural characterization of low resistive metallic Ni germanide growth on annealing of Ni-Ge multilayer

    Directory of Open Access Journals (Sweden)

    Mitali Swain

    2015-07-01

    Full Text Available Nickel-Germanides are an important class of metal semiconductor alloys because of their suitability in microelectronics applications. Here we report successful formation and detailed characterization of NiGe metallic alloy phase at the interfaces of a Ni-Ge multilayer on controlled annealing at relatively low temperature ∼ 250 °C. Using x-ray and polarized neutron reflectometry, we could estimate the width of the interfacial alloys formed with nanometer resolution and found the alloy stoichiometry to be equiatomic NiGe, a desirable low-resistance interconnect. We found significant drop in resistance (∼ 50% on annealing the Ni-Ge multilayer suggesting metallic nature of alloy phase at the interfaces. Further we estimated the resistivity of the alloy phase to be ∼ 59μΩ cm.

  14. Ternary germanides RERhGe{sub 2} (RE = Y, Gd-Ho) – New representatives of the YIrGe{sub 2} type

    Energy Technology Data Exchange (ETDEWEB)

    Voßwinkel, Daniel; Heletta, Lukas; Hoffmann, Rolf-Dieter; Pöttgen, Rainer, E-mail: pottgen@uni-muenster.de

    2016-11-15

    The YIrGe{sub 2} type ternary germanides RERhGe{sub 2} (RE = Y, Gd-Ho) were synthesized from the elements by arc-melting and characterized by powder X-ray diffraction. The structure of DyRhGe{sub 2} was refined from single crystal X-ray diffractometer data: Immm, a = 426.49(9), b = 885.0(2), c = 1577.4(3) pm, wR2 = 0.0533, 637 F{sup 2} values, 30 variables (300 K data). The structure contains two crystallographically independent dysprosium atoms in pentagonal prismatic and hexagonal prismatic coordination. The three-dimensional [RhGe{sub 2}] polyanion is stabilized through covalent Rh–Ge (243–261 pm) and Ge–Ge (245–251 pm) bonding. The close structural relationship with the slightly rhodium-poorer germanides RE{sub 5}Rh{sub 4}Ge{sub 10} (≡ RERh{sub 0.8}Ge{sub 2}) is discussed. Temperature-dependent magnetic susceptibility measurements reveal Pauli paramagnetism for YRhGe{sub 2} and Curie-Weiss paramagnetism for RERhGe{sub 2} with RE = Gd, Tb, Dy and Ho. These germanides order antiferromagnetically at T{sub N} = 7.2(5), 10.6(5), 8.1(5), and 6.4(5) K, respectively. - Graphical abstract: The germanides RERhGe{sub 2} (RE = Y, Gd-Ho) are new representatives of the YIrGe{sub 2} type.

  15. Formation and texture of palladium germanides studied by in situ X-ray diffraction and pole figure measurements

    Energy Technology Data Exchange (ETDEWEB)

    Geenen, F.A., E-mail: Filip.Geenen@UGent.be [Ghent University, Department of Solid-State Sciences, Krijgslaan 281 (S1), 9000 Gent (Belgium); Knaepen, W.; De Keyser, K. [Ghent University, Department of Solid-State Sciences, Krijgslaan 281 (S1), 9000 Gent (Belgium); Opsomer, K. [Interuniversitair Micro-Electronica Centrum (IMEC), Kapeldreef 75, 3001 Leuven (Belgium); Vanmeirhaeghe, R.L. [Ghent University, Department of Solid-State Sciences, Krijgslaan 281 (S1), 9000 Gent (Belgium); Jordan-Sweet, J.; Lavoie, C. [IBM T.J. Watson Research Center, Yorktown (United States); Detavernier, C. [Ghent University, Department of Solid-State Sciences, Krijgslaan 281 (S1), 9000 Gent (Belgium)

    2014-01-31

    The solid state reaction between 30 nm Pd films and various Ge substrates (Ge(100), Ge(111), polycrystalline Ge and amorphous Ge) was studied by means of in situ X-ray diffraction and in situ sheet resistance measurements. The reported phase sequence of Pd{sub 2}Ge followed by PdGe was verified on all substrates. The texture of the germanides was analysed by pole figure measurements on samples quenched in the Pd{sub 2}Ge and in the PdGe phase on both Ge(100) and (111) substrates. We report an epitaxial growth of Pd{sub 2}Ge on Ge(111) and on Ge(100). The formed PdGe has an axiotaxial alignment on Ge(111). On Ge(100), the axiotaxial texture is observed together with a fibre texture. The higher formation temperature of PdGe on Ge(111) could be related to the epitaxial alignment of the Pd{sub 2}Ge parent phase on Ge(111). - Highlights: • Solid-state reaction is studied on a Pd film with Ge substrates. • Pd2Ge grains have an epitaxial texture on both Ge 100 and Ge 111. • PdGe grains are found to grow with an axiotaxial texture. • Retarded PdGe formation on Ge111 is related with strong epitaxy of Pd2Ge.

  16. Magnetic properties of the germanides RE3Pt4Ge6 (RE=Y, Pr, Nd, Sm, Gd-Dy)

    International Nuclear Information System (INIS)

    Eustermann, Fabian; Eilers-Rethwisch, Matthias; Renner, Konstantin; Hoffmann, Rolf-Dieter; Poettgen, Rainer; Janka, Oliver; Oldenburg Univ.

    2017-01-01

    The germanides RE 3 Pt 4 Ge 6 (RE=Y, Pr, Nd, Sm, Gd-Dy) have been synthesized by arc-melting of the elements followed by inductive annealing to improve the crystallinity and allow for structural order. The compounds have been studied by powder X-ray diffraction; additionally the structure of Y 3 Pt 4 Ge 6 has been refined from single-crystal X-ray diffractometer data. It exhibits a (3+1)D modulated structure, indicating isotypism with Ce 3 Pt 4 Ge 6 . The crystal structure can be described as an intergrowth between YIrGe 2 - and CaBe 2 Ge 2 -type slabs along [100]. Temperature-dependent magnetic susceptibility measurements showed Pauli paramagnetism for Y 3 Pt 4 Ge 6 and Curie-Weiss paramagnetism for Pr 3 Pt 4 Ge 6 and Nd 3 Pt 4 Ge 6 . Sm 3 Pt 4 Ge 6 exhibits van Vleck paramagnetism, while antiferromagnetic ordering at T N =8.1(1) K and T N =11.0(1) K is observed for Gd 3 Pt 4 Ge 6 and Tb 3 Pt 4 Ge 6 , respectively.

  17. Superconductivity in ternary rare earth transition metal silicides and germanides with the Sc5Co4Si10-type structure

    International Nuclear Information System (INIS)

    Berg, L.S.

    1986-01-01

    A systematic study of the superconducting and normal state properties of some ternary rare earth transition metal silicides and germanides of the Sc 5 Co 4 Si 10 0-type is reported. Low temperature heat capacity measurements indicate the presence of a complicated phonon density of states in these structurally complex compounds. A better description of the phonon spectrum of the high T/sub c/ materials Sc 5 Rh 4 Si 10 , Sc 5 Ir 4 Si 10 , and Y 5 Os 4 Ge 10 , given by a model proposed by Junod et al., is presented and discussed. The large values of ΔC/γ/sub n/T/sub c/ and the electron-phonon coupling constant for these high T/sub c/ compounds indicate that they are strong-coupled superconductors. Relative to other ternary superconductors, many of these materials have large Debye temperatures. DC electrical resistivity measurements on these compounds show resistivity behavior deviating from those exhibited by simple metals. The rho(T) data for Y 5 Ir 4 Si 10 , Lu 5 Ir 4 Si 10 , and Y 5 Os 4 Ge 10 , indicate the presence of anomalies. Static molar magnetic susceptibility measurements performed on these compounds indicate (1) a small effective magnetic moment of 0.26μ/sub B/ on the Co atom and (2) anomalous behaviors in the Lu 5 Rh 4 Si 10 , Lu 5 Ir 4 Si 10 , Y 5 Ir 4 Si 10 , Lu 5 Ir 4 Ge 10 , and Y 5 Rh 4 Ge 10 data. Lastly, upper critical magnetic field measurements were performed on Sc 5 Co 4 Si 10 , Sc 5 Rh 4 Si 10 , Sc 5 Ir 4 Si 10 , Lu 5 Rh 4 Si 10 , Lu 5 Ir 4 Si 10 , and Y 5 Os 4 Ge 10

  18. New ternary superconducting germanides

    Science.gov (United States)

    Moschalkov, V. V.; Muttik, I. G.; Samarin, N. A.; Seropegin, Yu. D.; Rudometkina, M. V.

    1991-12-01

    We have studied the structure, electrical and magnetic properties of new ternary compounds with germanium and transition metals of IV and V groups (Ti 0.7V 0.3Ge 3, Hf 2V 3Ge, Zr 32-36V 32-36Ge 30-32, Hf 2Nb 3Ge 4, HfVGe, Zr 15-17V 39-40Ge 44-45, Hf 10.8-21.7V 36.0-42.8). The homogeneity fields for all new phases are determined. Resistivity (T) and magnetic susceptibility χ(T) are investigated at T=4.2…300 K. Two new superconductors have been found - Zr 32-36V 32-36Ge 30-32 and HfVGe with T c=4.7 K and 5.7 K, respectively.

  19. Magnesium substitutions in rare-earth metal germanides with the Gd5Si4 type. Synthesis, structure determination and magnetic properties of RE5-xMgxGe4 (RE=Gd-Tm, Lu and Y)

    Energy Technology Data Exchange (ETDEWEB)

    Sarrao, J L [Los Alamos National Laboratory; Thompson, Joe D [Los Alamos National Laboratory; Tobash, P H [UNIV. OF DE; Bobev, S [UNIV. OF DE

    2009-01-01

    A series of magnesium-substituted rare-earth metal germanides with a general formula RE{sub 5-x}Mg{sub x}Ge{sub 4} (x {approx} 1.0-2.3; RE =Gd-Tm, Lu, Y) have been synthesized by high-temperature reactions and structurally characterized by single-crystal X-ray diffraction. These compounds crystallize with the common Gd{sub 5}Si{sub 4} type in the orthorhombic space group Pnma (No. 62; Z =4; Pearson's code oP36) and do not appear to undergo temperature-induced crystallographic phase transitions down to 120 K. Replacing rare-earth metal atoms with Mg, up to nearly 45 % at., reduces the valence electron count and is clearly expressed in the subtle changes of the Ge-Ge and metal-metal bonding. Magnetization measurements as a function of the temperature and the applied field reveal complex magnetic structures at cryogenic temperatures, and Curie-Weiss paramagnetic behavior at higher temperatures. The observed local moment magnetism is consistent with RE+ ground states in all cases. In the magnetically ordered phases, the magnetization cannot reach saturation in fields up to 50 kOe. The structural trends across the series and the variations of hte magnetic properties as a function of the Mg content are also discussed. KEYWORDS: Rare-earth intermetallics, germanides, crystal structure,Gd{sub 5}Si{sub 4} type.

  20. Magnetic properties of the germanides RE{sub 3}Pt{sub 4}Ge{sub 6} (RE=Y, Pr, Nd, Sm, Gd-Dy)

    Energy Technology Data Exchange (ETDEWEB)

    Eustermann, Fabian; Eilers-Rethwisch, Matthias; Renner, Konstantin; Hoffmann, Rolf-Dieter; Poettgen, Rainer [Muenster Univ. (Germany). Inst. fuer Anorganische und Analytische Chemie; Janka, Oliver [Muenster Univ. (Germany). Inst. fuer Anorganische und Analytische Chemie; Oldenburg Univ. (Germany). Inst. fuer Chemie

    2017-07-01

    The germanides RE{sub 3}Pt{sub 4}Ge{sub 6} (RE=Y, Pr, Nd, Sm, Gd-Dy) have been synthesized by arc-melting of the elements followed by inductive annealing to improve the crystallinity and allow for structural order. The compounds have been studied by powder X-ray diffraction; additionally the structure of Y{sub 3}Pt{sub 4}Ge{sub 6} has been refined from single-crystal X-ray diffractometer data. It exhibits a (3+1)D modulated structure, indicating isotypism with Ce{sub 3}Pt{sub 4}Ge{sub 6}. The crystal structure can be described as an intergrowth between YIrGe{sub 2}- and CaBe{sub 2}Ge{sub 2}-type slabs along [100]. Temperature-dependent magnetic susceptibility measurements showed Pauli paramagnetism for Y{sub 3}Pt{sub 4}Ge{sub 6} and Curie-Weiss paramagnetism for Pr{sub 3}Pt{sub 4}Ge{sub 6} and Nd{sub 3}Pt{sub 4}Ge{sub 6}. Sm{sub 3}Pt{sub 4}Ge{sub 6} exhibits van Vleck paramagnetism, while antiferromagnetic ordering at T{sub N}=8.1(1) K and T{sub N}=11.0(1) K is observed for Gd{sub 3}Pt{sub 4}Ge{sub 6} and Tb{sub 3}Pt{sub 4}Ge{sub 6}, respectively.

  1. Superconductivity in Ternary Rare-Earth Transition Metal Silicides and Germanides with the SCANDIUM(5) COBALT(4) SILICON(10)-TYPE Structure.

    Science.gov (United States)

    Berg, Linda Sue

    A systematic study of the superconducting and normal state properties of some ternary rare earth transition metal silicides and germanides of the Sc(,5)Co(,4)Si(,10) -type is reported in this work. Low temperature heat capacity measurements indicate the presence of a complicated phonon density of states in these structurally complex compounds. A better description of the phonon spectrum of the high T(,c) materials, Sc(,5)Rh(,4)Si(,10), Sc(,5)Ir(,4)Si(,10), and Y(,5)Os(,4)Ge(,10), given by a model proposed by Junod et al.('1), is presented and discussed. The large values of (DELTA)C/(gamma)(,n)T(,c) and the electron-phonon coupling constant for these high T(,c) compounds indicate that they are strong-coupled superconductors. Relative to other ternary superconductors, many of these materials have large Debye temperatures. The BSC theory does not seem to afford an adequate description of the supercon- ducting state in these compounds. DC electrical resistivity measurements on these compounds show resistivity behaviors deviating from those exhibited by simple metals. The (rho)(T) data for Y(,5)Ir(,4)Si(,10), Lu(,5)Rh(,4)Si(,10), Lu(,5)Ir(,4)Si(,10), and Y(,5)Os(,4)Ge(,10), indicate the presence of anomalies. Static molar magnetic susceptibility measurements performed on these compounds indicate (1) a small effective magnetic moment of 0.26(mu)(,B) on the Co atom and (2) anomalous behaviors in the Lu(,5)Rh(,4)Si(,10), Lu(,5)Ir(,4)Si(,10), Y(,5)Ir(,4)Si(,10), Lu(,5)Ir(,4)Ge(,10), and Y(,5)Rh(,4)Ge(,10) data. It is suggested that the same mechanism, namely, the forma- tion of a charge- or spin-density wave, is causing the anomalous behaviors in both the resistivity and susceptibility data. Lastly, upper critical magnetic field measurements were performed on Sc(,5)Co(,4)Si(,10), Sc(,5)Rh(,4)Si(,10), Sc(,5)Ir(,4)Si(,10), Lu(,5)Rh(,4)Si(,10), Lu(,5)Ir(,4)Si(,10), and Y(,5)Os(,4)Ge(,10). Relative to the other five samples, Y(,5)Os(,4)Ge(,10) exhibits very high values for (-d

  2. The germanides Er{sub 5}Pd{sub 4}Ge{sub 8} and Tm{sub 5}Pd{sub 4}Ge{sub 8}. 3D [Pd{sub 4}Ge{sub 8}] polyanions with Ge{sub 2} dumb-bells and Ge{sub 4} chains in cis-conformation

    Energy Technology Data Exchange (ETDEWEB)

    Heying, Birgit; Rodewald, Ute C.; Poettgen, Rainer [Muenster Univ. (Germany). Inst. fuer Anorganische und Analytische Chemie

    2017-07-01

    Tm{sub 5}Pd{sub 4}Ge{sub 8} was synthesized by melting of the elements in an arc-melting furnace. The new germanide was characterized by powder and single-crystal X-ray diffraction: own structure type, P2{sub 1}/m, a=574.3(1), b=1380.4(3), c=836.4(1) pm, β=107.57(2) , V=0.6321 nm{sup 3}, wR2=0.0578, 2533 F{sup 2} values, 86 variables. The palladium and germanium atoms built up a three-dimensional [Pd{sub 4}Ge{sub 8}]{sup 15-} polyanionic network which contains a unique germanium substructure composed of the Zintl anions Ge{sub 2}{sup 6-} dumb-bells and Ge{sub 4}{sup 10-} chains in cis-conformation. The palladium atoms within the network have distorted square pyramidal germanium coordination. The three crystallographically independent thulium atoms have coordination numbers 15, 16 and 17 with partial motifs of the Frank-Kasper type polyhedra. The isotypic germanide Er{sub 5}Pd{sub 4}Ge{sub 8} forms only after annealing the arc-melted sample at 1070 K for 1 week: a=575.14(9), b=1386.3(3), c=838.4(1) pm, β=107.51(2) , V=0.6375 nm{sup 3}.

  3. Quaternary germanides RE{sub 3}TRh{sub 4}Ge{sub 4} (RE = Ce, Pr, Nd; T = Nb, Ta) - a new coloring variant of the aristotype AlB{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Hoffmann, Rolf-Dieter; Vosswinkel, Daniel; Poettgen, Rainer [Institut fuer Anorganische und Analytische Chemie, Universitaet Muenster, Corrensstrasse 30, 48149 Muenster (Germany); Matar, Samir F. [CNRS, Universite de Bordeaux, ICMCB, UPR 9048, 33600 Pessac (France)

    2016-09-15

    The quaternary germanides RE{sub 3}TRh{sub 4}Ge{sub 4} (RE = Ce, Pr, Nd; T = Nb, Ta) were synthesized from the elements by arc-melting and subsequent annealing in a muffle furnace. The structure of Ce{sub 3}TaRh{sub 4}Ge{sub 4} was refined from single-crystal X-ray diffractometer data: new type, Pbam, a = 719.9(2), b = 1495.0(3), c = 431.61(8), wR{sub 2} = 0.0678, 1004 F{sup 2} values, and 40 variables. Isotypy of the remaining phases was evident from X-ray powder patterns. Ce{sub 3}TaRh{sub 4}Ge{sub 4} is a new superstructure variant of the aristotype AlB{sub 2} with an ordering of cerium and tantalum on the aluminum site, whereas the honey-comb network is built up by a 1:1 ordering of rhodium and germanium. This crystal-chemical relationship is discussed based on a group-subgroup scheme. The distinctly different size of tantalum and cerium leads to a pronounced puckering of the [Rh{sub 4}Ge{sub 4}] network, which shows the shortest interatomic distances (253-271 pm Rh-Ge) within the Ce{sub 3}TaRh{sub 4}Ge{sub 4} structure. Another remarkable structural feature concerns the tantalum coordination with six shorter Ta-Rh bonds (265-266 pm) and six longer Ta-Ge bonds (294-295 pm). The [Rh{sub 4}Ge{sub 4}] network fully separates the tantalum and cerium atoms (Ce-Ce > 387 pm, Ta-Ta > 431 pm, and Ce-Ta > 359 pm). The electronic density of states DOS from DFT calculations show metallic behavior with large contributions of localized Ce 4f as well as itinerant ones from all constituents at the Fermi level but no significant magnetic polarization on Ce could be identified. The bonding characteristics described based on overlap populations illustrate further the crystal chemistry observations of the different coordination of Ce1 and Ce2 in Ce{sub 3}TaRh{sub 4}Ge{sub 4}. The Rh-Ge interactions within the network are highlighted as dominant. The bonding magnitudes follow the interatomic distances and identify differences of Ta bonding vs. Ce1/Ce2 bonding with the Rh and Ge

  4. Calcium substitution in rare-earth metal germanides with the hexagonal Mn{sub 5}Si{sub 3} structure type. structural characterization of the extended series RE{sub 5–x}Ca{sub x}Ge{sub 3} (RE=Rare-earth metal)

    Energy Technology Data Exchange (ETDEWEB)

    Suen, Nian-Tzu; Broda, Matthew; Bobev, Svilen, E-mail: bobev@udel.edu

    2014-09-15

    Reported are the synthesis and the structural characterization of an extended family of rare-earth metal–germanides with a general formula RE{sub 5–x}Ca{sub x}Ge{sub 3} (RE=Y, Ce–Nd, Sm, Gd–Tm and Lu; x<2). All twelve phases are isotypic, crystallizing with the Mn{sub 5}Si{sub 3} structure type (Pearson index hP16, hexagonal space group P6{sub 3}/mcm); they are the Ca-substituted variants of the corresponding RE{sub 5}Ge{sub 3} binaries. Across the series, despite some small variations in the Ca-uptake, the unit cell volumes decrease monotonically, following the lanthanide contraction. Temperature dependent DC magnetization measurements reveal paramagnetic behavior in the high temperature range, and the obtained effective moments are consistent with free-ion RE{sup 3+} ground state, as expected from prior studies of the binary RE{sub 5}Ge{sub 3} phases. The onset of magnetic ordering is observed in the low temperature range, and complex magnetic interactions (ferromagnetic/ferrimagnetic) can be inferred, different from the binary phases RE{sub 5}Ge{sub 3}, which are known as antiferromagnetic. In order to understand the role of Ca in the bonding, the electronic structures of the La{sub 5}Ge{sub 3} and the hypothetical compounds La{sub 2}Ca{sub 3}Ge{sub 3} and La{sub 3}Ca{sub 2}Ge{sub 3} with ordered metal atoms are compared and discussed. - Graphical abstract: The family of rare-earth metal–calcium–germanides with the general formula RE{sub 5–x}Ca{sub x}Ge{sub 3} (RE=Y, Ce–Nd, Sm, Gd–Tm and Lu) crystallize in the hexagonal space group P6{sub 3}/mcm (No. 193, Pearson symbol hP16) with a structure that is a variant of the Mn{sub 5}Si{sub 3} structure type. - Highlights: • The newly synthesized RE{sub 5–x}Ca{sub x}Ge{sub 3} (RE=Y, Ce–Nd, Sm, Gd–Tm and Lu) constitute an extended family. • The structure is a substitution variant of the hexagonal Mn{sub 5}Si{sub 3} structure type. • Ca-uptake is the highest in the early members, and

  5. Gadolinium scandium germanide, Gd2Sc3Ge4

    Directory of Open Access Journals (Sweden)

    Sumohan Misra

    2009-04-01

    Full Text Available Gd2Sc3Ge4 adopts the orthorhombic Pu5Rh4-type structure. The crystal structure contains six sites in the asymmetric unit: two sites are statistically occupied by rare-earth atoms with Gd:Sc ratios of 0.967 (4:0.033 (4 and 0.031 (3:0.969 (3, one site (.m. symmetry is occupied by Sc atoms, and three distinct sites (two of which with .m. symmetry are occupied by Ge atoms. The rare-earth atoms form two-dimensional slabs with Ge atoms occupying the trigonal-prismatic voids.

  6. Formation of nickel germanides from Ni layers with thickness below 10 nm

    Energy Technology Data Exchange (ETDEWEB)

    Jablonka, Lukas; Kubart, Tomas; Primetzhofer, Daniel; Abedin, Ahmad; Hellström, Per-Erik; Östling, Mikael; Jordan-Sweet, Jean; Lavoie, Christian; Zhang, Shi-Li; Zhang, Zhen

    2017-03-01

    The authors have studied the reaction between a Ge (100) substrate and thin layers of Ni ranging from 2 to 10 nm in thickness. The formation of metal-rich Ni5Ge3Ni5Ge3 was found to precede that of the monogermanide NiGe by means of real-time in situ x-ray diffraction during ramp-annealing and ex situ x-ray pole figure analyses for phase identification. The observed sequential growth of Ni5Ge3Ni5Ge3 and NiGe with such thin Ni layers is different from the previously reported simultaneous growth with thicker Ni layers. The phase transformation from Ni5Ge3Ni5Ge3 to NiGe was found to be nucleation-controlled for Ni thicknesses <5 nm<5 nm, which is well supported by thermodynamic considerations. Specifically, the temperature for the NiGe formation increased with decreasing Ni (rather Ni5Ge3Ni5Ge3) thickness below 5 nm. In combination with sheet resistance measurement and microscopic surface inspection of samples annealed with a standard rapid thermal processing, the temperature range for achieving morphologically stable NiGe layers was identified for this standard annealing process. As expected, it was found to be strongly dependent on the initial Ni thickness

  7. Electronic nature of zwitterionic alkali metal methanides, silanides and germanides - a combined experimental and computational approach.

    Science.gov (United States)

    Li, H; Aquino, A J A; Cordes, D B; Hase, W L; Krempner, C

    2017-02-01

    Zwitterionic group 14 complexes of the alkali metals of formula [C(SiMe 2 OCH 2 CH 2 OMe) 3 M], (M- 1 ), [Si(SiMe 2 OCH 2 CH 2 OMe) 3 M], (M- 2 ), [Ge(SiMe 2 OCH 2 CH 2 OMe) 3 M], (M- 3 ), where M = Li, Na or K, have been prepared, structurally characterized and their electronic nature was investigated by computational methods. Zwitterions M- 2 and M- 3 were synthesized via reactions of [Si(SiMe 2 OCH 2 CH 2 OMe) 4 ] ( 2 ) and [Ge(SiMe 2 OCH 2 CH 2 OMe) 4 ] ( 3 ) with MOBu t (M = Li, Na or K), resp., in almost quantitative yields, while M- 1 were prepared from deprotonation of [HC(SiMe 2 OCH 2 CH 2 OMe) 3 ] ( 1 ) with LiBu t , NaCH 2 Ph and KCH 2 Ph, resp. X-ray crystallographic studies and DFT calculations in the gas-phase, including calculations of the NPA charges confirm the zwitterionic nature of these compounds, with the alkali metal cations being rigidly locked and charge separated from the anion by the internal OCH 2 CH 2 OMe donor groups. Natural bond orbital (NBO) analysis and the second order perturbation theory analysis of the NBOs reveal significant hyperconjugative interactions in M- 1 -M- 3 , primarily between the lone pair and the antibonding Si-O orbitals, the extent of which decreases in the order M- 1 > M- 2 > M- 3 . The experimental basicities and the calculated gas-phase basicities of M- 1 -M- 3 reveal the zwitterionic alkali metal methanides M- 1 to be significantly stronger bases than the analogous silanides M- 2 and germanium M- 3 .

  8. The interplay of long-range magnetic order and single-ion anisotropy in rare earth nickel germanides

    International Nuclear Information System (INIS)

    Islam, Z.

    1999-01-01

    This dissertation is concerned with the interplay of long-range order and anisotropy in the tetragonal RNi 2 Ge 2 (R = rare earth) family of compounds. Microscopic magnetic structures were studied using both neutron and x-ray resonant exchange scattering (XRES) techniques. The magnetic structures of Tb, Dy, Eu and Gd members have been determined using high-quality single-crystal samples. This work has correlated a strong Fermi surface nesting to the magnetic ordering in the RNi 2 Ge 2 compounds. Generalized susceptibility, χ 0 (q), calculations found nesting to be responsible for both incommensurate ordering wave vector in GdNi 2 Ge 2 , and the commensurate structure in EuNi 2 Ge 2 . A continuous transition from incommensurate to commensurate magnetic structures via band filling is predicted. The surprisingly higher T N in EuNi 2 Ge 2 than that in GdNi 2 Ge 2 is also explained. Next, all the metamagnetic phases in TbNi 2 Ge 2 with an applied field along the c axis have been characterized with neutron diffraction measurements. A mixed phase model for the first metamagnetic structure consisting of fully-saturated as well as reduced-moment Tb ions is presented. The moment reduction may be due to moment instability which is possible if the exchange is comparable to the low-lying CEF level splitting and the ground state is a singlet. In such a case, certain Tb sites may experience a local field below the critical value needed to reach saturation

  9. The interplay of long-range magnetic order and single-ion anisotropy in rare earth nickel germanides

    Energy Technology Data Exchange (ETDEWEB)

    Islam, Z.

    1999-05-10

    This dissertation is concerned with the interplay of long-range order and anisotropy in the tetragonal RNi{sub 2}Ge{sub 2} (R = rare earth) family of compounds. Microscopic magnetic structures were studied using both neutron and x-ray resonant exchange scattering (XRES) techniques. The magnetic structures of Tb, Dy, Eu and Gd members have been determined using high-quality single-crystal samples. This work has correlated a strong Fermi surface nesting to the magnetic ordering in the RNi{sub 2}Ge{sub 2} compounds. Generalized susceptibility, {chi}{sub 0}(q), calculations found nesting to be responsible for both incommensurate ordering wave vector in GdNi{sub 2}Ge{sub 2}, and the commensurate structure in EuNi{sub 2}Ge{sub 2}. A continuous transition from incommensurate to commensurate magnetic structures via band filling is predicted. The surprisingly higher T{sub N} in EuNi{sub 2}Ge{sub 2} than that in GdNi{sub 2}Ge{sub 2} is also explained. Next, all the metamagnetic phases in TbNi{sub 2}Ge{sub 2} with an applied field along the c axis have been characterized with neutron diffraction measurements. A mixed phase model for the first metamagnetic structure consisting of fully-saturated as well as reduced-moment Tb ions is presented. The moment reduction may be due to moment instability which is possible if the exchange is comparable to the low-lying CEF level splitting and the ground state is a singlet. In such a case, certain Tb sites may experience a local field below the critical value needed to reach saturation.

  10. Crystal structure and physical properties of new Ca{sub 2}TGe{sub 3} (T = Pd and Pt) germanides

    Energy Technology Data Exchange (ETDEWEB)

    Klimczuk, T., E-mail: tomasz.klimczuk@pg.gda.pl [Faculty of Applied Physics and Mathematics, Gdansk University of Technology, Narutowicza 11/12, 80–233 Gdansk (Poland); Xie, Weiwei [Department of Chemistry, Princeton University, Princeton, NJ 08544 (United States); Winiarski, M.J.; Kozioł, R.; Litzbarski, L.S. [Faculty of Applied Physics and Mathematics, Gdansk University of Technology, Narutowicza 11/12, 80–233 Gdansk (Poland); Luo, Huixia; Cava, R.J. [Department of Chemistry, Princeton University, Princeton, NJ 08544 (United States)

    2016-11-15

    The crystallographic, electronic transport and thermal properties of Ca{sub 2}PdGe{sub 3} and Ca{sub 2}PtGe{sub 3} are reported. The compounds crystalize in an ordered variant of the AlB{sub 2} crystal structure, in space group P6/mmm, with the lattice parameters a = 8.4876(4) Å/8.4503(5) Å and c = 4.1911(3) Å/4.2302(3) Å for Ca{sub 2}PdGe{sub 3} and Ca{sub 2}PtGe{sub 3}, respectively. The resistivity data exhibit metallic behavior with residual-resistivity-ratios (RRR) of 13 for Ca{sub 2}PdGe{sub 3} and 6.5 for Ca{sub 2}PtGe{sub 3}. No superconducting transition is observed down to 0.4 K. Specific heat studies reveal similar values of the Debye temperatures and Sommerfeld coefficients: Θ{sub D} = 298 K, γ = 4.1 mJ mol{sup −1} K{sup −2} and Θ{sub D} = 305 K, γ = 3.2 mJ mol{sup −1} K{sup −2} for Ca{sub 2}PdGe{sub 3} and Ca{sub 2}PtGe{sub 3}, respectively. The low value of γ is in agreement with the electronic structure calculations.

  11. Structural and physical properties of the U.sub.9./sub.Fe.sub.7./sub.Ge.sub.24./sub. uranium germanide

    Czech Academy of Sciences Publication Activity Database

    Henriques, M.S.; Berthebaud, D.; Pereira, L.C.J.; Lopes, E.B.; Branco, M.B.C.; Noël, H.; Tougait, O.; Šantavá, Eva; Havela, L.; Carvalho, P.A.; Goncalves, A.P.

    2011-01-01

    Roč. 19, č. 7 (2011), s. 841-847 ISSN 0966-9795 Institutional research plan: CEZ:AV0Z10100520 Keywords : ternary alloy system * x-ray * crystal structure * electrical resistance and thermopower * magnetisation Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.649, year: 2011

  12. A novel rare earth zinc germanide, Y b{sub 2}Zn{sub 3}Ge{sub 3.1}; crystal structure and physical properties

    Energy Technology Data Exchange (ETDEWEB)

    Grytsiv, A [Institut fuer Physikalische Chemie, Universitaet Wien, Waehringerstrasse 42, A-1090 Vienna (Austria); Kaczorowski, D [W Trzebiatowski Institute of Low Temperature and Structure Research, Polish Academy of Sciences, P-50-950 Wroclaw, PO Box 1410 (Poland); Rogl, P [Institut fuer Physikalische Chemie, Universitaet Wien, Waehringerstrasse 42, A-1090 Vienna (Austria); Tran, V [W Trzebiatowski Institute of Low Temperature and Structure Research, Polish Academy of Sciences, P-50-950 Wroclaw, PO Box 1410 (Poland); Godart, C [CNRS-UPR209, ISCSA, 2-8 rue Henri Dunant, F94320 Thiais (France); Gofryk, K [W Trzebiatowski Institute of Low Temperature and Structure Research, Polish Academy of Sciences, P-50-950 Wroclaw, PO Box 1410 (Poland); Giester, G [Institut fuer Mineralogie und Kristallographie, Universitaet Wien, Althanstrasse 14, A-1090 Vienna (Austria)

    2005-01-19

    A novel ternary structure type has been determined from single crystals of Y b{sub 2}Zn{sub 3}Ge{sub 3.1} grownfrom zinc flux solvent. Y b{sub 2}Zn{sub 3}Ge{sub 3.1} crystallizes in a novel monoclinic structure type (a = 1.5804(2) nm, b 0.429 70(1) nm, c = 1.1524(1) nm; {beta} = 126.14(1) deg.) with space group C 2/m,Z = 4. The large ytterbium atoms are at the centres of pentagonal pyramids formed by Zn/Ge atoms. Zinc atoms are centred in distorted triangular prisms and polyhedra around germanium atoms are related to octahedra. The void at the centre of the Zn octahedra is only partially (20%) filled by Ge atoms. There are two positions for Yb atoms in the unit cell, which contain ions with valency slightly higher than 2+, as evidenced by x-ray absorption spectroscopy and bulk magnetic measurements. The compound exhibits metallic-like electrical conductivity, and its Seebeck coefficient shows a temperature variation characteristic of metals, being, however, fairly enhanced, as expected for intermediate valence systems.

  13. Superconductors

    International Nuclear Information System (INIS)

    Newkirk, L.R.; Valencia, F.A.

    1977-01-01

    The structural quality of niobium germanide as a high-transition-temperature superconducting material is substantially improved by the presence of about 5 at. percent oxygen. Niobium germanide having this oxygen content may readily be prepared as a bulk coating bonded to a metallic substrate by chemical vapor deposition techniques. 2 figures, 1 table

  14. Superconductors

    Science.gov (United States)

    Newkirk, Lawrence R.; Valencia, Flavio A.

    1977-02-01

    The structural quality of niobium germanide as a high-transition-temperature superconducting material is substantially improved by the presence of about 5 at. % oxygen. Niobium germanide having this oxygen content may readily be prepared as a bulk coating bonded to a metallic substrate by chemical vapor deposition techniques.

  15. Synthesis and characterization of the structural and magnetic properties of new uranium and copper-based silicides and germanides: study of the physical and hydridation properties of some compounds belonging to the Gd-Ni-X systems, where X = Ga, Al, Sn

    International Nuclear Information System (INIS)

    Pechev, St.

    1998-01-01

    Three novel phases, U 3 Cu 4 Si 4 , U 3 Cu 4 Ge 4 and UCuGe 1,77 , were prepared in the U - Cu - X (X = Si or Ge) ternary system. Their structural and magnetic properties were investigated. The magnetic structures of the first two compounds were determined by neutron diffraction. Structural and magnetic behaviour transitions occur as copper substitutes silicon atoms in the UCu x Si 2-x (0,28 ≤ x ≤ 0,96) solid solution. Thus, the structure of the compositions changes in the α-ThSi 2 (tetragonal) → AlB 2 (hexagonal) → Ni 2 In(hexagonal) sequence while a transition from a nonmagnetic to ferromagnetic then antiferromagnetic behaviour is observed. The magnetic properties of the different compositions are governed by a Kondo - RKKY -type interactions competition. Crystallographic disorder and magnetic frustrations are at the origin of a spin glass state between the ferro- and antiferromagnetic areas. The investigations of the GdNi 3 X 2 (X =Ga, Al, Sn) compounds revealed that their structural and magnetic properties are strongly dependent on the nature of the X element as well as the on thermal treatment. A CaCu 5 → HoNi 2,6 Ga 2,4 - type structure transition and a ferro - to antiferromagnetic behaviour evolution are favoured by the increase of the X - atom size. A commensurate modulated crystal structure (described also as a a HoNi 2,6 Ga 2,4 x a HoNi 2,6 Ga 2,4 x 2c HoNi 2,6 Ga 2,4 -type superstructure) has been observed for GdNi 3 Al 2 . Hydrogen absorption in Gd 3 Ni 6 Al 2 and GdNi 3 Al 2 weakens the strength of the magnetic interactions. (author)

  16. Non-trivial role of interlayer cation states in iron-based superconductors

    Science.gov (United States)

    Valenti, Roser; Guterding, Daniel; Jeschke, Harald O.; Glasbrenner, J. K.; Bascones, E.; Mazin, I. I.

    Unconventional superconductivity in iron pnictides and chalcogenides has been suggested to be controlled by the interplay of low-energy antiferromagnetic spin fluctuations and the particular topology of the Fermi surface in these materials. Under this assumption, one would expect the large class of isostructural and isoelectronic iron germanide compounds to be good superconductors, but they aren't. In this talk we will argue that superconductivity in iron germanides is suppressed by strong ferromagnetic tendencies, which surprisingly do not originate from changes in bond-angles or bond-distances with respect to iron pnictides, but are due to changes in the electronic structure in a wide range of energies happening upon substitution of atom species (As by Ge and the corresponding spacer cations). We will discuss the implications of these results in the general context of Fe-based superconductors. Funding by the Deutsche Forschungsgemeinschaft is acknowledged.

  17. Interfacial processes in the Pd/a-Ge:H system

    Science.gov (United States)

    Edelman, F.; Cytermann, C.; Brener, R.; Eizenberg, M.; Weil, R.; Beyer, W.

    1993-06-01

    The kinetics of phase transformation has been studied in a two-layer structure of Pd/a-Ge:H after vacuum annealing at temperatures from 180 to 500°C. The a-Ge:H was deposited at 250°C on both c-Si and cleaved NaCl substrates in an RF glow discharge from a GeH 4/H 2 mixture. It was found that, similarly to the Pd/c-Ge and the Pd/a-Ge (e-gun deposited) systems, in the case of 0.15-0.2 μm Pd/0.6-1.0 μm a-Ge:H interfacial germanides formed first through the production of Pd 2Ge (plus a small amount of PdGe), and then PdGe was produced. The growth of both compounds was found to be diffusion-controlled. The nonreacted a-Ge:H layer beneath the germanide overlayer crystallized at 400-500°C. A reverse sequence of germanides formation was revealed in the case of 50 nm Pd/30 nm a-Ge:H, studied by in situ heat treatment in the TEM utilizing non-supported samples. The first germanide detected was PdGe and then, as a result of PdGe and Ge reaction or the PdGe decomposition, Pd 2Ge formed. The temperature dependence of the incubation time before the first ˜ 10 nm PdGe grains formed, followed an Arrhenius curve with an activation energy of 1.45 eV.

  18. Uniaxial ferromagnetism of local uranium moments in hexagonal UBeGe

    Science.gov (United States)

    Gumeniuk, Roman; Yaresko, Alexander N.; Schnelle, Walter; Nicklas, Michael; Kvashnina, Kristina O.; Hennig, Christoph; Grin, Yuri; Leithe-Jasper, Andreas

    2018-05-01

    The new intermetallic uranium beryllium germanide UBeGe and its thorium analogon ThBeGe crystallize with the hexagonal ZrBeSi type of structure. Studies of magnetic, thermal, and transport properties were performed on polycrystalline samples between 1.8 and 750K. UBeGe is a uniaxial ferromagnet and there are indications for two magnetic transitions at TC(1 )≈160 K and TC(2 )≈150 K . The high paramagnetic effective moment μeff≈3.1 μB , x-ray absorption near-edge spectroscopy (XANES, 17-300 K), as well as theoretical DFT calculations indicate localized U 5 f2 states in UBeGe. ThBeGe is a diamagnetic metallic material with low density of states at the Fermi level.

  19. The ANTARES recoil time-of-flight spectrometer

    Energy Technology Data Exchange (ETDEWEB)

    Martin, J W; Russell, G J [New South Wales Univ., Kensington, NSW (Australia); Cohen, D D; Dytlewski, N [Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW (Australia)

    1997-12-31

    The Australian National Tandem for Applied Research (ANTARES), is a 8MV FN tandem particle accelerator at the Australian Nuclear Science and Technology Organisation. Research on the accelerator is divided between two groups, Accelerator Mass Spectrometry (AMS) and lon Beam Analysis (IBA). The IBA group carries out a range of research projects from nuclear physics to materials characterisation. The major IBA project on the accelerator is a recoil time-of-flight spectrometer which consists of two electrostatic time pulse generators and an ion-implanted surface barrier detector. The spectrometer is ideally suited to the profiling of layered multi-element materials, and has been used to characterise materials such as metal-germanides, optoelectronics, superconductors and catalytic converters. This paper will describe the time-of-flight system as well as some recent materials characterisation results. 1 refs., 3 figs.

  20. The ANTARES recoil time-of-flight spectrometer

    Energy Technology Data Exchange (ETDEWEB)

    Martin, J.W.; Russell, G.J. [New South Wales Univ., Kensington, NSW (Australia); Cohen, D.D.; Dytlewski, N. [Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW (Australia)

    1996-12-31

    The Australian National Tandem for Applied Research (ANTARES), is a 8MV FN tandem particle accelerator at the Australian Nuclear Science and Technology Organisation. Research on the accelerator is divided between two groups, Accelerator Mass Spectrometry (AMS) and lon Beam Analysis (IBA). The IBA group carries out a range of research projects from nuclear physics to materials characterisation. The major IBA project on the accelerator is a recoil time-of-flight spectrometer which consists of two electrostatic time pulse generators and an ion-implanted surface barrier detector. The spectrometer is ideally suited to the profiling of layered multi-element materials, and has been used to characterise materials such as metal-germanides, optoelectronics, superconductors and catalytic converters. This paper will describe the time-of-flight system as well as some recent materials characterisation results. 1 refs., 3 figs.

  1. Magnetic properties in the vortex state of Pr1-xNdxPt4Ge12 and PrPt3.88Fe0.12Ge12 superconductors

    Science.gov (United States)

    Chandra, L. S. Sharath; Chattopadhyay, M. K.

    2018-03-01

    We report the temperature and magnetic field dependence of magnetization of Pr1-xNdxPt4Ge12 (x = 0, 0.05 and 0.1) and PrPt3.88Fe0.12Ge12 below 10 K and up to 2 T magnetic field. When compared to the parent PrPt4Ge12, while the critical current density and flux pinning properties are enhanced in the Pr1-xNdxPt4Ge12 samples, they are considerably diminished in the PrPt3.88Fe0.12Ge12 sample. We argue that the observed changes are related to the way the substituting atoms at different crystallographic sites influence the superconductivity in these Germanide skutterudites.

  2. Contributions to the preparation of 241americium metal and a few 241americium silicides

    International Nuclear Information System (INIS)

    Wittmann, F.D.

    1980-01-01

    In order to take a closer look at the americium-silicon system, three further silicides of americium: Am 5 Si 3 , Am 2 Si 3 and AmSi 2 were prepared in addition to the already known americium monosilicide and starting from the knowledge gained from the latters preparation. Radiographic investigations were carried out into the temperature region of 900 0 C. They showed no change of structure in the three compounds. It was possible to prepare residue-free americium metal by reducing AmF 3 with Si, whereby the SiF 4 formed can be easily separated off as volatile compound, and the Am metal is brought into a very pure form by sublimation suitable for spectrochemical investigations. Attempts to prepare binary germanides and gallides of 241 americium were unsuccessful. (RB) [de

  3. High performance Ω-gated Ge nanowire MOSFET with quasi-metallic source/drain contacts.

    Science.gov (United States)

    Burchhart, T; Zeiner, C; Hyun, Y J; Lugstein, A; Hochleitner, G; Bertagnolli, E

    2010-10-29

    Ge nanowires (NWs) about 2 µm long and 35 nm in diameter are grown heteroepitaxially on Si(111) substrates in a hot wall low-pressure chemical vapor deposition (LP-CVD) system using Au as a catalyst and GeH(4) as precursor. Individual NWs are contacted to Cu pads via e-beam lithography, thermal evaporation and lift-off techniques. Self-aligned and atomically sharp quasi-metallic copper-germanide source/drain contacts are achieved by a thermal activated phase formation process. The Cu(3)Ge segments emerge from the Cu contact pads through axial diffusion of Cu which was controlled in situ by SEM, thus the active channel length of the MOSFET is adjusted without any restrictions from a lithographic process. Finally the conductivity of the channel is enhanced by Ga(+) implantation leading to a high performance Ω-gated Ge-NW MOSFET with saturation currents of a few microamperes.

  4. New members of the A2 M ‧ M2″ structure family (A=Ca, Sr, Yb, La; M ‧ = In , Sn , Pb; M ″ = Si , Ge)

    Science.gov (United States)

    Jehle, Michael; Dürr, Ines; Fink, Saskia; Lang, Britta; Langenmaier, Michael; Steckhan, Julia; Röhr, Caroline

    2015-01-01

    The new mixed tetrelides Sr2PbGe2 and Yb2SnGe2, several mixed Ca/Sr (AII) germanides A2II (Sn, Pb)Ge2 and two polymorphs of La2 InSi2 represent new members of the general structure family of ternary alkaline-earth/lanthanoid main group silicides/germanides A2 M ‧ M2″ (M ‧ = In , Sn , Pb ; M ″ = Si , Ge). All compounds were synthesized from melts of the elements and their crystal structures have been determined by means of single crystal X-ray diffraction. Sr2PbGe2 (Cmmm, a=402.36(11), b=1542.3(4), c=463.27(10) pm) crystallizes with the Mn2AlB2 -type structure. In exhibiting infinite planar Ge zig-zag chains, it represents one border of the compound series. The other borderline case, where only [Ge2 ] dumbbells are left as Ge building units, is represented by the Ca/Yb tin germanides Ca2SnGe2 and Yb2SnGe2 (Mo2FeB2 -type; P4/mbm, a=748.58(13)/740.27(7), c=445.59(8)/435.26(5) pm). In between these two border structures compounds with variable Si/Ge chain lengths could be obtained by varying the averaged size of the AII cations: Ca0.45Sr1.55PbGe2 (new structure type; Pbam, a=791.64(5), b=2311.2(2), c=458.53(3) pm) contains planar six-membered chain segments [Ge6 ]. Tetrameric pieces [Ge4 ] are the conspicuous structure elements in Ca1.16Sr0.84SnGe2 and La2 InSi2 (La2InNi2 -type; Pbam, a=781.01(2)/762.01(13), b=1477.95(3)/1494.38(6), c=457.004(9)/442.1(3) pm). The tetragonal form of 'La2 In Si2‧ (exact composition: La2In1.07Si1.93, P4/mbm, a=1309.11(12), c=443.32(4) pm) also crystallizes in a new structure type, containing only [Si3 ] trimers as cutouts of the planar chains. In all structures the Si/Ge zig-zag chains/chain segments are connected by In/Sn/Pb atoms to form planar M layers, which are separated by pure A layers. Band structure calculations within the FP-LAPW DFT approach together with the Zintl formalism, extended by the presence of hypervalent bonding of the heavier M ‧ elements, give insight into the chemical bonding of this series of p

  5. Superconductivity of ternary metal compounds prepared at high pressures

    CERN Document Server

    Shirotani, I

    2003-01-01

    Various ternary metal phosphides, arsenides, antimonides, silicides and germanides have been prepared at high temperatures and high pressures. These ternary metal compounds can be classified into four groups: [1] metal-rich compounds MM' sub 4 X sub 2 and [2] MM'X, [3] non-metal-rich compounds MXX' and [4] MM' sub 4 X sub 1 sub 2 (M and M' = metal element; X and X' = non-metal element). We have studied the electrical and magnetic properties of these materials at low temperatures, and found many new superconductors with the superconducting transition temperature (T sub c) of above 10 K. The metal-rich compound ZrRu sub 4 P sub 2 with a tetragonal structure showed the superconducting transition at around 11 K, and had an upper critical field (H sub c sub 2) of 12.2 tesla (T) at 0 K. Ternary equiatomic compounds ZrRuP and ZrRuSi crystallize in two modifications, a hexagonal Fe sub 2 P-type structure [h-ZrRuP(Si)] and an orthorhombic Co sub 2 P-type structure [o-ZrRuP(Si)]. Both h-ZrRuP and h-ZrRuSi have rather h...

  6. Nuclear reactor fuel structure containing uranium alloy wires embedded in a metallic matrix plate

    Science.gov (United States)

    Travelli, Armando

    1988-01-01

    A flat or curved plate structure, to be used as fuel in a nuclear reactor, comprises elongated fissionable wires or strips embedded in a metallic continuous non-fissionable matrix plate. The wires or strips are made predominantly of a malleable uranium alloy, such as uranium silicide, uranium gallide or uranium germanide. The matrix plate is made predominantly of aluminum or an aluminum alloy. The wires or strips are located in a single row at the midsurface of the plate, parallel with one another and with the length dimension of the plate. The wires or strips are separated from each other, and from the surface of the plate, by sufficient thicknesses of matrix material, to provide structural integrity and effective fission product retention, under neutron irradiation. This construction makes it safely feasible to provide a high uranium density, so that the uranium enrichment with uranium 235 may be reduced below about 20%, to deter the reprocessing of the uranium for use in nuclear weapons.

  7. Simultaneous aluminizing and chromizing of steels to form (Fe,Cr){sub 3}Al coatings and Ge-doped silicide coatings of Cr-Zr base alloys

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, M.; He, Y.R.; Rapp, R.A. [Ohio State Univ., Columbus, OH (United States). Dept. of Materials Science and Engineering

    1997-12-01

    A halide-activated cementation pack involving elemental Al and Cr powders has been used to achieve surface compositions of approximately Fe{sub 3}Al plus several percent Cr for low alloy steels (T11, T2 and T22) and medium carbon steel (1045 steel). A two-step treatment at 925 C and 1150 C yields the codeposition and diffusion of aluminum and chromium to form dense and uniform ferrite coatings of about 400 {micro}m thickness, while preventing the formation of a blocking chromium carbide at the substrate surfaces. Upon cyclic oxidation in air at 700 C, the coated steel exhibits a negligible 0.085 mg/cm{sup 2} weight gain for 1900 one-hour cycles. Virtually no attack was observed on coated steels tested at ABB in simulated boiler atmospheres at 500 C for 500 hours. But coatings with a surface composition of only 8 wt% Al and 6 wt% Cr suffered some sulfidation attack in simulated boiler atmospheres at temperatures higher than 500 C for 1000 hours. Two developmental Cr-Zr based Laves phase alloys (CN129-2 and CN117(Z)) were silicide/germanide coated. The cross-sections of the Ge-doped silicide coatings closely mimicked the microstructure of the substrate alloys. Cyclic oxidation in air at 1100 C showed that the Ge-doped silicide coating greatly improved the oxidation resistance of the Cr-Zr based alloys.

  8. Electronic structure and chemical bonding in LaIrSi-type intermetallics

    Energy Technology Data Exchange (ETDEWEB)

    Matar, Samir F. [Bordeaux Univ., Pessac (France). CNRS; Poettgen, Rainer [Muenster Univ. (Germany). Inst. fuer Anorganische und Analytische Chemie; Nakhl, Michel [Univ. Libanaise, Fanar (Lebanon). Ecole Doctorale Sciences et Technologies

    2017-05-01

    The cubic LaIrSi type has 23 representatives in aluminides, gallides, silicides, germanides, phosphides, and arsenides, all with a valence electron count of 16 or 17. The striking structural motif is a three-dimensional network of the transition metal (T) and p element (X) atoms with TX{sub 3/3} respectively XT{sub 3/3} coordination. Alkaline earth or rare earth atoms fill cavities within the polyanionic [TX]{sup δ-} networks. The present work presents a detailed theoretical study of chemical bonding in LaIrSi-type representatives, exemplarily for CaPtSi, BaIrP, BaAuGa, LaIrSi, CeRhSi, and CeIrSi. DFT-GGA-based electronic structure calculations show weakly metallic compounds with itinerant small magnitude DOSs at E{sub F} except for CeRhSi whose large Ce DOS at E{sub F} leads to a finite magnetization on Ce (0.73 μ{sub B}) and induced small moments of opposite sign on Rh and Si in a ferromagnetic ground state. The chemical bonding analyses show dominant bonding within the [TX]{sup δ-} polyanionic networks. Charge transfer magnitudes were found in accordance with the course of the electronegativites of the chemical constituents.

  9. Crystal, magnetic, calorimetric and electronic structure investigation of GdScGe1-x Sb x compounds

    Science.gov (United States)

    Guillou, F.; Pathak, A. K.; Hackett, T. A.; Paudyal, D.; Mudryk, Y.; Pecharsky, V. K.

    2017-12-01

    Experimental investigations of crystal structure, magnetism and heat capacity of compounds in the pseudoternary GdScGe-GdScSb system combined with density functional theory projections have been employed to clarify the interplay between the crystal structure and magnetism in this series of RTX materials (R  =  rare-earth, T   =  transition metal and X  =  p-block element). We demonstrate that the CeScSi-type structure adopted by GdScGe and CeFeSi-type structure adopted by GdScSb coexist over a limited range of compositions 0.65 ≤slant x ≤slant 0.9 . Antimony for Ge substitutions in GdScGe result in an anisotropic expansion of the unit cell of the parent that is most pronounced along the c axis. We believe that such expansion acts as the driving force for the instability of the double layer CeScSi-type structure of the parent germanide. Extensive, yet limited Sb substitutions 0 ≤slant x disappearance of the induced magnetic moments on Sc. For the parent antimonide, heat capacity measurements indicate an additional transition below the main antiferromagnetic transition.

  10. A new type of soft ferromagnetic alloys: RFe12-xGex

    International Nuclear Information System (INIS)

    Lachevre, V.; Barbara, B.; Fruchart, D.; Pontonnier, L.

    1998-01-01

    Ternary iron-rich rare earth germanides RFe 12-x Ge x with R=Y, La, Ce, Nd, Sm, Gd, Dy, Ho and Er reveal soft ferromagnetic properties. The structure, the microstructure and the soft magnetic properties of these materials have been studied versus the germanium content and the nature of the rare earth element. In the as-cast materials, at least three crystallized phases have been identified: α-Fe(Ge), RFe 2 Ge 2 and traces of Fe 3 Ge. The typical grain size is of some tens of micrometer. The Curie temperature of these alloys is rather high (i.e. >770 K). The transition temperature as well as the saturation magnetization are found to strongly depend on the nature of the R element. The rapidly quenched alloys appear fully homogenized compared with the as-cast materials and the grain size decreases to about one micrometer. Although X-ray diffraction patterns have shown that the two major phases remain present, the magnetic characteristics are fairly dependent on the earth rare element. For all the investigated materials, measurements of the hysterical behaviour reveal a very low coercivity level, i.e. H c <10 Oe. (orig.)

  11. HfO2 as gate dielectric on Ge: Interfaces and deposition techniques

    International Nuclear Information System (INIS)

    Caymax, M.; Van Elshocht, S.; Houssa, M.; Delabie, A.; Conard, T.; Meuris, M.; Heyns, M.M.; Dimoulas, A.; Spiga, S.; Fanciulli, M.; Seo, J.W.; Goncharova, L.V.

    2006-01-01

    To fabricate MOS gate stacks on Ge, one can choose from a multitude of metal oxides as dielectric material which can be deposited by many chemical or physical vapor deposition techniques. As a few typical examples, we will discuss here the results from atomic layer deposition (ALD), metal organic CVD (MOCVD) and molecular beam deposition (MBD) using HfO 2 /Ge as materials model system. It appears that a completely interface layer free HfO 2 /Ge combination can be made in MBD, but this results in very bad capacitors. The same bad result we find if HfGe y (Hf germanides) are formed like in the case of MOCVD on HF-dipped Ge. A GeO x interfacial layer appears to be indispensable (if no other passivating materials are applied), but the composition of this interfacial layer (as determined by XPS, TOFSIMS and MEIS) is determining for the C/V quality. On the other hand, the presence of Ge in the HfO 2 layer is not the most important factor that can be responsible for poor C/V, although it can still induce bumps in C/V curves, especially in the form of germanates (Hf-O-Ge). We find that most of these interfacial GeO x layers are in fact sub-oxides, and that this could be (part of) the explanation for the high interfacial state densities. In conclusion, we find that the Ge surface preparation is determining for the gate stack quality, but it needs to be adapted to the specific deposition technique

  12. Electrical characterisation of ruthenium Schottky contacts on n-Ge (1 0 0)

    Energy Technology Data Exchange (ETDEWEB)

    Chawanda, Albert, E-mail: albert.chawanda@up.ac.za [Department of Physics, University of Pretoria, Pretoria 0002 (South Africa); Department of Physics, Midlands State University, Bag 9055, Gweru (Zimbabwe); Nyamhere, Cloud [Department of Physics, Nelson Mandela Metropolitan University, Box 7700, Port Elizabeth 6031 (South Africa); Auret, Francois D.; Nel, Jacqueline M.; Mtangi, Wilbert; Diale, Mmatsae [Department of Physics, University of Pretoria, Pretoria 0002 (South Africa)

    2012-05-15

    Ruthenium (Ru) Schottky contacts were fabricated on n-Ge (1 0 0) by electron beam deposition. Current-voltage (I-V), deep level transient spectroscopy (DLTS), and Laplace-DLTS techniques were used to characterise the as-deposited and annealed Ru/n-Ge (1 0 0) Schottky contacts. The variation of the electrical properties of the Ru samples annealed between 25 Degree-Sign C and 575 Degree-Sign C indicates the formation of two phases of ruthenium germanide. After Ru Schottky contacts fabrication, an electron trap at 0.38 eV below the conduction band with capture cross section of 1.0 Multiplication-Sign 10{sup -14} cm{sup -2} is the only detectable electron trap. The hole traps at 0.09, 0.15, 0.27 and 0.30 eV above the valence band with capture cross sections of 7.8 Multiplication-Sign 10{sup -13} cm{sup -2}, 7.1 Multiplication-Sign 10{sup -13} cm{sup -2}, 2.4 Multiplication-Sign 10{sup -13} cm{sup -2} and 6.2 Multiplication-Sign 10{sup -13} cm{sup -2}, respectively, were observed in the as-deposited Ru Schottky contacts. The hole trap H(0.30) is the prominent single acceptor level of the E-centre, and H(0.09) is the third charge state of the E-centre. H(0.27) shows some reverse annealing and reaches a maximum concentration at 225 Degree-Sign C and anneals out after 350 Degree-Sign C. This trap is strongly believed to be V-Sb{sub 2} complex formed from the annealing of V-Sb defect centre.

  13. In situ observation of self-assembled Fe{sub 13}Ge{sub 8} nanowires growth on anisotropic Ge (1 1 0) surface

    Energy Technology Data Exchange (ETDEWEB)

    Li, Zhi-Peng, E-mail: LI.Zhipeng@nims.go.jp [Department of Physics, National University of Singapore, 2 Science Drive 3, S117542 (Singapore); Global Research Center for Environment and Energy based on Nanomaterials Science, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Tok, Engsoon [Department of Physics, National University of Singapore, 2 Science Drive 3, S117542 (Singapore); Foo, Yonglim [Institute of Materials Research and Engineering, 3 Research Link, S117602 (Singapore)

    2012-02-15

    Highlights: Black-Right-Pointing-Pointer Epitaxial Fe{sub 13}Ge{sub 8} nanowries growth and shape evolution on Ge (1 1 0) studied by in situ UHV-TEM. Black-Right-Pointing-Pointer Single type of morphology and unique orientation of nanowires formed at elevated temperatures. Black-Right-Pointing-Pointer Uniform control of the nanowires morphology at different temperatures can be succeeded. -- Abstract: Self-assembled iron germanide nanowires (NWs) were grown by directly depositing Fe onto a Ge (1 1 0) substrate, in an in situ ultra-high vacuum transmission electron microscope from 430 to 500 Degree-Sign C. All observed NWs had a similar length/width aspect ratio ({approx}8:1) at all deposition temperatures, as well as the same elongation orientation with respect to the underlying Ge (1 1 0) substrate. The growth dynamics was investigated by real time observations of NWs growth at elevated temperatures. It is elucidated that the formation of NWs in similar shape at all deposited temperatures is attributed to the similar activation energy barriers in length and width of NWs, which can result in the constant growth rate independent of growth temperatures. Furthermore, the difference in pre-exponential factor along the length and width of growing islands arose due to the anisotropic constraint of the Ge (1 1 0) substrate, leading to the unique elongation of NWs. This growth dynamics suggests the possibility of uniform control of the morphology of self-assembled NWs, as well as other morphologies of bottom-up fabricated devices, at different deposition temperatures.

  14. Structural, electronic and optical characteristics of SrGe{sub 2} and BaGe{sub 2}: A combined experimental and computational study

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Mukesh, E-mail: mkgarg79@gmail.com [Environmental Remediation Materials Unit, National Institute for Materials Science, Ibaraki 305-0044 (Japan); Umezawa, Naoto [Environmental Remediation Materials Unit, National Institute for Materials Science, Ibaraki 305-0044 (Japan); Imai, Motoharu [Superconducting Properties Unit, National Institute for Materials Science, Ibaraki 305-0047 (Japan)

    2015-05-05

    Highlights: • Charge transfer between cation and anion atoms observed first time in digermandies. • Study yields a band gap of ∼1 eV and ∼0.85 eV for SrGe{sub 2} and BaGe{sub 2}, respectively. • Band gap decrease with the application of hydrostatic pressure. • Localized cation d states lead to a large absorption coefficient (>7.5 × 10{sup 4} cm{sup −1}). - Abstract: SrGe{sub 2} and BaGe{sub 2} were characterized for structural, electronic and optical properties by means of diffuse reflectance and first-principles density functional theory. These two germanides crystallize in the BaSi{sub 2}-type structure, in which Ge atoms are arranged in tetrahedral configuration. The calculation indicates a charge transfer from Sr (or Ba) atoms to Ge atoms along with the formation of covalent bonds among Ge atoms in Ge tetrahedral. The computational results confirm that these two germanies are Zintl phase described as Sr{sub 2}Ge{sub 4} (or Ba{sub 2}Ge{sub 4}), which are characterized by positively charged [Sr{sub 2} (or Ba{sub 2})]{sup 2.59+} and negatively charged [Ge{sub 4}]{sup 2.59−} units acting as cation and anion, respectively. These compounds are indirect gap semiconductors with band gap estimated to be E{sub g} = 1.02 eV for BaGe{sub 2} and E{sub g} = 0.89 eV for SrGe{sub 2} which are in good agreement with our experimental measured values (E{sub g} = 0.97 eV for BaGe{sub 2} and E{sub g} = 0.82 eV for SrGe{sub 2}). Our calculations demonstrate that the band gaps are narrowed by application of hydrostatic pressure; the pressure coefficients are estimated to be −10.54 for SrGe{sub 2} and −10.06 meV/GPa for BaGe{sub 2}. Optical properties reveal that these compounds have large absorption coefficient (∼7.5 × 10{sup 4} cm{sup −1} at 1.5 eV) and the estimated high frequency (static) dielectric constant are, ε{sub ∞}(ε{sub 0}) ≈ 12.8(20.97) for BaGe{sub 2} and ε{sub ∞}(ε{sub 0}) ≈ 14.27(22.87) for SrGe{sub 2}.

  15. R{sub 4}Ir{sub 13}Ge{sub 9} (R=La, Ce, Pr, Nd, Sm) and RIr{sub 3}Ge{sub 2} (R=La, Ce, Pr, Nd): Crystal structures with nets of Ir atoms

    Energy Technology Data Exchange (ETDEWEB)

    Yarema, Maksym [Department of Inorganic Chemistry, Ivan Franko National University of Lviv, Kyryla i Mefodiya Str, 6, UA-79005 Lviv (Ukraine); Swiss Federal Laboratories for Materials Science and Technology (EMPA), Ueberlandstr. 129, CH-8600 Duebendorf (Switzerland); Zaremba, Oksana; Gladyshevskii, Roman [Department of Inorganic Chemistry, Ivan Franko National University of Lviv, Kyryla i Mefodiya Str, 6, UA-79005 Lviv (Ukraine); Hlukhyy, Viktor, E-mail: viktor.hlukhyy@lrz.tu-muenchen.de [Department Chemie, Technische Universitaet Muenchen, Lichtenbergstr. 4, D-85747 Garching (Germany); Faessler, Thomas F. [Department Chemie, Technische Universitaet Muenchen, Lichtenbergstr. 4, D-85747 Garching (Germany)

    2012-12-15

    The crystal structures of the new ternary compounds Sm{sub 4}Ir{sub 13}Ge{sub 9} and LaIr{sub 3}Ge{sub 2} were determined and refined on the basis of single-crystal X-ray diffraction data. They belong to the Ho{sub 4}Ir{sub 13}Ge{sub 9} (oP52, Pmmn) and CeCo{sub 3}B{sub 2} (hP5, P6/mmm) structure types, respectively. The formation of isotypic compounds R{sub 4}Ir{sub 13}Ge{sub 9} with R=La, Ce, Pr, Nd, and RIr{sub 3}Ge{sub 2} with R=Ce, Pr, Nd, was established by powder X-ray diffraction. The RIr{sub 3}Ge{sub 2} (R=La, Ce, Pr, Nd) compounds exist only in as-cast samples and decompose during annealing at 800 Degree-Sign C with the formation of R{sub 4}Ir{sub 13}Ge{sub 9}. The structure of Sm{sub 4}Ir{sub 13}Ge{sub 9} contains intersecting, slightly puckered nets of Ir atoms (4{sup 4})(4{sup 3}.6){sub 2}(4.6{sup 2}){sub 2} and (4{sup 4}){sub 2}(4{sup 3}.6){sub 4}(4.6{sup 2}){sub 2} that are perpendicular to [0 1 1] as well as to [0 -1 1] and [0 0 1]. The Ir atoms are surrounded by Ge atoms that form tetrahedra or square pyramids (where the layers intersect). The Sm and additional Ir atoms (in trigonal-planar coordination) are situated in channels along [1 0 0] (short translation vector). In the structure of LaIr{sub 3}Ge{sub 2} the Ir atoms form planar Kagome nets (3.6.3.6) perpendicular to [0 0 1]. These nets alternate along the short translation vector with layers of La and Ge atoms. - Graphical abstract: The crystal structures contain the nets of Ir atoms as main structural motif: R{sub 4}Ir{sub 13}Ge{sub 9} contains intersecting slightly puckered nets of Ir atoms, whereas in the structure of RIr{sub 3}Ge{sub 2} the Ir atoms form planar Kagome nets. Highlights: Black-Right-Pointing-Pointer The Ir-rich ternary germanides R{sub 4}Ir{sub 13}Ge{sub 9} (R=La, Ce, Pr, Nd, Sm) and RIr{sub 3}Ge{sub 2} (R=La, Ce, Pr, Nd) have been synthesized. Black-Right-Pointing-Pointer The RIr{sub 3}Ge{sub 2} compounds exist only in as-cast samples and decompose during annealing at 800

  16. Structural and Magnetothermal Properties of Compounds: Yb5SixGe4-x,Sm5SixGe4-x, EuO, and Eu3O4

    Energy Technology Data Exchange (ETDEWEB)

    Ahn, Kyunghan [Iowa State Univ., Ames, IA (United States)

    2007-01-01

    The family of R5SixGe4-x alloys demonstrates a variety of unique physical phenomena related to magneto-structural transitions associated with reversible breaking and reforming of specific bonds that can be controlled by numerous external parameters such as chemical composition, magnetic field, temperature, and pressure. Therefore, R5SixGe4-x systems have been extensively studied to uncover the mechanism of the extraordinary magneto-responsive properties including the giant magnetoresistance (GMR) and colossal magnetostriction, as well as giant magnetocaloric effect (GMCE). Until now, more than a half of possible R5SixGe4-x pseudobinary systems have been completely or partially investigated with respect to their crystallography and phase relationships (R = La, Pr, Nd, Gd, Tb, Dy, Er, Lu, Y). Still, there are other R5SixGe4-x systems (R = Ce, Sm, Ho, Tm, and Yb) that are not studied yet. Here, we report on phase relationships and structural, magnetic, and thermodynamic properties in the Yb5SixGe4-xand Sm5SixGe4-x pseudobinary systems, which may exhibit mixed valence states. The crystallography, phase relationships, and physical properties of Yb5SixGe4-x alloys with 0 ≤ x ≤ 4 have been examined by using single crystal and powder x-ray diffraction at room temperature, and dc magnetization and heat capacity measurements between 1.8 K and 400 K in magnetic fields ranging from 0 to 7 T. Unlike the majority of R5SixGe4-x systems studied to date, where R is the rare earth metal, all Yb-based germanide-silicides with the 5:4 stoichiometry crystallize in the same Gd5Si4-type structure. The magnetic properties of Yb5SixGe4-x materials are nearly composition

  17. Novel barium triel/tetrelides with the Pu3Pd5 structure type

    International Nuclear Information System (INIS)

    Duerr, Ines; Schwarz, Michael; Wendorff, Marco; Roehr, Caroline

    2010-01-01

    A series of ternary barium triel(M III )/tetrel(M IV )-ides Ba 3 M x III M 5-x IV (M III =Ga,In;M IV =Si,Ge,Sn;x=0-0.7) has been prepared from melts of the elements. They all crystallize with the Pu 3 Pd 5 type structure (orthorhombic, space group Cmcm) exhibiting isolated M 5 clusters of slightly distorted nido shape (square pyramids). For the silicides, where the binary border compound Ba 3 Si 5 does not exist, the Pu 3 Pd 5 type is stabilized by substituting 0.7 Si atoms per formula unit against Ga (Ba 3 Ga 0.7 Si 4.3 :a=1024.82(1),b=856.58(1),c=1024.18(1) pm, R1=0.0220) or by a very small substitution of In (Ba 3 In 0.1 Si 4.9 :a=1017.8(2),b=852.5(2),c=1020.1(3) pm, R1=0.0406). A comparable situation is found for the corresponding germanides, where 0.7 atoms of In (Ba 3 In 0.7 Ge 4.3 :a=1051.3(2),b=864.05(14),c=1054.7(3) pm, R1=0.0248) or Ga (Ba 3 Ga x Ge 5-x :a=1035.1(1),b=861.5(1),c=1036.8(1) pm, R1=0.0148) are necessary to stabilize a Ge-rich compound of this structure type. For the stannides, the situation is somewhat different, because the binary phase Ba 3 Sn 5 itself forms the Pu 3 Pd 5 type. In this case, the structure type remains stable up to a Ga content of 0.5 Ga/f.u. (Ba 3 Ga 0.5 Sn 4.5 :a=1100.41(14),b=896.19(11),c=1111.82(14) pm, R1=0.0169) and also with a substantial In content (Ba 3 In x Sn 5-x :x∼0.9(1);a=1110.5(2),b=900.0(2),c=1120.7(2) pm, R1=0.0262). As the five-atom nido cluster requires only 24 valence electrons per formula unit according to Zintl and Wade, an excess of electrons would be assumed for the binary tetrelides such as Ba 3 Sn 5 (26 v.e./f.u.) that even the maximal amount of triel substitution 0.7 M III /f.u. attained in the title compounds cannot sufficiently compensate for. An assessment of the geometric influence of varied valence electron counts however, coupled with a detailed analysis of the calculated electron densities and the partial densities of states in the energy region above the pseudo band gap at 24 v

  18. Discovery of Intermetallic Compounds from Traditional to Machine-Learning Approaches.

    Science.gov (United States)

    Oliynyk, Anton O; Mar, Arthur

    2018-01-16

    Intermetallic compounds are bestowed by diverse compositions, complex structures, and useful properties for many materials applications. How metallic elements react to form these compounds and what structures they adopt remain challenging questions that defy predictability. Traditional approaches offer some rational strategies to prepare specific classes of intermetallics, such as targeting members within a modular homologous series, manipulating building blocks to assemble new structures, and filling interstitial sites to create stuffed variants. Because these strategies rely on precedent, they cannot foresee surprising results, by definition. Exploratory synthesis, whether through systematic phase diagram investigations or serendipity, is still essential for expanding our knowledge base. Eventually, the relationships may become too complex for the pattern recognition skills to be reliably or practically performed by humans. Complementing these traditional approaches, new machine-learning approaches may be a viable alternative for materials discovery, not only among intermetallics but also more generally to other chemical compounds. In this Account, we survey our own efforts to discover new intermetallic compounds, encompassing gallides, germanides, phosphides, arsenides, and others. We apply various machine-learning methods (such as support vector machine and random forest algorithms) to confront two significant questions in solid state chemistry. First, what crystal structures are adopted by a compound given an arbitrary composition? Initial efforts have focused on binary equiatomic phases AB, ternary equiatomic phases ABC, and full Heusler phases AB 2 C. Our analysis emphasizes the use of real experimental data and places special value on confirming predictions through experiment. Chemical descriptors are carefully chosen through a rigorous procedure called cluster resolution feature selection. Predictions for crystal structures are quantified by evaluating

  19. Structure-composition sensitivity in 'Metallic' Zintl phases: A study of Eu(Ga1-xTtx)2 (Tt=Si, Ge, 0≤x≤1)

    International Nuclear Information System (INIS)

    You, Tae-Soo; Zhao Jingtai; Poettgen, Rainer; Schnelle, Walter; Burkhardt, Ulrich; Grin, Yuri; Miller, Gordon J.

    2009-01-01

    principles electronic structure calculations, rationalize the observed homogeneity ranges of the AlB 2 -type phases in both systems and the structural variations as a function of Tt content. - Abstract: A study of Eu(Ga 1-x Si x ) 2 and Eu(Ga 1-x Ge x ) 2 shows different compositional ranges for puckering of 6 3 nets and, for the germanides, two new commensurately modulated superstructures. Display Omitted