Search Results (687)

Doping provides an effective means to tailor the chemical properties of clusters and construct novel functional materials. However, the specific effects of rare-earth doping on the structural evolution and electronic properties of semiconductor clusters remain unclear. To address this, we systematically investigated the structures, growth patterns, electronic properties, and spectroscopic characteristics of Ge_n⁻ and LaGe_n^0/− clusters (n = 10–20) using the ABCluster global search method combined with the mPW2PLYP double-hybrid density functional. Notably, the global minimum (GM) structures of Ge_n⁻ (n = 12–20), confirmed based on calculated energies and measured photoelectron spectroscopy data, differ from previously reported structures. Starting from n = 12, the GM structure of the Ge_n⁻ cluster can be considered as formed by attaching an additional Ge_(n–9) or Ge_(n–10) subcluster to a capped tetragonal antiprism Ge₉ (or dicapped tetragonal antiprism Ge₁₀) subunit. The evolution pattern of LaGe_n (n = 10–19) clusters can be viewed as substitutional structures, in which a La atom substitutes one Ge atom in the Ge_(n+1)⁻ cluster. At n = 20, a cage-like structure is formed. For LaGe_n⁻ (n = 10–19), when n = 10–12 and 18, the structures are linked configurations, where the La atom connects two Ge subclusters. For the remaining clusters, although their global minimum structures tend toward linked configurations, they are fundamentally substitutional in nature. The GM structure of LaGe₂₀⁻ is an encapsulated configuration, with the La atom encapsulated at the center of the Ge cage. The average binding energies, relative stabilities, and HOMO–LUMO energy gaps of the clusters were evaluated. The photoelectron spectra of LaGe_n⁻ (n = 10–20) and the UV–vis absorption spectrum of the LaGe₂₀⁻ cluster were simulated. The results demonstrate that the LaGe₂₀⁻ superatom cluster with high Ih symmetry exhibits favorable optical properties, along with excellent chemical and thermodynamic stability, suggesting its potential as a promising building block for further exploration in optoelectronic-related applications. Full article

Terahertz (THz) radiation generated through ultrafast transient photocurrent mechanisms has become a cornerstone of modern THz photonics, enabling broadband coherent emission with sub-picosecond temporal resolution. This review provides a comprehensive and mechanism-driven analysis of THz pulse generation via photo-Dember diffusion currents, surface depletion field acceleration, and biased photoconductive antenna architectures. We present a comprehensive comparative analysis of wide- and low-bandgap material platforms, including III–V, II–VI, and group IV semiconductors, as well as two-dimensional materials, topological insulators, and Weyl semimetals, highlighting how their intrinsic properties, such as band structure, carrier mobility, recombination dynamics, doping, and dielectric response, govern their THz emission efficiency, bandwidth, and spectral tunability. Special emphasis is placed on germanium (Ge), which has re-emerged as a highly promising THz source material owing to its high carrier mobility, long diffusion lengths, strain-tunable band structure, and CMOS compatibility. We highlight the roles of doping, strain-induced direct transitions, and several fabrication techniques in controlling the nonlinear photoexcited charge-carrier dynamics in Ge, thereby unlocking enhanced broadband THz performance. Finally, we explore the emerging application prospects of THz radiation, ranging from non-invasive security screening to biochemical sensing and archeological preservation. By bridging fundamental material science with scalable device architectures, this review outlines current challenges, highlights evolving opportunities in novel materials, and charts future directions towards integrated THz technologies. Full article

Li n⁺ and In p⁺ diffusion contacts were fabricated on p-type 12N high-purity germanium (HPGe) single crystals by vacuum evaporation of thin-film sources followed by solid-state thermal diffusion. The effects of diffusion temperature on the near-surface structure, morphology, impurity distribution, and device response were systematically investigated. XRD and Raman analyses show that Li diffusion at 100–300 °C and In diffusion at 600–800 °C preserve the bulk Ge crystal structure, whereas higher diffusion temperatures induce surface roughening, near-surface disordering, and interfacial reactions. SIMS depth profiles combined with diffusion simulations confirm effective inward diffusion of both Li and In, with low-concentration tailing that is consistent with defect-assisted diffusion or interfacial trapping. The sample diffused with Li at 200 °C exhibits the lowest dark current, 8.07 × 10⁻⁸ A at −10 V. The final HPGe device with Li/In diffusion contacts shows a stable synchrotron X-ray photoconductive response, and the net response current increases from 4.48 × 10⁻⁷ to 1.15 × 10⁻⁶ A as the incident photon flux increases. These results demonstrate that low-leakage HPGe diffusion contacts require a balance between diffusion-layer formation and near-surface/interface stability, rather than a simple increase in thermal budget. Full article

This paper presents a two-dimensional magneto-photo-thermoelastic model for a fiber-reinforced anisotropic semiconductor half-space subjected to optical excitation and a variable gravity field. The formulation is developed within the framework of generalized photo-thermoelasticity by considering the coupled interactions among thermal, elastic, carrier-density, electromagnetic, and gravity-induced effects. The constitutive equations of a fiber-reinforced anisotropic medium are employed, while the influences of the magnetic field and gravity are incorporated into the governing equations. A suitable nondimensionalization procedure is introduced, and the resulting coupled system is solved analytically using the normal mode technique and eigenvalue approach. Numerical results are obtained for the temperature, carrier density, displacement components, and stress distributions. The influence of the gravity parameter on the physical fields is investigated in detail. The results indicate that gravity significantly affects the mechanical and stress responses, whereas its effect on the thermal and carrier-density fields is comparatively less pronounced. A comparative study between silicon and germanium semiconductors is also carried out, revealing noticeable differences in the amplitudes and attenuation behavior of the coupled fields due to variations in material properties. The present study provides useful insights into coupled multiphysical interactions in semiconductor structures and may be relevant to applications in optoelectronic devices, photonic systems, smart composite materials, and aerospace technologies. Full article

This study addresses the need for dark-current control and stable current response in planar high-purity germanium (HPGe) detectors for low-energy X-ray detection. A device fabrication strategy based on the coupled optimization of near-surface treatment, N/P junction formation, and guard-ring electrode design is proposed. Unlike previous studies that mainly focused on contact-layer fabrication, segmented electrode structures, low-noise readout, or response simulation, this work investigates low-damage near-surface construction, N-type and P-type contact-layer formation, and edge-related leakage-current regulation as an interconnected processing route. The relationship among the near-surface state, junction quality, electrode configuration, and edge-related leakage current is emphasized. Chemical mechanical polishing (CMP) reduced the surface roughness Sa of the HPGe crystal to 6.68 nm, providing a low-damage near-surface foundation for subsequent junction fabrication. On this basis, the optimized Li thermal diffusion process, namely 0.5 Å s⁻¹, 325 °C, and 5 min, formed an N-type contact layer with preserved lattice ordering and favorable electrical properties. B ion implantation combined with rapid thermal processing (RTP) achieved acceptor activation and implantation-damage recovery, and the condition with Rp = 198.1 nm showed relatively better structural recovery and electrical characteristics. After introducing the guard-ring electrode, the dark current of the device at −20 V decreased from 6.5 × 10⁻⁹ A to 2.03 × 10⁻⁹ A, and a stable switching current response was obtained under 12 keV monochromatic synchrotron X-ray irradiation. Geant4 simulations were further used as an auxiliary analysis to evaluate the effect of the guard-ring structure on the simulated response spectra and full-energy peak efficiency (FEPE) for low-energy X-rays. Overall, this study provides experimental evidence for process optimization of planar HPGe detectors with low dark current and stable low-energy current response. Full article

Organogermanium compounds, particularly carboxyethyl germanium sesquioxide (Ge-132), have been studied for decades because of their diverse biological effects, especially their antioxidant properties. However, the available literature remains fragmented and highly heterogeneous, which limits mechanistic interpretation. Although antiglycative activity has been described at the biochemical level, the downstream transcriptional effects of Ge-132 under glycative stress remain poorly characterized. Here, we combined an evidence-mapping analysis with targeted molecular analysis in a standardized cellular model to examine whether the antiglycative effects of Ge-132 are accompanied by coordinated transcriptional responses. The mapping guided selection of markers associated with glycative stress, including carbonyl detoxification, redox adaptation, autophagy, lysosomal function, and inflammatory signaling. Gene expression analysis revealed limited and selective transcriptional modulation under glycative stress conditions. In parallel, protein analysis showed reduced intracellular accumulation of advanced glycation end products (AGEs) in Ge-132–treated. These findings suggest that reduction of glycative damage can occur without proportional transcriptional activation of stress-response pathways under the conditions tested. However, alternative explanations, such as model constraints, acute exposure duration, or limited gene panel sensitivity, cannot be excluded. Full article

Silica-based optical fibers suffer radiation-induced attenuation (RIA) in radiation-intensive environments, severely reducing their lifespan. We propose a kinetic model based on the evolution of multiple color centers to accurately simulate defect density and quantitatively characterize RIA. The irradiation experiments were conducted using a Co-60 gamma-ray source at a dose rate of 1.25 Gy/s and a controlled temperature of 10 ± 2 °C, with measurements performed at 1310 nm and 1550 nm wavelengths. The model was experimentally validated using fluorine–germanium co-doped fibers. Fitting results demonstrate high accuracy, with a coefficient of determination (R²) > 0.999, normalized root mean square error (NRMSE) < 0.57%, and mean absolute error (MAE) < 0.74 dB/km. Furthermore, it successfully decouples complex macroscopic RIA signals into distinct transient and steady-state defect pools. This phenomenological decoupling enables band-dependent damage analysis and serves as a baseline for evaluating steady-state degradation of F-Ge co-doped fibers under constant irradiation. Full article

Beach sediments may contain natural radionuclides, fallout-derived radionuclides, naturally occurring radioactive material (NORM) or technologically enhanced naturally occurring radioactive material (TENORM), but their radiological significance depends on sediment dynamics and exposure scenario as much as on bulk activity concentration. RadSed-INT is introduced as a tiered field–laboratory protocol for assessing radioactivity in dynamic beach sediments. The protocol links in situ gamma screening, statistically designed transects, primary/confirmatory A/B sampling, high-purity germanium (HPGe) gamma-ray spectrometry, grain-size and heavy-mineral partitioning, vertical mini-core radiostratigraphy, and triggered dust, radon/thoron and ingestion pathway modules. Its central requirement is radiometric mass closure between directly measured bulk activity and the mass-weighted reconstruction from sediment fractions. External and internal doses are evaluated only for explicitly defined material status, exposure pathways, occupancy assumptions and regulatory domains; construction-material and NORM indices are retained as context-specific comparators, not universal beach-sediment limits. RadSed-INT defines escalation triggers from reconnaissance to confirmatory spatial, grain-size, vertical or aerosol investigations. This article is methodological and does not report new primary field data. Extended notation, a date-sensitive regulatory matrix, confounder checklists, implementation tables and a minimal worked example are included to support transparent and reproducible application of the core protocol logic. Full article

Germanium (Ge) is a high-tech critical metal typically hosted at trace levels in sphalerite, making its detection and characterization challenging in both primary ores and mine residues. This study presents a multi-scale analytical workflow combining laser-induced breakdown spectroscopy (LIBS), electron probe micro-analysis (EPMA), and multivariate statistics to detect, map and quantify Ge distribution in a representative Pb-Zn sample from the Les Malines deposit (France). µ-LIBS mapping enables rapid centimeter-scale screening at 15 µm resolution and identifies Ge-bearing domains over large areas, which are subsequently investigated at micrometer scale using EPMA chemical mapping and quantitative analyses. Results reveal a strong µm-scale heterogeneity of Ge distribution within sphalerite, with Ge systematically concentrated in an Fe-rich intermediate zonation associated with prismatic growth textures, while Cu/Cd/Ag are enriched in distinct collomorph domains. Multivariate statistical analyses (correlation matrices and PCA) confirm a strong geochemical structuring opposing an Fe/Ge association against a Cu/Cd/Ag pole. These findings demonstrate that Ge incorporation is controlled by localized growth conditions rather than bulk composition. The proposed workflow provides an efficient and scalable framework for exploration, enabling rapid targeting of critical metal enrichments and supporting their extension to multiple mineralization stages, Pb-Zn deposits, and other high-tech critical metals (HTCMs) such as Ga and In. Full article

To address the challenges of low germanium recovery and high reagent consumption during precipitation from strongly acidic solutions, this study developed a two-stage tannin process intensified by microfluidic mixing and systematically examined the synergistic effects of tannin dosage and pH on coordination chemistry. First-stage recovery rose from 45.23% to 91.28% as the tannin ratio increased from 5- to 15-fold, confirming that sufficient ligand promotes dense chelate formation. Optimising pH to 2.0–2.5 deprotonated tannin hydroxyls, enabling electrostatic–chelation synergy with Ge(OH)₃⁺ and yielding 79.88% recovery—a 20.28% improvement over pH 1.5. The staged second-stage process proved particularly effective: at pH 1.5, a “5-fold primary + 15-fold secondary” scheme achieved 92.04% total recovery with only 13.22-fold cumulative tannin, a 46.81% increase over the single-stage 5-fold treatment; at pH 2.5, a “5-fold + 10-fold” combination reached 95.44% recovery with just 8.67-fold reagent. Microfluidic processing refined particle size and intensified the Ge–O vibration at 864 cm⁻¹, indicating more stable coordination. Economic analysis reveals that efficiency plateaus beyond a 17-fold cumulative dosage, making staged addition the cost-effective choice. By harmonising staged coordination with enhanced mass transfer, this approach resolves the inherent conflict between precipitation depth and reagent overuse, delivering a sustainable strategy for germanium recovery. Full article

This article details the synthesis and structural characterization of a new metalloid germanium cluster 3 with bulky amide ligands. The cluster features a Ge₆ core stabilized by four -N(Si^tBuMe₂)₂ ligands and was obtained via reduction of the amido trichlorogermane 2 using potassium chips in toluene. Single-crystal X-ray diffraction analysis revealed that the Ge₆ core adopts a butterfly-shaped geometry with a Ge-Ge dumbbell unit, which contains two unsubstituted germanium atoms exhibiting prominent lone-pair characteristics. The Ge₆ core can also be classified as a nido cluster, with a cluster-bonding-electron count of 16, perfectly satisfying the 2n + 4 electron-counting rule. Combining the structural features of this nido cluster with the bond length distribution in the folded four-membered ring suggests that the Ge4 ring features a certain degree of electron delocalization. Additionally, two bis(amido)-substituted germylenes (4 and 6) were isolated and structurally characterized. They exhibit analogous structural features, with each germanium center adopting a two-coordinate V-shaped configuration, the Ge–N bond lengths being very similar, and the nitrogen atoms adopting a planar triangular geometry. Notably, compound 6, bearing bulkier -N(SiⁱPr₃)₂ substituents, exhibits a significantly larger N-Ge-N bond angle (120.58°) compared to the corresponding value of 113.54° observed for compound 4 with -N(Si^tBuMe₂)₂ substituents. This clearly demonstrates that the steric bulk of the substituents exerts a remarkable influence on the molecular geometry and σ-donor ability of the lone pairs on germanium centers. Full article

Critical metals such as gallium and germanium are strategic mineral resources widely used in advanced technology, including semiconductors and solar cells. These metals are recovered as by-products from the processing of Zn–Pb and bauxite ores. In China, the Sichuan–Yunnan–Guizhou (SYG) region is abundant in Zn–Pb and bauxite ore deposits, such as the Huize Zn–Pb–Ge deposit and the Wuchuan–Zheng’an–Daozhen (WZD) area Al–Ga deposit. Although previous studies have proposed models to explain the enrichment mechanisms of critical metals in this area, the metal sources of these deposits remain controversial. In this study, samples were collected from the Paleoproterozoic Kunyang Group to the Permian Emeishan basalts, and the metal sources of these deposits were traced by comparing the Pb isotopic ratios and Zn/Cd ratios of potential source rocks and deposits. The findings indicate: (1) The Pb isotopic compositions of most samples are relatively homogeneous, but certain differences exist among strata from different geological periods. (2) The metal sources of the Yunnan and Guizhou bauxite may both have been controlled by the underlying carbonate rocks, but the specific source horizons differ significantly between the two regions. (3) Based on the Pb isotopic compositions of regional strata and Zn–Pb deposits, it appears that the regional basement and sedimentary cover likely contributed significantly to the ore-forming metals, whereas the Emeishan basalts may have played a relatively minor role. However, due to the complex lithology and substantial thickness of the basement and cover strata in the SYG region, there may be issues of sampling inadequacy. Nonetheless, this study provides important foundational data and insights for tracing the metal sources of deposits in this region using Pb isotopes and Zn/Cd ratios. Full article

Radon (²²²Rn) is a noble, radioactive gas and tends to be accumulated in poorly ventilated enclosed spaces. Mainly due to its radioactive daughters and the α-particles emitted, ²²²Rn poses a risk of cancer and therefore its concentration in air and water should be kept under certain reference levels. Several methods have been developed to accurately measure ²²²Rn concentration in water, using α, β or γ counting. A well-established, but not the only, method involves γ-spectroscopy using a High-Purity Germanium (HPGe) detector to identify the ²²²Rn decay isotopes ²¹⁴Pb and ²¹⁴Bi, assuming they are in secular equilibrium with ²²²Rn. This technique requires costly, bulky equipment due to the HPGe’s operation at −196 °C and the need for substantial shielding. The present study introduces a more affordable and compact device, utilizing CdZnTe (CZT) crystals, which provide exceptional energy resolution in the 300 to 600 keV range, with nearly eight times the Full Width at Half Maximum (FWHM) of HPGe. Four stacked CZT detectors, each containing a 0.5 cm³ crystal, were compared with measurements from an HPGe detector. Water samples were collected from boreholes and taps in a region where radon concentration in water ranged from 10 to 900 Bq/L. The results are promising for samples around 100 Bq/L, considering the potential advancements of the device with larger CZT detectors. Additionally, the method has the potential for in situ use due to its handheld capability. Full article

Silicon–germanium (Si/SiGe) quantum dots represent a preeminent architecture for scalable quantum computing; however, their performance remains fundamentally constrained by environmental decoherence. This work presents a comparative simulation study of a two-qubit system in Si/SiGe, evaluating the fidelity of various noise modeling frameworks under realistic conditions, including $1/f$ charge noise and phonon-mediated relaxation. We benchmark the Lindblad Master Equation against the Bloch–Redfield Master Equation, the Semiclassical Stochastic Hamiltonian method and the Monte Carlo Wavefunction (Quantum Jumps). Our analysis reveals that while semiclassical models effectively capture pure dephasing ($T_2^{*}$) dynamics, they fail to account for energy relaxation ($T_1$) at cryogenic temperatures, erroneously driving the system toward a high-entropy maximally mixed state. We propose the Quantum Trajectories method to resolve this discrepancy by incorporating discrete dissipation events, providing a thermodynamically consistent semi-classical framework. To demonstrate the scalability of our approach, we extend the simulation to a 4-qubit register, showing that the Quantum Trajectories method remains numerically robust and thermodynamically consistent as the Hilbert space dimension increases. Furthermore, we perform a magnetic field optimization analysis, identifying an operational “sweet spot” within the 0.1–0.5 T range that optimally balances the trade-offs between relaxation and dephasing. Full article

Zinc germanium phosphide (ZnGeP₂) is an important nonlinear crystal for mid-infrared conversion, but its performance is limited by residual absorption and intrinsic impurity phases. In this study, polycrystalline ZnGeP₂ was synthesized by a modified two-temperature method, purified by inclined directional recrystallization for up to three cycles, and then grown into single crystals by the vertical Bridgman method. The resulting material was examined by shadow-projection imaging, transmission spectroscopy in the 650–2500 nm range, absorption measurements at 2.097 µm, laser-induced damage threshold (LIDT) testing, and powder X-ray diffraction. Repeated purification improved optical homogeneity and near-infrared transparency, while the absorption coefficient at 2.097 µm decreased from 0.45 to 0.30 cm⁻¹ after three purification cycles. Semi-quantitative PXRD analysis showed progressive suppression of intrinsic impurity phosphides, with phase purity increasing from 86.31% after the first cycle to 95.995% after the second and reaching 100% after the third within the detection limit of the method. However, the LIDT decreased with increasing purification number, indicating a trade-off between lower optical losses and damage resistance. These results demonstrate that inclined directional recrystallization is an effective pre-growth purification route for ZnGeP₂ and that the optimal number of purification cycles should be selected according to the intended application. Full article