Small Amount Of Ge Research Articles

Separation of silicon and germanium from the chlorination distillation residue based on co-precipitation of sodium-aluminum–silicon

Germanium (Ge) is known as a critical metal, and dust from coal burning is an important raw material for the extraction of Ge by the chlorination distillation process. Nevertheless, the residue produced by the chlorination distillation process (RCDP) also contains a considerable amount of Ge. The extraction of Ge from RCDP requires the conversion of Si and Ge into soluble compounds, and the efficient separation of large amounts of Si and Al from small amounts of Ge. In this study, Al, Si and Ge in RCDP were converted to soluble sodium slat by sodium roasting. Under the conditions of roasting temperature of 600 ℃, time of 120 min and the mass ratio of NaOH to RDCP of 3:1, 56.92 % of Al, 87.75 % of Si and 91.20 % of Ge are dissolved into solution. According to the formation mechanism of sodium aluminosilicate, the co–precipitation of Na–Al–Si can be promoted by adjusting the composition of the leaching solution to separate Si and Ge. Noteworthy, 73.97 % of Si have been removed by precipitation, while the precipitation ratio of Ge is only 8.77 %. Moreover, the Ge-containing solution is obtained with low Al–Si concentration (Al 0.37 g/L, Si 0.85 g/L and Ge 0.025 g/L). Overall, the obtained nano-microspherical non-dense cluster zeolite products have great potential for the removal of heavy metal ions from wastewater.

Efficient photon capture on germanium surfaces using industrially feasible nanostructure formation

Nanostructured surfaces are known to provide excellent optical properties for various photonics devices. Fabrication of such nanoscale structures to germanium (Ge) surfaces by metal assisted chemical etching (MACE) is, however, challenging as Ge surface is highly reactive resulting often in micron-level rather than nanoscale structures. Here we show that by properly controlling the process, it is possible to confine the chemical reaction only to the vicinity of the metal nanoparticles and obtain nanostructures also in Ge. Furthermore, it is shown that controlling the density of the nanoparticles, concentration of oxidizing and dissolving agents as well as the etching time plays a crucial role in successful nanostructure formation. We also discuss the impact of high mobility of charge carriers on the chemical reactions taking place on Ge surfaces. As a result we propose a simple one-step MACE process that results in nanoscale structures with less than 10% surface reflectance in the wavelength region between 400 and 1600 nm. The method consumes only a small amount of Ge and is thus industrially viable and also applicable to thin Ge layers.

Kinetic analysis on carbothermic reduction of GeO2 for germanium recovery from waste scraps

Germanium, as scarce and strategic resource, is widely used in infrared devices, polymerization catalysts and optical fibers. Manufacturing scraps and coal fly ash are the main secondary germanium resources, where germanium exists as GeO2. Carbothermic reduction method is a promising technology for germanium recovery from such wastes and its feasibility has been confirmed recently. However, the kinetics and reaction mechanism of the recovery process remained unclear, which blocked deep insight into the process and further improvement of recovery technology. In this study, the kinetics of carbothermic reduction of GeO2 as well as reaction mechanism was studied in detail. A transformation of reaction path was confirmed: Path I: Reduction product GeO desorbed from reaction region at the first stage; Path II: Ge became the main reduction product and evaporate slowly at the second stage. The kinetic parameters of these two paths were calculated where the kinetic model corresponded to an autocatalytic model. Germanium monoxide (GeO) was the main recovered species accompanied with a small amount of Ge and GeO2 and an overall reduction scheme was also proposed. These results can provide theoretical basics and implications for germanium recovery from waste scraps through carbothermic reduction method.

Ge-doped magnetite thin films with an enhanced resistance to oxidation

The ability of metal-doped magnetite (Fe3O4) thin films to resist oxidation during annealing in air was investigated. The films were prepared on glass substrates by radio-frequency sputtering using a target of metal chips set on a ceramic Fe3O4 disk. The metal elements used in this study were Ge, Mo, W, and Mg. The films were annealed at different temperatures in air and the activation energy of oxidation was estimated. The Ge-doped film was high stable against oxidation with an activation energy of 490 KJ/mol, which was 2.5 times larger than that of undoped film. Elemental mapping using energy dispersive X-ray microscopy (EDX) and selected area electron diffraction (SAED) revealed that the Ge-doped Fe3O4 film was composed of a heterostructure that consisted of α-Fe2O3 and Fe3O4 containing small amount of Ge.

The effects of germanium addition on properties of Ga-Sb-S chalcogenide glasses

Properties of the glasses are experimentally investigated when Ga is gradually substituted by Ge in Ga8Sb32S60 chalcogenide glass. The glass structure is also studied to elucidate the variations of the properties. While the substitution of Ga by Ge does not remarkably change the glass transition temperature Tg, the thermal stability against crystallization becomes optimum when half of the Ga atoms are replaced by Ge atoms. The short-wavelength absorption edge λS (or optical bandgap Eg) exhibits a remarkable decrease when a small amount of Ge is added, however, its value does not change significantly with further Ga substitution. As Ga is gradually replaced by Ge, the long-wavelength cut-off edge λL, the density ρ, the linear refractive index n, and the third-order nonlinear refractive index n2 decrease. It is shown that the property variations of the glasses could be explained by the evolution of the glass structure.

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

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

Improving soft magnetic properties in FINEMET-like alloys. A study

An approach to improve the soft magnetic properties of nanocomposite FINEMET-like alloys is presented by the study of the theoretical behavior of the coercive field with the crystallized fraction, Hc(νcr), curves where the total anisotropy is taken into account. These curves can exhibit a minimum value that should be used for a proper design of soft magnetic alloys, consisting in matching that value with the optimal crystallized fraction of the alloy. For this, the effect of Si, Ge, Co and Al on the magnetic properties on the material phases and on its microstructure was analyzed while a good relationship between theoretical results and data in the literature was found. Small amounts of Ge and/or Al can improve the magnetic properties of FINEMET while the addition of Co deteriorates the coercive field as is predicted by the theory. Simultaneous addition of two or more solute elements to the α-Fe crystals was also evaluated and discussed. Results indicate the importance of knowing the effect of the alloying element on the crystalline magnetostriction constant and on the crystallized fraction of the microstructure.

Crystalline monolayer surface of liquid Au–Cu–Si–Ag–Pd: Metallic glass former

It is demonstrated by means of x-ray synchrotron reflectivity and diffraction that the surface of the liquid phase of the bulk metallic glass forming alloy Au49Cu26.9Si16.3Ag5.5Pd2.3 consists of a two-dimensional crystalline monolayer phase for temperatures of up to about 50 K above the eutectic temperature. The present alloy as well as glass forming Au82Si18 and Au–Si–Ge alloys containing small amounts of Ge are the only metallic liquids to exhibit surface freezing well above the melting temperature. This suggests that the phenomena of surface freezing in metallic liquids and glass forming ability are related and probably governed by similar physical properties.

Magnetostriction, elasticity, and D03 phase stability in Fe–Ga and Fe–Ga–Ge alloys

The contrast between the saturation tetragonal magnetostriction, λγ,2 = (3/2)λ100, of Fe1−xGax and Fe1−yGey, at compositions where both alloys exhibit D03 cubic symmetry (second peak region), was investigated. This region corresponds to x = 28 at. % Ga and y = 18 at. % Ge or, in terms of e/a = 2 x + 3 y + 1, to an e/a value of ∼1.55 for each of the alloys. Single crystal, slow-cooled, ternary Fe1−x−y GaxGey alloys with e/a ∼1.55 and gradually increasing y/x were investigated experimentally (magnetostriction, elasticity, powder XRD) and theoretically (density functional calculations). It was found that a small amount of Ge (y = 1.3) replacing Ga in the Fe–Ga alloy has a profound effect on the measured λγ,2. As y increases, the drop in λγ,2 is considerable, reaching negative values at y/x = 0.47. The two shear elastic constants c′ = (c11− c12)/2 and c44 measured for four compositions with 0.06 ≤ y/x ≤ 0.45 at 7 K range from 16 to 21 GPa and from 133 to 138 GPa, respectively. Large temperature dependence was observed for c′ but not for c44, a trend seen in other high-solute Fe alloys. The XRD analysis shows that the metastable D03 structure, observed previously in slow-cooled Fe–Ga at e/a = 1.55, is replaced with two phases, fcc L12 and hexagonal D019, at just 1.6 at. % Ge. The two are the stable phases of the assessed Fe–Ga phase diagram at x ∼ 28. Notably, at y = 7.8, only the D03 phase (the equilibrium phase of Fe–Ge at e/a = 1.54) was found in the ternary alloy. The theory also shows that the D03 instability is removed for compositions with y ≥ 3.9, when D03 becomes the structure’s ground-state phase. Thus, the high, positive λγ,2 value for Fe–Ga at x = 28 could be the result of the high sensitivity of its metastable D03 structure.

Size control of nanocrystalline magnetite thin films containing a small amount of Ge

This study investigated the preparation and particle size control of nanocrystalline magnetite (Fe 3O 4) containing a small amount of Ge. Thin films were prepared by radio-frequency sputtering with a composite target of Ge chips set on a Fe 3O 4 compound target in a mixed atmosphere of Ar and O 2. X-ray diffraction revealed that the diffraction peak of magnetite gradually broadened as the oxygen ratio increased, with the mean grain size ranging from 26 to 2 nm. Transmission electron microscopy also revealed that the magnetite structurally changed from polycrystalline single phase to isolated granular nanocrystals. Magnetization at 8 × 10 5 A/m was monotonically reduced from 0.32 to 0.04 T, and coercivity was monotonically reduced from 4.2 × 10 4 to 2.1 × 10 3 A/m with increasing the oxygen ratio from 0 to 0.4%.

Atomic Layer Deposition of High-k Dielectric Layers on Ge and III-V MOS Channels

Ge and III-V semiconductors are potential high performance channel materials for future CMOS devices. In this work, we have studied Atomic Layer Deposition (ALD) of high-k dielectric layers on Ge and GaAs substrates. We focus at the effect of the oxidant (H2O, O3, O2, O2 plasma) during gate stack formation. GeO2, obtained by Ge oxidation in O2 or O3, is a promising passivation layer. The germanium oxide thickness can be scaled down below 1 nm, but such thin layers contain Ge in oxidation states lower than 4+. Still, electrical results indicate that small amounts of Ge in oxidation states lower than 4+ are not detrimental for device performance. Partial intermixing was observed for high-k dielectric and GeO2 or GaAsOx, suggesting possible correlations in the ALD growth mechanisms on Ge and GaAs substrates.

Fully strained Si 0.75Ge 0.25 epitaxial films with HfSiO gate dielectrics for high mobility channel metal-oxide semiconductor devices

The authors report on fully strained Si 0.75Ge 0.25 metal-oxide-semiconductor capacitors with HfSiO 2 high- k gate dielectric and TaN metal gate fabricated on Si substrates. Fully strained Si 0.75Ge 0.25 films are directly grown on Si substrates below the critical thickness. HfSiO 2 high- k gate dielectrics exhibit an equivalent oxide thickness of 13–18 Å with a permittivity of 17.7 and gate leakage current density lower than SiO 2 gate oxides by >100×. Interfacial oxide of the HfSiO 2/Si 0.75Ge 0.25 stack consists primarily of SiO 2 with a small amount of Ge and Hf. High performance SiGe field effect transistors are highly manufacturable with excellent electrical characteristics afforded by the fully strained HfSiO 2/SiGe gate stack.

Synthesis of carbon nanotubes, nanofibers and encapsulated nanoparticles by decomposition of acetylene on Ge modified Pd catalysts

Different carbon nanostructures were synthesized by decomposition of acetylene over alumina supported palladium-germanium catalysts. The addition of small amounts of Ge to the Pd(1%)/γ-Al 2 O 3 catalyst increases the yield of carbon nanotubes among other carbon products, in the decomposition of acetylene. The use of a higher Ge concentration (0.3%) in the catalyst induces the formation of carbon nanofibers. For larger Ge concentrations (0.5%) the bimetallic catalyst particles become encapsulated in a graphitic structure.

Microstructure–magnetic properties relationships in nanocrystalline Nd–Fe–Co–Ge–B annealed ribbons

AbstractIn this work, the effects of Ge addition on the microstructure and magnetic properties of some rapidly quenched Nd13.5Fe(74.9–z )Co5.5Gez B6 alloys with z = 0.0, 0.18, 0.36, 0.54, 0.72 and 0.9 prepared by a rapid solidification method were studied. For the first time, detailed microstructural study of nanometer size grain boundaries enriched with very small amount of Ge as well as Nd was carried out using 3 Dimensional Atom Probe (3DAP) technique. The magnitudes of B r and (BH )max were seen to increase for the samples substituted with up to 0.36 at% Ge in spite of the fact that Ge is a non‐magnetic atom. This was related to the observed change of Co concenteration in matrix phase. However, the magnetic properties deteriorated for the samples with Ge addition beyond 0.36 at%. The observed magnetic properties are discussed in relation with the observed microstructural changes monitored by 3DAP and TEM techniques. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Mn3(Cu1-xGex)Nの磁気体積効果と負膨張

Metallic manganese nitrides Mn3AN (A=Zn, Ga, etc) are well known for their large magnetovolume effect (MVE), a discontinuous volume expansion at the magnetic transition. However, MVE is exceptionally absent in Mn3CuN. We found that MVE is induced by a small amount of Ge in the Cu site. This seems to coincide with recovery of the cubic structure. By further Ge doping, the volume expansion becomes gradual (ΔT~100 K) and large negative thermal expansion (NTE) is exhibited around room temperature [α=-12×10-6 K-1 (α: coefficient of linear thermal expansion) for Mn3(Cu0.5Ge0.5)N]. Such a large, isotropic and non-hysteretic NTE is desirable for practical applications.

Magnetovolume Effect and Negative Thermal Expansion in Mn<SUB>3</SUB>(Cu<SUB>1−<I>x</I></SUB>Ge<I><SUB>x</SUB></I>)N

Metallic manganese nitrides Mn3AN (A=Zn, Ga, etc) are well-known for their large magnetovolume effect (MVE), i.e., a discontinuous volume expansion at the magnetic transition. However, MVE is exceptionally absent in Mn3CuN. We found that MVE is recovered by a small amount of Ge in the Cu site. This revival seems to coincide with recovery of the cubic structure. By further Ge doping, the volume expansion becomes gradual (ΔT∼100 K) and large negative thermal expansion (NTE) is exhibited around room temperature [α=−12×10−6 K−1 (α: coefficient of linear thermal expansion) for Mn3(Cu0.5Ge0.5)N]. Such a large, isotropic and non-hysteretic NTE is desirable for practical applications.

Metal-induced crystallization of amorphous Si 1− xGe x by rapid thermal annealing

Metal-induced crystallization (MIC) of amorphous Si 1− x Ge x ( x=0.2 and 0.3) thin films on SiO 2 by rapid thermal annealing (RTA) at 300–600 °C has been investigated. At low annealing temperature, Ni reacted with a-Si 1− x Ge x films to form Ni germanosilicides. The crystallization temperature of a-Si 0.7Ge 0.3 and a-Si 0.8Ge 0.2 was lowered from 500 to 400 °C and 600 to 500 °C, respectively, with capping Ni. The Ni germanosilicide grains were observed to form in the annealed Ni/a-Si 0.7Ge 0.3 and Ni/a-Si 0.8Ge 0.2 samples after annealing at 500 °C. The formation of island structure containing a small amount of Ge at the bottom of polycrystalline Si 1− x Ge x films is attributed to the preferential reactions of Ni with Si to Ge.

Solid phase reactions between Fe thin films and Si-Ge layers on Si

Solid phase reactions in Fe thin films on epi-Si 0.8Ge 0.2, poly-Si 0.7Ge 0.3, a-Si 0.8Ge 0.2, and a-Si 0.7Ge 0.3 layers on silicon have been investigated. The as-deposited samples were in situ annealed in the ultrahigh vacuum chamber at 400–800 °C for 30 min. The island structure was found to cause the abrupt increase in the sheet resistance of the annealed Fe/SiGe samples at 700–800 °C. The formation of FeSi islands containing a small amount of Ge is attributed to the preferential reactions of Fe with Si to Ge. As the annealing temperature was raised to 800 °C, the Fe(Si 1− x Ge x ) phase is the only phase found in the annealed Fe/epi-Si 0.8Ge 0.2 and Fe/poly-Si 0.7Ge 0.3 samples. On the other hand, at the annealing temperature above 700 °C, the β-Fe(Si 1− x Ge x ) 2 phase was observed in the annealed Fe/a-Si 0.8Ge 0.2 and Fe/a-Si 0.7Ge 0.3 but the Fe(Si 1− x Ge x ) is still the dominant phase. The results indicate that the formation of Fe disilicide was retarded by the presence of Ge atoms.

Ge Doping Effect on Properties of AgInSe2 Thin Films

The effect of Ge doping on the properties of AgInSe2 thin films has been investigated by the co-evaporation of AgInSe2 alloy chunks, Se and Ge on Corning 7059 glass substrates. Samples were nearly stoichiometric and contained very small amounts of Ge. They showed a highly [112]-oriented chalcopyrite structure, good optical transmittance spectra in the IR region (λ=1-2.6 µm) and an increase of n-type conductivity compared with the nondoped sample. Raman scattering suggested that the doped Ge atoms replaced some of the In atoms in the chalcopyrite structure. The Ge-doped sample grew uniformly from the beginning of film deposition.

Thermal stability and crystallization kinetics study of some Se-Te-Ge glassy alloys

Thermal stability and crystallization kinetics of (Se 85Te 15) 100 − x Ge x ( x = 0, 2, 5 and 10) glasses have been studied using differential scanning calorimetry (DSC), X-ray diffraction (XRD), optical microscopy (POM) and scanning electron microscopy (SEM). The variation of the glass transition temperature with composition suggests that a small amount of Ge ( ≤ 5 at.%) leads to an increase in the length of the Se-Te chains, whereas further enrichment in Ge (10 at.%) increases the number of Se-Te chains in the alloys. Thermal stability of these samples is discussed. For glassy alloys prone to crystallize, the emerging crystalline phase reflections correspond to h.c.p. Se(Te). Surface and bulk crystallization can be found and in both cases crystalline nuclei develop as spherulites. The activation energies for the glass transition and for crystallization have been calculated. The crystallization kinetics has been established and a discussion of the possible mechanisms involved in the crystallization process is presented.