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Abstract: The new ternary mixed lanthanum stannide/germanide La55Sn36.6Ge24.4 (orthorhombic, space group Cmcm, a =2373.98(5), b =2375.52(6), c =2378.64(5)pm, Z =4, R1=0.0728) was synthesized from stoichiometric melts of the three elements. Its complex structure contains a great variety of different tetrel anions, some known from the binary border compounds and new unusual Ge/Sn structural units: isolated Ge atoms (octahedrally coordinated by La), isolated Sn atoms (coordinated by 10 La cations), bent trimers [Sn3] and four-membered planar rings [Sn4] are also present in binary La germanides and stannides (i.e. La11Sn10, La3Sn4 or l.t.-LaSn). New tetrele anions are the eight-membered planar chain pieces [M8] (M=Ge, Sn), which exhibit both cis, trans and also linear conformation. Despite the presence of several mixed Ge/Sn sites, a tendency towards an alternation of Ge and Sn in the chain is apparent. The only extended structural elements of the title compound are polyanions [M24] consisting of eight-membered Ge rings, in which all atoms are bonded in a trigonal-planar geometry. In two directions, these rings are connected via two-bonded M pairs to form ribbons. In the orthogonal direction, two five-membered chain pieces are connected, which are similar in conformation and Ge/Sn distribution to the [M8] chains. The remaining four Ge atoms of the ring are connected to terminal tin atoms. The diversity of the anions and particularly the different conformations of the planar chains in La55Sn36.6Ge24.4 allows not only a comparison with the respective binary La germanides and stannides but also a study on the ‘coloring’ in tetrelides and a detailed analysis of the bond lengths of two-bonded Ge and Sn atoms. Despite the complex structure and the variety of tetrelide anions, a simple electron count reveals the title compound to be an electron precise Zintl phase. [Copyright &y& Elsevier]

Abstract: Self-assembled iron germanide nanowires (NWs) were grown by directly depositing Fe onto a Ge (110) substrate, in an in situ ultra-high vacuum transmission electron microscope from 430 to 500°C. All observed NWs had a similar length/width aspect ratio (∼8:1) at all deposition temperatures, as well as the same elongation orientation with respect to the underlying Ge (110) substrate. The growth dynamics was investigated by real time observations of NWs growth at elevated temperatures. It is elucidated that the formation of NWs in similar shape at all deposited temperatures is attributed to the similar activation energy barriers in length and width of NWs, which can result in the constant growth rate independent of growth temperatures. Furthermore, the difference in pre-exponential factor along the length and width of growing islands arose due to the anisotropic constraint of the Ge (110) substrate, leading to the unique elongation of NWs. This growth dynamics suggests the possibility of uniform control of the morphology of self-assembled NWs, as well as other morphologies of bottom-up fabricated devices, at different deposition temperatures. [Copyright &y& Elsevier]

Abstract: Phase relations have been established by electron probe microanalysis (EPMA) and X-ray powder diffraction (XPD) for the Sr-poor part of the ternary systems Sr–Zn–Si at 800°C and Sr–Zn–Ge at 700°C. In the Sr–Zn–Si system one new ternary compound SrZn2+x Si2−x (0≤x≤0.45) with CeAl2Ga2 structure and a statistical mixture of Zn/Si in the 4e site was found. Neither a type-I nor a type-IX clathrate phase was encountered. This system is characterized by formation of two further phases, i.e. SrZn1−x Si1+x with ZrBeSi-type (0.16≤x≤0.22) and SrZn1−x Si1+x with AlB2-type (0.35≤x≤0.65) with a random distribution of Zn/Si atoms in the 2c site. For the Sr–Zn–Ge system, the homogeneity regions of the isotypic phases SrZn1−x Ge1+x with ZrBeSi-type (0≤x≤0.17) and AlB2-type (0.32≤x≤0.56), respectively, have been determined. Whereas the germanide SrZn2+x Ge2−x (CeAl2Ga2-type) is characterized by a homogeneity region (0≤x≤0.5), the clathrate type-I phase Sr8Zn8Ge38 shows a point composition. [Copyright &y& Elsevier]

This article focuses on the synthesis and the crystal chemistry of six members of a series of rare-earth metal based germanides with general formula RELiGe2 (RE = La–Nd, Sm, and Eu). The structures of these compounds have been established by single-crystal X-ray diffraction (CaLiSi2 structure type, space group Pnma, Z = 4, Pearson symbol oP16). The chemical bonding within this atomic arrangement can be rationalized in terms of anionic germanium zigzag chains, conjoined via chains of edge-shared LiGe4 tetrahedra and separated by rare-earth metal cations. The structure can also be viewed as an intergrowth of AlB2-like and TiNiSi-like fragments, or as the result of the replacement of 50% of the rare-earth metal atoms by lithium in the parent structure of the REGe monogermanides. Except for LaLiGe2 and SmLiGe2, the remaining four RELiGe2 phases exhibit Curie–Weiss paramagnetism above about 50 K. In the low temperature regime, the localized 4f electrons in CeLiGe2, PrLiGe2, and SmLiGe2 order ferromagnetically, while antiferromagnetic ordering is observed for NdLiGe2 and EuLiGe2. The calculated effective magnetic moments confirm RE3+ ground states in all cases excluding EuLiGe2, in which the magnetic response is consistent with Eu2+ configuration (J = S = 7/2). The experimental results have been complemented by tight-binding linear muffin-tin orbital (TB-LMTO) band structure calculations. [ABSTRACT FROM AUTHOR]

The synthesis, structural characterization, and chemical-bonding peculiarities of the two new polar lanthanum-magnesium germanides La4Mg5Ge6 and La4Mg7Ge6 are reported. The crystal structures of these intemetallics were determined by single-crystal X-ray diffiraction analysis. The La4Mg5Ge6 phase crystallizes in the orthorhombic Gd4Zn5Ge6 structure type [Cmc21, oS6O, Z = 4, a = 4.5030(7) A, b = 20.085(3) A, c = 16.207(3) A, wR.2 = 0.0451, 1470 F2 values, 93 variables]. The La4Mg4Ge4 phase represents a new structure type with a monoclinic unit cell [C2/m, mS34, Z = 2, a = 16.878(3) A, b = 4.4702(9) A, c = 12.660(3) A, ß = l22.25(3)°, wR2 = 0.0375, 1466 F2 values, 54 variables]. Crystallographic analysis together with linear muffin-tin orbital band structure calculations reveals the presence of strongly bonded 3D polyanionic [Mg-Ge] networks balanced by positively charged La atoms in both stoichiometric compounds. The La4Mg5Ge6 compound is related to Zinti phases, showing a prominent density of states pseudogap at the Fermi leveL A distinctive feature of the La4Mg5Ge6 structure is the presence of Ge-Ge covalent dumbbells; in La4Mg7Ge6, the higher Mg content generates a polyanionic network consisting exclusively of Mg-Ge heterocontacts. Nevertheless, the frameworks of the two phases are structurally similar, as is highlighted in this work. [ABSTRACT FROM AUTHOR]

We have fabricated SiGe quantum dots (QDs) by means of a two-step Si ion implantation followed by thermal rapid thermal annealing (RTA) method. SiGe QDs with the 4-6 nm diameter are formed uniformly in the near-surface region of Ge substrate. The RTA processes are performed at 800 and 900 °C for 15 s, respectively. Both experimental and theoretical analysis indicates that the higher temperature (900 °C) RTA can enhance the growth of SiGe QDs. Two photoluminescence peaks are observed near 572 and 581 nm at room temperature. The mechanism of the luminescence from SiGe QDs is discussed. [ABSTRACT FROM AUTHOR]

Abstract: We examined the formation and morphological evolution of germanide formed in a ternary Ni/Zr-interlayer/Ge system using ex situ and in situ annealing experiments. Ni germanide in the Ni/Zr-interlayer/Ge system remained stable at temperatures up to 550°C whereas Ni germanide in a Ni/Ge system agglomerated and was unstable. Microstructural and chemical analyses of the Ni/Zr-interlayer/Ge system during and after in situ annealing in a transmission electron microscope confirmed that the Zr atoms were retained uniformly on the top region of the Ni germanide layer during the diffusion reaction. Ultimately, the level of agglomeration in the Ni germanide film was reduced by the Zr-interlayer, and the thermal stability of Ni germanide was improved. [Copyright &y& Elsevier]

Abstract: We have investigated the rapid thermal annealing behavior of electrical and microstructural properties of Ti (30nm) and Pt (30nm) contacts to n-type Ge substrates before and after rapid thermal annealing (RTA) at the temperatures in the range of 500–700°C for 30s under N2 ambient. Despite low work function, Ti contacts exhibited Schottky behavior at low RTA temperatures due to strong Fermi level pinning (FLP) effect. However, the Ti contacts showed Ohmic behavior after annealing at 700°C. Similarly, the Pt contacts formed at low temperatures annealing showed Schottky behavior as usually expected from Schottky–Mott theory. However, the annealing of Pt contacts at higher temperature (700°C) resulted in the Ohmic behavior. For both contacts, the abrupt transition of Schottky to Ohmic behavior could be associated with the significant increase in the leakage current under reverse bias condition caused by structural degradation of Ti- and Pt-germanide films. [Copyright &y& Elsevier]

Abstract: Mg germanide nanorods were successfully fabricated by interdiffusion of the Mg into Ge nanorods on Si substrates at 425 oC for 0.5h. It was observed that the Mg2Ge nanorod structures were formed by an interdiffusion process between the deposited Mg atoms and the Ge nanorods. Moreover, Mg2Si nanorods were formed by additional interdiffusion between the Mg2Ge nanorods and the Si substrates at 425 oC for 4h. The structural properties of the Mg2Ge and Mg2Si nanorods were characterized, and the growth evolution of the structural and morphological properties of the nanorods was discussed. [Copyright &y& Elsevier]

A series of binary rare-earth metal germanides RE5Ge3 (RE = La, Ce, Pr and Nd) adopting the Mn5Si3-type hexagonal structure is studied. These intermetallic phases show a complex magnetic behavior. Using a modification of the local density approximation (LSDA + U) the magnetic and electronic properties of these compounds are calculated. The spin-orbit coupling (SOC) was included using a full relativistic basis. Besides the structural parameters, bonding characters, total and partial densities of state and band structures are analyzed and compared with the experimental findings. [ABSTRACT FROM AUTHOR]

Hydrogen absorption of the CeFeSi- and CeScSi-type forms of GdTiGe was performed. Before hydrogenation they show an antiferromagnetic transition at around 412 K and a ferromagnetic transition at 376 K, respectively. Hydrogenation of both forms leads to formation of the same hydride GdTiGeH which crystallizes with a filled CeScSi-type structure where all the [Gd4] tetrahedra are filled by hydrogen. This hydride is paramagnetic in the temperature range 4-300 K. The slightly negative value of the paramagnetic Curie temperature θp confirms that all ferromagnetic interactions were destroyed in the case of the CeScSi-type form. From first-principles calculations with the PAW GGA methodology, the localization of hydrogen within the [Gd4] tetrahedra was confirmed through energetic stabilization. It was also seen that the energy changes significantly with volume, indicating the itinerant (delocalized) role of the electrons in the magnetism. [ABSTRACT FROM AUTHOR]

Abstract: We report on the optical property investigation of SiGe nanocrystals (NCs) prepared by electrochemical anodization (ECA) of SiGe layer grown by ultrahigh vacuum chemical vapor deposition (UHVCVD). At room temperature, SiGe NCs with higher Ge content demonstrate a redshift of the photoluminescence (PL) peak compared to Si NCs. It was found that the surface chemical composition, density, and the size of the SiGe NCs were very sensitive to the annealing conditions. Various spectroscopy measurements such as PL, FTIR, and XPS have been carried out to reveal the mechanism of the PL peak transition. The results indicated that the PL peak position was determined by two major factors, namely, interface state density and the size of SiGe NCs. It was shown that the higher the interface state density, the more significant the redshift of the peak position. While the smaller the size of the SiGe NCs, the more significant the quantum size effects become, resulting in the blueshift of the PL peak position. [Copyright &y& Elsevier]

We have investigated electrical and microstructural properties of Pt-germanides as a function of rapid thermal annealing (RTA) temperature. As increasing RTA temperatures, Pt films reacted with Ge and produced Pt-germanides. The Pt2Ge3 phase was completely transformed into PtGe2 at the RTA temperatures in the excess of 500°C. The specific contact resistivity (ρc) and sheet resistance (Rs) were investigated as a function of germanidation temperatures. Both ρc and Rs increased after the RTA process of 400°C, and then decreased with increasing annealing temperature. The increase in Rs and ρc at 400°C could be associated with the presence of a highly resistive Pt2Ge3 phase. RTA process at 700°C led to the severe degradation of surface and interface morphologies of a PtGe2 film caused by the agglomeration. This could be responsible for the main contribution to the increase in Rs and ρc. [ABSTRACT FROM AUTHOR]

The microstructural and electrical properties of Er-germanides formed by a solid state reaction between Er and Ge have been investigated at different germanide formation temperatures from 400 to 700°C. Er26Ge23 and Er3Ge4 phases were formed at a germanidation temperature of 400°C, followed by the formation of Er3Ge4 and Er2Ge3 at 500 to 600°C and then ErGe2.16 at 700°C. The sheet resistance gradually decreased with increasing annealing temperature up to 600°C, which could be associated with the phase transformation from Er-rich to Ge-rich Er-germanides. Er-germanides on n-type Ge showed Schottky behavior at low formation temperatures of less than 600°C. Above 600°C they exhibit Ohmic behavior. However, due to strong Fermi level pinning, Er-germanide contact to p-type Ge substrates was demonstrated to be Ohmic regardless of the annealing temperatures. The conversion of Schottky to Ohmic behavior could be attributed to a significant increase in current in the forward and reverse biases caused by the formation of square-shaped microvoids driven by Ge out-diffusion near the interface between germanides and the Ge substrate. [ABSTRACT FROM AUTHOR]

A new binary barium germanide BaGe3 was prepared by high-pressure and high-temperature reactions using a Kawai type multi-anvil press. It crystallizes in a hexagonal unit cell with a = 6.814(1) Å, c = 5.027(8) Å, and V = 202.2(5) ų (the space group P63/mmc, No. 194). The unit cell contains two layers along the c axis composed of Ba atoms and Ge3 triangular units. The triangular units stack along the c axis to form 1D columns in which the adjacent Ge3 units turn to opposite directions. The columns, therefore, can be described as the face-sharing stacking of elongated Ge6 octahedra. Each Ba atom is surrounded by six columns. BaGe3 is metallic and shows superconductivity at 4.0 K. The band structure calculations revealed that there are four conduction bands mainly composed of Ge 4p and Ba 5d orbitals. From Fermi surface analysis, we confirmed that three of them have a large contribution of Ge 4pz orbitals in the vicinity of the Fermi level and show a simple 1D appearance. The remaining one contains Ge 4px, 4py, and Ba 5d contributions and shows a 2D property. [ABSTRACT FROM AUTHOR]

Abstract: A new ternary compound, U9Fe7Ge24, was synthesized by arc-melting the elements, followed by annealing at 900 °C. This compound was characterized by single crystal and powder X-ray diffraction, magnetization, specific heat and electrical transport measurements. It crystallizes in an original tetragonal structure type (space group I4/mmm), with lattice parameters a = 12.3789(2) Å and c = 18.2881(3) Å. Three uranium, eighth germanium, and three iron crystallographic sites exist in this structure, with the atoms making a stacking of infinite chains along the a and b axis. From their interatomic distances strong interactions between the uranium and germanium atoms can be predicted. The magnetic and specific heat measurements down to 2 K do not show any magnetic transition. The Curie–Weiss behaviour with a negative paramagnetic Curie temperature θp = −94 K and reduced effective magnetic moment of μ eff = 2.13 μB/U indicate that the compound is rather far from onset of magnetism, presumably due to a strong hybridisation of the 5f and ligand states. The electrical transport measurements show a metallic behaviour. [Copyright &y& Elsevier]

We prepared a new binary lanthanum germanide, LaGe3, under high-pressure and high-temperature conditions (3-12 GPa, 500-1200°C). It crystallizes in the BaPb3 structure (the space group R3m) with lattice constants of a = 6.376(1) Å, = 22.272(3) Å, and V= 784.1(2) Å3. We refined the structure using Rietveld analysis from X-ray powder data. The structure is composed of two types of close-packed atom layers. In one layer, every La atom is surrounded solely by Ge atoms with the same distance of 3.188 Å. The other layer contains Ge3 regular, triangular cluster units with a Ge-Ge distance of 2.634 Å. The electron localization function and crystal orbital Hamilton population calculations suggest that the triangular cluster is composed of three Ge-Ge covalent bonds and that each Ge atom has a lone pair. The temperature dependence of the magnetic susceptibility and electrical conductivity measurements revealed that LaGe3 is metallic and shows superconductivity at 7.4 K. This critical temperature is highest for the La-Ge system. [ABSTRACT FROM AUTHOR]

Abstract: We have investigated the crystalline orientation dependence of the electrical properties of Mn germanide/Ge(111) and (001) Schottky contacts. We prepared epitaxial and polycrystalline Mn5Ge3 layers on Ge(111) and (001) substrates, respectively. The Schottky barrier height (SBH) estimated from the current density-voltage characteristics for epitaxial Mn5Ge3/Ge(111) is as low as 0.30eV, while the SBH of polycrystalline Mn5Ge3/Ge(001) is higher than 0.56eV. On the other hand, the SBH estimated from capacitance–voltage characteristics are higher than 0.6eV for both samples. The difference of these SBHs can be explained by the local carrier conduction through the small area with the low SBH regions in the epitaxial Mn5Ge3/Ge(111) contact. This result suggests the possibility that the lowering SBH takes place due to Fermi level depinning in epitaxial germanide/Ge(111) contacts. [Copyright &y& Elsevier]

Abstract: Dy thin films are grown on Ge(001) substrates by molecular beam deposition at room temperature. Subsequently, the Dy film is annealed at different temperatures for the growth of a Dy-germanide film. Structural, morphological and electrical properties of the Dy-germanide film are investigated by in situ reflection high-energy electron diffraction, and ex situ X-ray diffraction, atomic force microscopy and resistivity measurements. Reflection high-energy electron diffraction patterns and X-ray diffraction spectra show that the room temperature growth of the Dy film is disordered and there is a transition at a temperature of 300–330°C from a disordered to an epitaxial growth of a Dy-germanide film by solid phase epitaxy. The high quality Dy3Ge5 film crystalline structure is formed and identified as an orthorhombic phase with smooth surface in the annealing temperature range of 330–550°C. But at a temperature of 600°C, the smooth surface of the Dy3Ge5 film changes to a rough surface with a lot of pits due to the reactions further. [Copyright &y& Elsevier]

Abstract: Ultra-thin films of Dy are grown on Ge(001) substrates by molecular beam deposition near room temperature and immediately annealed for solid phase epitaxy at higher temperatures, leading to the formation of DyGe x films. Thin films of Dy2O3 are grown on the DyGe x film on Ge(001) substrates by molecular beam epitaxy. Streaky reflection high energy electron diffraction (RHEED) patterns reveal that epitaxial DyGe x films grow on Ge(001) substrates with flat surfaces. X-ray diffraction (XRD) spectrum suggests the growth of an orthorhombic phase of DyGe x films with (001) orientations. After the growth of Dy2O3 films, there is a change in RHEED patterns to spotty features, revealing the growth of 3D crystalline islands. XRD spectrum shows the presence of a cubic phase with (100) and (111) orientations. Atomic force microscopy image shows that the surface morphology of Dy2O3 films is smooth with a root mean square roughness of 10Å. [Copyright &y& Elsevier]

Superconducting ternary germanide SrPd2Ge2 single crystals (Tc= 2.70 K) with a ThCr2Si2-type structure were synthesized using a high-temperature metal flux method. Superconductivity was confirmed by temperature- and magnetic-field-dependent magnetization, electrical resistivity, and heat capacity measurements. Here, weak anisotropy in superconductivity was observed both parallel and perpendicular to the crystallographic c axis. Various superconductivity parameters, such as lower and upper critical fields, the temperature gradient of the upper critical field, and coherence length were estimated, and the upper critical value at T= 0 K was found to be much larger than the value for the polycrystalline sample. In addition, the anomalous temperature dependence of resistivity was observed in a temperature range of Tc (=2.70 K)⩽T⩽T* (=2.90 K) when a current was applied along the c axis, whereas the only slope change occurred at T* with a current perpendicular to the c axis, prior to a sharp superconducting transition at Tc. [ABSTRACT FROM AUTHOR]

Abstract: We report a scanning tunneling microscopy and spectroscopy study of the formation of platinum–germanide phases on Ge(111). Platinum was deposited on Ge(111) at room temperature and subsequently annealed at temperatures varying from 773K to 1173K. At annealing temperatures below 1073K, disordered germanide islands are found on the terraces. However, at temperatures above 1073K a new germanide phase nucleates at the pre-existing step edges of the Ge(111) surface. The electronic structure of this germanide phase exhibits band gaps below −2.2eV and above 1.8eV with respect to the Fermi level. In addition, several well defined electronic states are resolved within the energy range from −2.2eV to 1.8eV. We interpret these observations within the framework of the nearly free electron and quantum well state models. [Copyright &y& Elsevier]

Abstract: The magnetic and transport properties of ternary rare-earth chromium germanides RCr0.3Ge2 (R=Y and Tb–Er) have been determined. X-ray and neutron diffraction studies indicate that these compounds have the CeNiSi2-type structure (space group Cmcm) . Magnetic measurements reveal the antiferromagnetic ordering below T N equal to 18.5K (R=Tb), 11.8K (Dy), 5.8K (Ho) and 3.4K (Er). From the neutron diffraction data the magnetic structures have been determined. For TbCr0.3Ge2 and DyCr0.3Ge2 at low temperatures the magnetic ordering can be described by two vectors k 1 =(,0,0) and k 2 =(,0,), and k 1 ′=(,0,0) and k 2 ′=(,0,), respectively. In HoCr0.3Ge2 and ErCr0.3Ge2 the ordering can be described by one propagation vector equal to (,,0) and (0,0,0.4187(2)), respectively. In DyCr0.3Ge2 some change in the magnetic ordering is observed at T t =5.1K. In temperature range from T t to T N the magnetic ordering is given by one propagation vector k=(,0,0). YCr0.3Ge2 is a Pauli paramagnet down to 1.72K which suggests that in the entire RCr0.3Ge2 series the Cr atoms do not carry magnetic moments. All compounds studied exhibit metallic character of the electrical conductivity. The temperature dependencies of the lattice parameters reveal strong magnetostriction effect at the respective Nèel temperatures. [Copyright &y& Elsevier]

Experimental temperature dependences of the enthalpies of RGe (R=La, Pr, Gd, Dy, Ho, Lu) are used to calculate the melting enthalpies and temperature dependences of the heat capacity for other germanides with this structure. [ABSTRACT FROM AUTHOR]

Abstract: Ternary intermetallics SrMGe3 (M =Rh, Ir, Ni, Pd and Pt) have been prepared by arc melting. The crystal structure of these intermetallics was determined by single-crystal X-ray diffraction for M =Ir, Pd and Pt. The structure of those three intermetallics is BaAl4-derivative BaNiSn3-type with the space group I4mm (No. 107). The other two, Rh and Ni, are likely to take the same structure, speculated from the corresponding XRD patterns using the powder samples. Neither of them shows superconductivity down to 1.8K. [ABSTRACT FROM AUTHOR]

Palladium-induced crystallization of germanium at 350°C using different Pd thicknesses is carried out and the qualities of the poly-Ge films obtained are characterized. The crystal qualities of the Ge films are highly dependent on the thickness of Pd used, in which 55 Å is the optimal thickness to induce crystallization of a 418 nm thick Ge film. When a Pd layer thicker than 55 Å is used, it not only deteriorates the crystal quality of Ge but also increases the concentrations of PdGe and Pd2Ge in the Ge layer. The sheet resistance of the poly-Ge film decreases with increasing crystalline fraction when the Pd layer is thinner than 70 Å because the amount of Pd germanides is low, and the opposite trend is observed when the Pd layer is thicker than 70 Å due to the high concentration of Pd germanides in the film. The complex dielectric constants ⟨ε2⟩ of the poly-Ge films show not only the transition energy E1 and E1 + Δ1 peaks but also two other peaks at photon energies of 1.6 and 1.8 eV, which possibly are due to the presence of Pd germanides in the Ge layer. [ABSTRACT FROM AUTHOR]

The magnetic ordering in ErFe0.3Ge2 and ErNi0.65Ge2 compounds crystallizing in the orthorhombic structure of the CeNiSi2-type has been investigated by neutron diffraction and magnetic measurements. The Er magnetic moments have been found to order antiferromagnetically below 2.5 K in ErFe0.3Ge2 and 2.3 K in ErNi0.65Ge2. The magnetic structure of the former compound can be described by the propagation vector k = (0:044(1); 0; 0:384(1)). The Er magnetic moments are aligned along the a-axis and alternate with the sequence ++ -in the unit cell. At 1.5 K they are equal to 5.9(1) μB. In contrast, the magnetic unit cell of ErNi0.65Ge2 has been established to be equal to the chemical one. The magnetic moments in this compound are arranged in a collinear manner pointing along the a-axis with the sequence +-+-. The Er moment value measured at 1.5 K is 2.90(8) μB. [ABSTRACT FROM AUTHOR]

The phase formation of cobalt germanides on Ge(100) and Ge(111) substrates was investigated using in situ X-ray diffraction, starting from room-temperature sputter-deposited Co films. The formation temperature of the CoGe2 phase was dependent on the substrate orientation. X-ray pole figures and electron backscatter diffraction measurements were used to identify the texture and microstructure of the CoGe2 and the preceding Co5Ge7 films. A significant difference in preferential orientation was found in the Co5Ge7 films, depending on the substrate Orientation. This influences the formation temperature of the CoGe2 and results in the coexistence of Co5Ge7 and CoGe2 on Ge(111) in a large temperature window. [ABSTRACT FROM AUTHOR]

Abstract: A germanium/copper germanide/carbon (Ge/Cu3Ge/C) composite is prepared by the Pechini method using GeO2, CuSO4, and citric acid/ethylene glycol as the Ge, Cu and carbon sources, respectively. The microstructure and electrochemical properties of this nano-composite are compared to those of germanium/carbon (Ge/C) that is prepared without the copper precursor. In the latter composite, irregular-shaped submicron-sized (0.4–0.5μm) Ge particles are dispersed inside a carbon matrix. In the former, however, sphere-shaped nano-sized (<100nm) Ge particles are produced, inside of which a Cu3Ge phase is uniformly dispersed in nano-scale. The pure Ge component in both electrodes is lithiated up to Li15Ge4 after a lithiation down to 0.0V at a current density of 100mAg−1. The Cu3Ge-containing electrode gives a superior cycle and rate performance to that of the Cu3Ge-free counterpart. This difference has been ascribed to the favorable roles provided by the nano-sized Cu3Ge phase that is intimately contacted with the nano-sized Ge particles within a sphere. The electrochemical dilatometry study reveals that the electrode swelling is much smaller for the Cu3Ge-containing electrode, illustrating that the electrochemically inactive Cu3Ge phase serves as a buffer against a massive volume change encountered in the Ge component. [Copyright &y& Elsevier]

Abstract: The degradation and the recovery behavior of the device performance for SiGe diodes and p-MOSFETs irradiated by 2-MeV electrons are reported. For diodes, it is noted that both the reverse and forward current increase by irradiation. An interesting observation is that the forward current decreases after irradiation for a forward voltage larger than ~0.7V. This reduction can be explained by an increased resistivity of the Si substrate. The degradation recovers by thermal annealing after irradiation. For a fluence of 1×1015 e/cm2, the diode performance almost recovers to the initial condition after 250°C annealing. For the transistors, after irradiation, a slight negative shift of the threshold voltage and a decrease of the drain current for input and output characteristics have been observed together with a decrease of hole mobility. This is mainly due to the increase of the threshold voltage induced by positive charge trapping in the gate oxide. [Copyright &y& Elsevier]

Abstract: Early stages of strained silicon (sSi) relaxation during the growth on (100) Si0.8Ge0.2 pseudo-substrates with low threading dislocation density (3·10+4/cm²) have been studied. Threading dislocations are only observed in sSi layers at early stages of growth whereas Shockley partial dislocations appear at thicknesses of sSi above 18nm. By analyzing the dislocation types in different sSi layers we observed three different regimes of relaxation: [–] for sSi thickness below 15nm, no dislocation generation is observed, [–] for sSi thickness between 15nm and 18nm, threading dislocation density increases but no stacking faults are generated, [–] for sSi thickness above 18nm, threading dislocation density decreases as well as Shockley partial dislocation density increases due to the splitting of threading dislocations into partial dislocations. In this regime the stacking fault linear density has a logarithmic dependence with sSi thickness. We developed an analytical model to describe stacking fault linear density evolution with sSi thickness and we showed that 18nm threshold thickness for dislocation splitting corresponds to an intrinsic stacking fault energy of 90mJ/m² in sSi. [Copyright &y& Elsevier]

Abstract: Pulsed laser induced epitaxy (PLIE), based on melting/solidification processes induced by nanosecond laser pulses, is used to synthesize pseudomorphic Si1− x Ge x epilayers from 20 to 80nm thick Ge layers evaporated on a Si(100) wafer. Ge concentration and strain are characterized by transient reflectivity, energy dispersive X-ray analysis and X-ray diffraction from symmetric (004) and asymmetric (224) reflections. For a low Ge thickness or a high laser fluence, PLIE builds up only a pseudomorphic strained Si1− x Ge x layer with a graded Ge composition reaching x ≈19% near the surface. When the Ge amount is in excess to achieve this situation, PLIE forms additionally a relaxed Si1− x Ge x layer with x values up to ≈40% over the previous pseudomorphic layer. [Copyright &y& Elsevier]

Abstract: The new route to fabricate compositionally graded and highly-relaxed Si1-xGex layers using thermal oxidation at high temperatures is investigated. Ge atoms behavior during thermal oxidation of Si1-xGex layers is strongly dependent on the oxidation temperature. For low temperature oxidation processes Ge is incorporated as GeO2 in the grown oxide layer, while for higher temperatures it accumulates below the grown oxide into a layer with a higher concentration than the initial Si1-xGex. However, Si1-xGex layers oxidized at 1000°C did not show such an accumulation layer because Ge diffusion efficiently occurred, resulting in the formation of a compositionally graded and relaxed Si1-xGex layer. Such layers could be used as virtual substrates for the strained-Si and relaxed-SiGe applications. [Copyright &y& Elsevier]

Abstract: Uniaxially strained SiGe layers were fabricated with a newly developed selective-ion-implantation technique. The SiGe layer was grown on the Si substrate, into which laterally selective ion-implantation with stripe pattern was carried out prior to the SiGe growth. A strain-relaxation of the SiGe layer was largely enhanced due to ion-implantation-induced defects selectively in the ion-implanted area while it was hardly enhanced in the neighboring unimplanted area. However, micro-Raman mapping and X-ray diffraction reciprocal space mapping measurements obviously revealed that the relaxed SiGe in the implanted area remarkably influenced a strain state of the neighboring strained SiGe in the unimplanted area, that is, the strain along the stripe line direction was highly relieved due to the stress caused by the neighboring relaxed SiGe while the strain in the direction perpendicular to the line was well maintained. As a result, highly asymmetric strain state, that is, uniaxial strain was realized, where 4 times different relaxation ratios in the two directions were observed. These results indicate that the selective-ion-implantation technique developed in this study has a high potential to realize uniaxially strained Si/Ge channel devices with high mobility. [Copyright &y& Elsevier]

Abstract: In this work we present models and simulation results for diffusion in strained SiGe heterostructures. Our approach makes a comprehensive, physically-based, treatment of defect and dopant diffusion, self-diffusion (of Si and Ge) and interdiffusion, including some effects inherent to heterostructures. The models have been implemented in the DADOS code, within the framework of the atomistic kinetic Monte Carlo approach. The parameter set has been calibrated in the whole composition range, from silicon to germanium, both for relaxed and strained conditions, and an illustrative set of experiments has been simulated. [Copyright &y& Elsevier]

Abstract: Calculations based on Density Functional Theory are carried out to study interstitial generation close to the Si(100) surface with further consideration of effects related to the presence of substitutional Ge atoms on the surface. Defect structures, vacancy and Si interstitial, and associated energies are calculated. We observe that germanium atoms tend to increase the stability of created defects, promote the generation of interstitials through drastic structural changes and blocks the climb of Si interstitials towards the surface. [Copyright &y& Elsevier]

Abstract: SiGe-on-insulator (SGOI) substrates with different Ge fractions (Ge%) were fabricated using Ge condensation technique. High acceptor concentration (N A) in SGOI layer and interface-trap density (D it) at SGOI/buried oxide (BOX) interface were found by using back-gate metal–oxide–semiconductor field-effect transistor method. For the reduction of high N A and D it, Al deposition and the subsequent post-deposition annealing (Al-PDA) were carried out. As a comparison, a forming gas annealing (FGA) was also performed in H2 ambient. It was found that both Al-PDA and FGA effectively reduced N A and D it for low-Ge% SGOI. However, with an increase in Ge%, FGA became less effective while Al-PDA was very effective for the reduction of N A and D it. [Copyright &y& Elsevier]

Abstract: We studied the evolution of extended defects in relaxed and strained Si and SiGe structures after an amorphising implant. The investigated structures included three relaxed SiGe alloy layers with various Ge contents (20, 35 and 50at.%), a 40nm-thick tensely strained Si layer and a 40nm-thick compressively strained Si0.8Ge0.2 layer. Concerning the compositional effects, we found that the increase of Ge concentration in relaxed SiGe structures leads to: (i) an overall decrease of the defect stability and to (ii) an enhanced {311}-to-loops transformation. As for the strain effects, it is found that: (i) Tensile strain (in Si) retards the transformation of {311} defects into loops; (ii) compressive strain (in SiGe) enhances the transformation of {311}s into loops; (iii) in all cases, the overall defect stability is not strongly modified in the presence of strain. The observed results are discussed in terms of the various mechanisms involved, including the increase of the interstitial diffusivity in relaxed SiGe alloys (with respect to Si) and the strain effects on both interstitial equilibrium concentration and defect formation energy. [Copyright &y& Elsevier]

Abstract: The feasibility of applying the semi-superjunction (Semi-SJ) with SiGe-pillar (SGP) concept to Power MOSFET is studied in this paper. The electrical performances of SGP are compared with the conventional Power MOSFET through 3D device simulation work in terms of specific-on resistance , breakdown-voltage (BV), the effect to change the Ge mole fraction in the SGP and the thermal stabilization. The results show that the is reduced by 44% on the base of BVs reducing only 4.8%, tradeoff vs. BV and thermal stabilization of SGP are superior to that of conventional Semi-SJ since the strain effect inducing into the SGP structure in the low power device application. [Copyright &y& Elsevier]

Low temperature (ranging from 350 to 420°C) metal induced lateral crystallization of Ge using germanide forming metals Ni, Co, and Pd is performed. The lateral growth lengths and crystallized Ge films' quality are optimized when annealed at 375°C, above which self-nucleation in Ge hinders the metal induced crystallization process. At 375°C, the sample with Pd as the seed metal has the largest lateral growth length, while the sample using Co as the seed layer exhibits the largest crystal grain size. The experiments suggest that the lateral growth length is associated with the diffusivity of the metal and germanide in Ge, while the crystal quality is related to the lattice mismatch between germanide and Ge. [ABSTRACT FROM AUTHOR]

Ge−Ge double bonds: The reaction of elemental lithium, sodium, and germanium at 750 °C results in the Zintl phase Li3NaGe2, which, according to the Zintl–Klemm concept, contains [Ge=Ge]4− dumbbells with unprecedented short Ge−Ge distances. Based on structural, spectroscopic, and theoretical considerations, convincing evidence is given that Ge−Ge double bonds are in fact present. [ABSTRACT FROM AUTHOR]

Ge−Ge double bonds: The reaction of elemental lithium, sodium, and germanium at 750 °C results in the Zintl phase Li3NaGe2, which, according to the Zintl–Klemm concept, contains [Ge=Ge]4− dumbbells with unprecedented short Ge−Ge distances. Based on structural, spectroscopic, and theoretical considerations, convincing evidence is given that Ge−Ge double bonds are in fact present. [ABSTRACT FROM AUTHOR]

Abstract: We perform a theoretical investigation on the magnetism and orbital hybridization in ternary germanide Ce3Ni2Ge7 using the full-potential linearized augmented plane wave method (FP_LAPW) based on the density functional theory (DFT). The calculation with local spin density approximation (LSDA) predicts that there are two states for the Ce atoms due to the different environment: one (Ce1) is near the nonmagnetic state and the other (Ce2) is localized and magnetic. The orbital hybridization plays a key role in determining the state of Ce. On adding on-site Coulomb potential to the localized Ce2-4f orbit, the magnetic moment obtained from our calculation fits well with the experimental value. [Copyright &y& Elsevier]

Abstract: Reported are the synthesis, crystal structure determination and magnetic properties of new polymorphic forms of the rare-earth metal germanides Tb3Ge5 and Dy3Ge5. Both compounds are isostructural and crystallize with the hexagonal space group (No. 190, Z =2) with unit-cell parameters a =6.861(2)Å; c =8.339(6)Å for Tb3Ge5 and a =6.8387(10)Å; c =8.293(2)Å for Dy3Ge5, respectively. The structures are derivatives of the ubiquitous AlB2 type and can be regarded as its 6-fold superstructure (a′= a ×31/2 and c′= c ×2), arising from the long range ordering of Ge vacancies. They are therefore best described as flat Ge-layers, stacked in a hexagonal close-packed manner along the crystallographic c-axis, which are separated by layers of rare-earth metal atoms. Magnetic susceptibility measurements reveal that both Tb3Ge5 and Dy3Ge5 exhibit antiferromagnetic order at temperatures below 23K and 9K, respectively. [Copyright &y& Elsevier]

Abstract: Four new rare-earth metal tin germanides with general formulae RE 2[Sn x Ge1−x ]5 (RE =Nd, Sm; x ≈0.25–0.3) and RE[Sn x Ge1−x ]2 (RE =Gd, Tb; x ≈0.2–0.25) have been synthesized from the corresponding elements by high temperature reactions using Sn flux. Their structures have been established from single-crystal and powder X-ray crystallography: orthorhombic space group Cmcm (No. 63) with cell parameters a =4.1057(6)Å, b =35.992(5)Å, c =4.2534(6)Å for Nd2[Sn x Ge1−x ]5; a =4.0707(8)Å, b =35.550(7)Å, c =4.2095(8)Å for Sm2[Sn x Ge1−x ]5; a =4.2248(11)Å, b =30.451(8)Å, c =4.0013(11)Å for Gd[Sn x Ge1−x ]2, and a =4.1936(13)Å, b =30.230(9)Å, c =3.9793(12)Å for Tb[Sn x Ge1−x ]2, respectively. The structures of the two families can be described as being stacking variants of the ZrSi2 and DyGe3 types, respectively. They represent another example of site preferences between two group 14 elements, where the lighter Ge atoms preferentially form zig-zag chains while the square sheets (or double square sheets) are made up of Sn atoms, respectively. Magnetic susceptibility measurements show that all of the compounds order antiferromagnetically at low temperatures and their respective ordering temperatures are further corroborated by specific heat measurements. [Copyright &y& Elsevier]

In this letter, we report on the formation, of copper-germanide/germanium nanowire (NW) heterostructures with atomically sharp interfaces. The copper-germanide (Cu3Ge) formation process is enabled by a chemical reaction between metallic Cu pads and vapor−liquid−solid (VLS) grown Ge-NWs. The atomic scale aligned formation of the Cu3Ge segments is controlled by in situ SEM monitoring at 310 °C thereby enabling length control of the intrinsic Ge-NW down to a few nanometers. The single crystal Cu3Ge/Ge/Cu3Ge heterostructures were used to fabricate p-type Ge-NW field effect transistors with Schottky Cu3Ge source/drain contacts. Temperature dependent I/Vmeasurements revealed the metallic properties of the Cu3Ge contacts with a maximum current density of 5 × 107A/cm2. According to the thermoionic emission theory, we determined an effective Schottky barrier height of 218 meV. [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: Ternary intermetallics SrM2Ge2 (M=Ni and Ir) have been prepared by arc melting. The crystal structure of these intermetallics was determined by single-crystal X-ray diffraction. They are isostructural with the recently discovered superconductors (Ba,Sr)1−x (K,Cs) x Fe2As2 with ThCr2Si2-type structure with the space group I4/mmm (No. 139). The lattice parameters of SrNi2Ge2 and SrIr2Ge2 are a =0.41801(1) and c =1.02409(6)nm, and a =0.41916(2) and c =1.0674(1)nm, respectively. Neither of them shows superconductivity down to 1.8K. [Copyright &y& Elsevier]

Abstract: The formation energy, structural relaxation, and Mulliken charge of impurities in Mg2Ge are systematically investigated using first-principles calculations based on the density functional theory. Among the elements in groups Ia, IIIa, Ib, IIIb, and Vb, Sc, Y, La, P, N, As, Sb, and Bi are suggested as n-type dopants, whereas Li, Na, K, Rb, and B are suggested as p-type dopants. For Al, In, Ga, Ag, and Cu, the conduction type depends on the atomic chemical potentials of Mg and Ge. The formation energies of P, As, Sb, Bi, and Au in the Ge-site substitution as well as those of Li, Sc, and Y in the Mg-site substitution are negative at Mg- and/or Ge-rich limits, suggesting that these impurities have good solubility. The carrier type of impurity-doped Mg2Ge will be influenced by the types of dopants and the substitution site. The strong similarity between the formation energies of the groups Ib, IIIb, and Vb impurities in Mg2Ge and Mg2Si is observed. [Copyright &y& Elsevier]