Search Results (424)

Laser slicing has emerged as a promising low-kerf and low-damage technique for SiC wafer fabrication; however, its effects on the crystal integrity, near-surface modification, and charge-transport properties require further clarification. Here, a heavily N-doped 4° off-axis 4H-SiC wafer was sliced using an ultraviolet (UV) picosecond laser, and both laser-irradiated and laser-sliced surfaces were comprehensively characterized. X-ray diffraction and pole figure measurements confirmed that the 4H stacking sequence and macroscopic crystal orientation were preserved after slicing. Raman spectroscopy, including analysis of the folded transverse-optical and longitudinal-optical phonon–plasmon coupled modes, enabled dielectric function fitting and determination of the plasmon frequency, yielding a free-carrier concentration of ~3.1 × 10¹⁸ cm⁻³. Hall measurements provided consistent carrier density, mobility, and resistivity, demonstrating that the laser slicing process did not degrade bulk electrical properties. Multi-scale Atomic Force Microscopy (AFM), Angle-Resolved X-Ray Photoelectron Spectroscopy (ARXPS), Secondary Ion Mass Spectrometry (SIMS), and Transmission Electron Microscopy (TEM)/Selected Area Electron Diffraction (SAED) analyses revealed the formation of a near-surface thin amorphous/polycrystalline modified layer and an oxygen-rich region, with significantly increased roughness and thicker modified layers on the hilly regions of the sliced surface. These results indicate that UV laser slicing maintains the intrinsic crystalline and electrical properties of 4H-SiC while introducing localized nanoscale surface damage that must be minimized by optimizing the slicing parameters and the subsequent surface-finishing processes. Full article

With the discovery of amorphous oxide semiconductors, a new era of electronics opened. Indium gallium zinc oxide (IGZO) overcame the problems of amorphous and poly-silicon by reaching mobilities of ~10 cm²/Vs and demonstrating thin-film transistors (TFTs) are easy to manufacture on transparent and flexible substrates. However, mobilities over 30 cm²/Vs have been difficult to reach and other materials have been introduced. Recently, polycrystalline In₂O₃ has demonstrated breakthroughs in the field. In₂O₃ TFTs have attracted attention because of their high mobility of over 100 cm²/Vs, which has been achieved multiple times, and because of their use in scaled devices with channel lengths down to 10 nm for high integration in back-end-of-the-line (BEOL) applications and others. The present review focuses first on the material properties with the understanding of the bandgap value, the importance of the position of the charge neutrality level (CNL), the doping effect of various atoms (Zr, Ge, Mo, Ti, Sn, or H) on the carrier concentration, the optical properties, the effective mass, and the mobility. We introduce the effects of the non-parabolicity of the conduction band and how to assess them. We also introduce ways to evaluate the CNL position (usually at ~E_C + 0.4 eV). Then, we describe TFTs’ general properties and parameters, like the field effect mobility, the subthreshold swing, the measurements necessary to assess the TFT stability through positive and negative bias temperature stress, and the negative bias illumination stress (NBIS), to finally introduce In₂O₃ TFTs. Then, we will introduce vacuum and non-vacuum processes like spin-coating and liquid metal printing. We will introduce the various dopants and their applications, from mobility and crystal size improvements with H to NBIS improvements with lanthanides. We will also discuss the importance of device engineering, introducing how to choose the passivation layer, the source and drain, the gate insulator, the substrate, but also the possibility of advanced engineering by introducing the use of dual gate and 2 DEG devices on the mobility improvement. Finally, we will introduce the recent breakthroughs where In₂O₃ TFTs are integrated in neuromorphic applications and 3D integration. Full article

The present work systematically investigates the impact of multilayer architecture—specifically 5, 10, and 15 layers—on the structural, morphological, optical, and dielectric properties of zinc oxide (ZnO) thin films, aiming to tailor their characteristics for optoelectronic applications. The films were characterized using a comprehensive suite of techniques. X-ray diffraction (XRD) analysis of the 15-layer sample confirmed the formation of polycrystalline ZnO with a hexagonal wurtzite crystal structure, showing prominent (100), (002), and (101) diffraction peaks. Measurements indicated that the film thickness progressively increased from 43.81 nm for 5 layers to 80.68 nm for 15 layers. Concurrently, the surface roughness significantly decreased from 5.54 nm (5 layers) to 2.00 nm (15 layers) with increasing layer count, suggesting enhanced film quality and densification. Optical studies using ultraviolet–visible (UV-Vis) spectroscopy revealed an increase in absorbance and a corresponding decrease in transmittance in the UV-Vis spectrum as the film thickness increased. The calculated optical band gap showed a slight redshift, decreasing from 3.26 eV for the 5-layer film to 3.23 eV for the 15-layer film. Photoluminescence (PL) spectra exhibited characteristic near-band-edge UV emission, with the 5-layer film demonstrating the highest PL intensity. Furthermore, analysis of optical constants revealed that the refractive index, extinction coefficient, optical conductivity, and both the real and imaginary parts of the dielectric constant generally increased with an increasing number of layers, particularly in the visible region, while more nuanced and non-monotonic trends were observed in the UV range. These results underscore the significant influence of layer number on the physical properties of ZnO thin films, providing valuable insights for optimizing their performance in various optoelectronic devices. Full article

Ti-6Al-4V (TC4) alloy is widely used in aerospace and biomedical applications due to its excellent strength-to-weight ratio and corrosion resistance. Its plastic deformation behavior is strongly influenced by its microstructural characteristics, particularly grain size. In this study, a crystal plasticity model incorporating a Hall–Petch relationship was developed to simulate the plastic deformation of TC4, with explicit consideration of the effect of grain size on slip resistance. The model employs a thermally activated flow rule to describe the kinetics of slip systems, enabling accurate prediction of flow stress and strain hardening across different microstructural conditions. The model is calibrated and validated using experimental stress–strain data from uniaxial tensile tests on specimens with varying grain sizes. Simulation results demonstrate that the model successfully captures the grain-size-strengthening effect and predicts the corresponding evolution of local strain heterogeneity. Furthermore, a critical local equivalent plastic strain criterion was established, which effectively predicts the dependence of macroscopic failure strain on grain size. This work provides a physically based computational tool for optimizing TC4 processing parameters and predicting deformation under service conditions. Full article

With the rapid development of communication technologies such as 5G, yttrium iron garnet (YIG) has been widely applied in microwave devices and other systems owing to its low ferromagnetic resonance linewidth. Loss reduction and effects of doping on performance have been important research areas for garnet ferrite. This study prepared Ca²⁺, In³⁺, and Sn⁴⁺ codoped YIG ferrite samples with the chemical formula Y_3−xCa_xFe_5−x−yIn_ySn_xO₁₂ (x = 0.05–0.3) (y = 0.2, 0.45) via solid-state reaction. The analyses of the crystal structure, micromorphology, and magnetic properties enabled the identification of the causes of variations in parameters, such as saturation magnetization and coercivity. Theoretical calculations of the anisotropy constants clarified the patterns upon substituting Fe³⁺ with In³⁺ and Sn⁴⁺, revealing a shift in the positions of Fe³⁺ substitution. Finally, the primary factors influencing loss were identified, and the key process parameters influencing performance were determined. The resulting polycrystalline garnet ferrite exhibited an extremely low ferromagnetic resonance linewidth parameter (ΔH = 29 Oe) and a high density (>5.2 g/cm³). This study provides specific guidance on process parameters and element selection for high-performance, low-loss YIG materials, as well as a detailed theoretical explanation of the performance changes resulting from co-doping YIG with In³⁺ and Sn⁴⁺. Full article

NiO films were successfully deposited by sol–gel spin coating on Si, glass, and ITO-covered glass substrates. The impact of the film thickness (the different number of layers), annealing temperatures (from 300 to 500 °C), and the substrate type on the crystal structure, film morphology, optical, and vibrational properties was investigated. X-ray diffraction (XRD) revealed a polycrystalline structure and the appearance of the cubic NiO phase. Field Emission Scanning Electron Microscopy (FESEM) was applied to explore the surface morphology of NiO films, deposited on glass and ITO substrates. The oxidation states of Ni were determined by X-ray photoelectron spectroscopy (XPS). The presence of Ni²⁺ and Ni³⁺ states was supposed. UV–VIS–NIR spectroscopy revealed that NiO films possessed a high average transparency of up to 74.6% in the visible spectral range when they were deposited on glass substrates, and up to 76.9% for NiO films on ITO substrates. The thermal treatments and the film thickness slightly affected the film transparency in the spectral range of 450–700 nm. The work function (WF) of the samples was determined. This research showed that good properties of sol–gel NiO films can be compared to the properties of those films produced using complicated and expensive techniques. Full article

Semiconducting clathrates are a distinct class of inclusion compounds with considerable interest for thermoelectric applications. We report here the synthesis, crystal structure and thermoelectric properties of Sn₃₈Sb₈I₈. The compound was synthesized via planetary ball milling of the corresponding elements for 6 h and then sintering of amorphous mixture at 620 K for 3 days. The crystal structure of the polycrystalline product was determined via X-ray powder diffraction and Rietveld refinement as a type-I clathrate (a = 12.0390(2), space group Pm-3n, No. 223) with mixed-occupied Sn/Sb framework sites and fully occupied I guest sites. Further analysis on the chemical composition, nanomorphology and vibrational modes of the material was carried out via Induced-Coupled-Plasma–Mass Spectrometry, SEM/EDX microscopy and Raman spectroscopy, respectively. Thermoelectric measurements were performed on hot-pressed samples with ca. 98% of the crystallographic density. The clathrate compound behaves as an n-type semiconductor with a band gap of 0.737 eV and exhibits a maximum ZT of 0.0016 at 473 K. Theoretical calculations on the formation enthalpy, electron density of states and transport properties provide insights into the experimentally observed physical behavior. Full article

A crystal plasticity finite element model is developed and implemented to numerically study the deformation behavior of hexagonal close-packed metals using α-titanium as an example. The model takes into account micromechanical deformation mechanisms through dislocation slip along prismatic, basal, and first-order <c+a> pyramidal systems, as well as tensile twinning. Twin initiation follows a two-conditional criterion requiring that both the resolved shear stress in a twin system and the accumulated pyramidal slip simultaneously reach their critical values. Three-dimensional polycrystalline models are generated using the step-by-step packing method. The crystal plasticity constitutive model describing the deformation behavior of grains is integrated into the boundary-value problem of continuum mechanics, including dynamic governing equations. The three-dimensional problem is solved numerically using the finite element method. The micromechanical model is tested for an α-titanium single crystal along the [0001] direction and a polycrystal consisting of 50 grains. The numerical results reveal that twin propagation is controlled by the critical value of accumulated pyramidal slip, emphasizing the need for experimental calibration. The agreement between numerical and experimental results provides the model validation at the meso- and macroscales. Full article

Intermetallic NiMn-based Heusler alloys (HAs) have garnered considerable attention due to their multifunctionality and applications in various fields, including sensors, actuation, refrigeration, and waste heat harvesters. Among the NiMn-based alloys, Ni-Mn-Sn alloys have gained considerable attention since their structural and magnetic transformations were discovered. Many studies have been conducted with various compositions and shapes to investigate the physical properties of Ni-Mn-Sn alloys, which offer several advantages, including non-toxicity, low cost, and abundant constituents. The Co-doping effect on the physical properties of Ni-Mn-Sn alloys has been widely reported. This doping can rectify the ternary Ni-Mn-Sn Heusler compound’s brittleness by crystallizing a disordered face-centered cubic (fcc) γ-phase. In this study, a polycrystalline Ni₄₂Mn₄₆CoSn₁₁ Heusler alloy was prepared by high-frequency fusion (HF), using a Lin Therm 600 device, from pure Ni, Mn, Sn, and Co elements with appropriate proportions. X-ray diffraction, scanning electron microscopy, and magnetic magnetometry devices were used to study the structural, microstructural, and magnetic properties. The XRD results revealed the coexistence of a disordered 7 M martensite phase (~88%) and a disordered cubic solid solution γ-phase (~12%). The alloy underwent a second-order ferromagnetic-to-paramagnetic phase transition at a Curie temperature of 350 K. Landau and Hamad’s theoretical models were used to plot the magnetic entropy change. The magnetocaloric properties (the maximum entropy change value, ΔS_M, the full width at half maximum of the entropy change curve, δT_FWHM, the relative cooling power, RCP, and the heat capacity, ΔC_P,H) were calculated using isothermal magnetization curves with the phenomenological model of Hamad. Full article

This report focuses on the oxalate anion radical (C₂O₄^●−) formed during γ-radiolysis of polycrystalline oxalates: protonated oxalic acid (H₂C₂O₄·2H₂O), caesium oxalate (Cs₂C₂O₄), and potassium oxalate monohydrate (K₂C₂O₄·H₂O). Irradiation at 77 K generates stable radical species, revealed by EPR spectroscopy and supported by DFT calculations. In H₂C₂O₄·2H₂O, the primary axial signal (g_avg = 2.0035) is shown to arise from the structural relaxation of the HC₂O₄∙ radical into the intrinsically stable non-planar (D_2d) conformation, resolving the symmetry conflict with the planar crystal precursor. Numerical deconvolution confirmed the co-existence of this radical with the secondary HCO₂^● species, exhibiting distinct relaxation characteristics. In Cs₂C₂O₄, the broad isotropic signal (g ≈ 2.008) is attributed to the D_2d form. Quantitative analysis proved a sharp, thermodynamically driven structural conversion (D_2d→D_2h) upon annealing above 220 K, where the D₂h conformer (g_avg ≈ 2.011) becomes the dominant species (≈73%). In K₂C₂O₄·H₂O, the C₂O₄^●− radical undergoes rapid decomposition into the CO₂^●− radical (g_avg ≈ 2.0007) due to the kinetic instability of the primary species in that matrix. Our findings underscore the crucial role of computational assistance and quantitative numerical fitting in EPR studies: DFT provided crucial assistance and yielded satisfactory agreement in most cases, while clarifying the structural and kinetic stability governed by the local cationic environment. The stability of the most resistant radical forms persists up to 430 K in the caesium salt. Full article

Diamond, as an exceptional material with many superior properties, requires a single crystal in a reasonably large size for practical industrial applications. However, achieving large-area single-crystal diamond (SCD) growth without the formation of polycrystalline rims remains challenging. Microwave plasma chemical vapor deposition (MPCVD) using a gas mixture of 10% CH₄-H₂ was used for the homoepitaxial growth of (001) SCD. The effect of nitrogen gas addition in the range of 0–2000 ppm on lateral growth was investigated. Deposition with 180 ppm N₂ over a growth duration of 20 h to reach a thickness of 0.95 mm resulted in significantly enhanced lateral growth without the appearance of a polycrystalline diamond (PCD) rim for the grown diamond, and the total top surface area of SCD increased by an area gain of 1.6 relative to the substrate. The corresponding vertical and lateral growth rates were 47.3 µm/h and 52.5 µm/h, respectively. Characterization by Raman spectroscopy and atomic force microscopy (AFM) revealed uniform structural integrity across the whole surface from the laterally grown regions to the center, including the entire expanded area, in terms of surface morphology and crystalline quality. Moreover, measurements of the etch pit densities (EPDs) showed a substantial reduction in the laterally grown regions, approximately an order of magnitude lower than those in the central region. The high quality of the homoepitaxial diamond layer was further verified with (004) X-ray rocking curve analysis, showing a narrow full width at half maximum (FWHM) of 11 arcsec. Full article

A solvent-free, solid-state mechanochemical method was developed to synthesize the chalcohalide compound SbSI at room temperature. Dry high-energy planetary ball milling of elemental antimony, sulfur, and iodine produced a pure, stoichiometric polycrystalline SbSI powder with an orthorhombic structure. This powder was then sintered under mild thermal conditions to create dense targets. Amorphous SbSI thin films were subsequently deposited from these targets at room temperature using Pulsed Electron Deposition. The films maintained the correct stoichiometry and exhibited an optical bandgap of 1.89 eV. Post-deposition annealing at 90 °C in air successfully induced crystallization, demonstrating a viable, low-temperature, and eco-friendly route to produce polycrystalline SbSI thin films. This scalable approach has promising potential for optoelectronic and energy-harvesting applications. Full article

Ultrashort pulsed laser annealing is an efficient technique for crystallizing amorphous semiconductors with the possibility to obtain polycrystalline films at low temperatures, below the melting point, through non-thermal processes. Here, a multilayer structure consisting of alternating amorphous silicon and germanium films was annealed by mid-infrared (1500 nm) ultrashort (70 fs) laser pulses under single-shot and multi-shot irradiation conditions. We investigate selective crystallization of ultrathin (3.5 nm) a-Ge non-hydrogenated films, which are promising for the generation of highly photostable nanodots. Based on Raman spectroscopy analysis, we demonstrate that, in contrast to thicker (above 10 nm) Ge films, explosive stress-induced crystallization is suppressed in such ultrathin systems and proceeds via thermal melting. This is likely due to the islet structure of ultrathin films, which results in the formation of nanopores at the Si-Ge interface and reduces stress confinement during ultrashort laser heating. Full article

The development of single-crystal Ni-rich layered cathode materials (SC-NCMs) is regarded as an effective strategy to address the mechanical failure issues commonly associated with polycrystalline counterparts. However, the industrial production of SC-NCM faces challenges such as lengthy processing steps, high manufacturing costs, and inconsistent product quality. In this study, we innovatively propose a metal/organic framework (MOF)-mediated one-step synthesis strategy to achieve controllable structural preparation and in situ Nb⁵⁺ doping in SC-NCM. Using a Ni–Co–Mn-based MOF as both precursor and self-template, we precisely regulated the thermal treatment pathway to guide the nucleation and oriented growth of high-density SC-NCM particles. Simultaneously, Nb⁵⁺ was pre-anchored within the MOF framework, enabling atomic-level homogeneous doping into the transition metal layers during crystal growth. Exceptional electrochemical performance is revealed in the in situ Nb-doped SC-NCM, with an initial discharge capacity reaching 176 mAh/g at a 1C rate and a remarkable capacity retention of 86.36% maintained after 200 cycles. This study paves a versatile and innovative pathway for the design of high-stability, high-energy-density cathode materials via a MOF-mediated synthesis strategy, enabling precise manipulation of both morphology and chemical composition. Full article

Owing to the differences in crystallographic orientations among individual grains, dislocation structures in polycrystals are inherently inhomogeneous from grain to grain. Since intergranular incompatibility is inevitable during plastic deformation, it may consequently lead to unpredictable plastic strain localization, which in turn facilitates the initiation of fatigue crack. Therefore, to elucidate the mechanisms underlying inhomogeneous deformation in polycrystals, this study systematically examines the fatigue-induced dislocation structures in polycrystalline SUS316L stainless steel. We then directly compare them with those in copper single crystals to clarify the dependence of the dislocation structures on crystallographic orientation. SEM characterization demonstrates that high plastic strain near grain boundaries promotes the formation of secondary cell bands (CBs) overlapping the primary CBs, which is attributable to the simultaneous activation of multiple-slip systems under high plastic strain amplitudes. In addition to strain localization, competition among candidate secondary slip systems strongly governs the dislocation structures. Notably, a new type of deformation band (DB) on the (010) plane is identified in a non-coplanar double-slip-oriented grain, a feature not observed in single crystals, indicating that polycrystals accommodate plastic strain through distinct mechanisms. Detailed dislocation structure analysis provides theoretical guidance for mitigating fatigue crack initiation through the manipulation of dislocations. Full article