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Organogermane and organostannane compounds are valuable reagents in cross coupling reactions, and copper(I) germanide and stannanide complexes can provide convenient access to these compounds. This review presents the chemistry of copper(I) germanide and stannanide complexes, with a particular focus on systems at the frontier of organic and inorganic chemistry where structural characterisation of coordination complexes facilitates rationalisation of organic mechanisms. These species show both similarities to, and significant divergences from their lighter silanide congeners. For example, they are all viable sources of the relevant organotetranide anion, but in the cases of both germanium and tin, the tetranides can be accessed via direct deprotonation of the corresponding tetranes, a reaction unknown for silicon. Further divergences between copper(I) germanides and stannanides are highlighted; whilst both can be used in productive organic transformations to access organotetranes, catalytic reactions are only reported for germanium. The rather striking ability of triphenylstannanides to acts as sources of the phenyl anion are discussed; the mechanism of this reaction is still subject to discussion, but its absence in the chemistry of germanium and silicon is now well‐rationalised. We conclude this review by considering potential research directions in the synthesis and exploitation of copper(I) germanides and stannanides. [ABSTRACT FROM AUTHOR]

The Ni-stanogermanides were formed via an interfacial reaction between Ni film and a Ge1−xSnx (x = 0.083) epilayer grown on a Si substrate driven by thermal treatment, and their microstructural and chemical features were investigated as a function of a rapid thermal annealing (RTA) temperature. The Ni3(Ge1−xSnx) phase was formed at the RTA temperature of 300 °C, above which Ni(Ge1−xSnx) was the only phase formed. The fairly uniform Ni(Ge1−xSnx) film was formed without unreactive Ni remaining after annealing at 400 °C. However, the Ni(Ge1−xSnx) film formed at 500 °C exhibited large surface and interface roughening, followed by the formation of Ni(Ge1−xSnx) islands eventually at 600 °C. The Sn concentration in Ni(Ge1−xSnx) gradually decreased with increasing RTA temperature, implying the enhancement of Sn out-diffusion from Ni(Ge1−xSnx) grains during the Ni-stanogermanidation process at higher temperature. The out-diffused Sn atoms were accumulated on the surface of Ni(Ge1−xSnx), which could be associated with the low melting temperature of Sn. On the other hand, the out-diffusion of Sn atoms from Ni(Ge1−xSnx) along its interface was dominant during the Ni/Ge1−xSnx interfacial reaction, which could be responsible for the segregation of metallic Sn grains that were spatially confined near the edge of Ni(Ge1−xSnx) islands. [ABSTRACT FROM AUTHOR]

The TiMnSi2-type (space group Pbam) germanides ScTGe2 (T = Fe, Co, Ru, Rh) were synthesized from the elements by arc-melting. Single crystals were grown by annealing sequences of the arc-melted buttons in an induction furnace. The structures of ScFeGe2, ScRuGe2 and ScRhGe2 were refined from single-crystal X-ray diffraction data. In ScRuGe2, the ruthenium atoms have distorted octahedral germanium coordination (242–268 pm Ru–Ge). Three trans-face-sharing octahedra form a sub-unit which is condensed via common edges in c direction and connected via common corners with four adjacent blocks, forming a three-dimensional [RuGe2 type] substructure. The two crystallographically independent scandium sites have coordination numbers 15 (Sc1@Ge8Ru4Sc3) and 17 (Sc2@Ge7Ru6Sc4). Electronic band structure calculations for ScCoGe2 and ScRuGe2 show a net charge transfer from the scandium to the transition metal and germanium atoms, leading to a description with polyanionic networks Scδ+[TGe2]δ−. The two crystallographically independent Sc sites are easily distinguishable by 45Sc magic-angle spinning (MAS)-NMR spectroscopy. Isotropic chemical shift values and nuclear electric quadrupolar interaction parameters were deduced from an analysis of the triple-quantum (TQ)-MAS NMR spectra. The electric field gradient parameters deduced from these experiments are in good agreement with quantum-chemical calculations using the Wien2k code. Likewise, the two crystallographically independent iron sites in ScFeGe2 could be discriminated in the 57Fe Mößbauer spectra through their isomer shifts and quadrupole splitting parameters: δ = 0.369(1) mm s−1 and ∆EQ = 0.232(2) mm s−1 for Fe1 and δ = 0.375(2) mm s−1 and ∆EQ = 0.435(4) mm s−1 for Fe2 (data at T = 78 K). [ABSTRACT FROM AUTHOR]

Auger electron spectroscopy was used to determine the phase composition of Cr2GeC MAX phase thin films. A distinctive feature of the formation of carbon-containing MAX phases is the shape of carbon Auger peaks, which is characteristic of metal carbides spectra. Features of the Auger spectra in the presence of secondary phases of chromium germanides are found. Their presence can manifest itself in an increase in the energy of the germanium peaks, which is caused by a chemical shift during the formation of the Cr–Ge bond. Moreover, we have detected the accumulation of electronic charge, which can be explained by the features of the surface morphology. [ABSTRACT FROM AUTHOR]

The 1 : 2 reaction of the imidazole‐based dithiolate (2) with GeCl2 • dioxane in THF/TMEDA gives 3, a TMEDA‐complexed dithiolene‐based germylene. Compound 3 is converted to monothiolate‐complexed (5) and N‐heterocyclic carbene‐complexed (7) germanium(II) dithiolene complexes via Lewis base ligand exchange. A bis‐dithiolene‐based germylene (8), involving a 3c–4e S‐Ge‐S bond, has also been synthesized through controlled hydrolysis of 7. The bonding nature of 3, 5, and 8 was investigated by both experimental and theoretical methods. [ABSTRACT FROM AUTHOR]

Binary iron‐germanium phases are promising materials in magnetoelectric, spintronic or data storage applications due to their unique magnetic properties. Previous protocols for preparation of FexGey thin films and nanostructures typically involve harsh conditions and are challenging in terms of phase composition and homogeneity. Herein, we report the first example of single source chemical vapor deposition (CVD) of FexGey films. The appreciable volatility of [Ge[Fe2(CO)8]2], [Cl2GeFe(CO)4]2 and Me₂iPr₂NHC ⋅ GeCl2 ⋅ Fe(CO)4 allowed for their application as precursors under standard CVD conditions (Me₂iPr₂NHC=1,3‐diisopropoyl‐4,5‐dimethylimidazol‐2‐ylidene). The thermal decomposition products of the precursors were characterized by TGA and powder XRD. Deposition experiments in a cold‐wall CVD reactor resulted in dense films of FexGey. During the optimization of synthetic conditions for precursor preparation the new iron‐germanium cluster Cl2Ge[Fe2(CO)8]Ge[Fe2(CO)8] was obtained in experiments with a higher stoichiometric ratio of GeCl2 ⋅ 1,4‐dioxane vs. Fe2(CO)9. [ABSTRACT FROM AUTHOR]

Improving the thermal stability of Ni/GeSn intermetallics is of great importance to avoid surface degradation and Sn segregation. For this purpose, we studied the effects of pre-amorphization by ion implantation (PAI) of GeSn layers prior to metallization. The impact of Si, Ge, C, or Ge + C PAI was evaluated in terms of phase sequence, morpohological, and electrical evolution during the solid-state reaction. The overall phase sequence, followed by in situ x-ray diffraction, was comparable with or without PAI and went as follows: the Ni 5 (GeSn) 3 hexagonal phase was obtained first, followed by the mono-stanogermanide phase: Ni(GeSn). Nevertheless, the threshold temperature for phase formation varied. These variations, depending on the nature of the implanted ions, can be related to kinetic and/or thermodynamic factors as supported by the analysis of bibliography for silicides and germanides. Additionally, it was reported that the use of Si or Ge implantation did not significantly impacted the surface morphology of the layers. On the other hand, the implantation of C positively impacts the surface morphology evolution by delaying Sn long-range diffusion and Ni(GeSn) agglomeration. This trend was then highly beneficial for preserving electrical stability in an enhanced process window. [ABSTRACT FROM AUTHOR]

The calcium- and strontium- alumo-germanides SrxCa1–xAl2Ge2 (x ≈ 0.4) and SrAl2Ge2 have been synthesized and structurally characterized. Additionally, a binary calcium germanide CaGe has also been identified as a byproduct. All three crystal structures have been established from single-crystal X-ray diffraction methods and refined with high accuracy and precision. The binary CaGe crystallizes with a CrB-type structure in the orthorhombic space group Cmcm (no. 63; Z = 4; Pearson symbol oC8), where the germanium atoms are interconnected into infinite zigzag chains, formally [Ge]2−. The calcium atoms are arranged in monocapped trigonal prisms, centered by Ge atoms. SrxCa1−xAl2Ge2 (x ≈ 0.4) and SrAl2Ge2 have been confirmed to crystallize with a CaAl2Si2-type structure in the trigonal space group P3¯m1 (no. 164; Z = 1; Pearson symbol hP5), where the germanium and aluminum atoms form puckered double-layers, formally [Al2Ge2]2−. The calcium atoms are located between the layers and reside inside distorted octahedra of Ge atoms. All presented structures have a valence electron count satisfying the octet rules (e.g., Ca2+Ge2− and Ca2+[Al2Ge2]2−) and can be regarded as Zintl phases.

The Ni-stanogermanides were formed via an interfacial reaction between Ni film and a Ge1−xSnx (x = 0.083) epilayer grown on a Si substrate driven by thermal treatment, and their microstructural and chemical features were investigated as a function of a rapid thermal annealing (RTA) temperature. The Ni3(Ge1−xSnx) phase was formed at the RTA temperature of 300 °C, above which Ni(Ge1−xSnx) was the only phase formed. The fairly uniform Ni(Ge1−xSnx) film was formed without unreactive Ni remaining after annealing at 400 °C. However, the Ni(Ge1−xSnx) film formed at 500 °C exhibited large surface and interface roughening, followed by the formation of Ni(Ge1−xSnx) islands eventually at 600 °C. The Sn concentration in Ni(Ge1−xSnx) gradually decreased with increasing RTA temperature, implying the enhancement of Sn out-diffusion from Ni(Ge1−xSnx) grains during the Ni-stanogermanidation process at higher temperature. The out-diffused Sn atoms were accumulated on the surface of Ni(Ge1−xSnx), which could be associated with the low melting temperature of Sn. On the other hand, the out-diffusion of Sn atoms from Ni(Ge1−xSnx) along its interface was dominant during the Ni/Ge1−xSnx interfacial reaction, which could be responsible for the segregation of metallic Sn grains that were spatially confined near the edge of Ni(Ge1−xSnx) islands.

Calcium germanides with two mid‐late rare‐earth metals, Ca5−xGdxGe3 and Ca5−xTbxGe3 (x≈0.1−0.2), have been synthesized and structurally characterized. Additionally, a lanthanum‐rich germanide with calcium substitutions, La5−xCaxGe3 (x≈0.5) has also been identified. The three structures have been established from single‐crystal X‐ray diffraction methods and confirmed to crystallize with the Cr5B3‐type in the tetragonal space group I4/mcm (no. 140; Z=4; Pearson symbol tI32), where part of the germanium atoms are interconnected into Ge2‐dimers, formally [Ge2]6−. Rare‐earth metal and calcium atoms are arranged in distorted trigonal prisms, square‐antiprisms and cubes, centered by Ge or rare‐earth/calcium metal atoms. These studies show that the amount of trivalent rare‐earth metal atoms substituting divalent calcium atoms is in direct correlation with the lengths of the Ge−Ge bond within the Ge2‐dimers, with distance varying between 2.58 Å in Ca5−xGdxGe3 and 2.75 Å in La5−xCaxGe3. Such an elongation of the Ge−Ge bond is consistent with the notion that the parent Ca5Ge3 Zintl phase (e. g. (Ca2+)5[Ge2]6−[Ge4−]) is being driven out of the ideal valence electron count and further reduced. In this context, this work demonstrates the ability of the germanides with the Cr5B3 structure type to accommodate substitutions and wider valence electron count while maintaining their global structural integrity. [ABSTRACT FROM AUTHOR]

The calcium- and strontium- alumo-germanides SrxCa1–xAl2Ge2 (x ≈ 0.4) and SrAl2Ge2 have been synthesized and structurally characterized. Additionally, a binary calcium germanide CaGe has also been identified as a byproduct. All three crystal structures have been established from single-crystal X-ray diffraction methods and refined with high accuracy and precision. The binary CaGe crystallizes with a CrB-type structure in the orthorhombic space group Cmcm (no. 63; Z = 4; Pearson symbol oC8), where the germanium atoms are interconnected into infinite zigzag chains, formally [Ge]2−. The calcium atoms are arranged in monocapped trigonal prisms, centered by Ge atoms. SrxCa1−xAl2Ge2 (x ≈ 0.4) and SrAl2Ge2 have been confirmed to crystallize with a CaAl2Si2-type structure in the trigonal space group P 3 ¯ m1 (no. 164; Z = 1; Pearson symbol hP5), where the germanium and aluminum atoms form puckered double-layers, formally [Al2Ge2]2−. The calcium atoms are located between the layers and reside inside distorted octahedra of Ge atoms. All presented structures have a valence electron count satisfying the octet rules (e.g., Ca2+Ge2− and Ca2+[Al2Ge2]2−) and can be regarded as Zintl phases. [ABSTRACT FROM AUTHOR]

Based on the low‐cost and relatively high catalytic activity, considerable efforts have been devoted towards developing redox‐active transition metal (TM)‐oxygen electrocatalysts for the alkaline oxygen evolution reaction (OER) while the role of redox‐inactive alkaline earth metals has often been neglected in OER. Herein, for the first time, we developed a novel ternary intermetallic CaFe6Ge6 precatalyst, whose surface rapidly transforms into a porous ultrathin Ca−Fe−O heteroshell structure during alkaline OER through the oxidative leaching of surficial Ge. Benefiting from synergistic effects, this highly efficient OER‐active material with distinct Ca−Fe−O layers has a large electrochemical surface area and more exposed active Fe sites than a Ca‐free FeOx phase. Also, the presence of Ca in Ca−Fe−O is responsible for the enhanced transport and activation of hydroxyls and related OER reaction intermediate as unequivocally illustrated by a combination of quasi in‐situ Raman spectroscopy and various ex‐situ methods. [ABSTRACT FROM AUTHOR]

We fabricated a high-density array of silicon nanowires (SiNWs) with a diameter of 10 nm embedded in silicon germanium (SiGe0.3) to give a composite thin film for thermoelectric device applications. The SiNW array was first fabricated by bio-template mask and neutral beam etching techniques. The SiNW array was then embedded in SiGe0.3 by thermal chemical vapor deposition. The cross-plane thermal conductivity of the SiNW–SiGe0.3 composite film with a thickness of 100 nm was 3.5±0.3W/mK in the temperature range of 300–350 K. Moreover, the temperature dependences of the in-plane electrical conductivity and in-plane Seebeck coefficient of the SiNW–SiGe0.3 composite were evaluated. The fabricated SiNW–SiGe0.3 composite film displayed a maximum power factor of 1×103 W/m K2 (a Seebeck coefficient of 4.8×103 μV/K and an electrical conductivity of 4.4×103 S/m) at 873 K. The present high-density SiNW array structure represents a new route to realize practical thermoelectric devices using mature Si processes without any rare metals. [ABSTRACT FROM AUTHOR]

The first systematic study for the first phase to form during cobalt germanidation was conducted. Hexagonal β-Co5Ge3 was the first phase to form in case of cobalt germanidation on (100) Ge. This phase formed at a temperature as low as 227 °C. Monoclinic CoGe was experimentally shown to be the second phase to form at the same temperature. Our results are contrary to the previous reports suggesting monoclinic CoGe to be the first phase to form. This is mainly due to the experimental setup that was designed to detect all forming phases: in-situ XRD monitoring at constant low temperature long time anneals of 24-48 h. We also report for the first time that both β-Co5Ge3 and monoclinic CoGe phases that formed during cobalt germanidation were highly ordered partial epitaxial crystal orientations. [ABSTRACT FROM AUTHOR]

We present the pressure dependence of the electronic and dynamical properties of six different CoGe phases with orthorhombic Cmmm, hexagonal P6/mmm and P 6 ̄ 2m, monoclinic C2/m, cubic P2 1 3, and orthorhombic Pnma symmetries. Using first-principles DFT calculations and the direct force-constants method, we study the dynamical stability of individual phases under external pressure. We show that the orthorhombic (Cmmm) and hexagonal (P6/mmm) structures are unstable over a broad pressure range and most pronounced imaginary phonon soft mode in both cases leads to a stable hexagonal (P 6 ̄ 2m) structure of the lowest ground-state energy of all studied phases at ambient and low (below ∼ 3 GPa) external pressure. Under these conditions, the cubic structure has the highest energy, however, together with monoclinic and orthorhombic phases, it is dynamically stable and all these three structures can potentially coexist as meta-stable phases. Above ∼ 3 GPa , the cubic phase becomes the most energetically favorable. Fitting the Birch–Murnaghan equation of state, we derive bulk modulus for all mentioned phases. The results indicate relatively high resistance of CoGe to compression. Such conclusions are confirmed by band structure calculations. Additionally, we show that electronic bands of the hexagonal (P 6 ̄ 2m) phase reveal characteristic features of the kagome-like structure, while in the cubic phase the electronic bands contain spin-1 and double Weyl fermions. In both cases, the external pressure induces the Lifshitz transition, related to the modification of the Fermi surface topology. [Display omitted] • The P 6 ̄ 2m phase is most energetically favored in the absence of pressure. • All investigated phases possess similar mechanical properties, while the Cmmm and P6/mmm phases are unstable in a dynamic sense. • Above approximately 3 GPa, the P2 1 3 phase has the lowest energies. • External pressure induces the Lifshitz transition for both the P 6 ̄ 2m and P2 1 3 phases. [ABSTRACT FROM AUTHOR]

A new ternary lithium zinc germanide, Li13.83Zn1.17(2)Ge4, was synthesized by a high‐temperature solid state reaction of the respective elements. The crystal structure was determined by single‐crystal X‐ray diffraction methods. The new phase crystallizes in the body‐centered cubic space group I4‾ 3d (no. 220) with unit cell parameter of 10.695(1) Å. The crystal structure refinements show that the parent Li15Ge4 structure is stabilized as Li15−xZnxGe4 (x≈1) via random substitution of Li atoms by the one‐electron‐richer atoms of the element Zn, by virtue of which the number of valence electrons increases, leading to a more electronically stable system. The substitution effects in the parent Li15Ge4 structure were investigated through both theory and experiment, which confirm that the Zn atoms in this structure prefer to occupy only one of the two available crystallographic sites for Li. The preferred substitution pattern established from experimental results is supported by DFT electronic structure calculations, which also explore the subtleties of the chemical bonding and the electronic properties of the title compounds. [ABSTRACT FROM AUTHOR]

A new ternary lithium zinc germanide, Li13.83Zn1.17(2)Ge4, was synthesized by a high‐temperature solid state reaction of the respective elements. The crystal structure was determined by single‐crystal X‐ray diffraction methods. The new phase crystallizes in the body‐centered cubic space group I4‾ 3d (no. 220) with unit cell parameter of 10.695(1) Å. The crystal structure refinements show that the parent Li15Ge4 structure is stabilized as Li15−xZnxGe4 (x≈1) via random substitution of Li atoms by the one‐electron‐richer atoms of the element Zn, by virtue of which the number of valence electrons increases, leading to a more electronically stable system. The substitution effects in the parent Li15Ge4 structure were investigated through both theory and experiment, which confirm that the Zn atoms in this structure prefer to occupy only one of the two available crystallographic sites for Li. The preferred substitution pattern established from experimental results is supported by DFT electronic structure calculations, which also explore the subtleties of the chemical bonding and the electronic properties of the title compounds. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The syntheses and the characterization of two 17-atom endohedral Ge clusters, [Co2@Ge17]6− (1a) and [Ni2@Ge17]4− (2a), are reported. The anions 1a and 2a, which close the gap between the known 16- and 18-atom Ge clusters, are investigated by single crystal X-ray diffraction and by quantum chemical calculations. The structures mark a new example on the pathway for cluster growth towards larger clusters with icosahedral symmetry. Furthermore, the [Co@Ge10]3− anion (3a) is obtained from liquid ammonia. [ABSTRACT FROM AUTHOR]

A magnesiothermic reduction route has been presented to synthesize phase-pure germanides that are not readily available traditionally. The obtained ruthenium germanide (RuGe) serves as an efficient non-Pt electrocatalyst for hydrogen evolution, and its intrinsic activity is very close to that of Pt. Our combined theoretical and experimental study demonstrates that the remarkable performance is derived from the germanium-induced change in hydrogen site preference from hollow to efficient Ru top sites. [ABSTRACT FROM AUTHOR]

Theoretically, we have performed a systematic investigation on the passivants' effect on the geometrical and electronic properties of SixGe1-x nanowires. First-principles calculations revealed that, in the nanowires passivated by fluorine (F)/chlorine (Cl)/hydrogen (H) atoms, Si atoms preferred to segregate towards the surface due to the stronger Si-X bonds than that of Ge-X bonds (X = F, Cl, H). The energy barriers of X atoms' desorption is higher than that of the Si/Ge atoms' exchanging, inducing a feasible and strong surface segregation of Si atoms at proper temperature. Considering the Si/Ge interactions and mixing entropy, the composition profiles of Si/Ge distributions are obtained by minimizing the Gibbs free energy, which indicates the outmost layer of surface should be mostly occupied by Si. With total Si surface segregation, the diameter and shape of most stable SixGe1-x nanowires are found to be determined by the composition x and the passivants' chemical potential. In addition, charge distribution of near-gap levels can be modulated through the surface passivants. Our finding provides a practical avenue to tune the electronic properties of SixGe1-x nanowires, by modulating the morphologies of nanowires with the composition control of Si/Ge and the chemical potential of passivants. [ABSTRACT FROM AUTHOR]

Abstract Semiconductor strontium digermanide (SrGe2) has a large absorption coefficient in the near-infrared light region and is expected to be useful for multijunction solar cells. This study firstly demonstrates the formation of SrGe2 thin films via a reactive deposition epitaxy on Ge substrates. The growth morphology of SrGe2 dramatically changed depending on the growth temperature (300−700 °C) and the crystal orientation of the Ge substrate. We succeeded in obtaining single-oriented SrGe2 using a Ge (110) substrate at 500 °C. Development on Si or glass substrates will lead to the application of SrGe2 to high-efficiency thin-film solar cells.

The crystal structure of the ternary germanide Li2MnGe has been re‐evaluated from single‐crystal X‐ray diffraction data. This compound crystallizes in a non‐centrosymmetric superstructure of the ZrCuSiAs type (space group P4bm, Pearson code tP16), with the lattice parameters a = 6.088(4) Å, c = 6.323(4) Å. First‐principle calculations for the idealized structure predict antiferromagnetic exchange in the square Mn nets and semimetallic ground state. In addition, a new ternary phase with the composition Li2–xMn4+xGe5 (x ≈ 1.2) was discovered. It adopts the V6Si5 structure type (space group Ibam, Pearson code oI44), with the lattice parameters a = 7.570(2) Å, b = 16.323(3) Å, c = 5.057(1) Å. DSC/TG measurements show that this compound is thermally stable below 995 K. [ABSTRACT FROM AUTHOR]

We have investigated the structural, dynamical, elastic, and electronic properties of WGe2 and W5Ge3 compounds in different phases. We have considered the C11b (tetragonal, space group I4/mmm) and C23 (orthorhombic, space group Pnma) strukturbericht phases for WGe2 compound and D81 (tetragonal, space group I4/mcm), D8m (tetragonal space group I4/mcm) strukturbericht phases for W5Ge3 compound. The structural parameters, formation enthalpies, phonon dispersion curves, elastic constants, mechanical modulus, anisotropic factors, thermal conductivities, and electronic structures have been investigated using generalised gradient approximation within in the plane wave pseudopotential density functional theory. The calculated lattice constants are in a good agreement with the experimental data. The considered phases for WGe2 and W5Ge3 compounds have a metallic character. The results indicated that all phases for compounds are both mechanically stable and dynamically stable except for W5Ge3-D81. The anisotropy in some mechanical modulus has been investigated using several elastic anisotropy indexes and directional dependence of compressibility, Young's moduli, shear moduli, and Poisson's ratio. [ABSTRACT FROM AUTHOR]

We have investigated the structural, dynamical, elastic, and electronic properties of WGe2 and W5Ge3 compounds in different phases. We have considered the C11b (tetragonal, space group I4/mmm) and C23 (orthorhombic, space group Pnma) strukturbericht phases for WGe2 compound and D81 (tetragonal, space group I4/mcm), D8m (tetragonal space group I4/mcm) strukturbericht phases for W5Ge3 compound. The structural parameters, formation enthalpies, phonon dispersion curves, elastic constants, mechanical modulus, anisotropic factors, thermal conductivities, and electronic structures have been investigated using generalised gradient approximation within in the plane wave pseudopotential density functional theory. The calculated lattice constants are in a good agreement with the experimental data. The considered phases for WGe2 and W5Ge3 compounds have a metallic character. The results indicated that all phases for compounds are both mechanically stable and dynamically stable except for W5Ge3-D81. The anisotropy in some mechanical modulus has been investigated using several elastic anisotropy indexes and directional dependence of compressibility, Young's moduli, shear moduli, and Poisson's ratio. [ABSTRACT FROM AUTHOR]

The mesostructure of Mn1 – xFex Ge transition-metal monogermanides is studied by small-angle neutron scattering (SANS) and ultra-SANS in a wide concentration range of x = 0.0–1.0.It is shown that the main contribution to the scattering intensity for all concentrations x is made by scattering at crystallites with sharp boundaries and sizes of 1–10 μm, which is described by the squared Lorentzian function. An additional contribution to the scattering intensity as a result of scattering at an ensemble of defects is found as well, which is characteristic of manganese-rich samples. This contribution is well fitted by the power function Q–n with the exponent n = 3. The complementary scattering typical of iron-rich samples is described by an exponential function and also seems to be a part of scattering at sharp-boundary crystallites. [ABSTRACT FROM AUTHOR]

The quaternary rare earth nickel aluminum germanide series RENiAl4Ge2 (RE = Y, Sm, Gd–Tm, Lu) has been extended by several members. The compounds were synthesized from the elements by arc-melting, and single crystals of YNiAl4Ge2, GdNiAl4Ge2, and LuNiAl4Ge2 were grown from an aluminum flux. All members crystallize isostructurally in the rhombohedral SmNiAl4Ge2-type structure (R3̅m, Z = 3). The compounds can be described as a stacking of REδ+ and [NiAl4Ge2]δ− slabs with an ABC stacking sequence, or alternatively as stacking of CsCl and CdI2 building blocks. The results of the magnetic measurements indicate that all rare earth atoms are in a trivalent oxidation state. Of the RENiAl4Ge2 series, the members with RE = Sm, Gd–Dy exhibit antiferromagnetic ordering with a maximum Néel temperature of TN = 16.4(1) K observed for GdNiAl4Ge2. 27Al NMR spectroscopic investigations yielded spectra with two distinct signals, in line with the crystal structure, however, significantly different resonance frequencies of δisoms(YNiAl4Ge2) = 77(1) and 482(1) ppm as well as δisoms(LuNiAl4Ge2) = 90(1) and 467(1) ppm were observed. These indicate significantly different s-electron densities at the two crystallographically different Al atoms, in line with the results from DFT calculations. The Bader charge analysis confirms that the present compounds must be considered as germanides, as expected from the relative electronegativities of the constituent elements, while the low charges on Al and Y indicate significant covalent bonding. [ABSTRACT FROM AUTHOR]

The hydride NdMnSiH obtained by exposure of the ternary silicide NdMnSi under a pressure of 4 MPa of hydrogen at 523 K crystallizes in the tetragonal ZrCuSiAs-type structure where H atom occupies the tetrahedral [Nd4] sites. The hydrogenation of NdMnSi induces an increase in the unit cell volume close to 3.3%. The investigation of NdMnSiH by magnetization and specific heat measurements reveals the existence of two antiferromagnetic ordering, respectively, at TN1=565(5) K and TN2=103(4) K. Neutron powder diffraction shows that these Néel temperatures are associated with an antiferromagnetic arrangement of the (i) Mn substructure (TN1) and (ii) Nd substructure linked to a reorientation of the Mn one (TN2). Comparison of the TN1 and TN2 temperatures of NdMnSiH to those reported for the initial compound NdMnSi indicates a strong increase in TN1 (280 K→565 K) and a significant decrease in TN2 (185 K→103 K). The magnetic properties, magnetic structures, and values of Nd and Mn ordered magnetic moments are discussed using both band structure calculations and comparison with the behaviors of other ternary silicides and germanides based on manganese and rare earth elements. [ABSTRACT FROM AUTHOR]

The Ln n +1 M n X 3 n +1 (Ln = lanthanide, M = transition metal, and X = tetrel) homologous series provides a platform to study collective phenomena in quantum materials. In this work, we compare the crystal growth, structure, and magnetic properties of the n = 3 members of the Pr n +1 M n Ge 3 n +1 (M = Fe, Co) analogues, Pr 4 Fe 3 Ge 10 (a = 4.3207 (10) Å, b = 35.523 (8) Å, c = 4.2982 (15) Å, and V = 659.7 (3) Å3) and Pr 4 Co 3 Ge 10 (a = 4.3091 (12) Å, b = 35.750 (9) Å, c = 4.2807 (11) Å, and V = 659.4 (3) Å3). We determined that the ideal flux growth conditions for each compound are highly dependent on the concentration of Sn flux and quench temperature. Pr 4 Fe 3 Ge 10 orders ferromagnetically at 10 K along the c -direction while Pr 4 Co 3 Ge 10 orders antiferromagnetically at 16 K along the b -direction. For both compounds, we observed a magnetic moment higher than that expected for only Pr3+ ions (3.58 µ B /Pr), implying that the transition metal ions contribute to magnetic ordering (3.91, 3.48, and 3.69 µ B /Pr for Pr 4 Fe 3 Ge 10 , and 3.76, 4.04, and 3.83 µ B /Pr for Pr 4 Co 3 Ge 10 measured along the a- , b- , and c -directions, respectively). Moreover, the zero-field Mössbauer spectrum obtained at 4.2 K for Pr 4 Fe 3 Ge 10 demonstrates that the iron sites participate in magnetic ordering. [Display omitted] • Sn flux growth synthesis was tuned to yield 1–3 mm crystals of a homologous series. • The structural disorder of Pr4Fe3Ge10 was analyzed in terms of its subunits. • Pr4Fe3Ge10 and Pr4Co3Ge10 have transition metal contribution to magnetic ordering. • Mössbauer spectroscopy reveals Fe's contribution to the magnetism of Pr4Fe3Ge10. [ABSTRACT FROM AUTHOR]

The Ta–Ge system was thermodynamically modeled for the first time using the CALPHAD method incorporating both literature-derived phase equilibria data and new enthalpy of formation values for the intermetallic compounds. Density Functional Theory (DFT) calculations were employed to accurately determine enthalpy of formation values for key Ta–Ge compounds. The stable intermetallic phases (i.e., αTa 3 Ge, βTa 3 Ge, βTa 5 Ge 3 , and TaGe 2) were described as stoichiometric phases while the Liquid (L), Ta-rich solid solution (BCC-A2), and Ge-rich solid solution (Diamond-A4) were modeled as solution phases using the Compound Energy Formalism. Excess terms were described by the Redlich-Kister polynomials. The present thermodynamic model accurately describes phase equilibria and thermodynamic data, providing a reliable guide for designing alloys containing Ta and Ge. [ABSTRACT FROM AUTHOR]

We present the results of the magnetic susceptibility, magnetization, specific-heat, and electrical resistivity measurements on rare-earth iridium germanides Ce3Ir2Ge2 and La3Ir2Ge2, crystallizing in the La3Ni2Ga2-type orthorhombic crystal structure. The results reveal that Ce3Ir2Ge2 is a Kondo-lattice system showing characteristic -ln T dependence of magnetic resistivity at high temperatures, while there does not exist evident sign of long-range magnetic ordering at least down to 1.8 K. Instead, a short-range magnetic correlation occurs at about 3.5 K. The La-based compound was found to be a type-II superconducting material with a relatively high critical temperature TC=4.7 K. A number of the relevant parameters, such as lower critical field, upper critical field, coherence length, penetration depth, and Ginzburg–Landau parameter, were estimated for the La3Ir2Ge2 sample. [ABSTRACT FROM AUTHOR]

We present the results of the magnetic susceptibility, magnetization, specific-heat, and electrical resistivity measurements on rare-earth iridium germanides Ce3Ir2Ge2 and La3Ir2Ge2, crystallizing in the La3Ni2Ga2-type orthorhombic crystal structure. The results reveal that Ce3Ir2Ge2 is a Kondo-lattice system showing characteristic -ln T dependence of magnetic resistivity at high temperatures, while there does not exist evident sign of long-range magnetic ordering at least down to 1.8 K. Instead, a short-range magnetic correlation occurs at about 3.5 K. The La-based compound was found to be a type-II superconducting material with a relatively high critical temperature TC=4.7 K. A number of the relevant parameters, such as lower critical field, upper critical field, coherence length, penetration depth, and Ginzburg–Landau parameter, were estimated for the La3Ir2Ge2 sample. [ABSTRACT FROM AUTHOR]

The magnetic properties and magnetic structures of Nd2TGe6 (T = Ni and Cu) were studied by magnetometric and neutron diffraction measurements. Both compounds have an orthorhombic crystal structure of the Ce2CuGe6-type and are antiferromagnetic with the Néel temperatures of 6.4 K (Nd2NiGe6) and 9.8 K (Nd2CuGe6). Based on the neutron diffraction data the magnetic structures were determined. In the investigated compounds all magnetic moments are localized on the Nd atoms and form a collinear commensurate magnetic structure with the magnetic unit cell equal to the crystal one. The moments are parallel to the b-axis (T = Ni) or to the c-axis (T = Cu). The obtained magnetic structures are discussed on the basis of competition between the RKKY-type interactions and influence of Crystalline Electric Field (CEF). [ABSTRACT FROM AUTHOR]

The magnetic properties and magnetic structures of the R 2 TGe 6 compounds (T = Ni and Cu, R = Tb, Ho and Er) were studied by magnetometric and neutron diffraction measurements. All compounds have an orthorhombic crystal structure of the Ce 2 CuGe 6 -type and are antiferromagnetic with the Néel temperatures ranging from 6 K for Er 2 CuGe 6 up to 42 K for Tb 2 NiGe 6. Based on the neutron diffraction data the magnetic structures were determined for R 2 NiGe 6 (R = Tb, Er) and R 2 CuGe 6 (R = Ho, Er). In these compounds the magnetic moments localized on the rare earth element form a collinear commensurate magnetic structure. The magnetic unit cell is equal to the crystal one in R 2 NiGe 6 (R = Tb, Er) while it is doubled along the a-axis (propagation vector k = (½, 0, 0)) in R 2 CuGe 6 (R = Ho and Er). The obtained magnetic structures are discussed on the basis of competition between the RKKY-type interactions and influence of Crystalline Electric Field (CEF). • Neutron diffraction and magnetic data for R 2 TGe 6 are reported. • The compounds crystallize in the orthorhombic Ce 2 CuGe 6 -type structure. • R 2 TGe 6 (R = Nd, Tb, Ho, Er; T = Ni, Cu) are collinear antiferromagnets. • Magnetic structure depends on the R and T elements involved. [ABSTRACT FROM AUTHOR]

Abstract New compounds of composition R 3 Pt 4 Ge 13 have been successfully prepared with R = Dy, Ho, Er and Lu, by high-pressure (5–7 GPa) and high-temperature synthesis (up to 1073 K). Structural analysis confirms that all compounds crystallize in a non-centrosymmetric monoclinic structure (space group Cc). The magnetic properties of these four new compounds were studied, as well as those of Gd 3 Pt 4 Ge 13 , a known compound on which few physical studies have been published. The magnetic susceptibility of the Gd, Dy, Ho and Er compounds follow a Curie-Weiss law in the temperature range 20 K–300 K, consistent with a trivalent state of the R ions. At lower temperature, magnetization and heat capacity measurements reveal antiferromagnetic ordering in Gd 3 Pt 4 Ge 13 (T N = 6.2 ± 0.1 K) and a ferromagnetic one in Er 3 Pt 4 Ge 13 (T C = 2.2 ± 0.1 K). Dy 3 Pt 4 Ge 13 presents a magnetic order at T∗ = 1.8 ± 0.2 K. Ho 3 Pt 4 Ge 13 behaves as a Van Vleck type paramagnet below 10 K and Lu 3 Pt 4 Ge 13 is found to be diamagnetic between 2 K and 300 K. This last compound shows no superconducting transition down to 400 mK. Highlights • It is the first time that R 3 Pt 4 Ge 13, with R = Dy, Ho, Er and Lu, have been synthesized. • Originality of the syntheses carried out under high-pressure and high-temperature conditions. • Structural refinement confirms that they crystallize in the non-centrosymmetric structure; Cc space group. • We report on the first physical studies on these R 3 Pt 4 Ge 13 compounds with R = Gd, Dy, Ho, Er and Lu. [ABSTRACT FROM AUTHOR]

By means of ab initio calculations, we have estimated stability of 2D Me 2 X (Me = Mg , Ca, Sr, Ba and X = Si , Ge, Sn) in the T and Td phases, which are similar to the ones of 2D transition metal chalcogenides, in addition to their phonon spectra. The T phase is found to be more stable for 2D Ca 2 X , Sr 2 X and Ba 2 X , whereas the Td phase is predicted to be the ground state for 2D Mg 2 X. We have also discussed that imaginary frequencies in the calculated phonon spectra of 2D Me 2 X , which appeared in the vicinity of the Γ point, were not necessarily associated with the dynamic instability. [ABSTRACT FROM AUTHOR]

Abstract A systematic study on the existence of R 2 Pd 3 Ge 5 intermetallics with heavy rare earth metals (R = Gd–Lu) was conducted; only the Yb 2 Pd 3 Ge 5 was revealed to exist. Its crystal structure was established by X-ray powder diffraction and refined by means of Rietveld method. This compound crystallizes in the orthorhombic U 2 Co 3 Si 5 structure type (Ibam , oI 40, Z = 4, a = 10.2628(1), b = 12.0580(1), and c = 5.98251(6) Å), which represents an ordered derivative of the tI 10-ThCr 2 Si 2 prototype, ubiquitous among intermetallics. Magnetization and susceptibility measurements indicate that Yb 2 Pd 3 Ge 5 is a paramagnet with μ eff close to 0.8 μ B /Yb-atom, suggesting a nearly divalent Yb state. Electrical resistivity and Seebeck coefficient of the studied compound as a function of temperature confirm its metallic-like behavior. Highlights • Only Yb 2 Pd 3 Ge 5 was revealed to exist among R 2 Pd 3 Ge 5 intermetallics (R = Gd÷Lu). • Yb 2 Pd 3 Ge 5 crystallizes in the orthorhombic U 2 Co 3 Si 5 structure type (Ibam , oI 40, Z = 4). • Magnetic properties measurements confirm a nearly divalent Yb state in Yb 2 Pd 3 Ge 5. • Electrical resistivity studies confirm metallic-like behavior of Yb 2 Pd 3 Ge 5. [ABSTRACT FROM AUTHOR]

Trichlorosilylated tetrelides [(Cl3Si)3E]− have been prepared by adding 1 equiv of a soluble Cl− salt to (Cl3Si)4Si (E=Si) or 4 Si2Cl6/GeCl4 (E=Ge). To assess their donor qualities, the anions [(Cl3Si)3E]− (E=C, Si, Ge) have been treated with BCl3, AlCl3, and GaCl3. Both BCl3 and GaCl3 give 1:1 adducts with the anionic centers. AlCl3 leads to Cl− abstraction from [(Cl3Si)3E]− with formation of (Cl3Si)4E (E=Si or Ge). (Cl3Si)4Ge is cleanly converted to the perhydrogenated (H3Si)4Ge by use of Li[AlH4]. Another case of Cl− abstraction was observed for [(Cl3Si)3Ge⋅GaCl3]−, which reacts with GaCl3 to afford the neutral dimer [(Cl3Si)3Ge−GaCl2]2. Cornerstone added: The trichlorosilylated germanide [(Cl3Si)3Ge]− is readily accessible from GeCl4 and Si2Cl6/Cl−. All tetrelides [(Cl3Si)3E]− (E=C, Si, Ge) were found surprisingly nucleophilic and form adducts with BCl3 and GaCl3. The unique (Cl3Si)4Ge was obtained through an AlCl3‐induced rearrangement of [(Cl3Si)3Ge]−. [ABSTRACT FROM AUTHOR]

The equiatomic iron-silicides TFeSi as well as the corresponding germanides TFeGe with the electron-poor 4d and 5d transition metals (T=Zr, Nb, Hf, Ta) have been synthesized from the elements by arc-melting. All samples were characterized through their lattice parameters using powder X-ray diffraction (Guinier technique). Four structures were refined from single-crystal X-ray diffractometer data: a=640.16(3), b=393.45(5), c=718.42(6) pm, Pnma, 390 F2 values, 20 parameters, wR2=0.0294 for ZrFeSi (TiNiSi type), a=719.63(11), b=1119.27(7), c=649.29(7) pm, Ima2, 1103 F2 values, 54 parameters, wR2=0.0555 for NbFeGe (TiFeSi type), a=655.96(7), c=372.54(4) pm, P6̅2m, 251 F2 values, 15 parameters, wR2=0.0260 for HfFeGe (ZrNiAl type) and a=624.10(3), b=378.10(6), c=725.25(7) pm, Pnma, 369 F2 values, 20 parameters, wR2=0.0513 for TaFeGe (TiNiSi type). The common structural motif of the four different structures is the slightly distorted tetrahedral tetrel (tr) coordination of the iron atoms and a trigonal prismatic coordination of iron by T=Zr, Nb, Hf, Ta. Three compounds were characterized as Pauli-paramagnetic by measuring their susceptibility. The measurement of the electrical resistivity of NbFeSi characterises this compound as a good metal. Furthermore, 57Fe Mössbauer spectra of all compounds could be obtained at room temperature, revealing a clear correlation between the structural distortions and the quadrupole splitting parameters. [ABSTRACT FROM AUTHOR]

Analyzes carbon monoxide, maganese and nickle substituted Fe3.34Ge2 hexagonal germanides to perform tructural (x-ray and neutron diffraction), Mossbauer, and magnetic investigations. Methodology used to conduct the study; Information on single crystal x-ray diffraction; Details on the neutron powder diffraction; Findings of the study.

Presents a study which used the technique of electron-beam-induced current to examine the recombination activity of misfit dislocations in silicon/silicon germanide epilayers. Connection between material copper precipitates and misfit dislocations; Influence of hydrogen treatment on dislocation properties; Origin of recombination activity of misfit dislocations.

Presents a study which examined the relaxation in silicon/silicon germanide bilayers grown on top of SIMOX wafers as a function of temperature. Microstructure of the sample after annealing; Factors which contribute to the formation of the network of edge dislocation.

Presents a study which developed device quality a-silicon germanide: hydrogen alloy at low substrate temperature suitable for solar-cell fabrication using low flow rate of silane and germane and strong hydrogen dilution. Discussion on the optoelectronic properties of a-silicon germanide: hydrogen films; Correlation between optoelectronic properties and structural properties and midgap defect densities; Comparison of the quantum efficiencies of several Schottky barrier devices.

Presents a study which examined the local and long-range pattern sensitivities of selective Si[sub1-x]Ge[subx] chemical vapor deposition. Comparison of the observed behavior with the easier lateral transport of reactive species in the gas phase at lower pressures; Effect of pressure on pattern sensitivity; Discussion on the effect of adding hydrochloric acid in the oxide.

Presents a study that examined gas source molecular-beam epitaxy as a low-temperature silicon and silicon germanide epitaxial method. Techniques for the low-temperature silicon epitaxial method; Results of the gas source silicon germanide molecular-beam epitaxy; Details of the experimental procedure used.

Presents a study which examined the kinetics and mechanism of oxidation of silicon germanide alloys deposited epitaxially onto silicon substrates by low-temperature chemical vapor deposition. Role of germanium in oxidation; Electrical properties of the oxides formed under the conditions; Comparison with the mechanism of oxidation of pure silicon.

The equilibria involving the gaseous species above the Y–Ge and Y–Si alloy systems have been experimentally investigated by the high temperature mass spectrometer technique. The gaseous molecules YGe, YSi, and YSi2 were identified and their partial pressures were measured as a function of temperature. The experimentally determined reaction enthalpies were combined with appropriate literature data to obtain the following atomization energies, ΔH○a,0 and standard heats of formation, ΔH○f,298 , in kJ mol-1: YGe, 275.4 ± 11.4 and 522.4 ± 11.4; YSi, 253.8 ± 17.3 and 625.3 ± 17.3; YSi2, 800 ± 21 and 528 ± 21. [ABSTRACT FROM AUTHOR]

The nickel monogermanide (NiGe) phase is known for its electrical properties such as low ohmic and low contact resistance in group-IV-based electronics. In this work, thin films of nickel germanides (Ni–Ge) were formed by magnetron sputtering followed by flash lamp annealing (FLA). The formation of NiGe was investigated on three types of substrates: on amorphous (a-Ge) as well as polycrystalline Ge (poly-Ge) and on monocrystalline (100)-Ge (c-Ge) wafers. Substrate and NiGe structure characterization was performed by Raman, TEM, and XRD analyses. Hall Effect and four-point-probe measurements were used to characterize the films electrically. NiGe layers were successfully formed on different Ge substrates using 3-ms FLA. Electrical as well as XRD and TEM measurements are revealing the formation of Ni-rich hexagonal and cubic phases at lower temperatures accompanied by the formation of the low-resistivity orthorhombic NiGe phase. At higher annealing temperatures, Ni-rich phases are transforming into NiGe, as long as the supply of Ge is ensured. NiGe layer formation on a-Ge is accompanied by metal-induced crystallization and its elevated electrical resistivity compared with that of poly-Ge and c-Ge substrates. Specific resistivities for 30 nm Ni on Ge were determined to be 13.5 μΩ·cm for poly-Ge, 14.6 μΩ·cm for c-Ge, and 20.1 μΩ·cm for a-Ge.