Increasing Ge Content Research Articles

Phase transitions, Dirac and Weyl semimetal states in Mn1−xGexBi2Te4

Using angle-resolved photoemission spectroscopy (ARPES) and density functional theory (DFT), an experimental and theoretical study of changes in the electronic structure (dispersion dependencies) and corresponding modification of the energy band gap at the Dirac point (DP) for topological insulator (TI) have been carried out with gradual replacement of magnetic Mn atoms by non-magnetic Ge atoms when concentration of the latter was varied from 10% to 75%. It was shown that when Ge concentration increases, the bulk band gap decreases and reaches zero plateau in the concentration range of 45–60% while trivial surface states (TrSS) are present and exhibit an energy splitting of 100 and 70 meV in different types of measurements. It was also shown that TSS disappear from the measured band dispersions at a Ge concentration of about 40%. DFT calculations of band structure were carried out to identify the nature of observed band dispersion features and to analyze the possibility of magnetic Weyl semimetal state formation in this system. These calculations were performed for both antiferromagnetic (AFM) and ferromagnetic (FM) ordering types while the spin-orbit coupling (SOC) strength was varied or a strain (compression or tension) along the c-axis was applied. Calculations show that two different series of topological phase transitions (TPTs) may be implemented in this system, depending on the magnetic ordering. In the case of AFM ordering, the transition between TI and the trivial insulator phase passes through the Dirac semimetal state, whereas for FM phase such route admits three intermediate states instead of one (TI—Dirac semimetal—Weyl semimetal—Dirac semimetal—trivial insulator). Weyl points that form in the FM system along the direction annihilate when either the SOC strength decreases or a sufficient tensile strain is applied, which is accompanied by the corresponding TPTs. Model calculations of the influence of local magnetic ordering in AFM were carried out by alternating Mn layers with Ge-doped layers and showed that the magnetic Weyl semimetal state in this system is reachable at a Ge concentration of approximately 40% without application of any external magnetic fields.

Exploring Structural Changes in Ge-Te Amorphous Films Through Small-Angle Neutron Scattering

The structure of the glassy GexTe1−x system, with x = 0.17, 0.21, 0.28, 0.30, and 0.45, is studied using the small-angle neutron scattering (SANS) technique. The very-low-momentum-transfer region of the diffractogram exhibits distinct behaviour depending on the germanium content. A similar conclusion is drawn from the analysis of the first diffraction peaks observed at higher angles. This system exhibits three composition regions with distinct behaviours: a first zone of low Ge content (up to about 20–25 at.%), a third zone richer in Ge (from about 30 at.% and above), and a second transitional zone between them. These changes are reflected in the parameters that govern Porod’s region, as well as in the region where the first diffraction peaks appear, corroborating previous observations made using other experimental and simulation techniques. Our study provides experimental evidence that could open up new possibilities for conducting simulations using neutron data. The results presented here show that increasing Ge content leads to a strengthening of the intermediate-range order at the expense of a weakening of the short-range order.

Piezo Electric Properties of Epitaxial SiGe

Strain sensors are highly demanded in industrial fields such as for precise torque control of electrical motors as well as for manipulators of industrial robots to handle soft materials to recognize the state of grabbed objects(1,2). Polycrystalline-Si based membrane sensors have great potential for downscaled and monolithic integration because their small occupying area enables high density arrays with a relatively large physical change for high sensitivity. However, by downscaling, fluctuations of the device properties, due to variation of polycrystalline grain size, become more pronounced, which strongly reduces the sensing reliability of the devices. This fluctuation could be improved by switching from polycrystalline to single crystal material. In last three decades, polycrystalline Si has been widely used as an effective material for highly sensitive strain sensors. In this study, we evaluate piezo resistivity of epitaxial SiGe to assess its potential and feasibility for strain sensor applications.The piezo resistivity of epitaxial SiGe layers is investigated based on using the gauge factor (GF). 100 nm-thick, B-doped SiGe with 10, 20 and 30% Ge content is pseudomorphically grown using reduced pressure chemical vapor deposition on n-type Si(001). B concentrations are varied from ~1×1017 to ~1×1019cm-3 verified by SIMS measurements. The deposited SiGe is patterned by photolithography and dry etching to form a 16µm wide and 300µm long stripe as schematically shown in Fig. 1 (a). Afterwards the SiGe is passivated by 200nm thick SiO2 and windows for metal contact pads are opened. In order to ensure ohmic contact for the metal contact pads a layer stack consisting of Al/~30nm-thick Ni/Ni silicide/~50nm-thick ~1×1019cm-3 B-doped Si was deposited onto the SiGe layer as schematically shown in Fig. 1 (b). Then, the substrate is thinned down to 200µm and diced to 2×2cm2 square. The test structure is located at the center of the diced wafer. In order to prevent unintended relaxation of the deposited SiGe layer, temperatures for following post-epitaxy processes are limited to below 550°C.In order to measure the piezo resistivity, the resistance is determined using four-terminal measurement with bending the sample by four-point bending method as shown in Fig. 2(3). By the wafer bending, uniaxial compressive strain along the 300µm direction is externally applied. The GF is estimated by slope of relative resistivity as function of induced strain.In Fig. 3, GFs of the SiGe as function of resistivity with 10, 20 and 30% Ge content are summarized. For this experiment, SiGe growth is performed at 600°C for all samples. In the case of higher resistivity, (i.e. sample with lower B concentration), higher GF is observed. Within the same resistivity, slightly higher GF is obtained for the SiGe with higher Ge content. A possible interpretation would be, the GF is related to hole mobility. The hole mobility enhancement is expected by increased Ge content in the SiGe and externally introduced additional uniaxial compressive strain along current flow direction(4). In the case of higher carrier concentration, the hole mobility enhancement is less pronounced due to scattering. However, further investigation is required to understand the mechanism behind.Next, in order to discuss influence of the SiGe growth conditions on the GF, GF of Si0.8Ge0.2 grown different growth temperature is compared. Resistivity of all samples is 6×10-1Ωcm. In the parallel experiment, no plastic strain relaxations of the SiGe are confirmed for the process conditions used for this experiment. It seems even though Ge concentration, thickness and carrier concentrations are the same, electrical property of the deposited SiGe is influenced by changing the growth temperature.In order to investigate a possible reason of the influence of the SiGe growth condition on the GF, C-V characteristics of SiGe are evaluated by fabricating MOS structures. In order to reduce interface state density, a 10 nm thick Si cap layer is deposited on the SiGe layers to prevent Ge oxide formation at the oxide Si interface. The evaluation of electrical interface and bulk parameters by means of simultaneously measured high- and low frequency MOS C-V characteristics in non-steady state non-equilibrium indicate that lower density of recombination-generation centers are existing for the SiGe grown at lower temperature. Therefore, higher crystal quality is confirmed for the Si0.8Ge0.2 layer grown at lower temperature.These results shown here gives prospect for tuning of SiGe based piezo resistivity sensors.References(1) H. Liu et al., Nanomachines 8 10, 304 (2017)(2) M. Amjadi et al., Adv. Funct. Mater. 26 (11), 1678 (2016)(3) N. Inomata et al., Sens. Act. A, 346 16 113823 (2022)(4) M.V. Fischetti et al. J. Appl. Phys. 80, 2234 (1996) Figure 1

Structure and Electronic Properties of the A‐center in Si1−xGex Alloys: Insight from the Heyd–Scuseria–Ernzerhof Hybrid Functional Calculations

This study investigates the structure and electronic properties of the A‐center in Si1−xGex alloys (x = 0, 0.25, 0.50, 0.75, and 1), using the Heyd–Scuseria–Ernzerhof hybrid functional. It is found that the most stable structures form SiOSi bonds, with the other two atoms surrounding the A‐center being Ge atoms, which form a long bond between them. The behavior of the O atoms is significantly influenced by the Ge content. As it increases, the position of the O atom shifts relative to the surrounding atoms, thereby affecting the bond lengths and angles. The formation energy of the A‐center first decreases with increasing Ge content up to 0.75, which enhances the defect production; however, then it decreases from 0.75 to 1, thus suppressing defect production. The calculations are consistent with the experimental data, showing that the distance of the defect level from the conduction band minimum increases with Ge content, supporting the observed enthalpy changes in electron ionization.

Performance evaluation of polycrystalline Si1−xGex thin-film transistors fabricated by continuous-wave laser lateral crystallization on glass substrates

This study was aimed at elucidating the performance of continuous-wave laser lateral-crystallized (CLC) polycrystalline Si1−xGex (poly-Si1−xGex) thin-film transistors (TFTs). The transfer characteristics of the n-ch CLC poly-Si1−xGex TFTs (x = 0, 0.05, 0.1, and 0.3) exhibited a positive shift in the threshold voltage (Vth) with increasing Ge content. Furthermore, the off-current in the p-ch CLC poly-Si0.9Ge0.1 TFTs decreased with decreasing film thickness. These properties of the CLC poly-Si1−xGex TFTs can be attributed to the generation of acceptors and increment of gate SiO2/poly-Si1−xGex interface charge state with increasing Ge content. The generation of acceptors was also supported by Hall effect measurements. In addition, the thermal stability of acceptors up to 700 °C was elucidated through Hall effect measurements and TFT performance evaluations. Furthermore, we examined the origins of these acceptors. This experiment highlighted the sensitivity of Si1−xGex to Ge incorporation, even in small amounts.

Performance improvement of SOI Tunnel-FET using pure boron and Ge pocket layer

This article highlights the results of a source pocket-engineered heterojunction pure-boron SOI Tunnel-FET (SP-PB-TFET) for low-power applications. To achieve improved performance, a novel pure-boron silicon TFET structure is considered with Silicon–Germanium source, Germanium pocket. Based on experimental data, the on-state current of a SiGe source TFET increases with increasing Ge content in SiGe. Nevertheless, the off-state leakage current increases with the Ge content of SiGe. To mitigate the problem somewhat, a Ge-pocket could be incorporated into the source near the tunneling junction. The final results provide a high current ratio (Ion/Ioff) of 1011 and a steep subthreshold swing (SS) of 18 mV/Decade at a very low supply voltage of 0.7 V. Moreover, SP-PB-TFET is suitable for high-frequency appliances due to its high cut-off frequency. This work also addresses the impact of temperature analysis and interfacial traps on device performance. The proposed SP-PB-TFET provides excellent DC and analog performance, making it suitable for low-power, high-frequency applications.

Morphology and properties of Mg2Si phase modified by Ge in Mg-Si alloys

The modification effects of Ge on Mg2Si phase in a Mg-2.5Si alloy were studied by computational simulation and experimental investigation. Based on first-principles structural prediction and electronic structure calculation, Mg2(SixGe1-x) phases were structurally stable and had sufficient hardness and inherent toughness as a reinforcement phase. With the increase of Ge content, due to the preferential adsorption of Ge atoms on the {100} planes of Mg2Si crystal, the morphology of primary Mg2Si crystal changed from equilateral-dendrite to polygonal, and finally to quadrilateral. In Mg-2.5Si-0.5Ge alloy, Ge was almost completely dissolved in the Mg2Si phase, but a small amount of dispersed solute segregation with a size of 10–20 nm can be observed. In Mg-2.5Si-1Ge alloy, many Mg2Ge precipitates with a small amount of Si dissolved having a size of 20–50 nm and a lattice constant a of 0.644 nm were uniformly distributed in primary Mg2Si, and only one orientation relationship (OR) in form of [001]Mg2Ge || [001]Mg2Si, (001) Mg2Ge || (001)Mg2Si with a tiny rotational angle of 0.39° was found. The stiffness and hardness of Mg2Si phase decreased with the increase of Ge content. Despite Mg2(SixGe1-x) crystal models only considering the solid solution of Ge and neglecting segregation and precipitation, the theoretical predictions of mechanical properties remained consistent with experimental results. This agreement was primarily due to the unique OR between Mg2Ge precipitates and Mg2Si phase.

Predictive and prospective calibrated TCAD to improve device performances in sub-20 nm gate length p-FinFETs

In this paper we present an extended analysis of thsse impact of SiGe p-epi source/drain engineering on sub-20 nm gate length p-FinFETs performance for the N7 technology node. Different Ge concentrations and profiles (graded versus non-graded) are evaluated making use of properly calibrated drift-diffusion TCAD simulations. Calibration of simulations is based on advanced metrology and on Monte-Carlo simulations such that the resulting simulated ID-VG (in LIN and SAT regimes) matches the one measured on device. The calibrated TCAD simulator is then used to understand the limited performances of the device and to propose new source/drain epi architectures with graded and increased Ge content. A new p-FinFET design is fabricated and tested, confirming a boost in ON-current and a reduction of the parasitic resistance. Prospective TCAD work is also presented suggesting possible future improvements on p-epi source/drain and on local interconnect contacts.

Crystal growth, scintillation properties and silicon-germanium ratio concentration optimization of BGSO: An excellent scintillator for dual-readout calorimeter

Bismuth silicate-germanate (Bi4Ge3xSi3(1-x)O12) crystals are successfully grown with the modified Bridgman technique. The X-ray diffraction, transmittance spectra, radioluminescence spectra and scintillation properties of these crystals are investigated at different ratios of Ge and Si. Furthermore, the XEL peaks of BGSO crystals exhibit a red-shift with the increase of Ge content. Meanwhile, the light yield and energy resolution of crystals represent obviously variation with changing of Ge and Si contents in the crystal. Density-functional theory (DFT) calculations were performed for energy band structure and geometry optimizations of Bi4Ge2.4Si0.6O12 crystal. The calculated energy band of BGSO crystal is 3.957 eV, which is different from that of BSO and BGO crystals. The results of DOS and PDOS calculated by CASTEP package reveal that Si/Ge–O and Bi–O interactions play a critical role in the band gap of BGSO crystal.

Expansion of chromatic color range and improvement of mechanical properties on Cu–Ge supersaturated solid solution alloys

The Cu–Ge solid solution alloys have a limited color range and relatively low strength due to its limitation of Ge solubility for a solid solution α-Cu phase at room temperature. To extend chromatic color range and to improve mechanical properties of Cu–Ge solid solution alloys, the Cu–Ge alloys with relatively higher Ge content than solubility limit on equilibrium state were fabricated by induction casting. The as-cast Cu–Ge alloys with 7–10 at.%Ge exhibited dual-phase structure composed of α-Cu and ζ-Cu17Ge3 phases with dendritic structure. By annealing at 700 °C for various times and followed quenching processing, the alloys successfully transformed into the supersaturated α-Cu single-phase structure. To confirm the color difference between the supersaturated single α-phase alloys with a high Ge content and the as-cast single α-phase alloys with low Ge content, the reflectivity analysis, CIE L*a*b* color space system, and color difference indicator were used. As a result, it was confirmed that there was a distinct color difference between supersaturated single α-phase alloys and as-cast single α-phase alloys, and the reflectivity and color difference of the alloys significantly depended on Ge content. Moreover, the Vickers hardness of as-cast and solution treated single α-phase alloys highly improved with an increase of Ge content. The influence of Ge content on phase formation, chromaticity and mechanical properties of solid solution Cu–Ge alloys was systematically discussed.

Influence of Ge-doping on the collinear and non-collinear antiferromagnetic phases of Mn[formula omitted]Si[formula omitted] alloy

Effect of Ge-doping at the non-magnetic site (Si-site) of the Mn-based binary alloy Mn5Si3 has been explored through temperature-dependent x-ray diffraction, dc-magnetic, and electrical transport measurements. All the doped alloys show D88 type hexagonal structure with space group P63/mcm at room temperature and undergoes two structural distortions, hexagonal (P63/mcm) → orthorhombic (Ccmm) → orthorhombic (Cc2m), on cooling. The magnetic characters of these orthorhombic (Cc2m), orthorhombic (Ccmm), and hexagonal (P63/mcm) phases are non-collinear antiferromagnetic (AFM1), collinear antiferromagnetic (AFM2), and paramagnetic (PM), respectively. Doping of Ge results in a significant increase in the AFM1 to AFM2 transition temperature (TN1). However, the AFM2 to PM transition point remains unchanged. In addition, a reasonable increase in the critical field values of the AFM1 to AFM2 transition via another non-collinear antiferromagnetic phase (AFM1′) with increasing Ge concentration has been observed, indicating the strengthening of AFM1 and AFM1′ phases over the AFM2 phase. Such behaviors make the observation of unusual magnetic properties of undoped Mn5Si3 alloys, like inverted hysteresis loop (IHL) and thermomagnetic irreversibility (TI), more evident for these Ge-doped alloys. Further, this study unfolds the presence of conventional and inverse magnetocaloric effect and they found to decrease with Ge doping. An interesting interplay for positive and negative magnetoresistance has also been observed in all the studied alloys.

Evolution of Mn1-xGexBi2Te4 Electronic Structure under Variation of Ge Content.

One of the approaches to manipulate MnBi2Te4 properties is the magnetic dilution, which inevitably affects the interplay of magnetism and band topology in the system. In this work, we carried out angle-resolved photoemission spectroscopy (ARPES) measurements and density functional theory (DFT) calculations for analysing changes in the electronic structure of Mn1-xGexBi2Te4 that occur under parameter x variation. We consider two ways of Mn/Ge substitution: (i) bulk doping of the whole system; (ii) surface doping of the first septuple layer. For the case (i), the experimental results reveal a decrease in the value of the bulk band gap, which should be reversed by an increase when the Ge concentration reaches a certain value. Ab-initio calculations show that at Ge concentrations above 50%, there is an absence of the bulk band inversion of the Te pz and Bi pz contributions at the Γ-point with significant spatial redistribution of the states at the band gap edges into the bulk, suggesting topological phase transition in the system. For case (ii) of the vertical heterostructure Mn1-xGexBi2Te4/MnBi2Te4, it was shown that an increase of Ge concentration in the first septuple layer leads to effective modulation of the Dirac gap in the absence of significant topological surface states of spatial redistribution. The results obtained indicate that surface doping compares favorably compared to bulk doping as a method for the Dirac gap value modulation.

Computational design of a reliable intermediate-band photovoltaic absorber based on diamond.

To reduce the wide bandgap of diamond and expand its applications in the photovoltaic fields, a diamond-based intermediate-band (IB) material C-Ge-V alloy was designed by first-principles calculations. By replacing some C with Ge and V in the diamond, the wide bandgap of the diamond can be reduced sharply and a reliable IB, which is mainly formed by the d states of V, can be formed in the bandgap. With the increase of Ge content, the total bandgap of the C-Ge-V alloy will be reduced and close to the optimal value of an IB material. At a relatively low atomic concentration of Ge (below 6.25%), the IB formed in the bandgap is partially filled and varies little with the concentration of Ge. When further increasing the content of Ge, the IB moves close to the conduction band and the electron filling in the IB increases. The 18.75% content of Ge might be the limitation to form an IB material, and the optimal content of Ge should be between 12.5% and 18.75%. Compared with the content of Ge, the distribution of Ge has a minor effect on the band structure of the material. The C-Ge-V alloy shows strong absorption for the sub-bandgap energy photons, and the absorption band generates a red-shift with the increase of Ge. This work will further expand the applications of diamond and be helpful to develop an appropriate IB material.

Transformation of carrier recombination mechanism as increasing the Germanium content in Cu2ZnGexSn1-xS4 single crystal prepared by molten salt method

Return to the physics origin of Cu2ZnSnS4 type (CZTS-type, include CZGS, CZGTS, CZTSSe, etc.) material system, studying the influence of replacement elements on the optoelectronic properties by preparing high-quality single crystal materials to clarify the relationship between the key defect states of materials and carrier dynamics is the only way which must be passed to find efficient paths to improve the existing performance of CZTS-type optoelectronic devices. Herein, the optical behavior of high-quality Cu2ZnGexSn1-xS4 (CZGTS) single crystal prepared by the molten salt method and its relationship with Ge content were systematically studied using a photoluminescence (PL) and absorption tests at room temperature. Combined with the simple electrical tests, the transformation of carrier recombination mechanism as increasing the Germanium content in CZGTS single crystal before and after phase transition were reported for the first time. The transmission electron microscopy images, X-ray diffraction spectra and Raman scattering spectra of CZGTS were adopted to reveal the evolution mechanism of single crystal growth and phase transition caused by the change of Ge composition. The results show that the tunable blue-shift of PL peak emerges with the increase of Ge content and the excitation power dependence has a saturation phenomenon in the CZGTS single crystal particles. In consideration of the optical bandgap, PL peak position, PL intensity, carrier lifetime and the macroscopic resistivity, it is confirmed that the intrinsic PL behavior could be effectively tailored by different Ge amounts. Compared with the recombination PL of interband carrier (Ep > Eg) in Cu2ZnSnS4, the band tailed carriers (Ep < Eg) dominated by defect states would play a powerful role in CZGTS single crystal. Our work provides a strategy for tailoring the bandgap of CZGTS materials and a new perspective for understanding the influence of defect states on carrier dynamics.

Ge-Doped Optical Fibers for Passive and Active Radiation Detection Modes

Silica-based optical fibers made by Modified Chemical Vapor Deposition (MCVD) technique have been doped with different concentrations of germanium (Ge). After characterization of the thermoluminescence (TL) process in each of these fibers, their real-time responses were studied by radioluminescence (RL) under X-rays. First, the same counterintuitive trend was observed for the intensity of the two phenomena as a function of the Ge content, namely the decrease in TL and RL signals with increasing Ge content. This behavior was explained by the existence of thermally disconnected traps. Then, the RL response as a function of the dose-rate of the fiber doped with 1% Ge was judiciously chosen and investigated in detail. The results show that up to Total Ionizing Dose (TID) of 1.9 kGy(SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ), this response is not only insensitive to the accumulated dose effect but also exhibits an afterglow decay at the end of the radiation much faster than that of a Ce-doped fiber, a very useful feature where irradiations are repetitive as in the medical field of flash-therapy. In addition to the medical field where the Ge-doped fiber seems to be quite suitable, slightly larger core diameters would also allow this same fiber to meet the challenge of high sensitivity in the environmental radiation monitoring around nuclear power plants or radioactive waste storage areas.

THEORETICALLY PREDICTED DEVIATION IN PHYSICAL PROPERTIES OF GE-BI-S CHALCOGENIDE ALLOYS WITH COMPOSITIONAL VARIATIONS

Chalcogenide glasses (ChGs) semiconductors have several useful properties, especially in their technical applications. The present work explains the compositional dependence of many physical properties of GexBi5S95-x (x = 0, 10, 20, 30, 35 and 45 at. %). Increasing Ge content reduces the fraction of floppy modes, the lone pair electrons, the stoichiometric deviation, and the heat of atomization, while the average coordination number 〈r〉, constraints, density, and molar volume increased, indicating the alloys have moved from floppy to rigid mode. The average overall bond energy, electronegativity difference, band gap energy, and glass transition temperature were estimated by analyzing the bond energies and its distribution based on the bond ordered network model (CONM). It has been found that all these parameters increase with Ge ≤ 30 at. % and decrease with the further increase of Ge content. This behavior can be explained in terms of the network chemical percolation threshold proposed by Tanaka. This threshold represents a topological phase transition from a two-dimensional structure at r˂2.67 to a three-dimensional structure at r≥2.67. The incorporation of Ge into the glassy Bi-S system yields interesting physical properties such as threshold and phase transition, confirming this composition's suitability for optical storage media.

Vertical alignment control of self-ordered multilayered Ge nanodots on SiGe

Self-ordered multilayered Ge nanodots with SiGe spacers on a Si0.4Ge0.6 virtual substrate are fabricated using reduced-pressure chemical vapor deposition, and the mechanism of vertical ordering is investigated. The process conditions of Ge and SiGe layer deposition are H2-GeH4 at 550 °C and H2-SiH4-GeH4 at 500 °C–550 °C, respectively. By depositing the SiGe at 550 °C or increasing Ge content, the SiGe surface becomes smooth, resulting in vertically aligned Ge nanodots to reduce strain energy. Ge nanodots prefer to grow on the nanodot where the SiGe is relatively tensile strained due to the buried Ge nanodot underneath. By depositing at 500 °C and lowering Ge content, checkerboard-like surface forms, and the following Ge nanodots grow at staggered positions to reduce surface energy. The Ge nanodots are laterally aligned along the elastically soft 〈100〉 direction without pre-structuring resulting from the strain distribution.

Fragile-to-strong transition and the conversion of structural motifs in Ge-Se glass-forming liquids

Fragile-to-strong (F-S) transition in chalcogenide glass-forming liquids (GFLs) has attracted attention due to its significance in improving the performance of phase-change materials. The present work reports the general characteristics of the F-S transition in chalcogenide GexSe1-x system (0.2<x<0.33). In this composition range, the transition strength parameter f is basically constant and about 2.4. The reduced transition temperature Tf-s/Tg decreases with decreasing the liquid covalency (increasing Ge content). The structural conversion of corner-shared tetrahedra to edge-shared tetrahedra in Ge-Se supercooled liquids has been investigated. This structural conversion controls the liquid dynamics in the low-temperature region near Tg, where the liquid exhibits strong behavior. The rigid constraint is broken and the network becomes floppy in the high-temperature region, which makes the liquid show fragile behavior. These findings are expected to provide a method to tune the Tf-s value of chalcogenide GFLs and a possible structural scenario for the F-S transition in them.

Effect of Ge doping on the magnetic properties of Fe-6.5Si soft magnetic composites

In this work, the effect of Ge content on the soft magnetic properties and microstructure of FeSiGe soft magnetic powder cores (SMPCs) was systematically investigated. The results show that the addition of Ge is beneficial to increase the electrical resistivity of Fe93.5-xSi6.5Gex SMPCs, and the coercivity (Hc) shows a trend of decreasing and then increasing with the increase of Ge content. When the content of Ge is 2 wt%, the SMPCs exhibit the best magnetic properties with stable effective permeability of 78.4 up to 1 MHz, low core loss of 589.5 mW/cm3 at a maximum magnetic induction of 0.1 T and frequency of 50 kHz. By doping with Ge, the micro-vortex dots in the magnetic domain structure are reduced and the domain walls move more easily with the applied field, and the magnetic properties are improved.

A study of the structural, optical, and ferroelectric characteristics of Pb-Ge-Te nanocrystalline alloys as potential candidates for memory devices and Near-Infrared (NIR) applications

Pb50-xGexTe50 (x = 15, 20, 25, 30 at. %) nanocrystalline bulk alloys were prepared using solid-state direct reaction. X-ray diffraction and high-resolution transmission electron microscopy (HR-TEM) analysis of the reference structure (Ge = 15 at.%) revealed a slightly distorted cubic structure, with a lattice parameter of 6.43 Å and an inter-axis unit cell angle of 88.69°. Atomic force images' analysis and histograms displayed a homogenous particle size distribution in the nanoscale for all samples. Density measurements showed a gradual decrease from 7.89 to 6.98 g/cm3 with increasing Ge content in agreement with the calculated values. The polarization–field hysteresis behavior verifies the ferroelectric activity of the prepared alloys, suggesting them as potential candidates for non-volatile ferroelectric memory devices (NVFRAMs) applications. Optical properties analyzed using diffuse reflectance measurements exhibited direct transitions with a bandgap decreasing from 1.57 to 1.35 eV with increasing Ge content matching the near-infrared spectrum (NIR) perfectly.