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Long afterglow is a fascinating luminescence phenomenon exhibited by certain storage phosphors that emit visible light after being stimulated by ultraviolet rays. Strontium magnesium silicate phosphors doped with europium and dysprosium (Sr2MgSi2O7:Eu2+, Dy3+) have garnered attention in recent years. Enhancing the afterglow performance of these phosphors remains a significant challenge. In this study, we investigate the enhancement of afterglow performance in Sr2MgSi2O7:Eu2+, Dy3+ phosphors prepared via a sol–gel auto-combustion method using commercial silica (CS) and lab-made nanosilica (NS). Our results reveal that the afterglow performance of the NS-based phosphor is significantly improved, glowing with optimal intensity for a prolonged period compared to the CS-based phosphor. Time-resolved photoluminescence studies show that the average lifetime of the NS-based phosphor is enhanced tenfold compared to the CS-based phosphor, attributed to the improved crystallinity of the NS-based phosphor. Photoluminescence studies indicate that both phosphors exhibit comparable performance. Thermoluminescence studies suggest that the presence of multiple trap levels with varying trap depths in the NS-based phosphor allows it to exhibit extended afterglow emission than the CS-based phosphor. Structural, morphological, and optical properties of the phosphors were analyzed using x-ray diffraction, Fourier transform infrared, x-ray photoelectron spectroscopy, field emission scanning electron microscopy, and UV–vis techniques. The underlying mechanism of the afterglow is explained in detail. The prepared phosphor was used to create flexible and transparent labels with silicone rubber, which can serve as indicators during dark hours. [ABSTRACT FROM AUTHOR]

The advancement of neuromorphic computing in resistive random-access memory (RRAM) is crucial for the rapid expansion of artificial intelligence. Conventional metal oxide-based RRAM faces challenges in mimicking synaptic activity, leading to the exploration of new resistive switching (RS) materials. This study introduces a ZnO@β-SiC composite-based RRAM device that exhibits biological synapse-like functionality. The device shows self-compliance and forming-free RS at ∼0.8 V, where it also mimics synaptic responses such as potentiation, depression, and paired-pulse facilitation at low voltage stimuli (∼0.6 V, 40 ms) with learning and forgetting behavior. Moreover, the synaptic plasticity is analyzed through spike rate dependent plasticity, spike number dependent plasticity, and spike time dependent plasticity. Further, the transition from short-term plasticity to long-term plasticity is observed under more training pulses and lower interval stimuli. The observed RS mechanism and synaptic functionalities are explained by the electric field-driven formation and dissolution of conducting filaments of oxygen vacancies. The chemical properties and local electronic structure have been examined by x-ray photoelectron spectroscopy and x-ray absorption spectroscopy. To elucidate the atomistic memristive behavior and the contribution of different electrical parameters in RRAM, detailed conductive atomic-force microscopy and impedance analysis have been carried out. [ABSTRACT FROM AUTHOR]

Despite the many advantages afforded to the investigation of complex compositional systems by combinatorial sputtering, the application of this synthesis technique is hindered by high-throughput characterization bottlenecks. The recent application of translatable compositional and magnetic characterization techniques, such as precision Wavelength Dispersive X-ray Fluorescence (WDXRF) and Magneto-Optic Kerr Effect (MOKE), are enabling for full wafer mapping of film chemistry, magnetic moment, and coercivity, although under-applied. An example system that stands to benefit from the application of combinatorial sputtering and high-throughput characterization is lightly nitrided FexVyNz, which, among other doped FeN materials, is a candidate rare earth-free permanent magnet for electric motor and read/write head applications. Within this report, a combinatorial sputtering and characterization procedure, which leverages high-throughput WDXRF and MOKE mapping, is utilized to investigate the effects of V composition on the room temperature ferromagnetic properties of FexVyNz. Observations made using WDXRF and MOKE mapping are shown to closely agree with vibrating sample magnetometry and x-ray photoelectron spectroscopy measurements made on cleaved regions of interest from the parent wafer. It is observed that the inclusion of V deleteriously affects the saturated moment of FeN, resulting in complete macroscopic reduction at 18 at. %. A maximum film coercivity of 165 Oe is observed at 10 at. % V, likely contributed to by crystallographic texture due to processing, followed by a complete reduction along with the saturated moment. These observations support the high-throughput characterization approaches of WDXRF and MOKE to combinatorial synthesis workflows. [ABSTRACT FROM AUTHOR]

Research on gallium oxide (Ga2O3) has accelerated due to its exceptional properties, including an ultrawide bandgap, native substrate availability, and n-type doping capability. However, significant challenges remain, particularly in achieving effective p-type doping, which hinders the development of Ga2O3-based bipolar devices like heterojunction bipolar transistors (HBTs). To address this, we propose integrating mature III–V materials, specifically n-AlGaAs/p-GaAs as the emitter (E) and base (B) layers, with n-Ga2O3 as the collector (C) to form III–V/Ga2O3 n–p–n HBT. This hetero-material integration could be achieved using advanced semiconductor grafting techniques that could create arbitrary lattice-mismatched heterojunctions by introducing an ultrathin dielectric interfacial layer. This study focused on revealing the band alignment at the base–collector (B–C) junction using a n-Ga2O3 (2 ¯ 01) orientated substrate combined with p-GaAs for potential HBT applications. We discovered a type-II band alignment between p-GaAs and Ga2O3 (2 ¯ 01) , with the p-GaAs conduction band approximately 0.614 eV higher than that of Ga2O3 (2 ¯ 01). This staggered alignment allows for direct and efficient electron transport from the p-GaAs base to the n-Ga2O3 collector, avoiding the electron blocking issues present in p-GaAs/Ga2O3 (010) heterojunctions. Additionally, our study suggests the potentially existing type-II alignment between the (2 ¯ 01) and (010) Ga2O3 interfaces, highlighting the orientation-dependent band offsets. These findings are pivotal for developing high-performance Ga2O3-based HBTs, leveraging the strengths of Ga2O3 and well-established semiconductor materials to drive advancements in high-power electronics. [ABSTRACT FROM AUTHOR]

Waterjet-guided laser machining of silicon offers precision with minimal heat-affected zones (HAZs), but understanding the mechanisms behind laser-material interactions remains essential. This study first utilizes orthogonal experiments to reveal fundamental relationships between processing parameters (scanning cycle, laser fluence, scanning velocity, and waterjet pressure) on groove depth and the depth-to-HAZ ratio. These findings guide the in-depth investigation of laser-material mechanisms. The results indicate that the ablation rate decreases with increasing scanning cycles, a phenomenon primarily attributed to the different absorption rates of 532 nm laser light between silicon and silicon dioxide. This conclusion is supported by x-ray photoelectron spectroscopy(XPS) results, which reveal that the accumulation of silicon dioxide occurs as the scanning cycles increase. Additionally, a near-linear relation between the ablation rate and laser fluence is observed, as the ablated area is continuously exposed to high laser intensity regions. However, increasing laser fluence also leads to diminished processing quality due to greater thermal deformation in non-ablating regions. Last, increased scanning velocity is found to cause rougher surfaces, as insufficient heat diffusion leads to higher thermal stress and results in micro-crack formations. The results provide a detailed understanding of the laser-induced transformations in the material and highlight optimal conditions for reducing thermal damage while maintaining machining efficiency. This study advances the field of laser processing by offering insights into the mechanisms governing oxide formation, thermal cracking, and material deformation during silicon grooving, providing the foundation for future exploration of laser-material interaction dynamics. [ABSTRACT FROM AUTHOR]

Ultrathin electrospun nanofibrous membranes (NfMs) based on poly(γ-benzyl-L-glutamate) (PBLG) were prepared. Scanning electron microscopy analysis revealed the production of a high-quality, bead-free nanofibrous membrane. The membrane thicknesses, ranging from 1.7 to 4.5 μm, were found to correlate directly with membrane porosity. Raman scattering analysis was utilized to investigate the conformation of the PBLG nanofibrous membrane and to assess the effects of addition of 1 wt. % trifluoroacetic acid (TFA) into the PBLG solutions, as well as the impact of annealing at 70 °C. In addition, x-ray photoelectron spectroscopy (XPS) characterization was performed to elucidate the chemical composition of the PBLG nanofibrous membrane. The Raman and Fourier-transform infrared spectroscopy spectra indicated the characteristic α-helical conformation in both the PBLG solution and the PBLG nanofibrous membrane. Furthermore, a comparative analysis of Raman band profiles proved the absence of TFA after annealing, supporting the hypothesis of TFA evaporation post-annealing, which was subsequently confirmed by the XPS results. In addition, the results from the small punch test revealed a significant correlation between membrane thickness and stiffness, indicating that increased thickness enhances stiffness. This comprehensive study provides valuable insights into the structural and compositional properties of PBLG NfMs, laying the groundwork for future investigations into their potential applications in the field of tissue engineering. [ABSTRACT FROM AUTHOR]

Metal-first non-alloyed ohmic and Schottky contacts are fabricated on β -Ga 2 O 3 with a range of metal work functions (ϕ M). The resulting ohmic contacts are of high quality with a contact resistance (R c) as low as 0.069 ± 0.003 Ω mm. Measurements of the barrier heights (ϕ B) indicate that metal-first processing, which preserves the as-grown/bare-substrate surface, also partially un-pins the Fermi-level in (010) and ( 2 ¯ 01) oriented Ga 2 O 3. Depth-resolved XPS (x-ray photoelectron spectroscopy) measurements of the oxidation state throughout the contact metal at the contact– Ga 2 O 3 interface indicate that most non-alloyed contact metals are at least partially oxidized by room temperature redox reactions with the underlying Ga 2 O 3 , with metals with a lower ϕ M also demonstrating the greatest level of oxidation. As oxidation has been previously observed to enhance a metal's work function, this may imply that to-date observations of indices of surface behavior << 1 on β -Ga 2 O 3 , which have been attributed to severe Fermi-level pinning, may need to be corrected to account for this partial oxidation in addition to other surface modifications during device processing demonstrated in this work. [ABSTRACT FROM AUTHOR]

The features and the electronic character of the states for the Ni 2p x-ray photoelectron spectroscopy (XPS) of Ni(OH)2 were analyzed. This detailed analysis is based on ab initio molecular orbital wavefunctions for a cluster model of Ni(OH)2. The theory is validated by comparison with experiment. Then, advanced methods are used to explain and contrast the properties of different groups of ionic states. An important conclusion is that in most cases, the ionic states cannot be described with a single configuration or determinant. Despite this essential many-body character of the XPS, we demonstrate that it is possible to understand the origin of the main and satellite XPS features in terms of their orbital character. [ABSTRACT FROM AUTHOR]

The features and the electronic character of the states for the Ni 2p x-ray photoelectron spectroscopy (XPS) of Ni(OH)2 were analyzed. This detailed analysis is based on ab initio molecular orbital wavefunctions for a cluster model of Ni(OH)2. The theory is validated by comparison with experiment. Then, advanced methods are used to explain and contrast the properties of different groups of ionic states. An important conclusion is that in most cases, the ionic states cannot be described with a single configuration or determinant. Despite this essential many-body character of the XPS, we demonstrate that it is possible to understand the origin of the main and satellite XPS features in terms of their orbital character. [ABSTRACT FROM AUTHOR]

Phase-change memory emerges as a top contender for non-volatile data storage applications. We report here a systematic change in local structure and crystallization kinetics of binary GeTe thin films using temperature-dependent resistivity measurements, which offers single-stage crystallization at around 187 °C, corroborated with x-ray diffraction. Furthermore, the change in chemical bonding upon crystallization is determined through x-ray photoelectron spectroscopy core level spectra, which reveals the existence of Ge and Te components that align with the GeTe crystal structure. Also, an investigation was carried out employing a UV–Vis–NIR spectrophotometer to explore the evolution of optical bandgaps (E g) , Tauc parameter (B) representing the local disorder, and Urbach energy (E u) of the GeTe material, as it undergoes the transition from a disordered amorphous state to a crystalline state. As crystallization progresses, a consistent shift of E g from 0.92 to 0.70 eV corresponds to as-deposited amorphous at room temperature and crystalline at 250 °C, respectively. In addition, the reduction in E u (from 199.87 to 141.27 meV) and a sudden increase of B around crystallization temperature is observed upon increasing temperature, indicating direct observation of enhanced medium-range order and distortion in short-range order, respectively, in GeTe thin films, revealing improved structural and optical properties. These enhancements make the GeTe material ideal for data storage applications of phase-change memory for next-generation computing technology. [ABSTRACT FROM AUTHOR]

The current research investigates the potential advantages of optimally combining wide bandgap Al2O3 with high dielectric constant (high-κ) Ta2O5 for gate dielectric applications. Various compositions of 10 nm AlxTayO oxide films are grown on the Al0.3Ga0.7N/GaN heterostructure by co-sputtering Al and Ta metals, followed by thermal oxidation at 500 °C. The average root-mean-square roughness of the grown oxide films is ∼1.2–1.4 nm compared to 0.4 nm for as-deposited metal. X-ray photoelectron spectroscopy and transmission electron microscopyconfirm the formation and thickness of the grown oxide films. The bandgap (E g) of the oxide films calculated from O 1 s electron energy loss spectra show a linear increase from 4.85 eV for pure Ta2O5 to 6.4 eV for pure Al2O3. The dielectric constant (ε ox ) calculated from capacitance–voltage (C G − V G) measurements decreases linearly from 25.7 for Ta2O5 to 7.9 for Al2O3. The interface trap density (D it ) is estimated from the frequency dispersion of capacitance–voltage (C G − V G) characteristics. The DC and radio frequency (RF) characteristics of AlxTayO/Al0.3Ga0.7N/GaN high electron mobility transistor (HEMT) devices are measured and compared with the Schottky HEMT devices (without any gate oxide). Compared to Schottky HEMT devices, AlxTayO/Al0.3Ga0.7N/GaN HEMT devices show superior DC characteristics, which helps us achieve maximum RF output power. Furthermore, the OFF-state measurements show that the AlxTayO/Al0.3Ga0.7N/GaN HEMT devices can sustain higher source-to-drain voltages, from a minimum of 88 V on pure Ta2O5 metal-oxide-semiconductor (MOS)-HEMTs to a maximum of 138 V on pure Al2O3 MOS-HEMTs before the dielectric breakdown happens, compared to a 57 V breakdown voltage on Schottky HEMT devices. An oxide variation of AlxTayO, with Al composition ratio of 0.34, shows an exceptional ION/IOFF ratio of 4 × 1011, a gate leakage current of 8 × 10−12 A/mm, a near-ideal subthreshold slope of 63.8 mV/dec, and the unity current gain frequency ( f T) of 25.6 GHz. [ABSTRACT FROM AUTHOR]

Nitrogen-rich ultra-thin (1–2 nm thick) layers in diamond produced by high-temperature nitrogen ion (N2+) implantation at low N2+ energies studied by in situ x-ray photoelectron spectroscopy are reported. Nitrogen bonding at the subsurface region and its thermal stability, as well as structural defects in polycrystalline diamond (PCD) implanted with 200, 500, and 800 eV N2+ at room temperature (RT) and 600 °C at an ion dose of 4.5 × 1014 ions/cm2, are investigated. Implantation at RT leads to nitrogen bonding at interstitial and substitutional sites in the diamond lattice, which is associated with the C–N/C=N bond, lower intensity of the C≡N (nitrile-like) component associated with nitrogen bonding with carbon defects, and quaternary nitrogen. The relative composition of these chemical states varies with implantation energy, temperature, and post-implantation annealing temperature. Upon annealing the RT implanted layers above 500–600 °C, the interstitial nitrogen converts to substitutional nitrogen. This process competes with nitrogen desorption. The thermal stability of nitrogen increases with implantation energy. Implantation at 600 °C at 800 eV resulted in a significantly lower concentration of nitrile-like bonds and a lower density of structural defects compared to RT implantation at the same energy. These effects are associated with dynamic annealing, which becomes more significant at higher implantation energies. Upon high-temperature implantation, nitrogen mostly populates directly substitutional sites. Nitrogen implantation at low energy and high temperature may be a viable way to nitride diamond surfaces with reduced density of defects where nitrogen is selectively bonded to substitutional sites. Finally, a comparison between nitrogen implantation into PCD and Diamond (100) [Di(100)] surfaces is presented. [ABSTRACT FROM AUTHOR]

4-Hydroxypiridine (4-HPy) is a green chemistry corrosion inhibitor for low-carbon steel, valued for its environmental compatibility and low toxicity. Despite lower initial effectiveness than 4-mercapto/4-aminopyridine, 4-HPy's performance is markedly enhanced by halogen ions. By employing second harmonic generation (SHG) spectroscopy combined with electrochemical methods, Raman spectroscopy, atomic force microscopy, x-ray photoelectron spectroscopy, and in situ UV spectroscopy, this study elucidates the synergistic enhancement mechanism of 4-HPy with Cl−, Br−, and I− in 0.5 mol/L HCl solution. Time-dependent SHG measurements showed a two-step process of rapid adsorption and subsequent orientation change, with a proposed mechanism to interpret the temporal changes in SHG intensity. Deducing the adsorption kinetic equations and their application to the experimental data yields the adsorption rate (kad) and orientation change rate (Kre). Halogens reduce the orientation angle of 4-HPy, facilitating its adsorption on the substrate surface and effectively inhibiting corrosion via distinct mechanisms. Cl− and Br− ions primarily adsorb onto the metal surface, forming an adsorption film that not only enhances the subsequent adsorption of 4-HPy but also provides a protective effect for the metal surface. Conversely, I− forms mainly complexes with 4-HPy in solution, co-adsorbs onto the metal surface, and demonstrates a significant synergistic effect. This study revealed the synergistic efficacy hierarchy among halogen ions, with the order 4HPy + NaCl < 4HPy + NaBr < 4HPy + NaI. This study enhances our molecular-level understanding of the synergistic mechanism between halogen ions and corrosion inhibitors and provides valuable insights for designing and developing effective corrosion inhibitors. [ABSTRACT FROM AUTHOR]