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Si1 –xGex alloy nanoparticles with controlled composition have been obtained by nanosecond laser ablation of silicon–germanium targets in isopropanol. The synthesized product exhibits a polycrystalline structure and a unimodal size distribution with a predominant content of microparticles and retains the stoichiometry of the composition of the targets used for the synthesis. Nanothermometry with the detection and analysis of a Raman signal from single alloy nanoparticles with a size of ~200 nm demonstrates a threefold increase (in comparison with nanoparticles of pure silicon) in the heating efficiency of a nanomaterial with the composition Si0.45Ge0.55 by 785-nm laser radiation falling into the first "transparency window" of biological tissues. Stimulated by continuous infrared radiation, the diffusion of silicon atoms to the surface (when heated to 650 K) and their oxidation lead to the gradual transformation of alloy nanoparticles into germanium clusters encapsulated in a SiOx matrix. [ABSTRACT FROM AUTHOR]

The microstructure of Ti-6Al-4V titanium alloy produced by laser additive manufacturing is generally relatively coarse, so its mechanical properties have not yet achieved satisfactory results. After adding germanium element to titanium alloy, second phase particles can be formed, at the same time, due to strong bonding force between Ti and Ge atoms, there also have other strengthening effects that need to be revealed. Therefore, the effect of Ge addition on the microstructure and mechanical properties of additive manufactured Ti-6Al-4V alloy was studied in detail in this paper, which can provide more reference for optimizing the performance of titanium alloy manufactured with additives manufacturing. The pure Ge powder was ball milled with Ti-6Al-4V powder in several different proportions, and bulk samples were prepared by laser deposition manufacturing (LDM) with the mixed powder. The Germanium alloyed Ti-6Al-4V alloy's tensile strength and plasticity at room temperature increased about 25% and 10%, respectively, compared with LDMed Ti-6Al-4V alloy without Ge. According to the results of TEM and EDS, Ti and Ge reacted to form granular second phase Ti5Ge3, which distributes along the primary β grain boundary inhibit the growth of columnar crystals. Part of Ge solutes into α phase. Both microstructure refinement and solid solution are very effective in impeding the moving of dislocation, so that the Germanium alloyed LDMed Ti-6Al-4V alloy showed excellent tensile property at room temperature. [ABSTRACT FROM AUTHOR]

The possibility of partial substitution of Si for Ge in the structure of Bi2GeO5 during synthesis from the melt and the effect of the substitution on the structure of the synthesized material have been studied. The microstructure of the synthesized compounds after their complete decomposition has been investigated. Using the phase powder X-ray diffraction- and optical microscopy methods, it has been found that metastable phases of bismuth silicate and germanate with structures of the Aurivillius type form a continuous series of solid solutions. It is shown that a mixed structure composed of large Bi4Si(Ge)3O12 crystals and the Bi12Si(Ge)O20 + Bi4Si(Ge)3O12 point eutectic is obtained after the decomposition of compounds of the Bi2SiO5–Bi2GeO5 quasi-binary system, regardless of the percentage of substitution of Si for Ge. Upon slow heating up to annealing temperatures (at a rate of 13.5°C/min), a structure of decomposition that is more finely dispersed and uniform than the structure obtained upon rapid heating (when charg the material into an already preheated furnace), which is more coarsely grained and inhomogeneous. Moreover, regions with a large structure similar to a dendritic one can appear in the material when the contents of silicon and germanium oxides in the alloy are close to each other (20/30–30/20 mol %). Such regions differ slightly in chemical composition from the surrounding material and appear during both slow and rapid heating of the material to annealing temperatures. [ABSTRACT FROM AUTHOR]

A modified equation of state and a thermodynamically equilibrium model are used to numerically simulate the thermodynamic parameters of shock-wave loading of germanium in its pure form, as well as alloys with germanium as a component. The parameters of the equations of state for two phases of germanium are determined. The thermodynamic parameters are modeled for these Ge I and Ge II phases in the pressure range from 1 to 400 GPa. The shock adiabats for both phases are plotted, and the heat capacity values along the normal isobars and isochores and the entropy values for germanium as a function of temperature were calculated. The simulation results are compared with the results of other authors (both calculations and experiments). [ABSTRACT FROM AUTHOR]

Regularities of composition changes of silicon/germanium alloy thin films formed on a single-crystalline silicon substrate by electrochemical deposition of germanium into a porous silicon matrix with subsequent rapid thermal annealing (RTA) at temperatures of 750–950°C are studied. An analysis of the samples by Raman spectroscopy showed that an increase of the RTA temperature leads to a decrease in the germanium concentration in the formed film. A decrease of the RTA duration at a given temperature makes it possible to obtain films with a higher germanium concentration and to control the composition of thin silicon/germanium alloy films formed by changing the RTA temperature and duration. The obtained results on controlling the composition of silicon/germanium alloy films can be used to create functional electronic devices, thermoelectric power converters, and optoelectronic devices. [ABSTRACT FROM AUTHOR]

Among the main characteristics of silver and its alloys, tarnish resistance as well as surface brightness is essential. Alloying these materials with germanium has been shown to have considerable potential in providing tarnish protection. However, studies regarding the electrodeposited silver-germanium (Ag–Ge) alloy coatings are limited. The main objective of this study is to investigate the electrodeposition process of Ag-Ge alloy coatings with different Ge contents. In this regard, co-electrodeposition of Ag and Ge as an alloy coating was performed on pure copper substrates from a cyanide-based electrolyte. The effect of Ge incorporation on alloy composition, surface morphology, topography, texture, crystalline structure and cathodic efficiency of the obtained electrodeposits was investigated. Also corrosion properties of coatings were perused by polarization curves. Evaluation of the coatings was performed using different characterization techniques including XPS, SEM, FESEM, EDS, XRD, AFM, ICP, GIXRD, XRF, FTIR and electrochemical analysis. Results indicated that the optimum content of Ge in the coating was found to be 6 wt% regarding dense and uniform microstructure along with the best corrosion resistance. In addition, the X-ray diffraction patterns exhibited a shift in lattice parameter of Ag that was attributed to the Ag-Ge biphasic alloy formation. Moreover, the surface studies revealed a morphological transformation from nodular to cauliflower-like by increasing the Ge content of coating. The obtained polarization curves represent a remarkable decrease in Ag-6Ge alloy corrosion current density, about 20 times compared to Ag-0.5Ge and about 6 to pure silver. Discrepancies in characteristics between the Ag-Ge and pure Ag coatings were addressed and discussed. [ABSTRACT FROM AUTHOR]

The binary alloy germanium tin has already been presented as a direct group IV semiconductor at high tin concentrations and specific strain. Therefore, it offers a promising approach for the monolithic integrated light source towards the optical on-chip communication on silicon. However, the main challenge faced by many researchers is the achievement of high tin concentrations and good crystal quality. The key issues are the lattice mismatch to silicon and germanium, as well as the limited solid solubility of tin in germanium of less than 1%. Therefore, this paper presents a systematic investigation of the epitaxial growth conditions of germanium tin with tin concentrations up to 17%. For this, we performed two growth experiments utilizing molecular beam epitaxy. In one experiment, we varied the growth temperature for the epitaxy of germanium tin with 8% tin to investigate the inter-growth temperature stability. In the second experiment, we focused on the strain-relaxation of germanium tin, depending on different tin concentrations and doping types. The results of subsequent material analysis with x-ray diffraction and scanning electron microscopy allow us to narrow the epitaxial window of germanium tin. Furthermore, we present a possible explanation for the unique relaxation mechanism of germanium tin, which is significantly different from the well-known relaxation mechanism of silicon germanium. [ABSTRACT FROM AUTHOR]

As an important part of lead-acid batteries, the grid is mainly used to support active substances and conduct current. Currently, Pb-Ca-Sn-Al alloys are widely used as materials for valve-regulated lead-acid battery grids. The influence of bismuth, barium, strontium, and germanium as alloying additives on the physical and electrochemical behaviors of Pb-Ca-Sn-Al alloys was studied by the methods of metallographic, cyclic voltammetry, linear scanning voltammetry, AC impedance, and scanning electron microscopy. The results show that the addition of Bi and Ba can increase the grain size of the alloy and reduce the intergranular corrosion and corrosion rate of Pb-Ca-Sn-Al alloy. Furthermore, the addition of Bi and Ba could inhibit the growth of Pb (II) and PbO2 in corrosion layer and improve the corrosion resistance of the alloy. Significantly, Bi and Ba will reduce the oxygen evolution overpotential of the alloy by about 30 mV, which will play important roles on the maintenance-free performance of lead-acid batteries. Both Sr and Ge promote the grain corrosion and intergranular corrosion of the alloy, reducing the corrosion resistance of the alloy. Therefore, improving the performance and corrosion life of the grid by using additives is an important approach to further extending the service life of lead-acid batteries. [ABSTRACT FROM AUTHOR]

Germanium-lead films have been investigated as a new direct-bandgap group IV alloy. GePb films were deposited on Si via thermal evaporation of Ge and Pb solid sources using the layer inversion metal-induced crystallization method for comparison with the current laser-induced recrystallization method. Material characterization of the films using x-ray diffraction analysis revealed highly oriented crystallinity and Pb incorporation as high as 13.5% before and 5.2% after annealing. Transmission electron microscopy, scanning electron microscopy, and energy-dispersive x-ray mapping of the samples revealed uniform incorporation of elements and complete layer inversion. Optical characterization of the GePb films by Raman spectroscopy and photoluminescence techniques showed that annealing the samples resulted in higher crystalline quality as well as bandgap reduction. The bandgap reduction from 0.67 eV to 0.547 eV observed for the highest-quality material confirms the achievement of a direct-bandgap material. [ABSTRACT FROM AUTHOR]

The structural, electronic, magnetic, and optical properties of Mn-based Heusler Mn2ZrGa1−xGex (x = 0, 0.25, 0.5, 0.75, and 1) alloys are calculated by first-principles full-potential linearized augmented plane wave plus local orbital (FP-LAPW+lo) method. It is found that Mn2ZrGa1−xGex alloys are half-metallic ferrimagnetic and their magnetic moments are in good agreement with the Slater-Pauling relationship. The calculations reveal that all alloys have a pseudo-gap in the majority-spin channel except for x = 0.75 and x = 1 which have a real gap in the majority-spin channel. The spin polarization is quite large for whole series, and it reaches to a value of 100% for x = 0.75 and x = 1. Our calculated results clearly show that with the Ge substitution, the lattice parameter linearly decreases while the bulk modulus increases. Moreover, the calculated formation energies confirm that these alloys are stable chemically. The optical properties, including the real and imaginary parts of the dielectric function, reflectivity, and absorption spectra, were also investigated. The results show that the dominant behavior, at energy below 1 eV, is due to interactions of free electrons in the system. The increment of Ge concentration leads to an increase in the plasma frequency of metallic spin channel. [ABSTRACT FROM AUTHOR]

Ge-based alloys have drawn great interest as promising materials for their superior visible to infrared photoelectric performances. In this study, we report the preparation and optical properties of germanium-bismuth (GeBi) thin films by using molecular beam epitaxy (MBE). GeBi thin films belong to the n-type conductivity semiconductors, which have been rarely reported. With the increasing Bi-doping content from 2 to 22.2%, a series of GeBi thin film samples were obtained and characterized by X-ray diffraction, scanning electron microscopy, and atomic force microscopy. With the increase of Bi content, the mismatch of lattice constants increases, and the GeBi film shifts from direct energy band-gaps to indirect band-gaps. The moderate increase of Bi content reduces optical reflectance and promotes the transmittance of extinction coefficient in infrared wavelengths. The absorption and transmittance of GeBi films in THz band increase with the increase of Bi contents. [ABSTRACT FROM AUTHOR]

The oxidation and nitridation of the eutectic Cr-CrSi alloys during exposures in air was investigated with focus on the detailed mechanism of the attack. Exposures in synthetic air (N-21%O), and nitrogen (N-5%H) atmospheres revealed inward diffusion of nitrogen as the key mechanism for the nitridation process which was markedly higher in nitrogen compared to that in air. Post-exposure investigations proved selective nitridation of the Cr-solid solution phase in both synthetic air and N-5%H atmosphere. During oxidation in air, a continuous A15 silicide layer (CrSi) formed at the oxide-alloy interface inhibiting the internal nitridation. This layer formed exclusively in oxidizing atmosphere as a result of the primary oxidation and outward diffusion of chromium, and dissolution of the Cr-solid solution phase. The barrier character of the A15 phase against nitridation was evident based on microstructural and chemical investigations as well as on thermodynamic considerations. Long-term oxidation results indicated that overtime the protective A15 layer was damaged by the formation porosities and internal oxidation during exposure which led to internal selective nitridation. Additions of germanium (Ge) was found beneficial by supporting the formation of the self-protecting A15 layer with long-term protective behavior against internal nitridation for more than 1000 h. Graphical Abstract: [ABSTRACT FROM AUTHOR]

The glassy compositions of Ge Se Te Sb system, obtained using rapid melt quenching technique, have been characterized by calorimetric study at different heating rates in this study. A systematic investigation of the crystallization kinetics is carried out for these compositions. Composition corresponding to atomic % 8 of Sb has good thermal stability. The material exhibits the unique thermal properties, which makes it suitable to use for electrical or memory switching devices. Various thermal parameters, activation energies of glass transition and crystallization are calculated using relevant approaches. [ABSTRACT FROM AUTHOR]

Using surface mechanical attrition treatment (SMAT), a gradient structure composed of two gradient structure (GS) layers and a coarse grain (CG) layer was generated from a Cu-5.7 wt pct Ge alloy, significantly improving the yield strength of the sample. Unloading-reloading tests showed an unusual Bauschinger effect in these GS samples. The back stresses caused by the accumulated geometrically necessary dislocations (GNDs) on the GS/CG border increased with increasing strain. As found by electron backscatter diffraction (EBSD), the GNDs are mainly distributed in the gradient structured layer, and the density of the GNDs increase with increasing SMAT time. The effect of the back stress increased with increasing SMAT processing time due to the increase in the strain gradient. The pronounced Bauschinger effect in a GS sample can improve the resistance to forward plastic flow and finally contributes to the high strength of GS samples. [ABSTRACT FROM AUTHOR]

The results of studying the growth of filamentous Ge structures in aqueous electrolytes at various temperatures using In and Sn nanoparticle arrays as nucleation sites are given. The temperature of Ge cathodic deposition process from aqueous solutions has a significant effect on the layer structure deposited onto the surface. In the presence of metal particles in the molten state, filamentous Ge structures grow due to the cathodic reduction of Ge-containing ions on the electrode surface, followed by dissolution and crystallization in the melt at the substrate interface. The results obtained show the crucial role of liquid metal particles during the electrochemical formation of germanium nanowires. [ABSTRACT FROM AUTHOR]

The effects of alkaline earth strontium (Sr) additions on the microstructure and properties of Al–Si–Ge–Zn alloys and brazed joints were investigated. The results showed that the appropriate addition of Sr changed the morphology of β-GeSi phases from coarse needle-like to fine granular shapes effectively. Sr addition prevented the growth of Si by Sr adsorbing on the Si surface and caused the formation of many twins in Si. Sr addition had little impact on the melting temperature of the filler metals, but the spreading areas of Al–Si–Ge–Zn–xSr filler metals increased firstly and then decreased with the increase of Sr addition. In addition, the Sr addition optimized the microstructure of the brazed joints and improved the mechanical properties. Sound joints with high shear strength up to 152.4 ± 2.5 MPa could be obtained by applying Al–9.5Si–10Ge–15Zn–0.7Sr (all in wt%) filler metal. [ABSTRACT FROM PUBLISHER]

The article reports on the electronic structure of superlattices silicon (SiC) and germanium carbides (GeC). Topics mentioned include the calculations of the electronic structure of SiC and GeC, the Brillouin zone of the superlattices, and the binary crystal structure. Also mentioned are the valence bond calculation and the band gap widths of SiC and GeC.

The article presents several updates on various alloy phase diagrams for binary systems. Topics discussed include the disagreement or inconsistencies among the thermodynamic models of boron-iron (B-FE) phase diagram, the thermodynamic assessment for the chromium-zirconium (Cr-Zr) phase diagram, and the phase diagram for the germanium-nickel (Ge-Ni) phase diagram.

Herein, Cu and Cu-Ge alloys with different stacking fault energies (SFEs) are prepared via rolling at room temperature (RTR) and via a combination of high-pressure torsion (HPT) and RTR (HPT 1 RTR). The x-ray diffraction measurements reveal that the grain size, dislocation density, and twin density vary with the strain and SFEs. The tensile tests indicate that the strength of materials with medium SFEs increases initially and then slightly declines, while the ductility is enhanced by increasing the strain via HPT. In contrast, for low-SFE materials, enhanced strength and improved ductility may be achieved simultaneously through increasing the strain to a high level. The variation of strength with respect to strain is primarily dependent on the solute concentration and SFE. The underlying mechanisms governing the effect of strain and SFE on the microstructures and mechanical properties of the metals are also discussed. [ABSTRACT FROM AUTHOR]

Antimony-substituted Ge-Se-Te quaternary chalcogenide glasses have been synthesized using the melt quench technique. The bonding arrangements in the glassy matrices have been studied through infrared spectra in the spectral region from 50 cm to 300 cm. The effect of Sb addition on the optical properties has also been studied using ultraviolet-visible-infrared (UV-Vis-IR) spectroscopy on thin films of uniform thickness. The materials possess high refractive index and tunable bandgap with low values of optical loss. They also possess good infrared transparency regions, high refractive index, and low optical bandgap, making them suitable for use in photonic applications. [ABSTRACT FROM AUTHOR]

First-principles calculations were used to study intermetallic compounds in the Nb-Ge system, to gain a better understanding of the phase diagram and resolve conflicts reported in the literature. The enthalpy of formation with regard to temperature was calculated for all the intermetallic compounds, to investigate phase stabilities and phase equilibria at low and elevated temperatures. These results, combined with the electronic DOS, suggest that the tI32 (WSi-type) NbGe and NbGe compounds are stable over the whole temperature range. The stoichiometric cP8 NbGe becomes stable close to its melting temperature. Regarding different compositions of the cP8 NbGe, the calculations suggest the (Nb)(Nb,Ge) model for the NbGe phase instead of the proposed model, (Nb)(Nb,Ge,Va), where Va represents vacancy. The calculations show that the tI32 (CrB-type) NbGe, hP16 (MnSi-type) NbGe and NbGe compounds should be considered metastable. The elastic constants, bulk, shear, and Young's modulus, Poisson's ratio, and Debye temperature of the Nb, Ge, cP8 NbGe, tP32 NbGe, tI32 (CrB-type) NbGe, tI32 (WSi-type) NbGe, hP16 (MnSi-type) NbGe, NbGe and NbGe were calculated. These phases were found to be mechanically stable. Using the Cauchy pressure, Pugh's index of ductility, and the Poisson's ratio as criteria, the calculations suggest that the tI32 (CrB-type) NbGe and NbGe intermetallics should be brittle (with the latter being the most brittle) and the cP8 NbGe, tP32 NbGe, hP16 NbSi and NbGe ductile (with cP8 NbGe being the most ductile). [ABSTRACT FROM AUTHOR]

We have studied the performance of a resonant cavity enhanced photodetector using multiple quantum wells made with GeSn as the well and SiGeSn as the barrier. The structure shows type I band alignment and the GeSn well possess a direct gap. Strong quantum confined Stark effect in GeSn leads to strong absorption and high quantum efficiency. Similar parameters for a bulk GeSn with comparable width exhibiting Franz-Keldysh effect are found to be substantially lower. [ABSTRACT FROM AUTHOR]

Compressively strained $$\hbox {Ge}_{0.973}\hbox {Sn}_{0.027}$$ and $$\hbox {Ge}_{0.925}\hbox {Sn}_{0.075}$$ p-channel metal-oxide-semiconductor field-effect transistors (MOSFETs) are fabricated with low-temperature $$\hbox {Si}_{2}\hbox {H}_{6}$$ surface passivation. High crystallinity GeSn films epitaxially grown on a Ge(001) substrate are used for the device fabrication. The impacts of the Sn composition on the subthreshold swing $$S$$ , threshold voltage $$V_\mathrm{TH}$$ , on-state current $$I_\mathrm{ON}$$ , and effective hole mobility $$\mu _\mathrm{eff}$$ of the devices are investigated. GeSn pMOSFETs with different Sn compositions show a similar $$S$$ , indicating almost the same midgap density of interface states $$D_\mathrm{it}$$ . A positive shift of $$V_\mathrm{TH}$$ with an increase of the Sn composition is observed. A $$\hbox {Ge}_{0.925}\hbox {Sn}_{0.075}$$ pMOSFET exhibits a significant improvement in $$I_\mathrm{ON}$$ as compared to a device with a lower Sn composition, which is due to the superior hole mobility in a device with a higher Sn composition. $$\hbox {Ge}_{0.925}\hbox {Sn}_{0.075}$$ pMOSFETs achieve a peak effective hole mobility $$\mu _\mathrm{eff}$$ of $$500\,\hbox {cm}^{2}{\cdot }\hbox {V}^{-1}{\cdot } \hbox {s}^{-1}$$ , which is much higher than that of $$\hbox {Ge}_{0.973}\hbox {Sn}_{0.027}$$ devices. The enhancement of the compressive strain and chemical effect in the channel region with increased Sn composition leads to an improvement of $$\mu _\mathrm{eff}$$ . [ABSTRACT FROM AUTHOR]

Thermal and optical characterization of GeSnSe ( x = 14, 18, 22, 26) glasses has been carried out using differential scanning calorimetry and UV-VIS-NIR spectroscopy, respectively. Bulk samples were prepared using conventional melt quenching technique. Amorphous nature of the prepared samples was confirmed using X-ray diffraction. The transmission spectra of as deposited films, for normal incidence, were recorded in the range 400-2,500 nm. Optical constants such as absorption coefficient, refractive index and extinction coefficients have been determined using the envelope method. Dispersion of refractive index has been analyzed using single-effective oscillator model. Optical band gap has been measured using Tauc plots. Effect of composition variation on thermal and optical properties has been discussed in view of chemical bond approach. [ABSTRACT FROM AUTHOR]

In this paper, we present a simple and viable route for the synthesis of germanium-tin alloys (GeSn) from two different ionic liquids, namely, 1-butyl-1-methylpyrrolidinium trifluoromethylsulfonate ([Py]TfO) and 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide ([Py]TfN). Cyclic voltammetric analysis showed that in the presence of both SnCl and GeCl precursors, a shoulder peak is obtained which is related to the formation of GeSn. Constant potential deposition was performed to obtain GeSn thin films. Furthermore, on changing the concentration of GeCl and SnCl in [Py]TfO, the GeSn composition could be varied. [ABSTRACT FROM AUTHOR]

Tellurium-based glasses are suitable for storage devices due to their rapid amorphous-to-crystalline transformation. Alloys of Ge Se Sb Te ( y = 0, 2, 4, 6, 8, 10 at.%) have been synthesized using melt quench technique. Glass transition and crystallization kinetics of alloys have been investigated using differential thermal analysis at different heating rates (5, 10, 15, and 20 K min). The thermal stability of synthesized alloys has been investigated. Resistance to devitrification has been analyzed on the basis of activation energy for crystallization. [ABSTRACT FROM AUTHOR]

Silicon is the mainstream material for many nanoelectronic and photovoltaic applications. The understanding of oxygen related defects at a fundamental level is essential to further improve devices, as vacancy-oxygen defects can have a negative impact on the properties of silicon. In the present review we mainly focus on the influence of isovalent doping on the properties of A-centers in silicon. Wherever possible, we make comparisons with related materials such as silicon germanium alloys and germanium. Recent advanced density functional theory studies that provide further insights on the charge state of the A-centers and the impact of isovalent doping are also discussed in detail. [ABSTRACT FROM AUTHOR]

The structure, formation energy, and thermodynamic properties of SiGe alloys are investigated through first-principles method. The ordered and disordered structures of SiGe compounds are considered. Our results show that thermodynamic instabilities of SiGe alloys at 0 K can be judged from the calculated formation energy. However, the alloy might be prepared at specified environment owing to the entropy effects considered. Moreover, the temperature dependence of the heat capacity, Debye temperature and thermal expansion coefficient of ordered and disordered structures are discussed. [ABSTRACT FROM AUTHOR]

Chalcogenide alloys in the Ge-Sb-Te system are promising for application in phase-change memory devices. We investigated the influence of bismuth on the optical properties of GeSbTe thin films and established that the bismuth doping in them allows the optical contrast of the thin films to be increased by about 30% at a wavelength of 400 nm. The experimental results are explained in an assumption on the impurity substitution of bismuth for antimony. [ABSTRACT FROM AUTHOR]

Au-Ge alloys are promising materials for high-power and high-frequency packaging, and Ni is frequently used as diffusion barriers. This study investigates interfacial reactions in Au-12Ge/Ni joints at 300°C and 400°C. For the reactions at 300°C, typical interfacial morphology was observed and the diffusion path was (Au) 1 (Ge)/NiGe/Ni5Ge3/Ni. However, an interesting phenomenon - the formation of (Au,Ni,Ge)/NiGe alternating layers - was observed for the reactions at 400°C. The diffusion path across the interface was liquid/(Au,Ni,Ge)/NiGe/···/(Au,Ni,Ge)/NiGe/Ni2Ge/Ni. The periodic thermodynamic instability at the NiGe/Ni2Ge interface caused the subsequent nucleation of new (Au,Ni,Ge)/NiGe pairs. The thermodynamic foundation and mechanism of formation of the alternating layers are elaborated in this paper. [ABSTRACT FROM AUTHOR]

High-quality compressive-strained GeSn/Ge films have been deposited on Si(001) substrate using a mainstream commercial chemical vapor deposition reactor. The growth temperature was kept below 450°C to be compatible with Si complementary metal-oxide-semiconductor processes. Germanium tin (GeSn) layers were grown with different Sn composition ranging from 0.9% to 7%. Material characterizations, such as secondary-ion mass spectrometry, Rutherford backscattering spectrometry, and x-ray diffraction analysis, show stable Sn incorporation in the Ge lattice. Comparison of the Sn mole fractions obtained using these methods shows that the bowing factor of 0.166 nm (in Vegard's law) is in close agreement with other experimental data. High-resolution transmission electron microscopy and atomic force microscopy results show that the films have started to relax through the formation of misfit and threading dislocations. Raman spectroscopy, ellipsometry, and photoluminescence (PL) techniques are used to study the structural and optical properties of the films. Room-temperature PL of the films shows that 7% Sn incorporation in the Ge lattice results in a decrease in the direct bandgap of Ge from 0.8 eV to 0.56 eV. [ABSTRACT FROM AUTHOR]

Boron-doped GeSn alloys with atomic fractions of tin up to x = 0.08 were grown on n-Ge(001) substrates using solid-source molecular beam epitaxy, in order to study their structural properties. The total boron concentration in the alloys was ~ 10 cm as measured by secondary-ion mass spectroscopy, which also indicated low amounts of impurities such as carbon and oxygen. More than 90% of the Sn atoms occupied substitutional lattice sites in the alloy as determined by Rutherford backscattering spectrometry. High-resolution x-ray diffraction showed that the boron-doped GeSn alloys were single crystals that were completely strained with low defect densities and coherent interfaces for thickness up to 90 nm, and for Sn composition of 8%. The boron-doped GeSn/ n-Ge formed p- n junctions with conventional rectifying characteristics, indicating that the boron produced electrically active acceptor states. [ABSTRACT FROM AUTHOR]

An overview of the modified radiotracer based diffusion studies carried out at IGISOL is provided. The experimental procedures are briefly described followed by examples involving IGISOL as the key facility. In this respect the studies related to silicon-germanium (Si 1 − xGe x) alloys and on the related diffusion systematics are summarized. Another group of examples is related to mobility determination of lead isotopes in glass for verifying retrospective radon measurements. Finally an outlook to future possibilities related to employing radiotracers in solid state research is provided. [ABSTRACT FROM AUTHOR]

The optical, acoustic, and acousto-optic properties of new Ge-Se-Te-S and Ge-Se-Te alloys are studied. As a result of parameter optimization, efficient acousto-optic materials transparent in a wide infrared range (λ = 1.5-18 μm) are fabricated. [ABSTRACT FROM AUTHOR]

Electronic structure calculations are used to investigate the association of lattice vacancies and oxygen interstitials (known as A-centers) and compare them to vacancy-phosphorous atom pairs (known as E-centers) in silicon germanium (SiGe) alloys. The local environment surrounding the A-centers and E-centers is described by the application of the special quasirandom structures approach. It is calculated that the stability of the A-centers and the E-centers is not linearly dependent upon the germanium concentration. The nearest neighbor environment will exert a strong influence upon the stability of these defects. These defect pairs will behave differently with respect to the Ge concentration as the oxygen interstitial (in the A-center) and the phosphorous atom (in the E-center) interact with the host lattice in a different manner. The results are discussed in view of recent theoretical and experimental investigations. [ABSTRACT FROM AUTHOR]

Important technological applications are envisaged for GeSn alloys. They provide a route to obtain direct-gap group IV materials, tuneable by concentration. Therefore, these alloys are ideal candidates for optoelectronic devices, highly compatible with Si integrated circuits. Contrary to other binary alloys with group IV elements, homogeneous GeSn alloys, as required for device applications, have proven difficult to form above a certain temperature-dependent critical Sn concentration. Through a detailed ab-initio local defect study, and the proposal of a statistical model for the formation of these alloys, we predicted that a new type of Sn defect ( β-Sn), consisting of a single Sn atom in the centre of a Ge divacancy, might be formed. The environment of this defect relaxes towards a cubic octahedral configuration, facilitating the nucleation of white tin and its segregation, as found in amorphous samples. We confirmed that Sn would enter substitutionally in the Ge lattice, but above a temperature-dependent critical concentration, non-substitutional β-Sn defects should be formed, consistent with experimental observations. In this paper we introduce a two-site substitutional equivalent for the non-substitutional β-Sn defect in Ge, as needed in order to be able to include β-Sn in electronic structure calculations with effective-field electronic models for disorder, like the Virtual Crystal Approximation (VCA). The equivalent substitutional model is derived in order to take into account the different symmetries in the immediate environment of the substitutional α and non-substitutional β defect sites and their effect on the electronic structure. [ABSTRACT FROM AUTHOR]

In this article, we show how to produce materials consisting of regularly ordered Ge quantum dot lattices in an amorphous alumina matrix with a controllable Ge quantum dot size, shape, spacing, crystalline structure, and degree of regularity in their ordering. The production of such materials is achievable already at room temperature by magnetron sputtering deposition of a (Ge + AlO)/AlO multilayer. The materials show photoluminescence in the visible and ultraviolet light range, a size-dependent blue shift of the photoluminescence peak and an enhancement of its intensity by size reduction, indicating the quantum dot origin of the photoluminescence. The materials also exhibit excellent mechanical properties due to the alumina matrix. Their internal structure is shown to be highly resistive to irradiation with energetic particles for a large range of the irradiation parameters. [ABSTRACT FROM AUTHOR]

In this paper,we fabricate a lateral phase change memory device composed of a GeSbTe nanowire (GST NW) fully confined in a tungsten electrode nanogap. A SiNx spacer is used not only as etch mask for the fabrication of the GST NW, but also as sacrificial layer for the lift-off process, which makes it feasible to fully confine the GST NW in the metal electrode nanogap. Electrical characterization shows that the device has unprecedentedly low threshold current and SET voltage of only 16 μA and 80 mV, respectively. [ABSTRACT FROM AUTHOR]

A eutectic AuGe target immersed in distilled water was ablated by pulsed ultraviolet laser light. The structure of the ablated material was investigated by high-resolution transmission electron microscopy (HRTEM). The images show formation of nanowire structures of AuGe up to 100 nm in length, with widths of 5-10 nm. These nanostructures have Ge content significantly lower than the target material. Electron diffraction demonstrates that they crystallize in the α-AuGe structure. For comparison, laser ablation of pure Au and pure Ge targets was also performed under the same conditions. HRTEM shows that Ge forms spherical nanoparticles with a characteristic size of ~30 nm. Au forms spherical nanoparticles with diameters of ~10 nm. Similar to AuGe, it also forms chainlike structures with substantially lower aspect ratio. [ABSTRACT FROM AUTHOR]

In this study, the significant effect of the nonuniform composition in alloy quantum dots (QDs) on electronic structure is analyzed in depth. The equilibrium composition profiles in experimentally observed dome and barn shaped GeSi/Si QDs are determined by combining the finite element method and the method of moving asymptotes. Due to the composition variation, the total band edge of heavy hole is dominated by the band offset and spin-orbit coupling rather than the strain effect. The numerical results reveal that the wave function of heavy hole trends to be localized in the Ge-rich region at the top of the large QD. Moreover, the size effect gradually compensates the composition effect as the size of QD decreases. [ABSTRACT FROM AUTHOR]

The Ge-Zr system is assessed by means of calculation of phase diagram (CALPHAD) approach, supplemented with decisive experiments and enthalpies of formation computed via Vienna ab initio simulation package (VASP) code. Nine Ge-Zr alloys were prepared by arc melting the pure elements. The annealed samples were analyzed by means of XRD, optical microscopy, and SEM/EDX. Five compounds are observed in the equilibrium condition. The enthalpies of formation for ZrGe, ZrGe, and ZrGe are computed via first-principles calculations. These enthalpies of formation are used as key 'experimental data' in the CALPHAD approach in order to obtain the thermodynamic parameters with sound physical meaning. A consistent thermodynamic data set for the Ge-Zr system is finally obtained based on the present work and the literature data. Comparisons between the calculated and measured phase diagram and thermodynamic quantities show that the accurate experimental information is satisfactorily accounted for by the present thermodynamic description. [ABSTRACT FROM AUTHOR]

Two Al-Mg-Ge alloys with compositions Al-0.87Mg-0.43Ge (at. pct) and Al-0.59Mg-0.71Ge (at. pct) were investigated and compared using high-resolution transmission electron microscopy, annular dark-field scanning transmission electron microscopy, and nano-beam electron diffraction. The alloys contained fine needle- and lath-shaped precipitates after aging at 473 K (200 °C) for 16 hours, which produced hardnesses similar to those measured in comparable Al-Mg-Si alloys. The β″ phase was not observed. Instead, hardness was achieved by β′-like and disordered precipitates in the Mg-rich alloy, and U1-like and disordered precipitates in the Ge-rich alloy. In all cases, the fine precipitates had structures containing an ordered near-hexagonal network of Ge atoms with a = b ≈ 0.4 nm, which could be visualized directly in annular dark-field mode. The network is very similar to the recently discovered Si network that relates all precipitate structures in the Al-Mg-Si alloys. The orientation of the precipitate unit cells and the Ge network relative to the Al matrix differed from what has been observed for β′ and U1 in the Al-Mg-Si system. [ABSTRACT FROM AUTHOR]

The distributions of hydrogen-containing donors in GeSi (0 ≤ x ≤ 0.06) alloys implanted with hydrogen ions with an energy of 200 and 300 keV and a dose of 1 × 10 cm are studied. It is established that, at the higher ion energy, the limiting donor concentration after postimplantation heat treatment (275°C) is attained within ~30 min and, at the lower energy, within ~320 min. In contrast to donors formed near the surface, a portion of hydrogen-containing donors formed upon the implantation of ions with the higher energy possess the property of bistability. The limiting donor concentration is independent of the ion energy, but decreases from 1.3 × 10 to 1.5 × 10 cm, as the Si impurity content in the alloy is increased from x = 0.008 to x = 0.062. It is inferred that the observed differences arise from the participation of the surface in the donor formation process, since the surface significantly influences defect-formation processes involving radiation-induced defects, whose generation accompanies implantation. [ABSTRACT FROM AUTHOR]

The mechanism of the appearance of the magnetic order is considered for the GeMn alloys inside which ferromagnetic “nanocolumns” highly enriched with manganese are formed during the process of low-temperature growth. To describe this ordering, a model of effective exchange between ferromagnetic strings arranged inside a highly compensated nondegenerate semiconductor is suggested. [ABSTRACT FROM AUTHOR]

The character of reorganization of the short-range order and the scale structure during the ordering of glass forming melts is elaborated based on the results of diffraction and microscopic investigations of the ordered and glassy alloys in tellurium-germanium systems. For this purpose cooling curves reflecting the formation processes of structural levels in real time are analyzed and the effective activation energies are estimated. [ABSTRACT FROM AUTHOR]

Microstructures and thermoelectric properties of Ge1Sb2Te4 and Ge2Sb2Te5 chalcogenide semiconductors have been investigated to explore the possibility of their thermoelectric applications. The phase transformation from the face-centered cubic to hexagonal structure was observed in Ge2Sb2Te5 compounds prepared by the melt spinning technique. The Seebeck coefficient and electrical resistivity of the alloys were increased due to the enhanced scattering of charge carriers at grain boundaries. The maximum power factors of the rapidly solidified Ge1Sb2Te4 and Ge2Sb2Te5 attained 0.975×10-3 W m-1K-2 at 750 K and 0.767×10-3 W m-1K-2 at 643 K respectively, higher than those of water quenched counterparts, implying that thermoelectric properties of GeSbTe based layered compounds can be improved by grain refinement. The present results show this class of chalcogenide semiconductors is promising for thermoelectric applications. [ABSTRACT FROM AUTHOR]

The microstructural evolution of concentrated alloys is relatively less understood both in terms of experiments as well as theory. Laser resolidification represents a powerful technique to study the solidification behavior under controlled growth conditions. This technique has been utilized in the current study to probe experimentally microstructural selection during rapid solidification of concentrated Fe-25 atom pct Ge alloy. Under the equilibrium solidification condition, the alloy undergoes a peritectic reaction between ordered α[sub2] (B2) and its liquid, leading to the formation of ordered hexagonal intermetallic phase ϵ (DO[sub19]). In general, the as-cast microstructure consists of ϵ phase and ϵ—β eutectic and α[sub2] that forms as a result of an incomplete peritectic reaction. With increasing laser scanning velocity, the solidification front undergoes a number of morphological transitions leading to the selection of the microstructure corresponding to metastable α[sub2]/β eutectic to α[sub2] dendrite + α[sub2]/β eutectic to α[sub2] dendrite. The transition velocities as obtained from the experiments are well characterized. The microstructural selection is discussed using competitive growth kinetics. [ABSTRACT FROM AUTHOR]

The electron spin resonance (ESR) at phosphorus dopants in the P-doped Si1− x Ge x alloys (0 < x < 0.057) with the concentration of phosphorus in the range 1015–1016 cm−3 is studied at temperatures from 3 to 30 K. The ESR spectra of the alloys ( x > 0) are compared to the ESR spectra of similar silicon samples ( x = 0). It is found that, from the smallest Ge content x = 0.008, the ESR spectra contain two additional lines. It is assumed that these lines are due to phosphorus dopants located in clusters with higher Ge content. It is found that an increase in the Ge content in the alloys up to x = 0.024 yields only an increase in the concentration of such clusters. At x ≥ 0.024, the Ge content increases with x both inside and outside the clusters. [ABSTRACT FROM AUTHOR]

The results of studying the structural and electrical properties of structures produced by the method of direct bonding of Ge x Si1− x and Si wafers are reported. The wafers were cut from the crystals grown by the Czochralski method. Continuity of the interface and the crystal-lattice defects were studied by X-ray methods using synchrotron radiation and by scanning electron microscopy. Measurements of the forward and reverse current-voltage characteristics of the p-Ge x Si1− x / n-Si diodes made it possible to assess the effect of the crystallattice defects on the electrical properties of heterojunctions. Satisfactory electrical parameters suggest that the technology of direct bonding is promising for the fabrication of large-area Ge x Si1− x /Si heterojunctions. [ABSTRACT FROM AUTHOR]