Search Results (47)

Aluminum scandium nitride (Al_1−xSc_xN) is a promising ferroelectric material for non-volatile random-access memory devices and electromechanical sensors. However, adverse effects on polarization from electrical leakage are a significant concern for this material. We observed that the electrical conductivity of Al_1−xSc_xN thin films grown on epitaxial TiN(111) buffered Si(111) follows an Arrhenius-type behavior versus the growth temperature, suggesting that point defect incorporation during growth influences the electronic properties of the film. Photoluminescence intensity shows an inverse correlation with growth temperature, which is consistent with increased non-radiative recombination from point defects. Further characterization using secondary ion mass spectrometry in a focused ion beam/scanning electron microscope shows a correlation between trace Ti concentrations in Al_1−xSc_xN films and the growth temperature, further suggesting that extrinsic dopants or alloying components potentially contribute to the point defect chemistry to influence electrical transport. Investigation of the enthalpy of formation of nitrogen vacancies in Al_1−xSc_xN using density functional theory yields values that are in line with electrical conductivity measurements. Additionally, the dependence of nitrogen-vacancy formation energy on proximity to Sc atoms suggests that variations in the local structure may contribute to the occurrence of point defects, which, in turn, can impact electrical leakage. Furthermore, we have demonstrated ferroelectric behavior through electrical measurements and piezoresponse force microscopy after dc bias poling of films in spite of electrical conductivity spanning several orders of magnitude. Although electrical leakage remains a challenge in Al_1−xSc_xN, the material holds potential due to tunable electrical conductivity as a semiconducting ferroelectric material. Full article

Model experiments were performed on the interaction of swift heavy 220 MeV Xe ions with MgAl₂O₄ spinel crystal with (100), (110), and (111) planes. A computational analysis of the energy parameters of Xe ions in MgAl₂O₄ single crystal was performed, and an estimate of the ion range in the near-surface layer (14 μm) was provided. Optical absorption spectrum was analyzed using polarized light and EPR spectroscopy of initial and irradiated crystals. It has been established that at a fluence of 10¹³ cm⁻² in a sample with an orientation plane (110), 35% more optically active F-type centers are formed. It has been shown that optically active centers V|_Al–O⁻ are observed in an unusual, polarized beam. Full article

Laser-driven operations are a common approach for engineering one- and two-qubit gates in trapped-ion arrays. Measuring key parameters of these lasers, such as beam sizes, intensities, and polarizations, is central to predicting and optimizing gate speeds and stability. Unfortunately, it is challenging to accurately measure these properties at the ion location within an ultra-high vacuum chamber. Here, we demonstrate how the ions themselves may be used as sensors to directly characterize the laser beams needed for quantum gate operations. Making use of the four-photon Stark Shift effect in ¹⁷¹Yb⁺ ions, we measure the profiles, alignments, and polarizations of the lasers driving counter-propagating Raman transitions. We then show that optimizing the parameters of each laser individually leads to higher-speed Raman-driven gates with smaller susceptibility to errors. Our approach demonstrates the capability of trapped ions to probe their local environments and to provide useful feedback for improving system performance. Full article

Low energy N⁺ ion beam implantation has been used to create the novel rice mutant “shuangli”, which produces partially fertile spikelets containing double grains. Abnormal ovule development is a major cause of partial fertility and grain diversity in rice mutants. To elucidate the developmental mechanism of ovule diversity in shuangli, ovules undergoing development were stained using eosin Y and H33342 and observed using confocal laser scanning microscopy. Different developmental abnormalities were observed in the ovary, embryo sac, and ovule. Abnormal development was observed in 35.18% of the ovary structures, primarily manifesting as “tumor” like cell clusters, “false ovaries”, stamen degeneration, and double ovaries. In the embryo sac, abnormal development occurred in about 17.35% of the megaspore cells, including the formation of three nuclei, two daughter cells of asynchronously divided dyads, multiple megaspore tetrads, and “narrow and elongated” cavities. At the female gametogenesis stage, the abnormal development rate was 27.53%, mainly involving the degeneration of the central polar nucleus, egg apparatus, antipodal cell mass, or female germ unit. In shuangli, abnormal development occurred in 28.06% of the ovule structures, including lateral tissue, nucellar tissue, double ovules and double embryo sacs. Of the observed lateral tissues, 8.27% did not differentiate into sexual reproductive tissue, which affected the fertilization of the embryo sac, leading to atrophy and degeneration. A new abnormal tissue similar to the inner integument was found on both sides of the nucellar tissue, and the two specialized nucellar tissues appeared to have “staggered” growth within a single ovary. Of the examined ovules, 10.79% exhibited different types of double ovules, including heart-shaped, “anatropous”, “conjoined” structures. However, the double ovules typically developed synchronously, explaining the production of different sizes of the two grains in shuangli. In addition, “double” embryo sacs from two “twinborn” nucelli were found in one ovule, and the frequency of “double” embryo sacs was 3.60%. Therefore, ovule development diversity may result in fertilization or gradual degeneration after fertilization, explaining the lower fertility of shuangli at the embryological level. Full article

To date, many studies can be found in the literature attempting to explain the effects of temperature and humidity on the rate of corrosion processes. However, it is difficult to analyze the results of these studies and draw unambiguous conclusions due to the different test conditions as well as different electrochemical test methods for corrosion rates. Most of these studies concern concrete reinforced with ordinary steel. However, there is a lack of research and analysis conducted on prestressed elements. The purpose of this study was to evaluate the effect of temperature and humidity changes on the development of corrosion processes in prestressed concrete beams. Tests were performed both under conditions of increasing temperature and humidity, which were reproduced in a climatic chamber, as well as in an environment exposed to chloride ions. The process of migration of chloride ions into the concrete was accelerated by the application of an electric field. In addition, selected beams were subjected to prolonged loading to sustain the induced scratching. Corrosion rate tests were carried out using the non-destructive linear polarization method (LPR). Strength tests of the beams were also carried out, as well as displacement and deformation measurements using the Aramis system’s digital image correlation technique. The beams without chloride addition had a fairly stable low level of corrosion current density throughout the test period, indicating the passive state of the reinforcement, regardless of the environment in which they were placed and the additional loading. In an environment with a humidity of 30% and a temperature of 20 °C, the corrosion current density increment was much faster than for beams with chloride additives in an environment with a humidity of 90% and a temperature of 30 °C. A smaller increase in corrosion current density could be observed in beams that were scratched, compared to non-scratched beams. The results of the strength tests indicated that in beams subjected to accelerated migration of chloride ions, the deflection at scratching was significantly lower than in beams without chloride addition. Also in these beams, milder strains were registered on the surface of the elements at the time of scratching. Full article

Structured light encompasses a vast variety of light fields. It has unique properties such as non-uniform transverse intensity and a polarization pattern across their beam cross-sections. In this contribution, we discuss the photoexcitation of a single ionic target system driven by different sets of structured light modes. Specifically, we provide a compilation of transition amplitudes for various structured light modes interacting with atomic systems based on the first-order perturbation theory. To illustrate this, we will choose an electric quadrupole transition ($4s{}_{\mathrm{}}{}^2{S}_{1/2}_{\mathrm{}}^{\mathrm{}}\to 3d{}_{\mathrm{}}{}^2{D}_{5/2}_{\mathrm{}}^{\mathrm{}}$) in the target Ca⁺ ion driven by a structured light field. For this particular interaction, we examine how the beam parameters affect the population of magnetic sub-levels in the atomic excited state. Full article

Polarized heavy ions in storage rings are seen as a valuable tool for a wide range of research, from the study of spin effects in relativistic atomic collisions to the tests of the Standard Model. For forthcoming experiments, several important challenges need to be addressed to work efficiently with such ions. Apart from the production and preservation of ion polarization in storage rings, its measurement is an extremely important issue. In this contribution, we employ the radiative recombination (RR) of polarized electrons into the ground state of initially hydrogen-like, finally helium-like, ions as a probe process for beam diagnostics. Our theoretical study clearly demonstrates that the RR cross section, integrated over photon emission angles, is highly sensitive to both the degree and the direction of ion polarization. Since the (integrated) cross-section measurements are well established, the proposed method offers promising prospects for ion spin tomography at storage rings. Full article

Higher demands on extreme pressure lubrication performance are posed by stringent working conditions. In this study, the synergistic tribological properties of phosphate ammonium salt in combination with active sulfurized olefin (S1) and non-active sulfurized fatty acids (S2) were investigated to meet the needs under stringent working conditions. The anti-wear mechanisms were further explored using scanning electron microscopy (SEM) with EDS, X-ray photoelectron spectroscopy (XPS), X-ray absorption near-edge structure (XANES), and focused ion beam microscopy. The experimental results indicate that P-S2 demonstrates superior friction reduction and wear resistance under low loads, potentially attributable to its higher polarity, whereas P-S1 exhibits better wear resistance under high loads. P-S1 also shows superior extreme pressure performance attributed to its higher active sulfur content and stronger film-forming ability, evidenced by a thicker friction film (82.62 nm vs. 24.28 nm for P-S2). The study highlights that the variations in the synergistic tribological performance of phosphorus- and sulfur-based additives may link to differences in molecular structure, active sulfur content, polarity, and corrosiveness, with P-S1 demonstrating enhanced extreme pressure performance possibly through the formation of a multi-layered friction film of polyphosphate, sulfide, oligophosphate, and sulfate layers. Full article

In this study, the effects of pressure anisotropy and viscosity on the propagation of shock waves in spin-polarized degenerate quantum magnetoplasma are studied under the influence of the streaming energy of ion beams. The effects of different suitable plasma parameters on the shock wave’s potential profile are studied using the steady state solution of the Zakharov–Kuznetsov–Burgers (Z–K–B) equation, as well as the numerical simulation of the governing non-linear Z–K–B equation. First-order analysis of the non-linear wave propagation depicted a new beam-induced stable mode whose Mach number may be subsonic or supersonic depending on the anisotropic pressure combination in the presence of different spin density polarization ratios. This is the first observation of this new beam-induced stable mode in ion beam plasma, apart from the other existing modes of ion beam plasma systems, namely, the fast beam mode, the slow beam mode, the inherent ion acoustic mode, and the coupled mode, which also has unique propagation characteristics compared to the other modes. The spin density polarization ratio of spin-up and spin-down electrons have an unprecedented effect on the polarity and the direction of propagation of different shock wave modes in such plasma systems. Apart from the spin effect, anisotropic pressure combinations, as well as the viscosity of ions and ion beams, also play an outstanding role in controlling the nature of propagation of shock waves, especially in the newly detected beam-induced stable mode, and depending on the viscosity parameters of ions and ion beams, both oscillatory and monotonic shock waves can propagate in such plasma. Full article

This work provides theoretical calculations of fluorescence angular distribution and polarization within an XUV pump–XUV probe scheme designed for determining ultra-short lifetimes of highly charged heavy ions. The initial pumping leads to a non-zero alignment in the excited levels. After the probing stage, the anisotropies in angular distribution and polarization of subsequent fluorescence are significantly enhanced due to the existence of a previous alignment. Furthermore, two-photon sequential excitation from a ground state with zero angular momentum to a level with angular momentum one by two aligned linearly polarized photon beams is strictly prohibited by the selection rules and may be used as a diagnostic tool to determine beam misalignment. The present approach is based on the density matrix and statistical tensor framework. We provide the analytical form for the alignment parameters caused by successive photoexcitation either with linearly polarized photon beams, or with unpolarized photons. The analytical results can generally be used to compute angular distribution asymmetry parameters and linear polarization of subsequent fluorescence for a large array of atomic systems used in pump–probe experiments. Full article

An ultra-thin spiral diffractive lens (SDL) was fabricated by using focused ion beam milling on a fiber end-facet coated with a 100 nm thick Au film. Focusing vortex beams (FVBs) were successfully excited by the SDLs due to the coherent superposition of diffracted waves and their azimuth dependence of the phase accumulated from the spiral aperture to the beam axis. The polarization and phase characteristics of the FVBs were experimentally investigated. Results show that the input beams with various polarization states were converted to FVBs, whose polarization states were the same as those of the input beams. Furthermore, the focal length of the SDL and the in-tensity and phase distribution at the focus spot of the FVBs were numerically simulated by the FDTD method in the ultra-wide near-infrared waveband from 1300 nm to 1800 nm. The focal length was tuned from 21.8 μm to 14.7 μm, the intensity profiles exhibited a doughnut-like shape, and the vortex phase was converted throughout the broadband range. The devices are expected to be candidates for widespread applications including optical communications, optical imaging, and optical tweezers. Full article

The division of focal plane (DoFP) polarization detector has great potential for the development of aerospace polarimeters, but the existing commercial DoFP polarization detector cannot satisfy all the missions due to the diversity of satellite payloads. Here, we propose a method of directly writing a micro-polarizer array (MPA) on the detector surface based on focused ion beams (FIB) and fabricating a push-broom scanning DoFP polarization detector. The feasibility and low crosstalk of the solution were proved through testing, and the reasons for the low extinction ratio caused by oxidation were explained through characterization and numerical calculations. This scheme is not only applicable to DoFP polarization detectors but also provides ideas for the integration of other metasurface structures and detectors. Full article

Nanostructures can be produced on poly(ethylene terephthalate) (PET) foils by using a krypton fluoride (KrF) excimer laser with a wavelength of 248 nm and a pulse duration of about 20 ns. We show that surface nanoripples, nanodots, nanogrids, and hybrid patterns of ripples with dots or finer ripples on top can be fabricated. The effects of a water layer in front of the PET foil and of cooling during laser processing were investigated. For pattern formation, several irradiation parameters (pulse number, pulse energy, and polarization) were varied systematically. The spatial periods of the ripples were changed by adjusting the angle of incidence of the laser beam. All nanostructures were characterized by scanning electron microscopy, and relevant morphological parameters, such as peak-to-peak distances and spatial periods, were assessed. Shapes and heights of some structures were characterized by using focused ion beam cuts to avoid the tip-sample convolution effects typical of atomic force microscopy images. We further demonstrate nanoripple formation on PET foils as thin as 12 µm, 6 µm, and 1.4 µm. The remarkable variety of nanostructures on PET we present here enables customized fabrication for a wide range of applications. Full article

At the Relativistic Heavy Ion Collider (RHIC), the Polarized Atomic Hydrogen Gas Jet Target polarimeter (HJET) is employed for the precise measurement of the absolute transverse (vertical) polarization of proton beams, achieving low systematic uncertainties of approximately ${\sigma }_P^{\mathrm{syst}}/P\le 0.5\%$. The acquired experimental data not only facilitated the determination of single $A_{\mathrm{N}}\left(t\right)$ and double $A_{\mathrm{NN}}\left(t\right)$ spin analyzing powers for 100 and 255 GeV proton beams, but also revealed a non-zero Pomeron spin-flip contribution through a Regge fit. Preliminary results obtained for forward inelastic $p^{\uparrow }p$ and elastic $p^{\uparrow }A$ analyzing powers will be discussed. The success of the HJET at RHIC suggests its potential application for proton beam polarimetry at the upcoming Electron–Ion Collider (EIC), aiming for an accuracy of 1%. Moreover, the provided analysis indicates that the RHIC HJET target can serve as a tool for the precision calibration, with the required accuracy, of the ${}^3$He beam polarization at the EIC. Full article

Variations in the corrosion behavior of biomedical NiTi alloys in Cl⁻ containing and acidic environments present a problem with their biological implantation. The objective of this research was to evaluate the synergy of the microstructure, the corrosion behavior, and the biocompatibility of novel continuous-cast NiTi alloys and to compare them with commercial NiTi alloys. The two alloys have a practically identical nominal chemical composition, but they differ in production technology. The continuous casting technology involved vacuum induction melting of the basic components and vertical continuous casting, while the commercial NiTi alloy was produced through a process of casting, hot rolling, and forming into square shapes. The microstructure was revealed to determine the surface area and size of grains. The corrosion of a commercial nickel–titanium alloy and one prepared by a novel continuous casting method in acidic and chloride-containing solutions was studied via analytical and electrochemical tests. Localized corrosion characteristics related to oxide properties, when exposed to 9 g L⁻¹ NaCl solution, were examined with focused ion beam analysis and subsequent microchemical analysis of the formed corrosive products. Corrosion potential over time and the oxide film resistance were analyzed using linear polarization measurements. To obtain a preliminary estimate of biocompatibility, human fibroblast cells were used in indirect contact, i.e., alloy conditioning medium. The continuous casting method resulted in a reduction in the average grain size in comparison to the commercial sample and better corrosion stability of the sample in an acidic environment. Also, in a solution of 9 g L⁻¹ NaCl the commercial sample showed high values for the corrosion current density (j_corr = 6 μA cm⁻²), which indicated low corrosion resistance, while the continuous casting sample possessed much better corrosion stability and lower values for the corrosion current density (j_corr = 0.2 μA cm⁻²). In line with that, elemental analysis of the corroded surfaces showed higher Cl⁻ ion deposition over the surface layer of the commercial sample, suggesting local oxide breakdown. Moreover, NiTi_cc reached a value three times higher for polarization resistance (R_p = 270 kΩ cm²) over time in comparison to the commercial sample (R_p~100 kΩ cm²). Biocompatibility evaluation showed that human fibroblast cells exhibited altered metabolic activity. An MTT assay showed that cells’ mitochondrial activity dropped below that of control cells in the presence of both materials’ supernatants. Full article