Search

The electrochemical behavior of manganese silicide-germanides with different ratios of germanium and silicon is studied using the methods of voltammetry and impedance spectroscopy in 0.5 M aqueous sodium sulfate solution. It is shown that the oxidation stability of materials decreases with an increase in the ratio of germanium, which, unlike silicon, is incapable of forming a layer of stable oxides on the material surface. [ABSTRACT FROM AUTHOR]

The ternary germanide Mg5.57Ni16Ge7.43 (cubic, space group Fmm, cF116) belongs to the structural family based on the Th6Mn23‐type. The Ge1 and Ge2 atoms fully occupy the 4a (mm symmetry) and 24d (m.mm) sites, respectively. The Ni1 and Ni2 atoms both fully occupy two 32f sites (.3m symmetry). The Mg/Ge statistical mixture occupies the 24e site with 4m.m symmetry. The structure of the title compound contains a three‐core‐shell cluster. At (0,0,0), there is a Ge1 atom which is surrounded by eight Ni atoms at the vertices of a cube and consequently six Mg atoms at the vertices of an octahedron. These surrounded eight Ni and six Mg atoms form a [Ge1Ni8(Mg/Ge)6] rhombic dodecahedron with a coordination number of 14. The [GeNi8(Mg/Ge)6] rhombic dodecahedron is encapsulated within the [Ni24] rhombicuboctahedron, which is again encapsulated within an [Ni32(Mg/Ge)24] pentacontatetrahedron; thus, the three‐core‐shell cluster [GeNi8(Mg/Ge)6@Ni24@Ni32(Mg/Ge)24] results. The pentacontatetrahedron is a new representative of Pavlyuk's polyhedra group based on pentagonal, tetragonal and trigonal faces. The dominance of the metallic type of bonding between atoms in the Mg5.57Ni16Ge7.43 structure is confirmed by the results of the electronic structure calculations. The hydrogen sorption capacity of this intermetallic at 570 K reaches 0.70 wt% H2. [ABSTRACT FROM AUTHOR]

M n 5 G e 3 is a ferromagnetic phase of the Mn-Ge system that is a potential contact material for efficient spin injection and detection. Here, we investigate the creation of M n 5 G e 3 -based contacts on a Ge/SiGe quantum well heterostructure via solid-state synthesis. X-ray diffraction spectra fitting indicates the formation of M n 5 G e 3 -based contacts on bulk Ge and Ge/SiGe. High-resolution scanning transmission electron microscopy imaging and energy dispersive X-ray spectroscopy verify the correct M n 5 G e 3 -based phase formation. Schottky diode measurements, transmission line measurements, and Hall measurements reveal that M n 5 G e 3 -based contacts serve as good p-type contacts for Ge/SiGe quantum well heterostructures due to having a low Schottky barrier height of 0.10 e V (extracted from a M n 5 G e 3 /n-Ge analogue) and a contact resistance in the order of 1 k Ω. Furthermore, we show that these electrical characteristics have a gate-voltage dependence, thereby providing tunability. [ABSTRACT FROM AUTHOR]

Mn5Ge3 is a ferromagnetic phase of the Mn-Ge system that is a potential contact material for efficient spin injection and detection. Here, we investigate the creation of Mn5Ge3-based contacts on a Ge/SiGe quantum well heterostructure via solid-state synthesis. X-ray diffraction spectra fitting indicates the formation of Mn5Ge3-based contacts on bulk Ge and Ge/SiGe. High-resolution scanning transmission electron microscopy imaging and energy dispersive X-ray spectroscopy verify the correct Mn5Ge3-based phase formation. Schottky diode measurements, transmission line measurements, and Hall measurements reveal that Mn5Ge3-based contacts serve as good p-type contacts for Ge/SiGe quantum well heterostructures due to having a low Schottky barrier height of 0.10eV (extracted from a Mn5Ge3/n-Ge analogue) and a contact resistance in the order of 1 kΩ. Furthermore, we show that these electrical characteristics have a gate-voltage dependence, thereby providing tunability.

The equiatomic germanide LaNiGe was synthesized from the elements by arc‐melting and subsequent annealing at 1173 K for 14 days. Its non‐centrosymmetric LaPtSi type structure was refined from single‐crystal X‐ray diffractometer data: I41md, a = 420.80(6), c = 1440.3(3) pm, wR = 0.0477, 284 F2 values and 14 variables. The nickel and germanium atoms build up a three‐dimensional [NiGe]δ– polyanionic network (2 × 241 and 1 × 242 pm Ni–Ge) in which the lanthanum atoms fill cavities with coordination number 12. This picture of chemical bonding is supported by an evaluation of the electron localization function. Physical properties of LaNiGe were studied by means of magnetic susceptibility, magnetization, specific heat and electrical resistivity measurements. The compound was found to be a Pauli paramagnet with a molar magnetic susceptibility of about χ = 1.6 × 10–4 emu·mol–1·Oe–1. The temperature dependence of the electrical resistivity shows Bloch‐Grüneissen‐Mott behavior indicating the metallic character of LaNiGe, which is in full agreement with the results of electronic structure and density of states calculations. No superconducting transition was observed in the temperature regime down to 1.72 K. [ABSTRACT FROM AUTHOR]

We report two new variants of the X‐phase (orthorhombic, space group Pnnm) derived from the Mn–Co–Ge system. Two compositionally related crystals were investigated by means of single‐crystal X‐ray diffraction (XRD) and energy dispersive spectroscopy (EDS). The Mn14.9Co15.5Ge6.6 and Mn14Co16.2Ge6.8 intermetallic compounds are part of the homogeneity region of the X‐phase and adopt the Mn14(Mn0.11Co0.64Si0.25)23 structure type. The composition obtained from refinement of the XRD data is in agreement with the EDS results. In the present study, chemical disorder was only detected on the 8h positions. The ordering is compared with other members of the X‐phase family and shows that the degree of disordering depends on the chemical composition. No completely ordered variants of the X‐phase have yet been reported. [ABSTRACT FROM AUTHOR]

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.

The intermetallic compound CaFe 2 Ge 2 has been synthesized by ball-milling a stoichiometric mixture of pre-melted "FeGe" alloy with elemental Ca and subsequent annealing in welded niobium ampoule in a resistance furnace. Its crystal structure has been investigated by powder X-ray diffraction method: ThCr 2 Si 2 structure type (space group I 4/ mmm, Z = 2), a = b = 3.99366(4) Å, c = 10.7060(1) Å. Like iron-based superconductors, the main structural motif in CaFe 2 Ge 2 is a square-planar layer of Fe atoms that are tetrahedrally coordinated by Ge atoms. The (Fe 2 Ge 2) layers are alternating along the c -axis with the layers of Ca2+ cations and are interconnected via Ge–Ge bonds, resulting in a three-dimensional (Fe 2 Ge 2)2– polyanionic framework. The topological analysis of the Electron Localization Function (ELF) confirms 3D character of (Fe 2 Ge 2) layers similar to reported 122 iron tetrelides YFe 2 Ge 2 and CaFe 2 Si 2. CaFe 2 Ge 2 fills the gap in the row of Ca T 2 Ge 2 (T = Mn–Zn), being a fully-substituted variant (Ge/As) of the well-known superconducting collapsed tetragonal CaFe 2 As 2. Magnetic measurements revealed the occurrence of ferromagnetic order in CaFe 2 Ge 2 below 50 K. CaFe 2 Ge 2 has been synthesized by an unconventional solid-state method. This iron germanide crystallizes in the ThCr 2 Si 2 structure type. CaFe 2 Ge 2 is a fully-substituted (As/Ge) variant of iron-pnictide superconductor CaFe 2 As 2 and isoelectronic to its uncollapsed form. CaFe 2 Ge 2 orders ferromagnetically below 50 K. Image 1 • New ternary iron-germanide CaFe 2 Ge 2 has been synthesized by an unconventional solid-state method. • CaFe 2 Ge 2 is a fully-substituted (As/Ge) variant of iron-pnictide superconductor CaFe 2 As 2 and isoelectronic to its uncollapsed form. • CaFe 2 Ge 2 orders ferromagnetically below 50 K. [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]

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. [ABSTRACT FROM AUTHOR]

Our recent study on formal halide adducts of disilenes led to the investigation of the synthesis and properties of β-fluoro- and chlorodisilanides. The reaction of the functionalized neopentasilanes (Me3Si)3SiSiPh2NEt2 and (Me3Si)3SiSiMe2OMe with KOtBu in the presence of 18-crown-6 provided access to structurally related β-alkoxy- and amino-substituted disilanides. The obtained Et2NPh2Si(Me3Si)2SiK·18-crown-6 was converted to a magnesium silanide and further on to Et2NPh2Si(Me3Si)2Si-substituted ziroconocene and hafnocene chlorides. In addition, an example of a silanide containing both Et2NPh2Si and FPh2Si groups was prepared with moderate selectivity. Also, the analogous germanide Et2NPh2Si(Me3Si)2GeK·18-crown-6 could be obtained.

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- xGe x ( 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- xGe x, x = 0.5) crystallizes in the Y2Rh3Ge-type structure, which is an ordered variant of the cubic Laves phase MgCu2: space group R 3 m, a = 5.0300(7), c = 11.330(2) Å. hP36-MgNi2- xGe x 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) Å. 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. [ABSTRACT FROM AUTHOR]

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- xGe x ( 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- xGe x, x = 0.5) crystallizes in the Y2Rh3Ge-type structure, which is an ordered variant of the cubic Laves phase MgCu2: space group R 3 m, a = 5.0300(7), c = 11.330(2) Å. hP36-MgNi2- xGe x 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) Å. 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. [ABSTRACT FROM AUTHOR]

The germanides RE3Pt4Ge6 (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 TN = 8.1(1) K and TN = 11.0(1) K is observed for Gd3Pt4Ge6 and Tb3Pt4Ge6, respectively. [ABSTRACT FROM AUTHOR]

Tm5Pd4Ge8 was synthesized by melting of the elements in an arc-melting furnace. The new germanide was characterized by powder and single-crystal X-ray diffraction: own structure type, P21/m, a = 574.3(1), b = 1380.4(3), c = 836.4(1) pm, β = 107.57(2)°, V = 0.6321 nm3, wR2 = 0.0578, 2533 F2 values, 86 variables. The palladium and germanium atoms built up a three-dimensional [Pd4Ge8]15- polyanionic network which contains a unique germanium substructure composed of the Zintl anions Ge26- dumb-bells and Ge410- chains in cis-conformation. The palladium atoms within the network have distorted square pyramidal germanium coordination. The three crystallographically independent thulium atoms have coordination numbers 15, 16 and 17 with partial motifs of the Frank-Kasper type polyhedra. The isotypic germanide Er5Pd4Ge8 forms only after annealing the arc-melted sample at 1070 K for 1 week: a = 575.14(9), b = 1386.3(3), c = 838.4(1) pm, β = 107.51(2)°, V = 0.6375 nm³. [ABSTRACT FROM AUTHOR]

The structure and the chemical composition of Pd germanides formed on Ge(100) were investigated using transmission electron microscopy (TEM), in-situ X-ray diffraction (XRD), and atom probe tomography (APT). An ultrathin Si film used as a marker was deposited on Ge(100) prior to Pd film deposition in order to identify the diffusing species during the Pd 2 Ge growth. The observations evidenced the formation of a thin interfacial polycrystalline Pd 2 Ge layer during Pd room-temperature deposition on Ge(100). In-situ XRD thermal treatments ranging from 50 to 400 °C revealed that the Si marker had no influence on the sequential formation of Pd 2 Ge and PdGe. Ex situ APT and TEM characterizations showed that the Si marker layer was located closer to the Pd 2 Ge/Ge interface than to the Pd 2 Ge surface, after reaction. This result indicates that Ge and Pd self-diffusion are in the same order of magnitude during Pd 2 Ge growth. [ABSTRACT FROM AUTHOR]

Reactive pulsed laser deposition is a technique suitable for producing homogenous thin layers of silicon or germanium with high concentration of embedded manganese atoms. Linear calibration of EDS (Energy Dispersive X-ray Spectroscopy) was utilized for an elemental analysis of thin layers. MnSi and MnGe (manganese-silicon and manganese-germanium) layers containing non-oxidized Mn were obtained for Mn molar concentration in the range from 15 to 50%. Electron diffraction showed an amorphous character of MnSi layers. MnGe layers contained two different types of nanoparticles incorporated inside an amorphous matrix. The layers were semiconducting with resistivities from 10 − 3 to 10 − 5 Ω m. [ABSTRACT FROM AUTHOR]

Pr3Rh4Ge4 was synthesized by melting of the elements in an arc-melting furnace followed by annealing in a sealed tantalum ampoule in a muffle furnace. Structure refinement was based on temperature dependent single-crystal X-ray diffractometer data. At ambient temperature Pr3Rh4Ge4 adopts the U3Ni4Si4 type structure with strongly enhanced anisotropic displacement parameters for Rh1. Below 230 K additional reflections start to appear and at 110 K the structure could be described with the (3+1)D superspace group I2/ m(α0γ)00; α=1/2, γ=1/2; ( Z=2). This commensurately modulated structure could be refined with 1448 F2 values, 39 variables and residuals of wR=0.0417 for the main reflections and wR=0.1520 for the satellites of 1st order, [ a=408.36(2), b=421.12(3) and c=2504.4(2) pm]. The commensurate description could be transformed to a 3D supercell with space group A2/ m and Z=4: a=816.72(2), b=421.12(3), c=2537.5(1) pm, β=99.26(1)°, 1448 F2 values, 69 variables and wR=0.0499. The relation of the U3Ni4Si4 type structure, the (3+1)D modulated and the 3D supercell is discussed on the basis of a group-subgroup scheme. Temperature dependent magnetic susceptibility data reveal Curie-Weiss paramagnetism with an experimental moment of 3.72(2) μB/Pr atom and a Weiss constant of -12.6(5) K. No magnetic ordering is evident down to 3 K. [ABSTRACT FROM AUTHOR]

Pr3Rh4Ge4 was synthesized by melting of the elements in an arc-melting furnace followed by annealing in a sealed tantalum ampoule in a muffle furnace. Structure refinement was based on temperature dependent single-crystal X-ray diffractometer data. At ambient temperature Pr3Rh4Ge4 adopts the U3Ni4Si4 type structure with strongly enhanced anisotropic displacement parameters for Rh1. Below 230 K additional reflections start to appear and at 110 K the structure could be described with the (3+1)D superspace group I2/ m(α0γ)00; α=1/2, γ=1/2; ( Z=2). This commensurately modulated structure could be refined with 1448 F2 values, 39 variables and residuals of wR=0.0417 for the main reflections and wR=0.1520 for the satellites of 1st order, [ a=408.36(2), b=421.12(3) and c=2504.4(2) pm]. The commensurate description could be transformed to a 3D supercell with space group A2/ m and Z=4: a=816.72(2), b=421.12(3), c=2537.5(1) pm, β=99.26(1)°, 1448 F2 values, 69 variables and wR=0.0499. The relation of the U3Ni4Si4 type structure, the (3+1)D modulated and the 3D supercell is discussed on the basis of a group-subgroup scheme. Temperature dependent magnetic susceptibility data reveal Curie-Weiss paramagnetism with an experimental moment of 3.72(2) μB/Pr atom and a Weiss constant of -12.6(5) K. No magnetic ordering is evident down to 3 K. [ABSTRACT FROM AUTHOR]

Pd-Ge reactive-diffusion in two different samples Pd/Ge(001) and Pd/PdGe/Ge(001) was studied experimentally and theoretically, in order to clearly identify the driving force controlling the first-phase selection in the sequential phase formation regime. The experimental and theoretical results both show that only the atomic transport kinetic in the phases controls the first-phase selection: the phase exhibiting the fastest atomic self-diffusion forms first, even if its formation energy is not the lowest. [ABSTRACT FROM AUTHOR]

The quaternary germanides RE3 TRh4Ge4 ( RE = Ce, Pr, Nd; T = Nb, Ta) were synthesized from the elements by arc-melting and subsequent annealing in a muffle furnace. The structure of Ce3TaRh4Ge4 was refined from single-crystal X-ray diffractometer data: new type, Pbam, a = 719.9(2), b = 1495.0(3), c = 431.61(8), wR2 = 0.0678, 1004 F2 values, and 40 variables. Isotypy of the remaining phases was evident from X-ray powder patterns. Ce3TaRh4Ge4 is a new superstructure variant of the aristotype AlB2 with an ordering of cerium and tantalum on the aluminum site, whereas the honey-comb network is built up by a 1:1 ordering of rhodium and germanium. This crystal-chemical relationship is discussed based on a group-subgroup scheme. The distinctly different size of tantalum and cerium leads to a pronounced puckering of the [Rh4Ge4] network, which shows the shortest interatomic distances (253-271 pm Rh-Ge) within the Ce3TaRh4Ge4 structure. Another remarkable structural feature concerns the tantalum coordination with six shorter Ta-Rh bonds (265-266 pm) and six longer Ta-Ge bonds (294-295 pm). The [Rh4Ge4] network fully separates the tantalum and cerium atoms (Ce-Ce > 387 pm, Ta-Ta > 431 pm, and Ce-Ta > 359 pm). The electronic density of states DOS from DFT calculations show metallic behavior with large contributions of localized Ce 4f as well as itinerant ones from all constituents at the Fermi level but no significant magnetic polarization on Ce could be identified. The bonding characteristics described based on overlap populations illustrate further the crystal chemistry observations of the different coordination of Ce1 and Ce2 in Ce3TaRh4Ge4. The Rh-Ge interactions within the network are highlighted as dominant. The bonding magnitudes follow the interatomic distances and identify differences of Ta bonding vs. Ce1/Ce2 bonding with the Rh and Ge substructures. [ABSTRACT FROM AUTHOR]

The quaternary germanides RE3 TRh4Ge4 ( RE = Ce, Pr, Nd; T = Nb, Ta) were synthesized from the elements by arc-melting and subsequent annealing in a muffle furnace. The structure of Ce3TaRh4Ge4 was refined from single-crystal X-ray diffractometer data: new type, Pbam, a = 719.9(2), b = 1495.0(3), c = 431.61(8), wR2 = 0.0678, 1004 F2 values, and 40 variables. Isotypy of the remaining phases was evident from X-ray powder patterns. Ce3TaRh4Ge4 is a new superstructure variant of the aristotype AlB2 with an ordering of cerium and tantalum on the aluminum site, whereas the honey-comb network is built up by a 1:1 ordering of rhodium and germanium. This crystal-chemical relationship is discussed based on a group-subgroup scheme. The distinctly different size of tantalum and cerium leads to a pronounced puckering of the [Rh4Ge4] network, which shows the shortest interatomic distances (253-271 pm Rh-Ge) within the Ce3TaRh4Ge4 structure. Another remarkable structural feature concerns the tantalum coordination with six shorter Ta-Rh bonds (265-266 pm) and six longer Ta-Ge bonds (294-295 pm). The [Rh4Ge4] network fully separates the tantalum and cerium atoms (Ce-Ce > 387 pm, Ta-Ta > 431 pm, and Ce-Ta > 359 pm). The electronic density of states DOS from DFT calculations show metallic behavior with large contributions of localized Ce 4f as well as itinerant ones from all constituents at the Fermi level but no significant magnetic polarization on Ce could be identified. The bonding characteristics described based on overlap populations illustrate further the crystal chemistry observations of the different coordination of Ce1 and Ce2 in Ce3TaRh4Ge4. The Rh-Ge interactions within the network are highlighted as dominant. The bonding magnitudes follow the interatomic distances and identify differences of Ta bonding vs. Ce1/Ce2 bonding with the Rh and Ge substructures. [ABSTRACT FROM AUTHOR]

The thermal stability of PdGe on Ge(100) was investigated by scanning electron microscopy, X-ray diffraction and atom probe tomography. The initial PdGe film agglomerates when heated at high temperature (≥ 500 °C), forming spherical islands. This degradation is highly detrimental for PdGe ohmic contact fabrication in the Ge-based nano-electronics technology. However, capping the Pd layer with W before Pd-Ge reaction increases the thermal stability of the PdGe film up to 600 °C. In addition, the PdGe texture is modified if the sample is heated during Pd deposition, increasing the thermal stability of PdGe up to 700 °C with the W cap. [ABSTRACT FROM AUTHOR]

• Growth methods allow to tune the phase formation in the manganese germanide thin films. • The effective heat of formation model is a suitable framework to describe the phase formation. • The epitaxy of Mn5Ge3 on Ge(111) expands the range of the thermal stability of this compound. 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 Mn 5 Ge 3 or Mn 11 Ge 8 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 Mn 5 Ge 3 thermal stability was investigated. [ABSTRACT FROM AUTHOR]

The rhodium-rich germanides RERhGe ( RE = Y, Gd-Lu) were synthesized by arc-melting of the elements and subsequent annealing in a muffle furnace. The samples were characterized through Guinier powder patterns. The structures of YRhGe and TmRhGe were refined from X-ray single crystal diffractometer data: new type, Pnma, Z = 4, a = 1136.4(2) pm, b = 418.29(5) pm, c = 910.12(9) pm, wR2 = 0.0268, 707 F values for YRhGe and a = 1131.5(1) pm, b = 416.54(5) pm, c = 908.06(9) pm, wR2 = 0.0276, 719 F values for TmRhGe with 44 variables per refinement. The two crystallographically independent germanium sites both show distorted trigonal prismatic coordination by four rhodium and two rare earth atoms. The basic structural motifs are double prisms, similar to the structures of ZrFeSi and CeInAu. The shortest interatomic distances are observed for the Rh-Ge contacts within the three-dimensional [RhGe] polyanionic network which are further stabilized through weak Rh-Rh interactions. The calculations of the electronic structure within DFT done exemplarily for the yttrium compound show an itinerant like weak metal with a low density of states at the Fermi level and intricate chemical bonding due to the presence of two germanium sites interacting with the four rhodium sites. Graphical abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

We investigated the crystalline structure of a NiGe layer grown on Ge(0 0 1) substrate through the reactive deposition method. NiGe layers grown at 350 °C are a single crystalline, provided that they are thin enough—below 22 nm. The epitaxial relationship with the Ge(0 0 1) substrate is then as follows: NiGe(1 1 1)//Ge(0 0 1), and NiGe[0 1 ¯ 1]//Ge[1 1 0]. However, the NiGe layer becomes polycrystalline when the thickness reaches 22 nm or thicker. We proposed a two-step deposition method combined with solid-phase reaction to suppress the polycrystalline formation and successfully achieved an epitaxial NiGe layer over 22 nm-thick with an atomically flat interface. We also clarified that the Ge atom is the dominant diffusion species during the reactive deposition and that the Ni atom dominates during the solid-phase reaction. [ABSTRACT FROM AUTHOR]

The intermetallic compound CaCoSi was synthesized by solid state synthesis and investigated by means of X-ray diffraction (both powder and single crystal method): PbClF type structure, P4/ nmm (No.129): a = 3.977(1) Å, c = 7.089(5) Å, R1 = 0.0303, 121 F2, 9 variable parameters. CaCoSi contains isolated [CoSi]2- 2D layers in the ab plane, which are separated by Ca2+ cations along the c direction. The crystal chemistry and chemical bonding of CaCoSi are discussed in terms of LMTO band structure calculation and analyzed using the Electron Localization Function (ELF). [ABSTRACT FROM AUTHOR]

We have investigated the epitaxial formation and electrical properties of Ni germanide/Ge(110) contacts. X-ray diffraction and transmission electron microscopy measurements have revealed that Ni5Ge3 and NiGe layers are epitaxially formed on a Ge(110) substrate after annealing at 200–350°C. An epitaxial Ni5Ge3 layer is formed after annealing with the relationships Ni5Ge3(001)//Ge(110) and Ni5Ge3[311]//Ge[001]. We found that the orientation relationship between an epitaxial NiGe layer and Ge(110) substrate depends on the annealing temperature. When annealed at 300–350°C, the orientation relationship is NiGe(100)//Ge(110) and NiGe[001]//Ge[001], while at 200–230°C, the relationship is NiGe(102)//Ge(110) and NiGe[010]//Ge[001]. We demonstrate that the Schottky barrier height of the epitaxial NiGe(100)/Ge(110) contact is as low as 0.44eV, as estimated from the current density–voltage characteristics, while that of polycrystalline NiGe/Ge(001) is 0.55eV. [ABSTRACT FROM AUTHOR]

Abstract: The solid state reaction between 30nm Pd films and various Ge substrates (Ge(100), Ge(111), polycrystalline Ge and amorphous Ge) was studied by means of in situ X-ray diffraction and in situ sheet resistance measurements. The reported phase sequence of Pd2Ge followed by PdGe was verified on all substrates. The texture of the germanides was analysed by pole figure measurements on samples quenched in the Pd2Ge and in the PdGe phase on both Ge(100) and (111) substrates. We report an epitaxial growth of Pd2Ge on Ge(111) and on Ge(100). The formed PdGe has an axiotaxial alignment on Ge(111). On Ge(100), the axiotaxial texture is observed together with a fibre texture. The higher formation temperature of PdGe on Ge(111) could be related to the epitaxial alignment of the Pd2Ge parent phase on Ge(111). [Copyright &y& Elsevier]

In this work, state-of-the-art laser thermal annealing (LTA) is used to form germanide contacts on n-doped Ge, and is compared to results generated by rapid thermal annealing (RTA). Surface topography, interface quality, crystal structure, and material stoichiometry are explored for both techniques. For electrical characterization, specific contact resistivities ϱc are extracted. It is shown that LTA can produce a uniform contact with a remarkably smooth substrate interface, with ϱc 2-3 orders of magnitude lower than the equivalent RTA case. A ϱc of 2.84×10-7 Ω.cm2 is achieved for optimized LTA parameters. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

The ternary germanides RERh6Ge4 ( RE = Y, La, Pr, Nd, Sm-Lu) were obtained by arc-melting of the elements and subsequent annealing. Single crystals were grown from bismuth fluxes. The samples were studied by X-ray diffraction on powders. The structures of five members were refined from single crystal diffraction data: LiCo6P4 type, P $\bar{6}$ m2, a = 715.8(1), c = 387.33(8) pm, wR = 0.0238, 332 F2 values for LaRh6Ge4, a = 715.0(1), c = 384.96(7) pm, wR = 0.0211, 329 F2 values for PrRh6Ge4, a = 714.28(9), c = 382.57(6) pm, wR = 0.0136, 327 F2 values for SmRh6Ge4, a = 714.2(1), c = 381.6(1), wR = 0.0270, 327 F2 values for GdRh6Ge4, and a = 714.2(2), c = 379.0(1) pm, wR = 0.0273, 324 F2 values for HoRh6Ge4 with 19 variables per refinement. The RERh6Ge4 structures have two crystallographically independent germanium sites in trigonal prismatic coordination, manifesting the close structural relationship with metal-rich phosphides. Together, the rhodium and germanium atoms build up three-dimensional [Rh6Ge4] networks, which leave large channels for the rare earth atoms. Each rare earth atom has coordination number 20 with 12 Rh, 6 Ge, and 2 RE neighbors. Temperature dependent magnetic susceptibility measurements indicate Pauli paramagnetic behavior for YRh6Ge4, LaRh6Ge4, and LuRh6Ge4. The compounds RERh6Ge4 ( RE = Gd-Yb) are Curie-Weiss paramagnets. Antiferromagnetic ordering was observed at 8.4(5) K (GdRh6Ge4), 13.6(5) K (TbRh6Ge4), 5.1(5) K (DyRh6Ge4), and 8.9(5) K (YbRh6Ge4). DyRh6Ge4 and YbRh6Ge4 show metamagnetic transitions at 2.5(5) and 45(2) kOe, respectively. [ABSTRACT FROM AUTHOR]

Abstract. The ternary Zintl phase Ca3Ag1+ xGe3- x ( x = 1/3) was synthesized by the high-temperature solid-state technique and its crystal structure was refined from single-crystal diffraction data. The compound Ca3Ag1.32Ge2.68(1) adopts the Sc3NiSi3 type structure, crystal data: space group C2/ m, a = 10.813(1) Å, b = 4.5346(4) Å, c = 14.3391(7) Å, β = 110.05(1)° and V = 660.48(10) Å3 for Z = 4. Its structure can be interpreted as an intergrowth of fragments cut from the CaGe (CrB-type) and the CaAg1+ xGe1- x (TiNiSi-type) structures, and it therefore represents an alkaline-earth member of the structure series with the general formula R2+ nT2 X2+ n with n = 4. Unlike the rare-earth homologues that are fully ordered phases, one seventh of the atomic sites in the unit cell of the title compound are mixed occupied (roughly 2/3Ge and 1/3Ag), and this can be explained by the Zintl concept. The alloying of this phase using aluminum metal yielded the isotypic solid solution Ca3(Ag/Al)1+ xGe3- x, in which the aluminum for silver substitution is strictly localized in the TiNiSi substructure, revealing the very different functionality of the two building blocks. [ABSTRACT FROM AUTHOR]

Abstract: The germanides Sr7Ge6 and Ba7Ge6 as well as the stannide Ba3Sn2 were prepared by arc melting and annealing in welded tantalum ampoules using induction as well as resistance furnaces. The compounds were investigated by powder and single crystal X-ray diffraction. Sr7Ge6 and Ba7Ge6 crystallize in the Ca7Sn6 structure type (space group Pmna, Z=4: a=7.777(2)Å, b=23.595(4)Å, c=8.563(2)Å, wR 2=0.081 (all data), 2175 independent reflections, 64 variable parameters for Sr7Ge6 and a=8.0853(6)Å, b=24.545(2)Å, c=8.9782(8)Å, wR 2=0.085 (all data), 2307 independent reflections, 64 variable parameters for Ba7Ge6). Ba3Sn2 crystallizes in an own structure type with the space group P43212, Z=4, a=6.6854(2)Å, c=17.842(2)Å, wR 2=0.037 (all data), 1163 independent reflections, 25 variable parameters. In Sr7Ge6 and Ba7Ge6 the Ge atoms are arranged as Ge2 dumbbells and Ge4 four-membered atom chains. Their crystal structures cannot be rationalized according to the (8-N) rule. In contrast, Ba3Sn2 presents Sn2 dumbbells as a main structural motif and thereby can be described as an electron precise Zintl phase. The chemical bonding situation in these structures is discussed on the basis of partial and total Density Of States (DOS) curves, band structures including fatbands, topological analysis of the Electron Localization Function (ELF) as well as Bader analysis of the bond critical points using the programs TB-LMTO-ASA and Wien2k. While Ba3Sn2 reveals semiconducting behaviour, all germanides Ae 7Ge6 (Ae=Ca, Sr, and Ba) show metallic properties and a considerable π-bonding character between the Ge atoms of the four-membered chains and the dumbbells. The π-bonding character of the germanides is best reflected by the resonance hybrid structures {[Ge–Ge]6−/[GeGeGeGe]8−}↔{[Ge=Ge]4−/[Ge–Ge–Ge–Ge]10−}. [Copyright &y& Elsevier]

Abstract: We have demonstrated the formation of Ni(Ge1− y Sn y ) layers on Ge1− x Sn x layers by using solid-phase reaction for samples with Sn contents ranging from 2.0% to 6.5%. We have also investigated solid-phase reaction products in Ni/Ge1− x Sn x /Ge samples after annealing and the crystalline properties of nickel–tin–germanide layer/Ge1− x Sn x contact structures. After annealing at temperatures ranging from 350 to 550°C, the formation of polycrystalline Ni(Ge1− y Sn y ) layers has been observed on epitaxial Ge1− x Sn x layers with Sn contents ranging from 2.0% to 6.5%. We also observed anisotropic crystal deformation of NiGe with the incorporation of Sn atoms into substitutional sites in NiGe. In the case of the Ni/Ge1− x Sn x /Ge sample with a Sn content of 3.6%, the formation of an epitaxial Ni2(Ge1− z Sn z ) layer on the Ge1− x Sn x layer was found. The formation of β-Sn crystallites was observed after annealing at above 450°C in samples with a high Sn content of 6.5%. This β-Sn formation is due to the precipitation of Sn atoms. In all samples annealed at 350°C, the morphology of Ni–Ge–Sn layers is smooth and uniform. However, the surface roughness and interface roughness increase for an annealing temperature of 550°C. In particular, in the sample with a Sn content of 6.5%, the temperature at which agglomeration noticeably occurs is as low as 450°C. [Copyright &y& Elsevier]

Doppelt Ge ‐ bunden: Umsetzungen von elementarem Lithium und Natrium mit Germanium bei 750 °C führen zu der Zintl ‐ Phase Li3NaGe2, die gemäß dem Zintl ‐ Klemm ‐ Konzept [Ge=Ge]4− ‐ Hanteln mit beispiellos kleinen Ge ‐ Ge ‐ Abständen enthält. Auf Basis struktureller, spektroskopischer und theoretischer Untersuchungen werden überzeugende Belege für das tatsächliche Vorliegen von Ge ‐ Ge ‐ Doppelbindungen geliefert. [ABSTRACT FROM AUTHOR]

Doppelt Ge ‐ bunden: Umsetzungen von elementarem Lithium und Natrium mit Germanium bei 750 °C führen zu der Zintl ‐ Phase Li3NaGe2, die gemäß dem Zintl ‐ Klemm ‐ Konzept [Ge=Ge]4− ‐ Hanteln mit beispiellos kleinen Ge ‐ Ge ‐ Abständen enthält. Auf Basis struktureller, spektroskopischer und theoretischer Untersuchungen werden überzeugende Belege für das tatsächliche Vorliegen von Ge ‐ Ge ‐ Doppelbindungen geliefert. [ABSTRACT FROM AUTHOR]

Abstract: We performed single-crystal structure analysis of two ternary samarium platinum germanides SmPtGe2 and Sm2Pt3Ge5. SmPtGe2 crystallizes in the space group (S.G.) Immm (no. 71) with a =4.3679(9)Å, b =8.728(2)Å, c =16.378(4)Å, and V =624.4(2)Å3. This compound is isotypic with YIrGe2 having a Ge10Pt4 subunit composed of edge-sharing five- and six-membered rings. SmPtGe2 shows a metallic conductivity from room temperature down to 2K. The magnetic susceptibility measurement showed a 3+ oxidation state for the samarium. Sm2Pt3Ge5 crystallizes in the S.G. Ibam (no. 72) with a =10.174(1)Å, b =11.761(2)Å, c =6.2142(8)Å, and V =743.6(2)Å3. It is isotypic with U2Co3Si5 with a structure closely related to ThCr2Si2. [Copyright &y& Elsevier]

Abstract: The study on post metallization annealing (PMA) in electrical characteristics and interfacial properties of La2O3/Ge structures has been conducted. The PMA treatment in N2 ambient induces the growth of interfacial Ge oxide layer accompanied with decrease of capacitance value and interface trap density. The interface-layer growth is caused by the oxidation of Ge substrate due to the hydroxyl group absorbed in La2O3 from the ambient. The metal electrode capping might prevent the hydroxyl from evaporating during annealing, which enhances the interface reaction. On the other hand, leakage current increment has been observed for the sample with PMA in case of using Pt gate electrode. It is due to the diffusion of Pt and/or Ge and a Pt-germanide formation in La2O3 film during PMA. This leakage current increment can be suppressed by using Ta or W electrode which has less reactivity with Ge than Pt at high temperature. [Copyright &y& Elsevier]

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. [ABSTRACT FROM AUTHOR]

Abstract: The ternary rare-earth chromium germanides RECr x Ge2 (RE=Sm, Gd–Er) have been obtained by reactions of the elements, either in the presence of tin or indium flux, or through arc-melting followed by annealing at 800°C. The homogeneity range is limited to 0.25⩽x⩽0.50 for DyCr x Ge2. Single-crystal and powder X-ray diffraction studies on the RECr0.3Ge2 members revealed that they adopt the CeNiSi2-type structure (space group Cmcm, Z=4, a=4.1939(5)–4.016(2)Å, b=16.291(2)–15.6579(6)Å, c=4.0598(5)–3.9876(2)Å in the progression for RE=Sm to Er), which can be considered to be built up by stuffing transition-metal atoms into the square pyramidal sites of a “REGe2” host with the ZrSi2-type structure. (The existence of YbCr0.3Ge2 is also implicated.) Only the average structure was determined here, because unusually short Cr–Ge distances imply the development of a superstructure involving distortions of the square Ge net. Magnetic measurements on RECr0.3Ge2 (RE=Gd–Er) indicated that antiferromagnetic ordering sets in below T N (ranging from 3 to 17K), with additional transitions observed at lower temperatures for the Tb and Dy members. [Copyright &y& Elsevier]

Abstract: We present a systematic study of the Schottky barrier lowering induced by dopant segregation during nickel germanidation at NiGe/n-Ge(100) contacts. We used two different doping ions (As/P) and prepared two different NiGe layer thicknesses (30nm/60nm) at 400°C. NiGe was found to exhibit a smooth interface to the Ge substrate and a very low specific resistance of 15.1μΩcm. Both doping species, As and P, segregated at the NiGe/Ge interface during germanidation due to the snowplow effect. We found the concentration of dopants at the NiGe/Ge interface increases with increasing implantation dose. From low-temperature measurements, significant lowering of the effective Schottky-barrier height from 0.72eV at 0K for diodes without ion implantation to 0.38eV by P segregration was determined. With a value of only 0.19eV, arsenic was found to be superior to P for Schottky barrier lowering. [Copyright &y& Elsevier]

Abstract: An overview of silicides and germanides for nano-CMOS applications is presented. The historical evolution describing the migration from the use of Ti silicide to Co silicide to Ni silicide as contacting material is first discussed. These changes in silicide material were mainly motivated by the inability to form the target low resistivity silicide phase in small structures due to low nucleation density. This issue was found first for the low resistivity C54 TiSi2 at linewidths below 200nm and later for the low resistivity CoSi2, at linewidths below 40nm. A detailed description of scalability and thermal stability issues for NiSi is then presented. No nucleation issues were found in small structures for NiSi, which grows by diffusion or interface limited kinetics with Ni as main moving species. However, silicidation can be excessive in small structures due to Ni diffusion from surrounding areas, resulting in thicker films than targeted in small devices. This can be controlled by using a silicidation process with two rapid thermal processing steps, the first one to control the amount of Ni reacted and the second one to convert the silicide to the target low resistivity monosilicide phase. One of the main issues for applications of NiSi is its low thermal stability: thin NiSi films agglomerate at relatively low temperatures. The process window and thermal stability of Ni and Pt-based films reacted with Si, Si:Ge and Si:C substrates is reviewed. Addition of Ge is shown to degrade thermal stability while addition of C or Pt improves it. Contact resistivity considerations and implementation of dual band-edge silicides are discussed, as well as promising results for the extension of Ni-based silicides to future nodes. Finally a brief overview of germanides is presented discussing NiGe and PdGe as main candidates. [Copyright &y& Elsevier]

Abstract: We report silicide and germanide technology for ohmic contacts and metal gates of MOSFETs in this paper. We have investigated the control technology of NiSi/Si contact properties by incorporating third elements such as Ge and C for future ULSI applications. The work function and resistivity of various Ni and Pt germanides have been also examined as metal gate materials. The low resistivity and tunable work function of these silicides and germanides are desirable for future CMOS devices. [Copyright &y& Elsevier]

Abstract: A thin cobalt layer is deposited by electron beam evaporation onto a germanium substrate after an in situ cleaning annealing at 400 or 700°C. The effect of these pre-treatments on the Co/Ge Schottky barrier properties and on the germanide formation is investigated by using different techniques. A strong influence of the pre-treatment is observed. The pre-treatment at 700°C removes the native oxide but enhances the diffusion of contaminants. After post-metal deposition annealing, the sample pre-treated at 700°C shows a double layer structure due to interdiffusion, whereas some large isolated islands are present in the sample pre-treated at 400°C. [Copyright &y& Elsevier]

Abstract: There are many ternary intermetallic compounds with BaAl4-type and its derivative structures. LaPd2Ge2 is already known as one of the BaAl4-type superconductors with T c of 1.12K. We have synthesized a new intermetallic compound La3Pd4Ge4 with higher T c of 2.75K than that of LaPd2Ge2, which had the structure with the insertion of the AlB2-type layer in LaPd2Ge2. A detailed crystal structure analysis of La3Pd4Ge4 was carried out by neutron powder diffraction because it is useful to the analysis of small interplanar spacing. The neutron diffraction study indicates that La3Pd4Ge4 has U3Ni4Si4-type structure with a lower symmetry than that of LaPd2Ge2, and the typical interatomic distances of La3Pd4Ge4 are shorter than those of LaPd2Ge2. The coordination of Pd to three Ge in the AlB2-type layer of La3Pd4Ge4 is characteristic, which is not stabilized in other lanthanide-substituted intermetallics Ln3Pd4Ge4 (Ln=Y, Gd–Yb). [Copyright &y& Elsevier]

Abstract: The germanide Yb2Ru3Ge4 was synthesized from the elements using the Bridgman crystal growth technique. The monoclinic Hf2Ru3Si4 type structure was investigated by X-ray powder and single crystal diffraction: C2/c, Z=8, a=1993.0(3)pm, b=550.69(8)pm, c=1388.0(2)pm, β=128.383(9)°, wR 2=0.0569, 2047 F 2 values, and 84 variables. Yb2Ru3Ge4 contains two crystallographically independent ytterbium sites with coordination numbers of 18 and 17 for Yb1 and Yb2, respectively. Each ytterbium atom has three ytterbium neighbors at Yb–Yb distances ranging from 345 to 368pm. The shortest interatomic distances occur for the Ru–Ge contacts. The three crystallographically independent ruthenium sites have between five and six germanium neighbors in distorted trigonal bipyramidal (Ru1Ge5) or octahedral (Ru2Ge6 and Ru3Ge6) coordination at Ru–Ge distances ranging from 245 to 279pm. The Ru2 atoms form zig-zag chains running parallel to the b-axis at Ru2–Ru2 of 284pm. The RuGe5 and RuGe6 units are condensed via common edges and faces leading to a complex three-dimensional [Ru3Ge4] network. [Copyright &y& Elsevier]

Abstract: We have proposed Metal Source/Drain MOSFETs (MSD-MOSFETs) with Ge-on-Insulator (GOI) channels using germanides as source/drain metal material. Here the characterization of Schottky barrier hieght (SBH) at the germanide/Ge interfaces is a key issue for a Ge channel MSD-MOSFET. However, there are few published reports on the subject. In this paper, we present the results of the characterization of platinum germanide/Ge interfaces. SBHs of platinum germanide/n- and p-Ge(100) junctions were evaluated to examine the applicability of platinum germanide to MSD-MOSFETs. The SBH for platinum germanide/p-Ge(100) was found to be as low as 0.1 eV over a wide range of anneal temperatures. As a result, we conclude that platinum germanide is a promising S/D material for Ge channel MSD-MOSFETs. [Copyright &y& Elsevier]

Abstract: In this study, we survey Schottky diode property of both p-metal (Ni) germanide and n-metal (Zr, Er and Yb) germanide in contact with Ge (100). Our experimental results demonstrate that Φ p values obtained for NiGe/n-Ge is − 0.07 eV, and Φ n values for YbGe/p-Ge is 0.139 eV, the lowest hole barrier so far reported. In addition, NiGe Schottky source/drain p-MOSFET with HfO2/TaN gate stack and AlN/SiO2 stacked spacer were fabricated and measured. The drain current at V D = V G − V th =− 1.5 V is ∼ 4.0 μA/μm of the gate length L G =8 μm device. The I on/I off ratio is ∼ 103, and sub-threshold swing is 137 mV/dec. [Copyright &y& Elsevier]

Abstract: The new compounds [K(C12H24O6)][Rb(C12H24O6)]2Ge9 ·6NH3, [Rb(C12H24O6)]3Ge9 ·9NH3 and [Cs(C12H24O6)]3Ge9 ·6NH3 were prepared by the extraction of binary and ternary phases of the nominal composition K2Rb2Ge9, Rb4Ge9 and K2Cs2Ge9 with liquid ammonia in the presence of 18-crown-6. The resulting crystals were characterized by low temperature X-ray structure analysis. All of them contain the 21 electron cluster , which is coordinated by alkali metal cations in ion-paired arrangements. The cages were assigned their specific point group symmetry and were compared with hitherto known structures. [Copyright &y& Elsevier]

Microstructural evolution has been investigated as a function of substrate temperature in Ge–4 at.%Cr films grown by molecular beam epitaxy (MBE), by employing transmission electron microscopy (TEM); the TEM results have been correlated to the magnetic properties. Magnetometry measurements show that samples grown at substrate temperatures of 200 °C and above are paramagnetic. Significantly different microstructures have been shown to evolve, depending on the substrate temperature (Ts) during MBE growth. For Ts=200 °C, the film consists of elongated rods, or “noodles” of the equilibrium Cr11Ge19 phase. For Ts=400 °C, a nanodispersion of metastable Cr11Ge8 equiaxed precipitates form within the Ge-matrix. It is thus proposed that for Ts=400 °C a supersaturated Ge–Cr solid-solution is initially formed from the vapor phase, followed by solid-state precipitation. At Ts=200 °C, precipitation analogous to a cellular/discontinuous transformation results in the formation of cooperatively grown rod-like or noodle shaped microstructures. [Copyright &y& Elsevier]