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A Nowotny chimney-ladder (NCL) chromium germanide (CrGeγ) with varying compositions has been synthesized under high pressure. Crystal structure parameters of the NCL CrGeγ have been calculated by Le Bail refinement based on the superspace group. The refined γ of CrGeγ increases with the synthesis pressure, indicating an increasing Ge content. The NCL CrGeγ phases are ferromagnetic at T = 2 K regardless of their composition, and the magnetic transition temperature (TC) increases when the γ becomes higher. It is noteworthy that CrGe1.763 and CrGe1.774 synthesized at P = 10 and 14 GPa have magnetic transition temperatures of T = 295 and 333 K above room temperature, respectively. Surprisingly, the magnetic transition temperature has changed by ΔTC = 270 K, although the γ values of the raw material and the sample synthesized at P = 14 GPa differ by only Δγ = 0.05, corresponding to an atomic concentration of 0.62 atom %. The synthesis pressure acts as an essential parameter in tuning the composition of the NCL phase. Accordingly, the high-pressure synthesis may significantly control several physical characteristics of NCL phases by utilizing compositional and structural modulation.

Identifying novel classes of precatalysts for the oxygen evolution reaction (OER by water oxidation) with enhanced catalytic activity and stability is a key strategy to enable chemical energy conversion. The vast chemical space of intermetallic phases offers plenty of opportunities to discover OER electrocatalysts with improved performance. Herein we report intermetallic nickel germanide (NiGe) acting as a superior activity and durable Ni‐based electro(pre)catalyst for OER. It is produced from a molecular bis(germylene)‐Ni precursor. The ultra‐small NiGe nanocrystals deposited on both nickel foam and fluorinated tin oxide (FTO) electrodes showed lower overpotentials and a durability of over three weeks (505 h) in comparison to the state‐of‐the‐art Ni‐, Co‐, Fe‐, and benchmark NiFe‐based electrocatalysts under identical alkaline OER conditions. In contrast to other Ni‐based intermetallic precatalysts under alkaline OER conditions, an unexpected electroconversion of NiGe into γ‐NiIIIOOH with intercalated OH−/CO3 2− transpired that served as a highly active structure as shown by various ex situ methods and quasi in situ Raman spectroscopy., A xanthene‐based bis(germylene)‐Ni complex is used as a molecular precursor for the synthesis of ultra‐small NiGe nanostructures, which can generate a γ‐NiOOH structure with intercalated species. This displays exceptional catalytic activity and long‐term durability for the oxygen evolution reaction (OER).

Herein, we report on intermetallic iron germanide (Fe6Ge5) as a novel oxygen evolution reaction (OER) precatalyst with a Tafel slope of 32 mV dec−1 and an overpotential of 272 mV at 100 mA cm−2 in alkaline media. Furthermore, we uncover the in situ formation of a core–shell like structure that slowly collapses under OER conditions.

Yb3Co4Ge13 is the first example of a Remeika phase with a 3D + 3 [space group P3n(α,0,0)000(0,α,0)000(0,0,α)000; a = 8.72328(1) A, α = 0.4974(2)] modulated crystal structure. A slight shift of the composition towards higher Yb-content (i.e. Yb3.2Co4Ge12.8) leads to the disappearance of the satellite reflections and stabilization of the disordered primitive cubic [space group Pmn, a = 8.74072(2) A] Remeika prototype structure. The stoichiometric structurally modulated germanide is a metal with hole-like charge carriers, where Yb-ions are in a temperature-dependent intermediate valence state varying from +2.60 to +2.66 for the temperature range 85–293 K. The valence fluctuations have been investigated by means of temperature dependent X-ray absorption spectroscopy, magnetic susceptibility and thermopower measurements.

High-temperature solid-state reactions of the respective elements afforded the new transition metal Zintl phases Ca3CuGe3 (Sc3NiSi3 type, monoclinic C2/m – i7, Pearson code mC28), Ca6MnxAg2−x+zGe6−z (own type, monoclinic P21/m – e14, Pearson code mP28) and, Ca5MnxAg2−x+zGe5−z (Ca5MgAgGe5 type, orthorhombic Pnma – c12, Pearson code oP48) as evidenced by single-crystal X-ray diffraction. They are additional representatives of the recently discovered homologous series Ca2+nM2+zGe2+n−z, already reported with M = Ag, Mg. These new phases were rationally prepared, after speculation that Cu and Mn could replace the isovalent Ag and Mg, respectively, to yield isostructural phases. Their crystal chemistry is discussed using established ‘structure directing rules’. Their structures are best described according to the Zintl–Klemm formalism as (Ca2+)(2+n)[M2+zGe2+n−z)]2(2+n)− featuring (poly-)germanide oligomers, [Gen](2n+2)− with n = 1–5. These Zintl anions interact with the highly polarizing small M (Cu, Ag, Mn) cations through their terminal Ge atoms, while the central Ge atoms are in trigonal prismatic coordination with the active metal Ca. Electronic structure calculations using density functional theory (DFT) were conducted on the idealized fully ordered model of “Ca3MGe3” (Sc3NiSi3 type) with M = Cu, Ag for an analysis of the chemical bonding and structure stabilizing factors. Our findings suggest that new transition metal Zintl phases can be obtained through partial to complete replacement of the highly polarizing small s-block cations (Li, Mg) in the Ca–(Li,Mg)–(Ge,Si) system by their isovalent transition metals like Ag, Cu, and Mn. However, due to differences in coordination requirements and possible strong metal–metal bonding between the d-block elements, the resulting transition metal phases may not be isostructural with their Li and Mg counterparts, even when featuring the same type of Zintl anions.

(Cl3Si)4Ge (1; 91%) is accessible from GeCl4, the Si2Cl6/[nBu4N]Cl silylation system, and excess SiCl4. A key intermediate step involves Cl− sequestration with AlCl3 in the course of the reaction between the first-formed germanide [(Cl3Si)3Ge]− and SiCl4. The related adduct Cl2(Me2EtN)SiGe(SiCl3)2 (2; quantitative conversion) was prepared either by amine-induced cleavage of 1 or by a bottom-up synthesis starting from GeCl4 and Si2Cl6.

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 Zr ...

The binary strontium germanide SrGe6 was synthesized at high-pressure high-temperature conditions of approximately 10 GPa and typically 1400 K before quenching to ambient conditions. At ambient pressure, SrGe6 decomposes in a monotropic fashion at T = 680(10) K into SrGe2 and Ge, indicating its metastable character. Single-crystal X-ray diffraction data indicate that the compound SrGe6 adopts a new monoclinic structure type comprising a unique three-dimensional framework of germanium atoms with unusual cages hosting the strontium cations. Quantum chemical analysis of the chemical bonding shows that the framework consists of three- and four- bonded germanium atoms yielding the precise electron count Sr[(4bGe0]4[(3b)Ge−]2 in accordance with the 8 − N rule and the Zintl concept. Conflicting with that, a pseudo-gap in the electronic density of states appears clearly below the Fermi level, and elaborate bonding analysis reveals additional Sr–Ge interactions in the concave coordination polyhedron of the strontium atoms.

With ALD-Co on n+ -Ge (ND of $2\times {10}^{{19}}\text {cm}^{\text {-3}}$ ) as the platform, annealing schemes including rapid thermal annealing (RTA) and laser thermal annealing (LTA) were employed to study its impact on the characteristics of CoGe2. CoGe2 formed by LTA shows no agglomeration and a low $\rho _{\text {c}}$ of $1.3\times {10}^{\text {-8}} \Omega $ -cm2 which is reduced by 54 % as compared to the counterpart RTA. In addition, a uniform and atomically smooth CoGe2 with nearly epitaxial crystal structure is also achieved by LTA. Furthermore, LTA-formed CoGe2 does not require any barrier layer during formation which is in stark difference to other germanides and would greatly improve line resistance of the ever scaled contact trench. The promising results mainly stem from the low thermal budget with significant thermal gradient/shallow heat distribution of LTA that effectively limits excess surface Co diffusion and grooving effect, proving the high contact performance enabler beyond 5 nm node.

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 RE δ+ 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 T N = 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 δ iso ms(YNiAl4Ge2) = 77(1) and 482(1) ppm as well as δ iso ms(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.

Effects of carbon implantation (C-imp) on the contact characteristics of Ti/Ge contact were investigated. The C-imp into Ti/Ge system was developed to reduce severe Fermi-level pinning (FLP) and to improve the thermal stability of Ti/Ge contact. The current density (J)-voltage (V) characteristics showed that the rectifying behavior of Ti/Ge contact into an Ohmic-like behavior with C-imp. The lowering of Schottky barrier height (SBH) indicated that the C-imp could mitigate FLP. In addition, it allows a lower specific contact resistivity (ρc) at the rapid thermal annealing (RTA) temperatures in a range of 450–600 °C. A secondary ion mass spectrometry (SIMS) showed that C-imp facilitates the dopant segregation at the interface. In addition, transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS) mapping showed that after RTA at 600 °C, C-imp enhances the diffusion of Ge atoms into Ti layer at the interface of Ti/Ge. Thus, carbon implantation into Ge substrate can effectively reduce FLP and improve contact characteristics.

Single crystals of dicerium trialuminium tetragermanide, Ce2Al3Ge4, have been synthesized from a high-temperature reaction using an eutectic mixture of Al and Ge as a metal flux. Through single-crystal X-ray diffraction it was established that Ce2Al3Ge4 crystallizes in the centrosymmetric space group Cmce (No. 64) with the Ba2Cd3Bi4 structure type (Pearson code oC36). Five atoms compose the asymmetric unit, i.e. one Ce, two Al, and two Ge atoms, all in special positions with Wyckoff symbols 8f (Ce), 4a and 8e (Al), and 8e and 8f (Ge). The structure can be described as a three-dimensional network of Al and Ge atoms, with Ce atoms occupying the cavities of the framework.

International audience; We have studied the stability of manganese germanide thin films grown on Ge(111) substrates by three different growth methods: solid phase epitaxy, reactive deposition epitaxy and co-deposition. By combining X-ray diffraction and magnetic measurements, we demonstrate that we can form either Mn5Ge3 or Mn11Ge8 thin films depending on the growth processes. In the case of solid phase epitaxy, we explain the phase formation sequence by taking into consideration the kinetic and thermodynamic processes involved. Tuning phase formation of the manganese germanide thin films was determined using in situ X-ray diffraction and the effect of the thin film thickness on the Mn5Ge3 thermal stability was investigated.

Surface processes for porous Ge (PGe) formed by low-energy high-dose implantation of Ag+ with an energy of E = 30 keV and a current density J = 5 μA/cm2 in dependence of the radiation dose D = 6.2·1014–1.5·1017 ion/cm2 where observed. Using X-ray photoelectron spectroscopy, it was found that for selected implantation conditions at D ≥ 9.3·1015 ion/cm2, Ag nanoparticles were synthesized in Ge, but formation of silver germanide (GeAg4) was not occur. Using scanning electron and atomic-force microscopy it was found that with increasing D up to ~1.9 × 1016 ion/cm2 , a layer of porous germanium (Ag:PGe) is formed, accompanied by swelling of the implanted Ge surface up to 25 nm thick. With a further increase of D > 1.9·1016 ion/cm2, the opposite effect is observed, which consists of sputtering PGe at a constant rate of ~3.6 nm/min and an sputtering yield of ~17.2.

Two-dimensional materials are at the forefront of material research in the past decade. Besides graphene, there exist large groups of its heavier analogues, silicon- and germanium-based two-dimensi...

Novel ternary intermetallic phase Ce2RuGe was synthesized via arc-melting of the constituents and subsequent annealing at 700°С. Its crystal structure was determined from the powder X-ray diffraction data collected at room temperature. The compound crystallizes in the orthorhombic structure of a new type: space group Pmmn (No. 59), lattice parameters: a = 4.38235(5) A, b = 4.31818(5) A, c = 9.91496(15) A, Z = 2, Pearson symbol oP8. In the fully ordered unit cell of Ce2RuGe, there are two crystallographic positions for Ce atoms, single site with Ru atoms, and single site with Ge atoms, each with the multiplicity of two. The crystal structure is built of infinite zigzag-like chains of the Ru and Ge atoms, propagating along the [010] direction. The essential feature is a very short interatomic distance between the Ce1 atoms and the Ru atoms being equal to 2.226(2) A, while the Ce2–Ru distance is of regular length. This structural property gives rise to distinctive physical behavior of the compound that exhibits the coexistence of valence fluctuations associated with unstable 4f shell of the Ce1 ions and a long-range magnetic ordering that emerges in the Ce2 ions sublattice. As revealed by means of magnetization, heat capacity and electrical resistivity measurements, Ce2RuGe orders antiferromagnetically at TN = 12.0(1) K, and becomes ferromagnetic below TC = 8.5(3) K.

This work presents preparation of nickel germanide (Ni2Ge) thin films by atomic layer deposition (ALD). The films were grown using NiCl2(tmpda) (tmpda = N,N,N',N',-tetramethyl-1,3-propanediamine) and tributylgermanium hydride serving as a new, efficient reducing agent. This is the first time ALD NixGey films are prepared directly upon the combination of two precursors and without any annealing treatment. NixGey is an important contact material for enabling Ge-based transistors and thus circumventing the scaling issues related to current microelectronics. The Ni2Ge process was examined at low temperatures of 160-200 degrees C. Self-limiting, saturative growth with a high growth rate of 0.91 angstrom/cycle was observed at 180 degrees C. The films were thoroughly analyzed in terms of morphology, crystallinity, composition, and resistivity. The Ni2Ge films were pure, with the sum of contaminants being less than 1 at. %. Owing to their high purity, the films exhibited low resistivity, suggesting suitability for contact applications.

State of the art of cobalt germanide contacts to semiconductor devices is reviewed in this article. First, evolution of contacts is covered from the dawn of the transistor to present day. The history of contact has three stages: (a) elemental metals as direct contacts to the semiconductor with focus on aluminum, (b) self-aligned silicide contacts, and, recently, (c) the paradigm shift that emphasizes the interface contact resistivity. The second section outlines the current role of germanium in the semiconductor industry and the reasons cobalt germanide is an ideal contact material to germanium and silicon germanium semiconductor devices. Fundamental physical properties of cobalt germanides are presented next. Models for phase formation sequence are, then, detailed. This is followed by a comprehensive survey of the experimental results of formation of cobalt germanides. Those results are discussed and reconciled. Factors affecting the resulting phases and their quality are identified and some optimum choices for the experimental parameters are pointed based on the survey. After that, electrical properties of the contact are discussed. The role of germanium crystal orientation in ohmic and Schottky properties of the contact is analyzed. Fermi level pinning (FLP) plays a role mainly on metal/(100) n-type Ge interfaces. The role of FLP is minimal on p-type Ge and other crystalline orientations. Schottky barrier heights (SBH’s) for cobalt and cobalt germanide contacts reported in the literature are surveyed. Mechanisms of FLP and methods adopted by the industry to depin the fermi level at the interface are outlined. The electrical properties section is concluded with a subsection that focuses on the effect of the crystallinity of the contact material on its electrical behavior. Crystalline cobalt germanides are expected to have lower interface resistivities compared to those calculated based on the SBH survey. The role of heat during Co deposition to obtain epitaxial germanides is pointed. Finally, current challenges and future trends of cobalt germanide contacts are summarized.

The reaction system GeCl2 ⋅dioxane/LiSTsi (Tsi=C(SiMe3 )3 ) opens a fruitful area in germanium chemistry, depending on the stoichiometry and solvent used during the reaction. For example, the reaction of GeCl2 ⋅dioxane in toluene with two equivalents of the thiolate gives the expected germylene Ge(STsi)2 in excellent yield. This germylene readily reacts with hydrogen and acetylene, however, in a non-selective way. By using an excess amount of the thiolate and toluene as the solvent, the germanide [Ge(STsi)3 ][Li(thf)] is obtained. Performing the same reaction in thf leads to a C-H activation of thf to give (H7 C4 O)Ge[STsi](μ2 -S)2 Ge[STsi]2 , in which the thf molecule is still intact. Using a sub-stoichiometric amount of the thiolate leads to the heteroleptic compound [ClGe(STsi)]2 and to the insertion product (thf)Ge[S-GeCl2 -Tsi]2 , in which additional GeCl2 molecules insert into the C-S bonds of Ge(STsi)2 . The synthesis and the experimentally determined structures of all compounds are presented together with first reactivity studies of Ge(STsi)2 .

Different established synthesis methods such as melt-casting followed by annealing as well as melt-spinning or ball-milling followed by hot-pressing or spark plasma sintering may significantly influence the properties of thermoelectric materials. The comparison of microstructures obtained by different synthesis routes (water-quenching and melt-spinning followed by spark plasma sintering) reveals the indirect nature of the beneficial influence of cobalt germanide precipitates on the thermoelectric properties of germanium telluride and germanium antimony tellurides (GST materials). Cobalt germanide precipitates significantly influence the thermoelectric properties of GST materials: the thermoelectric figure of merit zT of (GeTe)17Sb2Te3 obtained by quenching melts in water increases from 1.6 to 1.9 (at 450 °C) by introducing cobalt germanide precipitates. They drastically reduce the grain and sub-grain sizes of the GST matrix. Melt-spinning followed by spark plasma sintering leads to nanoscopic cobalt germanide precipitates, whose effect on the thermoelectric properties, especially the phononic thermal conductivity, surprisingly seems to be marginal. This is due to the already significantly reduced (sub-)grain sizes in such polycrystalline GST samples as revealed by orientation (“channeling”) contrast in backscattered-electron micrographs. Melt-spun and spark-plasma-sintered GST material exhibits similar thermoelectric figures of merit zT values as water-quenched samples with cobalt germanide precipitates. In addition to providing easier access to samples with small (sub-)grains by simple quenching, the precipitates may stabilize the GST or GeTe microstructure by Zener pinning as cobalt is insoluble in the matrix material. This is very favorable concerning cyclability during thermoelectric measurements and potential applications. The heterostructured materials and their thermoelectric properties are long-term stable. Hall effect measurements of heterostructured GST (melt-spun and spark-plasma-sintered) indicate that the charge carrier concentration is near optimum.

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.

A new germanide ThIrGe has been synthesized and characterized by X-ray diffraction, transmission electron microscopy, electrical resistivity, magnetic susceptibility and thermodynamic measurements. The structural refinement shows that, in contrast to tetragonal ThIrSi, ThIrGe crystallizes in the TiNiSi-type orthorhombic structure with the Pnma space group (a = 7.2321(2) A, b = 4.3802(1) A, and c = 7.7107(2) A), which is the first Th-based ternary equiatomic intermetallic compound of this structural type. Below Tc = 5.25 K, ThIrGe becomes a weak-coupling type-II superconductor with a fully isotropic superconducting gap. The Sommerfield coefficient, upper critical field, and Ginzburg–Laudau parameter are determined to be 11.8 mJ mol−1 K−2, 2.9 T, and 19.9, respectively. First-principles calculations indicate that the density of states at the Fermi level are dominated by a hybridized contribution from the orbitals of Th, Ir and Ge, and are enhanced by the spin–orbit coupling. In addition, we demonstrate that the structural difference between ThIrGe and ThIrSi can be understood in terms of the Gibbs formation energy.

The reaction of GeCl2·dioxane with 2 equiv of the thiolate LiSHyp [Hyp = Si(SiMe3)3] yields the germanide (12-crown-4)2Li[Ge(SHyp)3] (1). A small structural variation in the substituent leads to a ...

The new ternary germanide La4MgGe10–x was synthesized by De Negri et al. [1] during the investigation of the phase equilibria at 500 °C for the La–Mg–Ge system (see Chap. 1). During the study on the R2LiGe6 (see Chap. 4, Table 4.3) compounds, the 4:1:(10–x) stoichiometry phase turned out to form also with Li and R = La, Ce, Pr, Nd. These findings fostered the investigation of the title compounds existence along the R series with both Mg and Li. In this chapter preliminary results on their crystal structure solution are also presented.

Titanium germanium intermetallics (TixGey) were directly prepared from titanium oxide (TiO2) and germanium oxide (GeO2) powders mixture by using an electrodeoxidation process. The electrochemical experiment was carried out in a molten flux CaCl2-NaCl at 800 °C with a potential of 3.0 V. The results show that monolithic germanide Ti5Ge3 intermetallic can be directly produced from TiO2-GeO2 or CaTiO3-GeO2 precursors (both molar ratios are 5:3), and the obtained Ti5Ge3 powders exhibit homogenous particle structure. In addition, the phase composition of the final product can be dramatically affected by the initial molar ratio of TiO2 to GeO2. The reaction mechanism of the electrodeoxidation process was discussed based on the experimental results. It is suggested that the electrodeoxidation process is an environmentally friendly method for the preparation of Ti-Ge intermetallics.

This letter represents the first direct experimental demonstrations and mechanism proposal regarding abnormal palladium diffusion into germanium (Ge). Our experiments indicated that excess Ge atoms among palladium germanide alloy formation indirectly induce the abnormal out-diffusion of mass palladium atoms into Ge. Consequently, palladium germanide alloy on both n-type and p-type Ge form ohmic-like Schottky junctions. To identify this phenomenon, first-principle calculations and technology computer-aided design simulation were used to evaluate the electrical influence of palladium atoms in Ge. We discovered that the activated palladium atoms in Ge induce large midgap bulk-trap states, which contribute to a severe increment of trap-assisted tunneling current at the palladium germanide/Ge junction.

Spectra of sixteen optical functions of Mg2Ge at 77 K in the energy interval 0–11 eV are determined. The main features and the general patterns of behavior of the optical functions are established. They contain six maxima and shoulders caused by interband transitions and metastable excitons. The integral spectrum of the dielectric permittivity e2(E) at 77 K in the energy interval 2–5 eV comprising six maxima and shoulders is decomposed into sixteen elementary transition bands caused by exciton and interband transitions of transverse and longitudinal types. The supposed nature and the localization of transition bands in the optical spectra of magnesium germanide is proposed proceeding from the known results of theoretical calculations.

Single crystals of the ternary Pr3Co2+xGe7 and Ln3Co2+xGe7–ySny (Ln = Pr, Nd, Sm) adopting a disordered version of the La3Co2Sn7 structure type have been prepared via flux-growth methods and characterized by single crystal X-ray diffraction. The structure consists of two lanthanide crystallographic sites with one occupying a cuboctahedral coordination environment and a second in a trigonal prismatic environment. The structure can also be described as an intergrowth of AuCu3 and CeNiSi2 structure types, and the stability of the germanide analogues requires Sn incorporation and Co site preferences. Magnetic properties of the Pr3Co2+xGe7–ySny series are highlighted with the Sn-substituted Pr3Co2.514(5)Ge6.66(7)Sn0.360(2) orders magnetically near 5.8 K, while the germanide Pr3Co2.3376(5)Ge7.056(7) exhibits magnetic transitions at 5.3 and 9.3 K, arising from the magnetic sublattices with field-dependent magnetization revealing three metamagnetic transitions at 0.46, 0.80, and 2.1 T.

We investigated nano-floating gate memory having a charge trap layer (CTL) composed of cobalt germanide nanostructure (ns-CoGe). A tunneling oxide layer; a CTL containing Co, Ge, and Si; and a blocking oxide layer were sequentially deposited on a p-type silicon substrate by RF magnetron sputtering and low-pressure chemical vapor deposition. We optimized the CTL formation conditions by rapid thermal annealing at a somewhat low temperature (about 830 °C) by considering the differences in Gibbs free energy and chemical enthalpy among the components. To characterize the charge storage properties, capacitance–voltage (C–V) measurements were performed. Further, we used X-ray photoelectron spectroscopy for chemical analysis of the CTL. In this work, we not only report that the C–V measurement shows a remarkable opening of the memory window for the ns-CoGe compared with those of nanostructures composed of Co or Ge alone, but also clarify that the improvement in the memory characteristics originates in the nanostructure formation, which consists mainly of Co-Ge bonds. We expect ns-CoGe to be a strong candidate for fabrication of next-generation memory devices.

Magnetic and transport properties of triangular-lattice Ni 1.8 Ge single crystal have been studied. The results reveal that Ni 1.8 Ge is a metal with an obvious magnetic anisotropy. The compound exhibits ferrimagnetic correlations along both directions. However, the long-range magnetic order was not observed due to the geometrical frustration arising from the triangular nickel lattice. At low temperature, the electron-magnon scattering and spin fluctuation have obvious contributions to the resistivity and magnetoresistance, indicating the existence of short-range dynamic magnetic ordering.

The method of germanium and silicon regeneration from waste germanium lenses and photovoltaic cells was successfully verified with the total yield of germanium of above 97 wt %. The preparation of magnesium germanide, magnesium silicide, and their mixtures in an optimized semiopened reactor was investigated in detail. Obtained products were characterized by dispersive Raman spectroscopy, scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDX) and X-ray diffraction (XRD), which confirmed high conversion, homogeneity, and crystallinity of prepared products. The measured data, together with data obtained from the literature, served as input parameters for a mathematical model. Subsequent hydrolysis of prepared products to obtain germanium and silicon hydrides was observed by Fourier transform infrared spectroscopy (FTIR) and by gas chromatography mass spectrometry (GC/MS). A successful separation of hydrolysis products to individual hydrides was also performed. Magnesium hydrogen pho...

International audience; URu0.29Ge2 is a new germanide crystallizing in a monoclinic structure (C2/c space group, lattice parameters a = 4.098(1) angstrom, b = 15.936(3) angstrom, c = 4.045(1) angstrom and beta = 90.091(2)degrees) derived from the CeNiSi2-type. It undergoes a ferromagnetic ordering at T-c = 63 K, which manifests itself as distinct anomalies in temperature variations of the magnetization, specific heat and electrical resistivity. Just below T-c the T-dependent resistivity exhibits a broad hump, which hints at complex magnetic structure of the compound, while below 5 K it shows an upturn that likely arises due to atomic disorder in the crystal lattice.

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

Experimentally studied F-43m structured Li 2 ZnGe ternary germanide is investigated theoretically by evaluating the electronic structure, thermodynamic stability and thermoelectric efficiency using the full-potential method. The calculated lattice parameter and structural characterization agree well with the experimental results. The thermoelectric properties are calculated within the temperature range of 0–1200 K. The computed value of figure of merit is 0.40 at 1200 K and Seebeck coefficient is 150 μV/K specifying n-type nature. The electrical conductivity is high mainly due to high carrier mobility, while total thermal conductivity is moderate due to low lattice thermal conductivity. The estimated figure of merit projects it as a potential thermoelectric material for high temperature power generation.

A novel ternary intermetallic germanide CeIrGe 2 has been studied by means of x-ray diffraction, magnetization, specific heat and electrical resistivity measurements, performed in wide ranges of temperature and external magnetic fields. The compound crystallizes in an orthorhombic structure of the CeNiSi 2 -type (space group Cmcm ). It exhibits a Kondo lattice behavior and orders antiferromagnetically at 4 K.

The novel cerium germanide Ce2IrGe3 was studied by means of x-ray diffraction, magnetic, electrical transport and heat capacity measurements. The compound was found to crystallize with slightly disordered hexagonal structure of Ce2CoSi3-type. The experimental results revealed that Ce2IrGe3 is a ferromagnetic-like Kondo lattice that orders at T C = 4 K .

In a simple and convenient way, mesoporous germanium nanoparticles (mp-Ge NPs) are prepared by a "metathesis" reaction of magnesium germanide (Mg2Ge) and zinc chloride (ZnCl2) in an autoclave at 300 °C. Investigated as anode materials for lithium-ion batteries, the prepared mp-Ge NPs exhibit a high capacity retention of 1048 mA h g-1 at 1 C after 1000 cycles and a high rate capacity of 727.1 mA h g-1 at 10 C in Li-Ge half cells. Additionally, a 3.4 V lithium-ion full cell (Ge-LiCoO2) with an energy retention of 85% (∼268.8 W h kg-1) over 100 cycles is achieved.

The process to form Ti germanide on P-implanted Ge ( $ {2} \times {10}^{ {19}}$ cm−3) with low contact resistivity ( $\rho _{c}$ ) was developed. Sequential deposition of Ti and TiN on n-Ge without annealing leads to rectifying ${I}$ – ${V}$ characteristic due to Fermi level pinning. With 600 °C annealing, Ohmic-like ${I}$ – ${V}$ behavior was achieved due to Ti germanide (C54 phase included) formation that depins Fermi level and makes $\rho _{c}$ of ${1.5}\times {10}^{{{-{5}}}} ~\Omega -\text {cm}^{{{2}}}$ and Schottky barrier height for electron ( $\Phi _{\text {BN}}$ ) of 0.22 eV. Even for 700 °C annealing, the Ti germanide exhibits comparable $\rho _{c}$ and good thermal stability without agglomeration, which is a concern of NiGe. By adopting additional P implantation after germanide, $\rho _{c}$ and $\Phi _{\text {BN}}$ can be further improved to ${3.6}\times {10}^{{{- {6}}}}~\Omega $ -cm2 and 0.17 eV, respectively. The improvement is ascribed to the enhanced dopant segregation at the germanide/Ge interface that results in stronger dipoles and more significantly reduced $\Phi _{\text {BN}}$ and $\rho _{c}$ . The Ti germanide process paves a promising path to enable a next-generation Ge technology.

Results of an investigation of the surface of germanium nanostructured by means of ion implantation are presented. Single-crystalline germanium (c-Ge) plates were irradiated by 40-keV cobalt Co+ ions in a dose range of (2–8) × 1016 ion/cm2. Evolution of the germanium surface morphology with increasing ion dose was studied by method of scanning electron microscopy. It is established that an increase in the ion implantation dose is accompanied by gradual formation of a surface layer consisting of spherical particles with diameters of ~150 nm. Analysis of the X-ray diffraction patterns of samples was indicative of the appearance of nanosized cobalt germanide (CoGe) particles in the ion-implanted surface layer.

Germanium plays an important role in biomedical utilizations, mainly for inducing erythropoietic, antimicrobial, antiviral, antimutagenic, and immunomodulating effects. The biological applications of organic germanium have been gradually reported in recent years; however, the intrinsic poor biodegradation of most inorganic nanomaterials prevent their further in vivo applications and clinical translation in biomedicine. Herein, two-dimensional (2D) quasi-freestanding and fully biodegradable germanene nanosheets have been synthesized from Zintl-phase ladder-shaped binary germanide (CaGe2), which feature intriguing physiochemical properties for photo-triggered therapeutics and photoacoustic diagnostic imaging, as well as excellent biocompatibility, in addition to the excellent degradability compared with other typical 2D biomaterials. This work presents a novel type of 2D structured inorganic germanium biomaterial featuring attractive biomedical multifunctionalities, which is expected to benefit clinical and translational medicine.

The germanides RE 3Pt4Ge6 (RE=Y, Pr, Nd, Sm, Gd–Dy) have been synthesized by arc-melting of the elements followed by inductive annealing to improve the crystallinity and allow for structural order. The compounds have been studied by powder X-ray diffraction; additionally the structure of Y3Pt4Ge6 has been refined from single-crystal X-ray diffractometer data. It exhibits a (3+1)D modulated structure, indicating isotypism with Ce3Pt4Ge6. The crystal structure can be described as an intergrowth between YIrGe2- and CaBe2Ge2-type slabs along [100]. Temperature-dependent magnetic susceptibility measurements showed Pauli paramagnetism for Y3Pt4Ge6 and Curie-Weiss paramagnetism for Pr3Pt4Ge6 and Nd3Pt4Ge6. Sm3Pt4Ge6 exhibits van Vleck paramagnetism, while antiferromagnetic ordering at T N=8.1(1) K and T N=11.0(1) K is observed for Gd3Pt4Ge6 and Tb3Pt4Ge6, respectively.

The influence of the partial substitution of Ni atoms by the similarly sized but electron-richer Ge atoms with a similar electronegativity in the binary Laves phase MgNi2 is investigated. A small degree of substitution in MgNi2–xGex (x = 0.1) leads to the change of the hexagonal MgNi2-type structure (C36) to the cubic C15 type, whereas higher amounts of Ge lead to the formation of the two new Laves phases Mg2Ni3Ge and MgNi1.30(5)Ge0.70, which were synthesized by the direct reaction of the elements in alumina and niobium crucibles using an induction furnace. The crystal structures of the two phases were determined by single-crystal X-ray diffraction. Mg2Ni3Ge (hR18-MgNi2–xGex, x = 0.5) crystallizes in the Y2Rh3Ge-type structure, which is an ordered variant of the cubic Laves phase MgCu2: space group R3m, a = 5.0300(7), c = 11.330(2) A. hP36-MgNi2–xGex with x = 0.70(6) crystallizes as a superstructure of the hexagonal Laves phase MgZn2: space group P63/mcm, a = 8.6946(2), c = 7.8127(3) A. MgNi1.3Ge0.7 represents a new structure type. Gradual substitution of Ni by Ge in the Laves phase MgNi2 corresponds to an increase in the valence electron concentration (VEC) in the ternary phase system and leads to the series MgCu2 (C15 type), hR18-Mg2Ni3Ge (superstructure of MgCu2 type), and hP36-MgNi1.3Ge0.7 (superstructure of MgZn2 type). The electronic structures are discussed based on band structure calculations, and the results are compared to the pristine Laves phase MgNi2, MgCu2, and MgZn2 with VEC = 2/3, 4/3 and 2, respectively.

The electrical properties of Cu-germanide(Cu 3 Ge)/n-type Ge Schottky contacts formed as a result of a solid state reaction between Cu and n-type Ge were investigated as a function of the rapid thermal annealing (RTA) temperature and correlated with its microstructural evolution driven by the RTA process. The variations of the barrier height of Cu 3 Ge/n-type Ge Schottky rectifiers caused by the RTA process were determined using current-voltage ( I - V ) and capacitance-voltage ( C - V ) methods. The Cu 3 Ge film formed after annealing at 400 °C exhibited a relatively uniform surface and interface morphology. This led to the formation of a laterally homogenous Schottky barrier in the Cu 3 Ge/n-type Ge Schottky diode, resulting in an improvement of its rectifying I - V behavior. On the other hand, after annealing above 500 °C, the Cu 3 Ge film was severely agglomerated without film continuity and eventually evolved into isolated islands at 600 °C. Such structural degradation of Cu 3 Ge led to a rapid decrease in the barrier height and an increase in the reverse leakage current of the Cu 3 Ge/n-type Ge Schottky diode. The electric field dependence of the reverse current showed that the reverse leakage current in the Cu 3 Ge/n-type Ge Schottky diodes was dominated by a Poole-Frenkel emission mechanism, regardless of the RTA temperatures.

Nickel germanide (NiGe) was formed from atomic layer deposition (ALD) Ni on Ge and a subequent annealing process; the Ni film with low resistivity ( $34~\mu \Omega \cdot \text {cm}$ ) at 15 nm was obtained by N2 + H2 plasma treatment after Ni precursor injection. The formed NiGe film showed low specific contact resistivity ( $\rho _{c})$ values of 9.01 $\mu \Omega \cdot \text {cm}^{2}$ for an NiGe/n+Ge contact and 3.61 $\mu \Omega \cdot \text {cm}^{2}$ for an NiGe/p+Ge contact. These values were comparable to those obtained using sputtered Ni. In addition, the ALD process-based NiGe showed excellent thermal/electrical stability up to 600 °C.

Palladium germanide thin films were investigated for infrared plasmonic applications. Palladium thin films were deposited onto amorphous germanium thin films and subsequently annealed at a range of temperatures. X-ray diffraction was used to identify stoichiometry, and Scanning Electron Micrographs, along with Energy Dispersive Spectroscopy (EDS) was used to characterize composition and film quality. Resistivity was also measured for analysis. Complex permittivity spectra were measured from 0.3 to 15 µm using IR ellipsometry. From this, surface plasmon polariton (SPP) characteristics such as propagation length and mode confinement were calculated and used to determine appropriate spectral windows for plasmonic applications with respect to film characteristics. Films were evaluated for use with on-chip plasmonic components.

In this paper, we demonstrated the enhancement of thermal stability of nickel germanide (NiGe) alloy up to 600 °C by using titanium nitride (TiN) metal capping. A high ${I}_{ \mathrm{\scriptscriptstyle ON}}/{I}_{ \mathrm{\scriptscriptstyle OFF}}$ ratio of $2.9 \times 10^{5}$ was achieved by capping TiN metal on Ni for NiGe alloy formation at 600 °C. Detailed analyses were performed for realizing the mechanism for TiN capping on NiGe/Ge, including vertical element diffusion profile observation through depth-profiling X-ray photoelectron spectroscopy (XPS), element diffusion distribution by energy-dispersive X-ray spectroscopy mapping, and direct junction leakage current path detection by conductive atomic force microscopy. The experimental results indicated that TiN capping can reduce the risk of agglomeration and form a graded NiGe/Ge Schottky junction that is beneficial for suppressing the degradation of junction leakage. Subsequently, we compared the electrical performance of TiN/NiGe/n-Ge at various N/Ti ratios of TiNs. Based on the depth-profiling XPS results and electrical performance, TiN with an N/Ti ratio of approximately 1:1 can resist the Ni and Ge diffusion, which facilitates the suppression of the agglomeration process. However, the TiN capping layers with an N/Ti ratio of less than approximately 1:1 (Ti-rich) were not favorable for resisting Ni and Ge diffusion.

The new ternary intermetallic with high content of germanium, CeRuGe 5 , was found in the course of reinvestigation of the Ce-Ru-Ge system at 700 °C. The compound crystallizes in the tetragonal structure of new type (space group I 4/ mcm ) with the unit cell parameters: a = 6.1414(6) A, c = 13.751(3) A, Z = 4, Pearson symbol tI 28. The structure of CeRuGe 5 can be presented as [CeGe 3 ] and [RuGe 2 ] slabs alternating along the tetragonal c -axis. It is shown that the new structure of CeRuGe 5 and the known before structure of Sm 2 Ru 5 Ga 9 are derivatives from the common prototype – HoCoGa 5 . By means of magnetic, heat capacity and electrical transport measurements, the novel compound CeRuGe 5 was established to be a metallic Curie-Weiss paramagnet due to stable 4 f 1 electronic configuration of trivalent Ce ions. No intrinsic long-range magnetic ordering was found down to 1.7 K.