X-ray Diffraction Measurements Research Articles

Oxygen diffusion coefficients in ferroelectric hafnium zirconium oxide thin films

Oxygen diffusion coefficients in the metastable ferroelectric phase of polycrystalline hafnium zirconium oxide (HZO) thin films have been quantified using 18O tracers and time-of-flight secondary ion mass spectrometry. 11.5 nm thick HZO films containing 16O were deposited by plasma-enhanced atomic layer deposition followed by post-metallization annealing to crystallize into the ferroelectric phase. A 1.2 nm thick HZO layer containing 18O was then deposited using thermal atomic layer deposition with H218O as a reactant. Thermal anneals were conducted at 300, 350, and 400 °C and the ferroelectric phase confirmed after the anneals by x-ray diffraction, infrared spectroscopy, and electrical property measurements. 18O depth profiles were measured and fit with a thin film diffusion equation to determine the oxygen diffusion coefficients. Oxygen diffusion coefficients ranged from approximately 2 × 10−18 cm2/s at 300 °C to 5 × 10−17 cm2/s at 400 °C with an activation energy of 1.02 ± 0.24 eV.

Annealing-Tunable Charge Density Wave in the Magnetic Kagome Material FeGe.

The unprecedented phenomenon that a charge density wave (CDW) emerges inside the antiferromagnetic (AFM) phase indicates an unusual CDW mechanism associated with magnetism in FeGe. Here, we demonstrate that both the CDW and magnetism of FeGe can be effectively tuned through postgrowth annealing treatments. Instead of the short-range CDW reported earlier, a long-range CDW order is realized below 110K in single crystals annealed at 320 °C for over 48h. The CDW and AFM transition temperatures appear to be inversely correlated with each other. The onset of the CDW phase significantly reduces the critical field of the spin-flop transition, whereas the CDW transition remains stable against minor variations in magnetic orders such as annealing-induced magnetic clusters and spin-canting transitions. Single-crystal x-ray diffraction measurements reveal substantial disorder on the Ge1 site, which is characterized by displacement of the Ge1 atom from the Fe_{3}Ge layer along the c axis and can be reversibly modified by the annealing process. The observed annealing-tunable CDW and magnetic orders can be well understood in terms of disorder on the Ge1 site. Our study provides a vital starting point for the exploration of the unconventional CDW mechanism in FeGe and of kagome materials in general.

III-Nitride Magnetron Sputter Epitaxy on Si: Controlling Morphology, Crystal Quality, and Polarity Using Al Seed Layers.

Group III-nitride semiconductors have been subject of intensive research, resulting in the maturing of the material system and adoption of III-nitrides in modern optoelectronics and power electronic devices. Defined film polarity is an important aspect of III-nitride epitaxy as the polarity affects the design of electronic devices. Magnetron sputtering is a novel approach for cost-effective epitaxy of III-nitrides nearing the technological maturity needed for device production; therefore, control of film polarity is an important technological milestone. In this study, we show the impact of Al seeding on the AlN/Si interface and resulting changes in crystal quality, film morphology, and polarity of GaN/AlN stacks grown by magnetron sputter epitaxy. X-ray diffraction measurements demonstrate the improvement of the crystal quality of the AlN and subsequently the GaN film by the Al seeding. Nanoscale structural and chemical investigations using scanning transmission electron microscopy reveal the inversion of the AlN film polarity. It is proposed that N-polar growth induced by Al seeding is related to the formation of a polycrystalline oxygen-rich AlN interlayer partially capped by an atomically thin Si-rich layer at the AlN/Si interface. Complementary aqueous KOH etch studies of GaN/AlN stacks demonstrate that purely metal-polar and N-polar layers can be grown on a macroscopic scale by controlling the amount of Al seeding.

Facile synthesis of g-C3N4@porphyrin nanofiber composite via self-assembly as photoelectrode for efficient photoelectrochemical water splitting

The creation of self-assembled porphyrin nanostructures and their organised arrays has garnered significant attention, with the objective of mimicking natural light-harvesting mechanisms and energy storage, as well as pioneering novel nanostructured materials for use in photocatalytic processes. This study explored the formation of porphyrin nanofibers onto the surface of g-C3N4 via self-assembly, creating a photoelectrode with remarkable potential for efficient photoelectrochemical (PEC) water splitting. By integrating these two distinct materials, the resultant hybrid structure leverages the unique properties of both components, enhancing the overall performance of the photoelectrochemical system. The fabrication process involves acid-base neutralization-induced self-assembly, leading to the formation of a well-distributed composite. The resulting photoelectrode exhibits improved charge separation and enhanced light absorption properties. Experimental analyses, encompassing techniques such as scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and photocurrent measurements, validate the successful integration of the hybrid material and its notable photocatalytic efficiency. The porphyrin nanofiber was evenly distributed over the surface of the generated g-C3N4@porphyrin hybrid material. The photoelectrochemical measurements showed a remarkable enhancement in the photocurrent when using g-C3N4@porphyrin photoelectrode in the light-irradiating condition compared to the dark condition. The possible PEC water-splitting mechanism by g-C3N4@porphyrin photoelectrode was also proposed and discussed. This work showcases a promising avenue for advancing the field of photoelectrochemical water splitting through innovative material design and assembly strategies.

Growth of high quality polycrystalline InGaO thin films by spray pyrolysis for coplanar thin-film transistors on polyimide substrate

The current mobile devices are moving towards flexible electronics. Introducing crystalline oxide semiconductors on flexible substrates is important to satisfy the requirements of high-resolution displays on flexible substrates. This study investigates the low-cost, as-grown polycrystalline (Poly) InGaO thin film transistor by spray pyrolysis on polyimide (PI) substrate. Grazing Incidence X-ray Diffraction (GI-XRD) measurements demonstrate that In0.8Ga0.2O, In0.7Ga0.3O, and In0.5Ga0.5O compositions exhibit crystallization on-set temperatures of ∼330, ∼350, and ∼415°C, respectively. Poly-In0.7Ga0.3O thin film with lower oxygen-vacancy (∼15 %) and less than 5 % O-H group could be achieved at the substrate temperature of 370°C. The hysteresis-free device performance with an average saturation mobility of 43.73 cm2V−1s−1 has been obtained using the poly-In0.7Ga0.3O with optimized N2O plasma treatment on the poly-oxide thin film. The TFTs show remarkable stability under humid environments and various stress conditions such as positive bias temperature, negative bias temperature, and mechanical stresses. In addition, the 96-stage gate shift register made of poly-In0.7Ga0.3O TFTs by spray pyrolysis exhibits the rising and falling times of less than 820 ns. Therefore, the poly-In0.7Ga0.3O TFTs by spray pyrolysis could be used for high-resolution, cost-effective, flexible active-matrix light-emitting displays.

FINITE ELEMENT ANALYSIS OF CHANGING OF STRESS CONDITION CAUSED BY DIAMOND BURNISHING

The article is aspected to the finite element modelling of stress in subsurface layer of aluminium alloy workpiece during diamond burnishing process. This cold forming process is a simple, cost-effective finishing method that can be used to improve surface integrity and provide compressive residual stress. Available with these, durability and quality enhancement of the components can be reached, but improperly chosen burnishing parameters can distort the efficiency of the plastic deformation process. In order to optimize this, a 2D FEM model is created including the real surface integrity of the workpiece which was measured with AltiSurf 520 surface roughness measuring device. The method is simulated using DEFORM-2D software, corresponding to the numerical values of burnishing parameters implemented in practice as well, thereby allowing a comparative analysis with the results of X-ray diffraction measurement.

Microwave-Assisted Hydrothermal Synthesis of Nanosheet Layered Hexagonal Spinel Ferrites for Efficient Electromagnetic Wave Absorbing.

A microwave-induced combustion method has been utilized to prepare nanosized powders of hexagonal spinel ferrites using urea and glycine as fuel. The structural and electromagnetic absorption of these products was investigated using X-ray diffraction (XRD). From the (3,1,1) and (1013) peaks in XRD measurements, it was seen that the samples we synthesized were nanosized spinel and y-phase hexagonal ferrite. In addition, Fourier-transform infrared measurements showed that the synthesized samples had high absorption values showing Fe-O, which is between 878 to 4000 cm-1, and metal-oxygen transitions, which are between the 700 and 2500-3000 cm-1 in the spinel and hexagonal phases. From the scanning electron microscope image of the particles, it is seen that they are homogeneous, filled structures with ∼35-40 nm. It appears from vector network analyzer measurements that the synthesized 1.5 mm thick composite materials have very high electromagnetic absorption properties and that these composites can also be used in electromagnetic interference, Wi-Fi applications, and health.

Preparation, structural, morphological, optical, electrical, mechanical, and thermal properties of perovskite SrTiO3 nanoparticles boosted PVA/PEO blend for flexible optoelectronic and capacitor applications

Strontium titanate nanoparticles (SrTiO3 NPs) were produced via the solid-state reaction method. Then, they were used to enhance the structural, mechanical, electrical, and dielectric properties of polyvinyl alcohol (PVA)/polyethylene oxide (PEO) blend for energy storage applications. For this purpose, SrTiO3 NPs were dispersed in the polymer blend to fabricate nanocomposite films using a solution casting method. The nanocomposite films were then characterized using a variety of instruments, such as transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier-Transform Infrared spectroscopy (FTIR), Ultraviolet/Visible spectroscopy (UV/visible), and impedance analyzers. Based on XRD and TEM measurements, the synthesized SrTiO3 NPs have a cubic perovskite phase and a diameter that varies between 70 and 160 nm. Additionally, according to XRD measurements, adding SrTiO3 NPs to PVA/PEO reduces the crystallinity of the resulting nanocomposites. In addition, the surface morphology and elemental composition were demonstrated through the utilization of scanning electron microscope.(SEM) and energy dispersive X-ray spectroscopic analysis (EDX) spectra, where PVA and PEO polymers formed a homogenous and rough surface, and the SrTiO3 NPs of low concentrations were spread out within the blend's structure. Analysis of the FTIR peaks revealed prominent characteristic peaks associated with vibrational groups that change randomly with the concentration of SrTiO3 NPs. With increasing SrTiO3 NPs concentration, the nanocomposite UV/visible absorbance, optical bandgap energies, and refractive index were calculated and discussed. Impedance studies conclude that the amount of SrTiO3 NPs in a mixture raises the mixture's AC electrical conductivity, dielectric loss, and dielectric constant. The mechanical characteristics, such as Young's modulus, yield strength, and strain at failure, were assessed by examining the tensile test of prepared films. The thermal stability of PVA/PEO-SrTiO3 nanocomposite films were studied by thermogravimetric analysis (TGA). These experimental results point to the potential for employing the produced nanocomposites in optoelectronic and capacitive energy storage systems.

Growth of AlGaN alloys with ∼ 90 % AlN mole fraction by plasma-assisted molecular beam epitaxy: Indication of phase-segregation effects

AlGaN alloys with very high AlN mole fraction (∼90 %) were grown by plasma-assisted molecular beam epitaxy (PA-MBE) and their alloy properties were investigated by high-resolution X-ray diffraction (HR-XRD) measurements. Growth was carried out employing a series of group III/V ratios and for samples grown under a high group-III regime, phase-segregation in the alloy was evident from a characteristic splitting of the AlGaN (0002) peak in the HR-XRD pattern. With decreasing excess group-III conditions the separation of peak positions continuously reduced, till a single peak was observed. However, for samples where such splitting was absent, spontaneous superlattice peaks were seen at lower incident angles of the XRD patterns indicating the presence of long-range atomic ordering (LRAO). Thus, for AlGaN alloys with extremely high Al content, effects of phase-segregation, or of LRAO were observed, depending on the kinetics of growth. These results on phase-segregation effects are expected to promote the development of high-efficiency deep ultraviolet emitters for skin-safe germicidal action by mitigating the detrimental effect of dislocations and related non-radiative recombination centers through carrier localization processes at potential minima.

Facile synthesis and characterization of PbS thin films doped with various aluminum concentrations for photovoltaic applications

In this study, aluminum doped lead sulfide (PbS:Al) thin films were deposited on soda lime glass substrates using chemical bath deposition (CBD) technique. The structural, morphological, optical and electrical properties of as-deposited PbS thin films were studied as a function of Al concentration (0, 2, 4, 6, 8 at. %). The deposited films can be analyzed using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), x-ray diffraction (XRD), UV-Vis-NIR spectroscopy and Hall measurement. From SEM, it was evident that the thickness of the films decreased from 750 nm (0 at. %) to 280 nm (8 at. %) with increased Al concentration. XRD analysis revealed that the prepared films exhibited face centered cubic structure without any other binary phases. The average crystallite size of the films decreased from 33.71 to 20.45 nm. The direct optical band gap values were increased from 0.90 to 1.29 eV. The optical parameters such as refractive index (n), extinction coefficient (k), real (ɛ 1) and imaginary (ɛ 2) parts of the dielectric constant were 1.51–2.04, 0.0035–0.0075, 2.50–6.20 and 0.005–0.16 respectively. The absorption coefficient (α) of all the deposited films was in the range of ≈105 cm−1. The electrical resistivity of the deposited films was found in the range of 102–103 Ω·cm. The overall analysis indicate that the deposited PbS:Al thin film shows promise as an absorbing layer for heterojunction solar cell devices.

Radiation-Induced Synthesis and Superparamagnetic Properties of Ferrite Fe3O4 Nanoparticles.

Ultra-small magnetic Fe3O4 nanoparticles are successfully synthesized in basic solutions by using the radiolytic method of the partial reduction in FeIII in the presence of poly-acrylate (PA), or by using the coprecipitation method of FeIII and FeII salts in the presence of PA. The optical, structural, and magnetic properties of the nanoparticles were examined using UV-Vis absorption spectroscopy, high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and SQUID magnetization measurements. The HRTEM and XRD analysis confirmed the formation of ultra-small magnetite nanoparticles in a spinel structure, with a smaller size for radiation-induced particles coated by PA (5.2 nm) than for coprecipitated PA-coated nanoparticles (11 nm). From magnetization measurements, it is shown that the nanoparticles are superparamagnetic at room temperature. The magnetization saturation value Ms = 50.1 A m2 kg-1 of radiation-induced nanoparticles at 60 kGy is higher than Ms = 18.2 A m2 kg-1 for coprecipitated nanoparticles. Both values are compared with nanoparticles coated with other stabilizers in the literature.

Unraveling the Irreversible Storage of Dimethyl Carbonate-Solvated Hexafluorophosphate Anions in Graphite Electrode.

LiPF6 dissolved in dimethyl carbonate (DMC) is one of the cheapest groups of electrolyte solutions in dual-ion batteries. Generally, the discharge capacity of anion storage delivered by the graphite cathode grows with increasing LiPF6 concentration. This fact is consistent with the irreversible storage of DMC-solvated PF6-, and then, the underlying mechanism is clarified by the electrochemical tests and ex situ X-ray diffraction (XRD) measurements of graphite cathodes as well as infrared (IR) and Raman spectroscopy characterizations of solutions. Moreover, quaternary ammonium salts have facile dissociation, which can effectively regulate the solvation state of the anion and the interaction between ion pairs in the electrolyte. A small amount of tetrabutylammonium hexafluorophosphate (TBAPF6) is introduced into the highly concentrated LiPF6-DMC solution to improve the performance of the graphite cathode. The discharge capacity of the Li/graphite cell has increased by approximately 50%. This effect is also correlated with the solvation state of the anion. This study provides an insightful clue for the choice of electrolyte solution in dual-ion batteries.

Excitonic emission and phonon anharmonicity in Cs3Sb2Br9

We investigate emission characteristics, phonon–phonon, and electron–phonon interactions in a lead-free halide perovskite Cs3Sb2Br9 through temperature-dependent photoluminescence, Raman scattering, and x-ray diffraction measurements. The exciton–optical phonon coupling leads to below bandgap broad emissions, arising from self-trapped excitons recombination. The anomalous temperature dependence of the lowest frequency Raman mode is attributed to the phonon–phonon and electron–phonon interactions. The temperature-dependent x-ray diffraction measurement reveals a minimum in the volume thermal expansion coefficient at around 120 K. We also quantify the quasiharmonic contributions to the phonon frequency shift for all Raman modes.

Synthesis of ZnO and CuO–ZnO nanocomposites for photo-conducting and dielectric applications

Zinc oxide (ZnO) and its composites has garnered a tremendous attention lately due to its effective role in electronic and optoelectronic applications. The present manuscript reports the synthesis and characterization of ZnO and CuO–ZnO nanocomposites. These samples were synthesized using precipitation technique and studied for voltage-dependent dielectrics and photoconductivity properties. Structural properties were thoroughly investigated using powder X-ray diffraction (PXRD) measurements. The composite material revealed decreased crystallinity and increased strain in the material. Optical absorption measurements were recorded using UV–vis diffusion reflectance measurements and the changes in the absorbance spectrum corresponding bandgap is explored. The obtained band gap is comparatively less for the composite material when compared with prestine ZnO. Structural morphology of the synthesized materials was observed and compared and changes in the composites when compared with the ZnO. Drastic changes in the morphology is witnessed. Electrical response of these synthesized semiconductors was studied using I–V and dielectric measurements. CuO–ZnO samples show a very clear sensitivity to the voltage dependent dielectric properties compared to ZnO. The composite and ZnO are studied using I–V measurements and the light dependent I–V measurements and composite revealed photo sensitivity. Drastic change in the conductivity is witnessed inferring the material to be used in optoelectronic application. Dielectric, Impedance, dielectric loss, AC conductivity and modulus index of the materials were explored by subjecting the materials to impedance measurements. The materials were also explored with different voltages and compared. The composite material revealed drastic variations for change in the voltage and measured parameters were compared with the ZnO.

Impact of Temperature Optimization of ITO Thin Film on Tandem Solar Cell Efficiency.

This study examined the impact of temperature optimization on indium tin oxide (ITO) films in monolithic HJT/perovskite tandem solar cells. ITO films were deposited using magnetron sputtering at temperatures ranging from room temperature (25 °C) to 250 °C. The sputtering target was ITO, with a mass ratio of In2O3 to SnO2 of 90% to 10%. The effects of temperature on the ITO film were analyzed using X-ray diffraction (XRD), spectroscopic ellipsometry, and sheet resistance measurements. Results showed that all ITO films exhibited a polycrystalline morphology, with diffraction peaks corresponding to planes (211), (222), (400), (440), and (622), indicating a cubic bixbyite crystal structure. The light transmittance exceeded 80%, and the sheet resistance was 75.1 Ω/sq for ITO deposited at 200 °C. The optical bandgap of deposited ITO films ranged between 3.90 eV and 3.93 eV. Structural and morphological characterization of the perovskite solar cell was performed using XRD and FE-SEM. Tandem solar cell performance was evaluated by analyzing current density-voltage characteristics under simulated sunlight. By optimizing the ITO deposition temperature, the tandem cell achieved a power conversion efficiency (PCE) of 16.74%, resulting in enhanced tandem cell efficiency.

Valence instability and collapse of ferromagnetism in EuB[formula omitted] at high pressures

Despite the simplicity of their cubic crystal lattice, rare-earth hexaborides display complex physical properties including a (long debated) onset of metallization via magnetic polaron formation at Tc1≈ 15 K preceding ferromagnetic ordering at Tc2≈ 12 K. In this work, we used applied pressure to tune the interplay between electronic structure and magnetism in EuB6. We probed the magnetism, valence, and structure of EuB6 under quasi-hydrostatic pressures up to 30 GPa using X-ray techniques. Our findings show evidence for collapse of ferromagnetism above 20 GPa following a monotonic increase of mean Eu valence. While X-ray diffraction measurements in the paramagnetic state at room temperature show that the lattice retains cubic symmetry, a measurable quadrupole interaction seen by time-domain synchrotron Mössbauer spectroscopy suggests a lowering of symmetry associated with magnetic ordering, becoming more prominent across the magnetic transition. The interplay between conduction band electron count and magnetism observed under applied pressure in EuB6 opens possibilities for fine-tuning metallization and magnetic properties of similar Eu-based semi-metal systems.

Rubik’s cube PBA frameworks for optimizing the electrochemical performance in alkali metal-ion batteries

PBA frameworks have stood out among metal–organic frameworks because of their easy preparation, excellent stability, porous structures, and rich redox properties. Unfortunately, their non-ideal conductivity and significant volume expansion during cycling prevent more widespread application in alkali-metal-ion (Li+, Na+, and K+) batteries. By changing the type and molar ratio of metal ions, Rubik’s PBA frameworks with infinite structural variations were obtained in this study, just like the Rubik’s cube undergoes infinite changes during the rotation. X-ray adsorption fine structure measurements have documented the existence and determined the coordination environment of the metal ions in the Rubik’s PBA framework. Benefiting from the more stable Rubik’s cube structures with diverse composition, enhanced conductivity, and greater adsorption capacity, the obtained Rubik’s cubes CoM-PBA anodes, especially CoZn-PBA deliver the enhanced cycling and rate performance in all the alkali-metal-ion batteries. The findings are supported by density functional theory calculations. Ex-situ X-ray photoelectron spectroscopy, and in-situ X-ray diffraction measurements were undertaken to explore the storage mechanism of CoZn-PBA anodes. Our results further demonstrate that the Rubik’s cube PBA framework-based materials could be widely applied in the field of alkali-metal-ion batteries.

Growth of Size-Tunable Ag2O Polyhedra and Revelation of Their Bulk and Surface Lattices.

By primarily adjusting the reagent amounts, particularly the volume of AgNO3 solution introduced, Ag2O cubes with decreasing sizes from 440 to 79 nm, octahedra from 714 to 106 nm, and rhombic dodecahedra from 644 to 168 nm are synthesized. 733 nm cuboctahedra are also prepared for structural analysis. With in-house X-ray diffraction (XRD) peak calibration, shape-related peak shifts are recognizable. Synchrotron XRD measurements at 100 K reveal the presence of bulk and surface layer lattices. Bulk cell constants also deviate slightly. They show a negative thermal expansion behavior with shrinking cell constants at higher temperatures. The Ag2O crystals exhibit size- and facet-dependent optical properties. Bandgaps red-shift continuously with increasing particle sizes. Optical facet effect is also observable. Moreover, synchrotron XRD peaks of a mixture of Cu2O rhombicuboctahedra and edge- and corner-truncated cubes exposing all three crystal faces can be deconvoluted into three components with the bulk and the [111] microstrain phase as the major component. Interestingly, while the unheated Cu2O sample shows clear diffraction peak asymmetry, annealing the sample to 450 K yields nearly symmetric peaks even when returning the sample to room temperature, meaning even moderately high temperatures can permanently change the crystal lattice.

Analysis of high temperature phase transformation behavior of ultra-low-carbon steel using X-ray topography, diffraction, and synchronized temperature measurement

Despite the technical importance of δ/γ phase transition in steel alloys, conventional thermal analysis techniques like calorimetry lack precise kinetics measurement. This study introduces an integrated approach combining X-ray topographic imaging, diffraction, and precise temperature measurement to overcome these limitations. This methodology allows for the accurate quantification of recalescence due to release of latent heats from solidification and solid-state phase transformation. It also enables tracking of the fractional volume changes of the δ phase during continuous cooling. We demonstrate that in Ultra-Low Carbon steels, the δ to γ transformation occurs rapidly in the single γ phase region far below the solidus temperature in the phase diagram, and this transformation accelerates further in the higher cooling rate. Furthermore, it can be inferred that in phase transformation, its rate becomes a critical factor in the temperature increase resulting from the released latent heat, overshadowing the influence of undercooling during continuous cooling.

Synchrotron radiation excited luminescence of Eu, Er, and Tm codoped β-Ga2O3 thin film

Ga2O3 thin film with Eu, Er, and Tm codoping was prepared on Si substrate by pulsed laser deposition. The obtained codoping film has a monoclinic Ga2O3 structure identified by X-ray diffraction and Raman measurements. The excitation wavelength-dependent photoluminescence measurements were performed using synchrotron radiation sources with photon energies both below and above bandgap. Moreover, temperature-dependent PL measurements were carried out from 30 to 300 K to systematically investigate the PL characteristics of codoped Eu3+, Er3+, Tm3+ ions in the Ga2O3 film. Typical luminescent bands originating from Eu3+, Er3+, and Tm3+ dopants were concurrently observed in the PL spectra. The codoping film emits a near purple light when it was excited at 30 K, which gradually shifts to the orange region as the temperature rises to 300 K. This color evolution results from different quenching rates of Eu3+, Er3+, and Tm3+ dopants with the increase of temperature. These findings provide a solid foundation for Si-compatible full-color displays using RE doped Ga2O3.