Sample records for germanides

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

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


    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.

  2. Ferromagnetic germanide in Ge nanowire transistors for spintronics application.

    Tang, Jianshi; Wang, Chiu-Yen; Hung, Min-Hsiu; Jiang, Xiaowei; Chang, Li-Te; He, Liang; Liu, Pei-Hsuan; Yang, Hong-Jie; Tuan, Hsing-Yu; Chen, Lih-Juann; Wang, Kang L


    To explore spintronics applications for Ge nanowire heterostructures formed by thermal annealing, it is critical to develop a ferromagnetic germanide with high Curie temperature and take advantage of the high-quality interface between Ge and the formed ferromagnetic germanide. In this work, we report, for the first time, the formation and characterization of Mn(5)Ge(3)/Ge/Mn(5)Ge(3) nanowire transistors, in which the room-temperature ferromagnetic germanide was found through the solid-state reaction between a single-crystalline Ge nanowire and Mn contact pads upon thermal annealing. The atomically clean interface between Mn(5)Ge(3) and Ge with a relatively small lattice mismatch of 10.6% indicates that Mn(5)Ge(3) is a high-quality ferromagnetic contact to Ge. Temperature-dependent I-V measurements on the Mn(5)Ge(3)/Ge/Mn(5)Ge(3) nanowire heterostructure reveal a Schottky barrier height of 0.25 eV for the Mn(5)Ge(3) contact to p-type Ge. The Ge nanowire field-effect transistors built on the Mn(5)Ge(3)/Ge/Mn(5)Ge(3) heterostructure exhibit a high-performance p-type behavior with a current on/off ratio close to 10(5), and a hole mobility of 150-200 cm(2)/(V s). Temperature-dependent resistance of a fully germanided Mn(5)Ge(3) nanowire shows a clear transition behavior near the Curie temperature of Mn(5)Ge(3) at about 300 K. Our findings of the high-quality room-temperature ferromagnetic Mn(5)Ge(3) contact represent a promising step toward electrical spin injection into Ge nanowires and thus the realization of high-efficiency spintronic devices for room-temperature applications.

  3. Anisotropic thermal expansion of Ni, Pd and Pt germanides and silicides

    Geenen, F. A.; Knaepen, W.; Moens, F.; Brondeel, L.; Leenaers, A.; Van den Berghe, S.; Detavernier, C.


    Silicon or germanium-based transistors are nowadays used in direct contact with silicide or germanide crystalline alloys for semiconductor device applications. Since these compounds are formed at elevated temperatures, accurate knowledge of the thermal expansion of both substrate and the contact is important to address temperature depending effects such as thermal stress. Here we report the linear coefficients of thermal expansion of Ni-, Pd- and Pt-based mono-germanides, mono-silicides and di-metal-silicides as determined by powder-based x-ray diffraction between 300 and 1225 K. The investigated mono-metallic compounds, all sharing the MnP crystal structure, as well as Pd2Si and Pt2Si exhibit anisotropic expansion. By consequence, this anisotropic behaviour should be taken into account for evaluating the crystal unit’s cell at elevated temperatures.

  4. Understanding and engineering of NiGe/Ge junction formed by phosphorus ion implantation after germanidation

    Oka, Hiroshi, E-mail:; Minoura, Yuya; Hosoi, Takuji; Shimura, Takayoshi; Watanabe, Heiji [Department of Material and Life Science, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871 (Japan)


    Modulation of the effective electron Schottky barrier height (eSBH) of NiGe/Ge contacts induced by phosphorus ion implantation after germanide formation was investigated by considering local inhomogeneity in the eSBH. Systematic studies of NiGe/Ge contact devices having various germanide thicknesses and ion implantation areas indicated the threshold dopant concentration at the NiGe/Ge interface required for eSBH modulation and negligible dopant diffusion even at NiGe/Ge interface during drive-in annealing, leading to variation in the eSBH between the bottom and sidewall portions of the NiGe regions. Consequently, this method makes it possible to design source/drain contacts with low-resistivity Ohmic and ideal rectifying characteristics for future Ge-based transistors.

  5. Comparative study of metallic silicide-germanide orthorhombic MnP systems.

    Connétable, Damien; Thomas, Olivier


    We present a comparative study of the structural, energetic, electronic and elastic properties of MX type MnP systems (where X=Si or Ge, and M=Pt, Pd or Ni) using first-principles calculations. The optimized ground state properties of these systems are in excellent agreement with the experimental values. A detailed comparative study of the elastic properties of polycrystalline structures is also presented. We analyze the relationship between the composition and the properties of the systems. Finally, we present the properties of NiSi1-xGex alloys. We show that these properties depend linearly on the Ge content of the alloy. This work has important consequences for semiconductor devices in which silicides, germanides and alloys thereof are used as contact materials.

  6. The ternary germanides UMnGe and U2Mn3Ge

    Hoffmann, Rolf-Dieter; Pöttgen, Rainer; Chevalier, Bernard; Gaudin, Etienne; Matar, Samir F.


    The title compounds were prepared by induction levitation melting of the elemental components and subsequent annealing. UMnGe (Pnma, a = 686.12(9), b = 425.49(6) and c = 736.5(1) pm) adopts the orthorhombic structure of TiNiSi and U2Mn3Ge (P63/mmc, a = 524.3(2) and c = 799.2(3) pm) possesses the hexagonal Mg2Cu3Si-type structure (ordered variant of the hexagonal Laves phase MgZn2). Both structures were refined from X-ray powder data to residuals of RI = 0.021 and 0.014 for UMnGe and U2Mn3Ge, respectively. The manganese and germanium atoms in UMnGe build up a three-dimensional [MnGe] network of ordered Mn3Ge3 hexagons with Mn-Ge distances ranging from 248 to 259 pm. The uranium atoms are coordinated by two tilted Mn3Ge3 hexagons. The manganese atoms in U2Mn3Ge build up Kagomé networks with 252 and 272 pm Mn-Mn distances which are connected via the germanium atoms (254 pm Mn-Ge) to a three-dimensional network. A remarkable feature of the U2Mn3Ge structure is a short U-U distance of 278 pm between adjacent cavities of the [Mn3Ge] network. From DFT based electronic structure calculations both germanides are found more cohesive than the Laves phase UMn2, thus underpinning the substantial role of Mn-Ge bonding. Calculations for both germanides show ferrimagnetic ground states with antiparallel spin alignments between U and Mn. The valence bands show bonding characteristics for interactions of atoms of different chemical natures and significant Mn-Mn bonding in U2Mn3Ge. Preliminary investigation of UMnGe by magnetization measurements confirms an antiferromagnetic arrangement below TN = 240 K.

  7. Novel palladium germanide schottky contact for high performance schottky barrier ge MOSFETs and characterization of its leakage current mechanism.

    Oh, Se-Kyung; Shin, Hong-Sik; Kang, Min-Ho; Lee, Ga-Won; Lee, Hi-Deok


    The leakage current mechanism of Palladium (Pd) germanide Schottky contact on n-type Ge-on-Si substrate is analyzed in depth. The electric field dependent analysis shows that the dominant leakage current mechanism is the Poole-Frenkel emission due to the existence of deep level traps in the depletion region of the Pd germanide/n-type Ge Schottky diode. The analysis of the dependence of leakage current on temperature also shows that the Poole-Frenkel emission and generation current are the dominant components below 100 degrees C and that the Schottky emission related to thermionic emission of majority carriers over a potential barrier is the main cause of this dominance at high temperature region.

  8. Ternary germanides RERhGe2 (RE = Y, Gd-Ho) - New representatives of the YIrGe2 type

    Voßwinkel, Daniel; Heletta, Lukas; Hoffmann, Rolf-Dieter; Pöttgen, Rainer


    The YIrGe2 type ternary germanides RERhGe2 (RE = Y, Gd-Ho) were synthesized from the elements by arc-melting and characterized by powder X-ray diffraction. The structure of DyRhGe2 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 F2 values, 30 variables (300 K data). The structure contains two crystallographically independent dysprosium atoms in pentagonal prismatic and hexagonal prismatic coordination. The three-dimensional [RhGe2] 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 RE5Rh4Ge10 (≡ RERh0.8Ge2) is discussed. Temperature-dependent magnetic susceptibility measurements reveal Pauli paramagnetism for YRhGe2 and Curie-Weiss paramagnetism for RERhGe2 with RE = Gd, Tb, Dy and Ho. These germanides order antiferromagnetically at TN = 7.2(5), 10.6(5), 8.1(5), and 6.4(5) K, respectively.

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

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


    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 [\\bar{1}10](111) \\parallel Ge [\\bar{1}10](001). 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.

  10. Probing lithium germanide phase evolution and structural change in a germanium-in-carbon nanotube energy storage system.

    Tang, Wei; Liu, Yanpeng; Peng, Chengxin; Hu, Mary Y; Deng, Xuchu; Lin, Ming; Hu, Jian Zhi; Loh, Kian Ping


    Lithium alloys of group IV elements such as silicon and germanium are attractive candidates for use as anodes in high-energy-density lithium-ion batteries. However, the poor capacity retention arising from volume swing during lithium cycling restricts their widespread application. Herein, we report high reversible capacity and superior rate capability from core-shell structure consisting of germanium nanorods embedded in multiwall carbon nanotubes. To understand how the core-shell structure helps to mitigate volume swings and buffer against mechanical instability, transmission electron microscopy, X-ray diffraction, and in situ (7)Li nuclear magnetic resonance were used to probe the structural rearrangements and phase evolution of various Li-Ge alloy phases during (de)alloying reactions with lithium. The results provide insights into amorphous-to-crystalline transition and lithium germanide alloy phase transformation, which are important reactions controlling performance in this system.

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

    Geenen, F.A., E-mail: [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)


    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.

  12. Normal-state charge dynamics of ternary platinum germanide superconductor La{sub 2}Pt{sub 3}Ge{sub 5}

    Song, S. J.; Moon, S. J. [Dept. of Physics, Hanyang University, Seoul (Korea, Republic of); Sung, N. H.; Cho, B. K. [Gwangju Institute of Science and Technology, Gwangju (Korea, Republic of)


    We report on the infrared spectroscopic studies of the normal-state electronic response of rare-earth ternary platinum germanide superconductor La{sub 2}Pt{sub 3}Ge{sub 5}. We analyzed the temperature-dependent optical conductivity spectra using the Drude-Lorentz oscillator model. We found that the two Drude responses with distinct scattering rates are required to explain the charge dynamics at 10 K while a single Drude mode could reproduce the far-infrared conductivity at higher temperatures. Our results indicated the two-band character of the electronic structure and highlighted the disparate temperature evolution of the electrodynamics of the two electronic states.

  13. Structural, elastic, electronic properties and stability trends of 1111-like silicide arsenides and germanide arsenides MCuXAs (M = Ti, Zr, Hf; X = Si, Ge) from first principles

    Bannikov, V.V.; Shein, I.R. [Institute of Solid State Chemistry, Ural Branch of the Russian Academy of Sciences, 620990 Ekaterinburg (Russian Federation); Ivanovskii, A.L., E-mail: [Institute of Solid State Chemistry, Ural Branch of the Russian Academy of Sciences, 620990 Ekaterinburg (Russian Federation)


    Highlights: Black-Right-Pointing-Pointer Silicide arsenides and germanide arsenides of Ti, Zr, Hf are probed from first principles. Black-Right-Pointing-Pointer Structural, elastic, electronic properties and stability trends are evaluated. Black-Right-Pointing-Pointer Bulk moduli of HfCuSiAs and HfCuGeAs are the largest among all 1111-like phases. Black-Right-Pointing-Pointer Chemical bonding is analyzed. - Abstract: The tetragonal (s.g. I4/nmm; no. 129) silicide arsenide ZrCuSiAs is well known as a structural type of the broad family of so-called 1111-like quaternary phases which includes now more than 150 representatives. These materials demonstrate a rich variety of outstanding physical properties (from p-type transparent semiconductors to high-temperature Fe-based superconductors) and attracted a great interest as promising candidates for a broad range of applications. At the same time, the data about the electronic and elastic properties of the ZrCuSiAs phase itself, as well as of related silicide arsenides and germanide arsenides are still very limited. Here for a series of six isostructural and isoelectronic 1111-like phases which includes both synthesized (ZrCuSiAs, HfCuSiAs, ZrCuGeAs, and HfCuGeAs) and hypothetical (TiCuSiAs and TiCuGeAs) materials, systematical studies of their structural, elastic, electronic properties and stability trends are performed by means of first-principles calculations.

  14. 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)

    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


    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.

  15. 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

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


    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}.

  16. 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}

    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)


    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

  17. Many metals make the cut: quaternary rare-earth germanides RE4M2InGe4 (M = Fe, Co, Ni, Ru, Rh, Ir) and RE4RhInGe4 derived from excision of slabs in RE2InGe2.

    Oliynyk, Anton O; Stoyko, Stanislav S; Mar, Arthur


    The formation of quaternary rare-earth (RE) germanides containing transition metals (M's) from groups 6 to 10 was investigated through arc-melting and annealing reactions at 800 °C; about 50 new compounds were obtained. These include several new series of quaternary germanides RE4M2InGe4 (M = Fe, Co, Ru, Rh, Ir), previously known only for M = Mn and Ni; additional members of RE4Ni2InGe4 extended to other RE substituents; and a different but closely related series RE4RhInGe4. Detailed crystal structures were determined by single-crystal X-ray diffraction studies for 20 compounds. Monoclinic structures in space group C2/m are adopted by RE4M2InGe4 (Ho4Ni2InGe4-type, a = 15.1-16.5 Å, b = 4.1-4.4 Å, c = 6.9-7.3 Å, β = 106.2-108.6°) and RE4RhInGe4 (own type, a = 20.0-20.2 Å, b = 4.2-4.3 Å, c = 10.1-10.2 Å, β = 105.0-105.3°). Both structures contain frameworks built from MGe4 tetrahedra, InGe4 square planes, and Ge2 dimers, delimiting tunnels occupied by RE atoms. These structures can also be derived by cutting slabs along different directions from the more symmetrical RE2InGe2 structure. Although the Ge2 dimers are relatively invariant, the InGe4 square planes can undergo distortion to form two sets of short versus long In-Ge distances. This distortion results from a competition between M-Ge bonding in the MGe4 tetrahedra and In-Ge bonding in the InGe4 square planes.

  18. On the structures of the rare-earth metal germanides from the series REAl1-xGe3 (RE = Nd, Sm, Gd, Tb, Dy, Ho; 0.6 < x < 0.9). A tale of vacancies at the Al sites and the concomitant structural modulations.

    Zhang, Jiliang; Liu, Yanyan; Shek, Chan Hung; Wang, Yingmin; Bobev, Svilen


    A series of ternary rare-earth metal aluminum germanides with the general formula REAl1-xGe3 (RE = Nd, Sm, Gd, Tb, Dy, and Ho; 0.6 < x < 0.9) have been synthesized by direct fusion of the corresponding elements. Their structures have been characterized by single-crystal X-ray diffraction and selected area electron diffraction methods. The average structure for all members is a representative of the orthorhombic SmNiGe3-type structure (Pearson symbol oS20, space group Cmmm), where the Al atoms occupy the Ni site, and the deep off-stoichiometry is due to statistical vacancies at this position. Considering long-range ordering of the vacancies, a monoclinic and a different orthorhombic structure, which represent idealized ordered variants, are possible, and the structural evolution depending on the nature of the rare-earth metals and the amount of vacancies at the aluminum site are discussed. Commensurate and incommensurate structural modulations based on these parent structures are also observed by electron diffraction, attesting to the great structural complexity in these systems. Magnetic susceptibility measurements are presented and discussed, along with the results from electronic band-structure calculations.

  19. Gadolinium scandium germanide, Gd2Sc3Ge4

    Sumohan Misra


    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.

  20. Research data supporting "Unconventional superconductivity in the layered iron germanide YFe2Ge2"


    Data is grouped according to the figures in the publication which it supports. Fig. 1 shows resistivity vs. temperature at various applied magnetic fields in YFe2Ge2, and the .txt datasets give the data underlying this diagram. Fig. 2 shows how resistive superconducting transition temperatures depend on sample quality, as measured by the residual resistance ratio, and the .txt dataset gives the underlying table of data. Fig. 3 shows heat capacity and magnetisation data taken at low temperatur...

  1. Magnetic ordering in ternary germanide Nd{sub 2}CuGe{sub 6}

    Li, D.X. [Institute for Materials Research, Tohoku University, Oarai, Ibaraki 311-1313 (Japan)]. E-mail:; Nimori, S. [Tsukuba Magnet Laboratory, National Institute for Materials Science, 3-13 Sakura, Tsukuba 305-0003 (Japan); Li, Y.X. [School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300130 (China); Koyama, K. [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Shiokawa, Y. [Institute for Materials Research, Tohoku University, Oarai, Ibaraki 311-1313 (Japan)


    We have performed a systematic investigation on a well-annealed polycrystalline Nd{sub 2}CuGe{sub 6} sample by measuring its AC and DC susceptibility {chi}(T), magnetization M(H), magnetic relaxation M(t), electrical resistivity {rho}(T) and specific heat C(T). The sharp peak observed at about T {sub N} = 9.4 K in {chi} {sub AC}(T), {chi} {sub DC}(T) and C(T) curves, respectively, indicates the occurrence of an antiferromagnetic order, which is further confirmed by the sudden decrease in {rho}(T) at the same temperature. In the magnetically ordered state, M(H) shows an evident metamagnetic transition. Moreover, the {chi} {sub DC}(T) and M(t) measurements reveal evident irreversible magnetism and long-time magnetic relaxation effect below T {sub N} indicating the metastable characters of the magnetically ordered state. The formation of the metastable magnetic state cannot be explained as glass freezing of the neodymium magnetic moments in the Ce{sub 2}CuGe{sub 6}-type orthorhombic Nd{sub 2}CuGe{sub 6} sample.

  2. Assessment of thermodynamic functions of formation for rare earth silicides, germanides, stannides and plumbides

    Witusiewicz, V.T. [Nat. Acad. of Sci. of the Ukraine, Kyyiv (Ukraine). Physico-Technological Inst. of Metals and Alloys; Sidorko, V.R. [Frantsevich Institute of Materials Science, National Academy of Sciences of the Ukraine, 3 Krzhizhanovsky St., 252180, Kyyiv (Ukraine); Bulanova, M.V. [Frantsevich Institute of Materials Science, National Academy of Sciences of the Ukraine, 3 Krzhizhanovsky St., 252180, Kyyiv (Ukraine)


    A critical assessment has been made of the available data on thermodynamic properties of binary compounds of lanthanide metals, scandium and yttrium (R) with IV group p elements (X{identical_to}Si, Ge, Sn and Pb), obtained mainly through the direct e.m.f and calorimetric methods. On the basis of the most reliable data the following empirical relation was derived which allows the estimation of entropies of formation for the intermetallics ({Delta}{sub f}S) by using the enthalpies of formation per mole of A{sub m/(m+n)}B{sub n/(m+n)} compound ({Delta}{sub f}H) together with the melting (T{sub m,I}) and boiling temperatures (T{sub b,I}) of the components I (I element of A,B):{Delta}fSm=aRmn(m+n)23TmTb(m+n)2mn+bTb{Delta}f?Hm,where {Delta}fSm={Delta}fS-(m{Delta}mSA+n{Delta}mSB)m+n; {Delta}fHm={Delta}fH-(m{Delta}mHA+n{Delta}mHB)m+n;T and macr;m=(Tm,A+Tm,B)/2 and T{sub b}=(T{sub b,A}+T{sub b,B})/2; {Delta}{sub m}S{sub A} and {Delta}{sub m}H{sub A} are the entropy and enthalpy of melting of the components, respectively; m and n are stoichiometric coefficients of a binary A{sub m}B{sub n} compound; a and b are empirical coefficients, and R is the gas constant.The calculated entropy values for the R-X intermetallics are in agreement with experimental data available. (orig.)

  3. Anisotropic fluorocarbon plasma etching of silicon/silicon germanide heterostructures and plasma etching-induced sidewall damage

    Ding, Ruhang

    Plasma etching is a critical tool in the fabrication of Si/SiGe heterostructure quantum devices, but with challenges addressed herein, including (1) control of etch profiles and (2) damage to etched feature sidewalls that affects device performance. (1) Fluorocarbon-based plasma etching often results in device profiles with undercuts due to preferential etching of SiGe over silicon. A C4F8/N2/Ar etch plasma gas mixture introduced here has been successfully used to achieve straight sidewalls through heterostructure layers by formation of a fluorocarbon inhibitor film on feature sidewalls to prevent undercutting. (2) Chemical and structural changes in the semiconductor at feature sidewalls associated with plasma-surface interactions are considered damage, as they affect band structure and electrical conduction in the active region of the device, known as the 2-dimensional electron gas (2DEG). In experiments designed to better understand the mechanisms of plasma-induced sidewall damage, damage to straight wires was characterized both by the width of a non-conductive "sidewall depletion" region at the device sidewall, and by the noise level factor, gamma H/N, determined from spectra of low frequency noise. Observed increases in sidewall depletion width with increasing etch depth are tentatively attributed to the increase in total number of defects with increased plasma exposure time. Excess negative charge incorporated into the fluorocarbon inhibitor film could be another contributing factor. Other factors considered, including defects at the bottom of etched features as well as leakage current bypassing the wire, are ruled out as their contribution is expected to diminish as the distance between the 2DEG and feature bottom increases. The noise level factor, gammaH /N, shows a maximum with increasing etch depth, possibly the result of two competing effects: increasing ion dose and decreasing leakage current. The noise level shows a minimum at an ion bombardment energy of ˜100 eV, while the sidewall depletion width is independent of bias voltage, within experimental uncertainty. A proposed explanation of the noise trend involves two competing effects as ion energy increases: the increase in damage caused by each bombarding ion and the reduction in total ion dose due to shorter etch times and reduced ion flux to the sidewalls.

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

    Islam, Z.


    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.

  5. Superconductors

    Newkirk, Lawrence R.; Valencia, Flavio A.


    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.

  6. Report for in-situ 7Li NMR experiment in PNNL Phase -1

    Hu, Jian Zhi [Pacific Northwest National Laboratory


    To understand the detailed local structural evolution, an in-situ 7Li NMR study was performed. An operando identification of the lithium germanide phases under various cycling regimens permitted understanding of the kinetics of phase transition between different structural phases, including the amorphous phases, and how these correlated with capacity retention. Combining data from TEM and in-situ 7Li NMR, we discovered that the phase inter-conversion during cycling was mediated by co-existing amorphous and crystalline phases, and that the high capacity observed was correlated with an over-lithiated lithium germanide phase.

  7. Nontrivial Role of Interlayer Cation States in Iron-Based Superconductors.

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


    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. Based on this premise, one would also expect the large class of isostructural and isoelectronic iron germanide compounds to be good superconductors. As a matter of fact, they, however, superconduct at very low temperatures or not at all. In this work we establish 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 and chalcogenides, 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). Our results indicate that superconductivity in iron-based materials may not always be fully understood based on d or d-p model Hamiltonians only.

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

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


    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.

  9. 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; Synthese et caracterisation des proprietes structurales et magnetiques de nouveaux siliciures et germaniures a base d'uranium et de cuivre: etude des proprietes physiques et d'hydruration de quelques composes appartenant aux systemes Gd-Ni-X ou X = Ga, Al, Sn

    Pechev, St


    Three novel phases, U{sub 3}Cu{sub 4}Si{sub 4}, U{sub 3}Cu{sub 4}Ge{sub 4} and UCuGe{sub 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{sub x}Si{sub 2-x} (0,28 {<=} x {<=} 0,96) solid solution. Thus, the structure of the compositions changes in the {alpha}-ThSi{sub 2}(tetragonal) {yields} AlB{sub 2}(hexagonal) {yields} Ni{sub 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{sub 3}X{sub 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{sub 5} {yields} HoNi{sub 2,6}Ga{sub 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{sub HoNi{sub 2,6}}{sub Ga{sub 2,4}} x a{sub HoNi{sub 2,6}}{sub Ga{sub 2,4}} x 2c{sub HoNi{sub 2,6}}{sub Ga{sub 2,4}}-type superstructure) has been observed for GdNi{sub 3}Al{sub 2}. Hydrogen absorption in Gd{sub 3}Ni{sub 6}Al{sub 2} and GdNi{sub 3}Al{sub 2} weakens the strength of the magnetic interactions. (author)

  10. Contribution à la cristallochimie des isotypes de ThCr 2Si 2 et CaBe 2Ge 2. I. Les systèmes La T2- xT' xGe 2 ( T, T' = Ru, Rh, Pd, Ir, Pt) et La 1- xCa xCa xIr 2Ge 2: Distribution des éléments de transition dans le type CaBe 2Ge 2

    Venturini, G.; Malaman, B.; Roques, B.


    There are several singularities in the systems investigated. Although the three germanides La T2Ge 2( T = Ru, Rh, Pd) are isostructural with ThCr 2Si 2, a complete solid solution occurs only between LaRu 2Ge 2 and LaRh 2Ge 2; in the system LaRh 2Ge 2LaPd 2Ge 2, there is a range of CaBe 2Ge 2-type solid solutions. The lattice constants of the ThCr 2Si 2-type compounds vary curiously according to the valence electron concentration (VEC). The CaBe 2Ge 2-type germanides are confined in a narrow range of VEC. The new compound CaIr 2Ge 2 is then of the ThCr 2Si 2-type while LaIr 2Ge 2 is of the CaBe 2Ge 2-type. In the latter structural type, the square pyramids of Ge atoms are favorite sites for Ir or Pt atoms. These results are discussed.

  11. A study on NiGe-contacted Ge n+/p Ge shallow junction prepared by dopant segregation technique

    Tsui, Bing-Yue; Shih, Jhe-Ju; Lin, Han-Chi; Lin, Chiung-Yuan


    In this work, the effect of dopant segregation on the NiGe/n-Ge contact is studied by experiments and first-principles calculations. Both Al-contacted and NiGe-contacted n+/p junctions were fabricated. Phosphorus and arsenic ions were Implanted Before Germanide (IBG) formation or Implanted After Germanide (IAG) formation. The NiGe-contacted junction always exhibit higher forward current than the Al-contacted junction due to dopant segregation. First principles calculations predict that phosphorus atoms tend to segregate on both NiGe side and Ge side while arsenic atoms tend to segregate at Ge side. Since phosphorus has higher activation level and lower diffusion coefficient than arsenic, we propose a phosphorus IBG + arsenic IAG process. Shallow n+/p junction with junction depth 90 nm below the NiGe/Ge interface is achieved. The lowest and average contact resistivity is 2 × 10-6 Ω cm2 and 6.7 × 10-6 Ω cm2, respectively. Methods which can further reduce the junction depth and contact resistivity are suggested.

  12. A note on the reactions in the Ti-Ge system

    Joshua Pelleg


    Full Text Available Formations of germanides in thin films of the Ti-Ge system were investigated by XRD after furnace annealing for 1 hour. Ti6Ge5 seems to be the first phase formed while TiGe2 is the end phase with the lowest resistivity. The existence of the phase Ti5Ge3 was confirmed which forms at higher temperatures than Ti6Ge5. The presence of a thin TiO2 layer was observed by TEM. Which of the phase exists or is missed depends on composition of the constituents comprising the film, their thickness and temperature of reaction. Three phases are observed to coexist on the Ge substrate, which are Ti5Ge3, Ti6Ge5 and TiGe2. A schematic suggestion is presented for explaining the coexistence of two or more phases. The concept of formation and coexistence of two phases at lower temperatures is also proposed.

  13. Magnetic properties and electronic structure of Gd{sub 3}Cu{sub 4}X{sub 4} (X=Ge,Sn)

    Szytula, A.; Penc, B.; Wawrzynska, E. [M. Smoluchowski Institute of Physics, Jagiellonian University, Reymonta 4, 30-059 Krakow (Poland); Jezierski, A. [Institute of Molecular Physics, Polish Academy of Sciences, Smoluchowskiego 17, 60-179 Poznan (Poland); Zygmunt, A. [W. Trzebiatowski Institute of Low Temperature and Structure Research, Polish Academy of Sciences, Okolna 2, 50-442 Wroclaw (Poland)


    Polycrystalline samples of Gd{sub 3}Cu{sub 4}X{sub 4}(X=Ge,Sn) were investigated by means of magnetometry and XPS. Additionally, calculations of the electronic structures with the TB-LMTO method were performed for both compounds. They were found to be antiferromagnets; the stannide - below 13 K and the germanide - below 11 K. The electronic structures determined from the photoemission spectra agree well with the results of the calculations. Analysis of the core levels indicates presence of the Cu{sup +1} ions in both compounds. Besides, charge transfers from the Cu and Ge atoms, the latter only in Gd{sub 3}Cu{sub 4}Ge{sub 4}, were detected. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  14. Oxidation Behavior of Germanium- and/or Silicon-Bearing Near-α Titanium Alloys in Air

    Kitashima, Tomonori; Yamabe-Mitarai, Yoko


    The effect of germanium (Ge) and/or silicon (Si) addition on the oxidation behavior of the near-α alloy Ti-5Al-2Sn-4Zr-2Mo was investigated in air at 973 K (700 °C). Ge addition decreased the oxidation resistance because of the formation of a Ge-rich layer in the substrate at the TiO2/substrate interface, enhancing Sn segregation at the interface. In addition, a small amount of Ge dissolved in the external Al2O3 layer. These results reduced the aluminum activity at the interface, suppressed the formation of Al2O3, and increased the diffusivity of oxygen in the oxide scales. The addition of 0.2 and 0.9 wt pct Si was beneficial for improving oxidation resistance. The effect of germanide and silicide precipitates in the matrix on the oxide growth process was also discussed.

  15. A neutron diffraction study of the R{sub 15}Ge{sub 9}C compounds (R = Ce, Pr, Nd)

    Tencé, S., E-mail: [Université Grenoble Alpes, Institut Néel, BP166, F-38042 Grenoble (France); CNRS, Institut Néel, Rue des Martyrs, F-38042 Grenoble (France); Institut de Chimie de la Matière Condensée de Bordeaux (ICMCB), Université de Bordeaux, 87 Avenue Docteur Albert Schweitzer, 33608 Pessac Cedex (France); Isnard, O. [Université Grenoble Alpes, Institut Néel, BP166, F-38042 Grenoble (France); CNRS, Institut Néel, Rue des Martyrs, F-38042 Grenoble (France); Wrubl, F. [Department of Chemistry, University of Genoa, Via Dodecaneso 31, 16146 Genoa (Italy); Manfrinetti, P. [Department of Chemistry, University of Genoa, Via Dodecaneso 31, 16146 Genoa (Italy); Institute SPIN – CNR, Corso Perrone 24, 16152 Genoa (Italy)


    Highlights: • Neutron diffraction study was performed on the germanides R{sub 15}Ge{sub 9}C (R = Ce, Pr, Nd). • The interstitial carbon atoms occupy mainly the site 2b in (1/3 2/3 ∼1/2). • The three compounds display canted ferromagnetic structures with k = [0 0 0]. • Carbon insertion strongly modifies the magnetic properties of the parent germanides. - Abstract: In this work we report the results of the neutron diffraction investigation performed on the germanides R{sub 15}Ge{sub 9}C, for R = Ce, Pr and Nd (La{sub 15}Ge{sub 9}Fe-type, hP50, P6{sub 3}mc, Z = 2), to refine the crystal superstructure of these compounds and determine their magnetic structures. The interstitial carbon atoms occupy mainly the 2b Wyckoff site in the position (1/3 2/3 ∼1/2) and also, with a smaller occupancy rate, the Wyckoff site 2a at (0 0 ∼1/2). In the magnetic state, the three compounds display predominantly a ferromagnetic behavior with the propagation vector k = [0 0 0]. These results are in agreement with the magnetization measurements, with T{sub C} = 10, 30 and 80 K as Curie temperature of Ce{sub 15}Ge{sub 9}C, Pr{sub 15}Ge{sub 9}C and Nd{sub 15}Ge{sub 9}C, respectively. Ce{sub 15}Ge{sub 9}C and Nd{sub 15}Ge{sub 9}C present a ferromagnetic alignment of the R moments along the c-axis and an antiferromagnetic spin arrangement within the (a–b) plane. For Pr{sub 15}Ge{sub 9}C the ferromagnetic contribution is found within the (a–b) plane, as previously observed for the isotypic compound Tb{sub 15}Si{sub 9}C. The carbides crystal structure possesses four inequivalent rare earth sites carrying different magnetic moments, leading to mean values of 0.9 μ{sub B}/Ce, 1.1 μ{sub B}/Pr and 2.2 μ{sub B}/Nd for Ce{sub 15}Ge{sub 9}C, Pr{sub 15}Ge{sub 9}C and Nd{sub 15}Ge{sub 9}C, respectively. The magnetic structures of these R{sub 15}Ge{sub 9}C compounds differ strongly from those of their parent R{sub 5}Ge{sub 3} germanides, but present strong similarities with the

  16. Evaporation-based Ge/.sup.68 Ga Separation

    Mirzadeh, Saed; Whipple, Richard E.; Grant, Patrick M.; O'Brien, Jr., Harold A.


    Micro concentrations of .sup.68 Ga in secular equilibrium with .sup.68 Ge in strong aqueous HCl solution may readily be separated in ionic form from the .sup.68 Ge for biomedical use by evaporating the solution to dryness and then leaching the .sup.68 Ga from the container walls with dilute aqueous solutions of HCl or NaCl. The chloro-germanide produced during the evaporation may be quantitatively recovered to be used again as a source of .sup.68 Ga. If the solution is distilled to remove any oxidizing agents which may be present as impurities, the separation factor may easily exceed 10.sup.5. The separation is easily completed and the .sup.68 Ga made available in ionic form in 30 minutes or less.

  17. The ANTARES recoil time-of-flight spectrometer

    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)


    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.

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

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


    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 (La2 InNi2 -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

  19. Magnetic and magnetocaloric properties of the high-temperature modification of TbTiGe.

    Tencé, S; Gaudin, E; Isnard, O; Chevalier, B


    The high-temperature form (HT) of the ternary germanide TbTiGe was prepared by melting. The investigation of HT-TbTiGe by x-ray and neutron powder diffractions shows that the compound crystallizes in the tetragonal CeScSi-type structure (space group I4/mmm; a = 404.84(5) and c = 1530.10(9) pm as unit cell parameters). Magnetization and specific heat measurements as well as neutron powder diffraction performed on HT-TbTiGe reveal a ferromagnet having T(C) = 300(1) K as the Curie temperature; the Tb-moments are aligned along the c-axis. This magnetic ordering is associated with a modest magnetocaloric effect around room temperature. The isothermal magnetic entropy change ΔS(m) was determined from the magnetization data; ΔS(m) reaches, respectively, a maximum value of  - 4.3 and  - 2.0 J K(-1) kg(-1) for a magnetic field change of 5 and 2 T.

  20. Discovery of Lorentz-violating type II Weyl fermions in LaAlGe

    Xu, Su-Yang; Alidoust, Nasser; Chang, Guoqing; Lu, Hong; Singh, Bahadur; Belopolski, Ilya; Sanchez, Daniel S.; Zhang, Xiao; Bian, Guang; Zheng, Hao; Husanu, Marious-Adrian; Bian, Yi; Huang, Shin-Ming; Hsu, Chuang-Han; Chang, Tay-Rong; Jeng, Horng-Tay; Bansil, Arun; Neupert, Titus; Strocov, Vladimir N.; Lin, Hsin; Jia, Shuang; Hasan, M. Zahid


    In quantum field theory, Weyl fermions are relativistic particles that travel at the speed of light and strictly obey the celebrated Lorentz symmetry. Their low-energy condensed matter analogs are Weyl semimetals, which are conductors whose electronic excitations mimic the Weyl fermion equation of motion. Although the traditional (type I) emergent Weyl fermions observed in TaAs still approximately respect Lorentz symmetry, recently, the so-called type II Weyl semimetal has been proposed, where the emergent Weyl quasiparticles break the Lorentz symmetry so strongly that they cannot be smoothly connected to Lorentz symmetric Weyl particles. Despite some evidence of nontrivial surface states, the direct observation of the type II bulk Weyl fermions remains elusive. We present the direct observation of the type II Weyl fermions in crystalline solid lanthanum aluminum germanide (LaAlGe) based on our photoemission data alone, without reliance on band structure calculations. Moreover, our systematic data agree with the theoretical calculations, providing further support on our experimental results. PMID:28630919

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

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


    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.

  2. Ternary and quaternary Ni(Si)Ge(Sn) contact formation for highly strained Ge p- and n-MOSFETs

    Wirths, S.; Troitsch, R.; Mussler, G.; Hartmann, J.-M.; Zaumseil, P.; Schroeder, T.; Mantl, S.; Buca, D.


    The formation of new ternary NiGeSn and quaternary NiSiGeSn alloys has been investigated to fabricate metallic contacts on high Sn content, potentially direct bandgap group IV semiconductors. (Si)GeSn layers were pseudomorphically grown on Ge buffered Si(001) by reduced pressure chemical vapor deposition. Ni, i.e. the metal of choice for source/drain metallization in Si nanoelectronics, is employed for the stano-(silicon)-germanidation of highly strained (Si)GeSn alloys. We show that NiGeSn on GeSn layers change phase from well-oriented Ni5(GeSn)3 to poly-crystalline Ni1(GeSn)1 at very low annealing temperatures. A large range of GeSn compositions with Sn concentrations up to 12 at.%, and SiGeSn ternaries with large Si and Sn compositions from 18%/3% to 4%/11% are investigated. In addition, the sheet resistance, of importance for electronic or optoelectronic device contacts, is quantified. The incorporation of Si extends the thermal stability of the resulting low resistive quaternary phase compared to their NiGeSn counterparts.

  3. New high temperature modification of CeTiGe: structural characterization and physical properties.

    Chevalier, B; Hermes, W; Gaudin, E; Pöttgen, R


    The new high temperature form (HT) of the ternary germanide CeTiGe was prepared by annealing at 1373 K. The investigation of HT-CeTiGe by x-ray powder diffraction shows that the compound crystallizes in the tetragonal CeScSi type structure (space group I4/mmm; a=414.95(2) and c=1590.85(10) pm as unit cell parameters). Electrical resistivity, thermoelectric power, magnetization and specific heat measurements performed down to 2 K on HT-CeTiGe reveal a non-magnetic strongly correlated electron system; the specific heat divided by temperature attains a value of 0.635 J mol(-1) K(-2) at 2 K. The comparison of the physical properties of the two crystallographic modifications of CeTiGe suggests a decrease of the hybridization J(cf) between 4f(Ce) and conduction electrons in the sequence LT-CeTiGe [Formula: see text]-CeTiGe (CeScSi type). © 2010 IOP Publishing Ltd

  4. Magnetic structures and physical properties of Tm3Cu4Ge4 and Tm3Cu4Sn4.

    Baran, S; Kaczorowski, D; Szytuła, A; Gil, A; Hoser, A


    Tm(3)Cu(4)Ge(4) crystallizes in the orthorhombic Gd(3)Cu(4)Ge(4)-type crystal structure (space group Immm) whereas Tm(3)Cu(4)Sn(4) crystallizes in a distorted variant of this structure (monoclinic space group C2/m). The compounds were studied by means of neutron diffraction, specific heat, electrical resistivity and magnetic measurements. Analysis of experimental data revealed the presence of an antiferromagnetic order below 2.8 K in both compounds. In Tm(3)Cu(4)Ge(4) the magnetic unit cell is doubled in respect to the crystal unit cell and the magnetic structure can be described by a propagation vector k = [0, 1/2, 0]. A larger magnetic unit cell was found in Tm(3)Cu(4)Sn(4), given by a propagation vector k = [1/2, 1/2, 0] (for simplicity the orthorhombic description is used for both the germanide and the stannide). Close to 2 K, in each compound an incommensurate antiferromagnetic order develops. This low-temperature magnetic phase is characterized by a propagation vector k = [1/4, 0, k(z)], where k(z) is close to 0.49 and 0.47 in Tm(3)Cu(4)Ge(4) and Tm(3)Cu(4)Sn(4), respectively. The antiferromagnetic phase transitions are clearly seen in the bulk magnetic and specific heat data of both compounds.

  5. Low Temperature Heat Capacity of Layered Superconductors SrNi2Ge2 and SrPd2Ge2

    Hung, T. L.; Chen, I. A.; Huang, C. H.; Lin, C. Y.; Chen, C. W.; You, Y. B.; Jian, S. T.; Yang, M. C.; Hsu, Y. Y.; Ho, J. C.; Chen, Y. Y.; Ku, H. C.


    Low-temperature heat capacity C( T) of the weakly electron-correlated SrNi2Ge2 122-layer compound undergoes a superconducting transition with onset at 1.4 K and a bulk T c =0.75 K, where heat-capacity jump ratio ΔC( T c )/ γT c =0.88-1.05. A small average superconducting energy gap E g (ave)=2.21 kT c =0.14 meV is derived for this multi-gap superconductor. Similar results for isostructural SrPd2Ge2 include T c (onset)=3.5 K, bulk T c of 2.92 K, ΔC( T c )/ γT c =0.70 and E g (ave)=2.54 kT c =0.64 meV. The higher T c onset could be associated with stoichiometric 1:2:2 grains in the polycrystalline samples. In addition, deviations of E g / kT c from the BCS ratio of 3.5 suggest that, just like their iron-based counterpart, these 122-layer germanides may also exhibit an unconventional, fully-opened multi-gap s-wave superconductivity.

  6. "Nanoparticle-in-alloy" approach to efficient thermoelectrics: silicides in SiGe.

    Mingo, N; Hauser, D; Kobayashi, N P; Plissonnier, M; Shakouri, A


    We present a "nanoparticle-in-alloy" material approach with silicide and germanide fillers leading to a potential 5-fold increase in the thermoelectric figure of merit of SiGe alloys at room temperature and 2.5 times increase at 900 K. Strong reductions in computed thermal conductivity are obtained for 17 different types of silicide nanoparticles. We predict the existence of an optimal nanoparticle size that minimizes the nanocomposite's thermal conductivity. This thermal conductivity reduction is much stronger and strikingly less sensitive to nanoparticle size for an alloy matrix than for a single crystal one. At the same time, nanoparticles do not negatively affect the electronic conduction properties of the alloy. The proposed material can be monolithically integrated into Si technology, enabling an unprecedented potential for micro refrigeration on a chip. High figure-of-merit at high temperatures (ZT approximately 1.7 at 900 K) opens up new opportunities for thermoelectric power generation and waste heat recovery at large scale.

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

    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


    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.

  8. Magnetic, Caloric and Crystallographic Properties of Dy5(SixGe1-x)4 Alloys

    Ivchenko, Vitaliy Vladislavovich [Iowa State Univ., Ames, IA (United States)


    Polycrystals of the intermetallic compound of the Dy5(SixGe1-x)4 system, where x = 0, 0.25, 0.5, 0.625, 0.675, 0.725, 0.75, 0.775, 0.825, 0.875, and 1, have been prepared by electric-arc-melting on water-cooled copper hearth in an argon atmosphere. A study of phase relationships and crystallography in the pseudobinary system Dy5(SixGe1-x)4 using X-ray powder diffraction data and optical metallography was completed. It revealed that silicides in the composition range from 0.825 to 1 crystallize in the Gd5Si4-type crystal structure: germanides in the composition range from 0 to 0.625 crystallize in the Sm5Ge4-type structure, and alloys with intermediate composition range from 0.675 to 0.775 crystallize in the monoclinic Gd5Si2Ge2-type structure. The -ΔSm values were determined from magnetization measurements for 7 alloys. The alloys with a monoclinic crystal structure which belong to an intermediate phase region have large MCE value, which exceeds those observed in the other two phase regions by 300 to 500%. The nature of the observed magnetic and structural transformations in the Dy5(SixGe1-x)4 system seems to be similar with those reported for the Gd5(SixGe1-x)4 system. However, the interval and concentration range of three different phase regions in the Dy5(SixGe1-x)4 system are different from that observed in Gd-based alloys. A non-collinear ordering of magnetic moments at low temperature was observed for the alloys with monoclinic crystal structure. The Dy5Si3Ge alloy exhibited FM phase transition below Curie temperature. A series of magnetic transitions were observed at low temperature in the Dy5(SixGe1-x

  9. Photoemission Study of the Rare Earth Intermetallic Compounds: RNi2Ge2 (R=Eu, Gd)

    Park, Jongik [Iowa State Univ., Ames, IA (United States)


    EuNi2Ge2 and GdNi2Ge2 are two members of the RT2X2 (R = rare earth, T = transition metal and X = Si, Ge) family of intermetallic compounds, which has been studied since the early 1980s. These ternary rare-earth intermetallic compounds with the tetragonal ThCr2Si2 structure are known for their wide variety of magnetic properties, Extensive studies of the RT2X2 series can be found in Refs [ 1,2,3]. The magnetic properties of the rare-earth nickel germanides RNi2Ge2 were recently studied in more detail [4]. The purpose of this dissertation is to investigate the electronic structure (both valence band and shallow core levels) of single crystals of EuNi2Ge2 and GdNi2Ge2 and to check the assumptions that the f electrons are non-interacting and, consequently, the rigid-band model for these crystals would work [11], using synchrotron radiation because, to the best of our knowledge, no photoemission measurements on those have been reported. Photoemission spectroscopy has been widely used to study the detailed electronic structure of metals and alloys, and especially angle-resolved photoemission spectroscopy (ARPES) has proven to be a powerful technique for investigating Fermi surfaces (FSs) of single-crystal compounds.

  10. Theoretical predictions of novel superconducting phases of BaGe3 stable at atmospheric and high pressures.

    Zurek, Eva; Yao, Yansun


    A series of new superconducting binary silicides and germanides have recently been synthesized under high-pressure high-temperature conditions. A representative member of this group, BaGe3, was theoretically investigated using evolutionary structure searches coupled with structural analogies in the pressure range from 1 atm to 250 GPa, where three new phases were discovered. At 1 atm, in addition to the synthesized P63/mmc phase, we predicted two new phases, I4/mmm and Amm2, to be dynamically stable. The Amm2 structure comprises Ge clusters and triangular prisms intercalated with Ba and Ge atoms, a unique structural motif unknown to this group. The I4/mmm structure has been previously synthesized in binary silicides and is calculated to be thermodynamically stable in BaGe3 between 15.6 and 35.4 GPa. Above 35.4 GPa, two new phases of P6̅m2 and R3̅m symmetry become the global minima and remain so up to the highest pressure considered. These two phases have very similar enthalpies, and both feature layers of double Kagome nets of Ge intercalated with Ba-Ge layers. The predicted phases are suggested to be metallic with itinerant electrons and to be potentially superconducting from the considerable electron-phonon coupling strength. Density functional perturbation calculations combined with the Allen-Dynes-modified McMillan formula were used to estimate the superconducting critical temperatures (Tc) for these new phases, which, with slight pressure variations, are comparable to the experimental Tc measured for the P63/mmc phase.

  11. Research progress of high mobility germanium based metal oxide semiconductor devices%高迁移率 Ge沟道器件研究进展∗

    安霞; 黄如; 李志强; 云全新; 林猛; 郭岳; 刘朋强; 黎明; 张兴


    Germanium based metal oxide semiconductor (MOS) device has been a research hotspot and considered as a po-tential candidate for future complementary MOS (CMOS) technology due to its high and symmetric carrier mobility. However, the poor quality of gate dielectric/channel interface significantly restricts the performance of germanium based MOS devices. Besides, the solid-solubility and activation concentration of dopants in Ge are both quite low, and the dopants diffuse fast in Ge, which makes it difficult to achieve ultra-shallow junction with high dopant concentration, especially for Ge NMOS devices. To solve these problems, different techniques are proposed and overviewed. The proposed nitrogen-plasma-passivation method can effectively suppress the regrowth of germanium sub-oxide and reduce the interface state density. Thus the performance of the fabricated Ge NMOS device is significantly improved. To enhance the n-type dopant ac-tivation in Ge, the multiple implantation technique and the multiple annealing technique are proposed. High electrical activation over 1 × 1020 cm−3 is achieved, and the corresponding contact resistivity is reduced to 3.8 × 10−7 Ω·cm2. Besides, the implantation after germanide (IAG) technique is first proposed to modulate the Schottky barrier height (SBH). The record-low electron SBH of 0.10 eV is obtained by IAG technique, and the optimized process window is given. In addition, the poor thermal stability of NiGe restricts the further improvement of performance of Ge MOS device. P and Sb co-implantation technique and novel ammonium fluoride pretreatment method are proposed to improve the thermal stability of NiGe. The electrical characteristic of NiGe/Ge diode is also improved simultaneously. The results provide the guidelines for further enhancing the performances of germanium-based MOS devices.

  12. Synthetic, structural, and theoretical investigations of alkali metal germanium hydrides--contact molecules and separated ions.

    Teng, Weijie; Allis, Damian G; Ruhlandt-Senge, Karin


    The preparation of a series of crown ether ligated alkali metal (M=K, Rb, Cs) germyl derivatives M(crown ether)nGeH3 through the hydrolysis of the respective tris(trimethylsilyl)germanides is reported. Depending on the alkali metal and the crown ether diameter, the hydrides display either contact molecules or separated ions in the solid state, providing a unique structural insight into the geometry of the obscure GeH3- ion. Germyl derivatives displaying M--Ge bonds in the solid state are of the general formula [M([18]crown-6)(thf)GeH3] with M=K (1) and M=Rb (4). The compounds display an unexpected geometry with two of the GeH3 hydrogen atoms closely approaching the metal center, resulting in a partially inverted structure. Interestingly, the lone pair at germanium is not pointed towards the alkali metal, rather two of the three hydrides are approaching the alkali metal center to display M--H interactions. Separated ions display alkali metal cations bound to two crown ethers in a sandwich-type arrangement and non-coordinated GeH3- ions to afford complexes of the type [M(crown ether)2][GeH3] with M=K, crown ether=[15]crown-5 (2); M=K, crown ether=[12]crown-4 (3); and M=Cs, crown ether=[18]crown-6 (5). The highly reactive germyl derivatives were characterized by using X-ray crystallography, 1H and 13C NMR, and IR spectroscopy. Density functional theory (DFT) and second-order Møller-Plesset perturbation theory (MP2) calculations were performed to analyze the geometry of the GeH3- ion in the contact molecules 1 and 4.

  13. Magneto-structural correlations in rare-earth cobalt pnictides

    Thompson, Corey Mitchell

    Magnetic materials are used in many applications such as credit cards, hard drives, electric motors, sensors, etc. Although a vast range of magnetic solids is available for these purposes, our ability to improve their efficiency and discover new materials remains paramount to the sustainable progress and economic profitability in many technological areas. The search for magnetic solids with improved performance requires fundamental understanding of correlations between the structural, electronic, and magnetic properties of existing materials, as well as active exploratory synthesis that targets the development of new magnets. Some of the strongest permanent magnets, Nd 2Fe14B, SmCo5, and Sm2Co17, combine transition and rare-earth metals, benefiting from the strong exchange between the 4f and 3d magnetic sublattices. Although these materials have been studied in great detail, the development of novel magnets requires thorough investigation of other 3d-4 f intermetallics, in order to gain further insights into correlations between their crystal structures and magnetic properties. Among many types of intermetallic materials, ternary pnictides RCo 2Pn2 (R = La, Ce, Pr, Nd; Pn = P, As) are of interest because, despite their simple crystal structures, they contain two magnetic sublattices, exchange interactions between which may lead to rich and unprecedented magnetic behavior. Nevertheless, magnetism of these materials was studied only to a limited extent, especially as compared to the extensive studies of their silicide and germanide analogues. The ThCr2Si2 structure type, to which these ternary pnictides belong, is one of the most ubiquitous atomic arrangements encountered among intermetallic compounds. It accounts for over 1000 known intermetallics and has received increased attention due to the recently discovered FeAs-based superconductors. This dissertation is devoted to the investigation of magnetostructural relationships and anomalous magnetic behaviors in rare

  14. High-temperature thermochemistry of transition metal borides, silicides and related compounds. Final report

    Klemppa, Ole J.


    Earlier this year in collaboration with Dr. Susan V. Meschel we prepared a major review paper which gives a comprehensive summary of what our laboratory has accomplished with support from DOE. This paper is No.43 in the List of Publications provided. It was presented to TMS at its National Meeting in Nashville, TN last March. A copy of the manuscript of this paper was recently mailed to DOE. It has been submitted for publication in Journal of Alloys and Compounds. This review paper summarizes our observed trends in the enthalpies of formation of TR-X and RE-X compounds (where X is a IIIB or IVB element) in their dependence of the atomic number of the transition metal (TR) and the lanthanide metal (RE). In this paper our measured enthalpies of formation for each alloy family are compared for the 3d, 4d and 5d transition metal elements. We also compare our experimental results with predicted values based on Miedema's semi-empirical model. Data are presented for the carbides, silicides, germanides and stannides in Group IVB, and for the borides and aluminides in Group IIIB. During the past year (1999-2000) we have extended our work to compounds of the 3d, 4d and 5d elements with gallium (see papers No.40, No.41, and No.45 in the List of Publications). Fig. 1 (taken from No.45) presents a systematic picture of our experimental values for the most exothermic gallide compounds formed with the transition elements. This figure is characteristic of the other systematic pictures which we have found for the two other IIIB elements which we have studied and for the four IVB elements. These figures are all presented in Ref. No.43. This paper also illustrates how the enthalpy of formation of compounds of the IIIB and IVB elements with the lanthanide elements (with the exception of Pm, Eu and Yb) depend on the atomic number of RE. Finally our results for the RE-X compounds are compared with the predictions of Gschneidner (K.A. Gschneidner, Jr., J. Less Common Metals 17, 1

  15. Synthesis, structural characterization and properties of SrAl{sub 4−x}Ge{sub x}, BaAl{sub 4−x}Ge{sub x}, and EuAl{sub 4−x}Ge{sub x} (x≈0.3–0.4)—Rare examples of electron-rich phases with the BaAl{sub 4} structure type

    Zhang, Jiliang; Bobev, Svilen, E-mail:


    Three solid solutions with the general formula AEAl{sub 4−x}Ge{sub x} (AE=Eu, Sr, Ba; 0.32(1)≤x≤0.41(1)) have been synthesized via the aluminum self-flux method, and their crystal structures have been established from powder and single-crystal X-ray diffraction. They are isotypic and crystallize with the well-known BaAl{sub 4} structure type, adopted by the three AEAl{sub 4} end members. In all structures, Ge substitutes Al only at the 4e Wyckoff site. Results from X-rays photoelectron spectroscopy on EuAl{sub 4−x}Ge{sub x} and EuAl{sub 4} indicate that the interactions between the Eu{sup 2+} cations and the polyanionic framework are enhanced in the Ge-doped structure, despite the slightly elevated Fermi level. Magnetic susceptibility measurements confirm the local moment magnetism, expected for the [Xe]4f{sup 7} electronic configuration of Eu{sup 2+} and suggest strong ferromagnetic interactions at cryogenic temperatures. Resistivity data from single-crystalline samples show differences between the title compounds, implying different bonding characteristics despite the close Debye temperatures. A brief discussion on the observed electron count and homogeneity ranges for AEAl{sub 4−x}Ge{sub x} (AE=Eu, Sr, Ba) is also presented. - Graphical abstract: AEAl{sub 4−x}Ge{sub x} (AE=Eu, Sr, Ba; 0.32(1)≤x≤0.41(1)), three “electron-rich” phases with BaAl{sub 4} structure type have been synthesized and characterized. Display Omitted - Highlights: • Three BaAl{sub 4}-type ternary aluminum germanides have been synthesized with Eu, Sr and Ba. • Eu, Sr and Ba cations have no apparent influence on the solubility of Ge. • The Ge atoms substitute Al on one of two framework sites, thereby strengthening the interactions between the cations and the polyanionic framework.

  16. 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

    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: [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)


    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 ( 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

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

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


    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

  18. Phase equilibria in the La–Mg–Ge system at 500 °C and crystal structure of the new ternary compounds La{sub 11}Mg{sub 2}Ge{sub 7} and LaMg{sub 3−x}Ge{sub 2}

    De Negri, S., E-mail: [Università degli Studi di Genova, Dipartimento di Chimica e Chimica Industriale, via Dodecaneso 31, 16146 Genova (Italy); Solokha, P.; Skrobańska, M. [Università degli Studi di Genova, Dipartimento di Chimica e Chimica Industriale, via Dodecaneso 31, 16146 Genova (Italy); Proserpio, D.M. [Università degli Studi di Milano, Dipartimento di Chimica, Via Golgi 19, 20133 Milano (Italy); Samara Center for Theoretical Materials Science (SCTMS), Samara State University, Samara 443011 (Russian Federation); Saccone, A. [Università degli Studi di Genova, Dipartimento di Chimica e Chimica Industriale, via Dodecaneso 31, 16146 Genova (Italy)


    The whole 500 °C isothermal section of the La–Mg–Ge ternary system was constructed. The existence and crystal structure of three ternary compounds were confirmed: La{sub 2+x}Mg{sub 1−x}Ge{sub 2} (τ{sub 2}, P4/mbm, tP10–Mo{sub 2}FeB{sub 2}, 0≤x≤0.25), La{sub 4}Mg{sub 5}Ge{sub 6} (τ{sub 3}, Cmc2{sub 1}, oS60–Gd{sub 4}Zn{sub 5}Ge{sub 6}) and La{sub 4}Mg{sub 7}Ge{sub 6} (τ{sub 4}, C2/m, mS34, own structure type). Five novel compounds were identified and structurally characterized: La{sub 11}Mg{sub 2}Ge{sub 7} (τ{sub 1}, P4{sub 2}/ncm, tP88-8, own structure type, a=1.21338(5), c=1.57802(6) nm), LaMg{sub 3−x}Ge{sub 2} (τ{sub 5}, P3{sup ¯}1c, hP34-0.44, own structure type, x=0.407(5), a=0.78408(4), c=1.45257(7) nm), La{sub 6}Mg{sub 23}Ge (τ{sub 6}, Fm3{sup ¯}m, cF120–Zr{sub 6}Zn{sub 23}Si, a=1.46694(6) nm), La{sub 4}MgGe{sub 10−x} (τ{sub 7}, x=0.37(1), C2/m, mS60-1.46, own structure type, a=0.88403(8), b=0.86756(8), c=1.7709(2) nm, β=97.16°(1) and La{sub 2}MgGe{sub 6} (τ{sub 8}, Cmce, oS72–Ce{sub 2}(Ga{sub 0.1}Ge{sub 0.9}){sub 7}, a=0.8989(2), b=0.8517(2), c=2.1064(3) nm). Disordering phenomena were revealed in several La–Mg–Ge phases in terms of partially occupied sites. The crystal structures of La{sub 11}Mg{sub 2}Ge{sub 7} and LaMg{sub 3−x}Ge{sub 2} are discussed in details. The latter is a √3a×√3a×2c superstructure of the LaLi{sub 3}Sb{sub 2} structure type; the symmetry reduction scheme is shown in the Bärnighausen formalism terms. - Graphical abstract: La–Mg–Ge isothermal section at 500 °C and group–subgroup relation between the LaLi{sub 3}Sb{sub 2} (parent type) and LaMg{sub 3−x}Ge{sub 2} (derivative) structures. - Highlights: • Novel La−Mg−Ge compounds structure determination from X-ray single crystal data. • Disordering phenomena as common features of the studied germanides. • Bärnighausen formalism as a useful tool for accurate structure determination. • Full isothermal section of the La

  19. Gate stack and channel engineering: Study of metal gates and germanium channel devices

    Todi, Ravi M.

    resistivity measurements, and work function extraction. The work function has been determined from MOS capacitor and Schottky diodes. The need for electron and hole mobility enhancement and the progress in the development of high-kappa gate stacks, has lead to renewed interest in Ge MOSFETs. The p-MOS mobility data for Ge channel devices have been reported. The results indicate greater than 2 x improvements in device mobility as compared to standard Si device. A low frequency noise assessment of silicon passivated Ge p-MOSFETs with a TiN/TaN/HfO2 gate stack has been made. For the first time we also report results on low frequency noise characterisation for a Ge P+- n junctions with and without Ni germanidation.