Grazing Incidence Angle Research Articles

Analysis of Resonant Soft X-ray Reflectivity of Anisotropic Layered Materials

We present here a method for the quantitative prediction of the spectroscopic specular reflectivity line-shape in anisotropic layered media. The method is based on a 4 × 4 matrix formalism and on the simulation from the first principles (through density functional theory—DFT) of the anisotropic absorption cross-section. The approach was used to simulate the reflectivity at the oxygen K-edge of a 3,4,9,10-perylene-tetracarboxylic dianhydride (PTCDA) thin film on Au(111). The effect of film thickness, orientation of the molecules, and grazing incidence angle were considered. The simulation results were compared to the experiment, permitting us to derive information on the film geometry, thickness, and morphology, as well as the electronic structure.

Design of Pt/C X-ray supermirror by needle optimization

Needle optimization is widely used in visible and infrared region, but it is rarely utilized in X-ray and extreme ultraviolet waveband. We use Needle optimization to design Pt/C X-ray supermirrors, and the grazing incidence angles are 1.0, 1.4, and 1.7 degree, respectively. A modified target is introduced into optilayer software. A good result is obtained by Optilayer software combined with IMD software. The difference of design results between block method and needle optimization is discussed.

Ultra-thin Hf0.5Zr0.5O2 thin-film-based ferroelectric tunnel junction via stress induced crystallization

We report on 4.5-nm-thick Hf0.5Zr0.5O2 (HZO) thin-film-based ferroelectric tunnel junctions (FTJs) with a tungsten (W) bottom electrode. The HZO on the W electrode exhibits stable ferroelectricity with a remanent polarization of 14 μC/cm2, an enhanced tunneling electroresistance of 16, and excellent synaptic properties. We found that a large tensile stress was induced on a HZO thin film, owing to a low thermal expansion coefficient of the W bottom electrode. The low thermal expansion coefficient results in the effective formation of an orthorhombic phase, even in an ultra-thin HZO film. This was verified by a comparative study of the electrical characteristics, grazing-angle incidence x-ray diffraction, and residual stress measurement of the HZO film on various bottom electrodes with different thermal expansion coefficients. In addition, this study demonstrates the suitable functions of the FTJ for electronic synapses, such as analog-like resistance transition under various pulse schemes. The fabricated stress-engineered FTJ exhibits an appropriate conductance ratio, linearly modulated long-term potentiation and depression characteristics, and excellent reliability. These characteristics render FTJs ideal electronic devices for neuromorphic computing systems.

Influence of annealing conditions on tripe-layer TiO2/Si3N4/SiO2 antireflection coatings for GaAs solar cells

In this work, TiO2/SiO2/Si3N4 triple-layer antireflection coatings (TLARC) were prepared on GaAs substrate by RF sputtering and Plasma Enhanced Chemical Vapor Deposition (PECVD). Influence of annealing conditions on the structure and optical properties of TLARC were also investigated. The structure and optical proprieties were analyzed by Grazing Incidence Angle X-ray Diffraction (GIXRD) Fourier Transform Infrared Spectroscopy (FT-IR), Atomic Force Microscopy and UV-VIS spectroscopy. The experimental results were summarized as follows: diffraction peaks of SiO2, Si3N4 and TiO2 respectively appeared in the as-deposited status, and after annealing, new diffraction peak at 25.2° corresponds to TiO2 was confirmed by checking out PDF cards; Stretching vibration of Ti=O, Si-O-Si and N-Si-N was confirmed by FT-IR spectrum; The average reflectance of the TLARC after annealing at 750 °C and holding for 5 min reached the lowest value, which was approximately 7.84 %.

Phosphorene pnp junctions as perfect electron waveguides

The current flow in phosphorene pnp junctions is studied. At the interfaces of the junction, omni-directional total reflection takes place, named anti-super-Klein tunneling, as this effect is not due to an energetically forbidden region but due to pseudo-spin blocking. The anti-super-Klein tunneling confines electrons within the junction, which thus represents a perfect lossless electron waveguide. Calculating the current flow by applying Green’s function method onto a tight-binding model of phosphorene, it is observed that narrow electron beams propagate in these waveguides like light beams in optical fibers. The perfect guiding is found for all steering angles of the electron beam as the total reflection does not rely on the existence of a critical angle. For low electron energies and narrow junctions, the guided modes of the waveguide are observed. The waveguide operates without any loss only for a specific orientation of the junction. For arbitrary orientations, minor leakage currents are found, which, however, decay for low electron energies and grazing incidence angles. It is shown that a crossroad-shaped pnp junction can be used to split and direct the current flow in phosphorene. The proposed device, a phosphorene pnp junction as a lossless electron waveguide may not only find applications in nanoelectronics but also in quantum information technology.

A review on the fabrication technology of X-ray reflector

This article reviews on the fabrication advancement of X-ray reflect mirror fabrication in terms of technical requirements, fabrication and metrology development. Synchrotron radiation source, as a revolutionary light source, provides one of the most high-performance X-ray for scientific research, where reflect mirror plays an essential role in X-ray beam focusing. The short wavelength of X-ray demands reflecting photons only at a grazing angle of incidence on the extremely high-precision and smooth surface. Fabrication of such mirrors requires highly specialized equipment and technology that only a few foreign optic manufacturers possess, whereas manufacturers in China is laggard in this area. It is imperative to develop fabrication capability domestically as two synchrotron radiation facilities are under construction and several more projects are about to launch in the near future in China.

Monochromatic Kirkpatrick–Baez microscope combining a spherically bent crystal and a multilayer mirror

Most Kirkpatrick–Baez (KB) microscopes for imaging monochromatic laser-produced plasma are composed of two concave multilayer mirrors; their energy resolution (ΔE/E) is approximately 1×10−1. In this study, a new type of monochromatic KB microscope combining a spherically bent crystal and a multilayer mirror was developed. As the spherically bent crystal features a narrow spectral bandwidth, it can attain a high energy resolution. In addition, the grazing incidence angle on the crystal is significantly larger than that on a multilayer mirror; therefore, a large collection solid angle and a high spatial resolution can be achieved. A prototype consisting of a spherically bent mica crystal and a mirror coated with Ni/C multilayers was constructed to demonstrate the feasibility and performance of the proposed KB microscope. In the backlight imaging experiment performed, the microscope achieved a spatial resolution of approximately 10μm throughout a 200μm field of view at 4.51 keV, with ΔE/E = 4.9 ×10−3. The proposed KB microscope featuring a high energy and spatial resolution is expected to be a novel experimental tool for inertial confinement fusion (ICF) diagnostics.

Effects of surface undulations on asymmetric X-ray diffraction: a rocking-curve topography study.

The results are reported of an X-ray diffraction study of an Si crystal designed and fabricated for very asymmetric diffraction from the 333 reflection for X-ray energies of 8.100 and 8.200 keV. A crystal with an asymmetry angle of 46 ± 0.1° between the surface and the (111) planes was studied. The grazing angles of incidence were near 1.08 and 0.33° for these two energies, respectively. Features arising from surface undulations were not observed at 8.100 keV, but were observed at 8.200 keV. The results at 8.100 keV allow an alternative explanation based on strain near the surface to be ruled out. Topographic images were obtained as a function of rocking angle, and in the case of 8.200 keV the surface morphology is evident. The results are found to be in agreement with dynamical X-ray diffraction calculations made with the Takagi-Taupin equations specialized to a surface having convex or concave features, as reported in the accompanying paper [Macrander (2020). J. Appl. Cryst. 53, 793-799].

Refraction of Fast Ne Atoms in the Attractive Well of a LiF(001) Surface.

Ne atoms with energies of ≤3 keV are diffracted under grazing angles of incidence from a LiF(001) surface. For a small momentum component of the incident beam perpendicular to the surface, we observe an increase in the elastic rainbow angle together with a broadening of the inelastic scattering profile. We interpret these two effects as the refraction of the atomic wave in the attractive part of the surface potential. We use a fast, rigorous dynamical diffraction calculation to find a projectile-surface potential model that enables a quantitative reproduction of the experimental data for ≤10 diffraction orders. This allows us to extract an attractive potential well depth of 10.4 meV. Our results set a benchmark for more refined surface potential models that include the weak van der Waals region, a long-standing challenge in the study of atom-surface interactions.

Curved Lipid Interfaces Studied with Grazing Incident SANS

Curved cell membranes are important for the function of the cell, both for compartmentalization in organelles within the cell, as well as for cellular mitosis. It has also been shown that the curvature of a lipid membrane can affect the concentration of membrane bound proteins. In this project we have used semiconductor nanowires in order to study the effect of curvature on phospholipid bilayers and membrane proteins. We have previously demonstrated the formation of a supported phospholipid bilayer on nano wires via vesicle fusion, which can be used as a proxy to curved membranes. Based on fluorescence recovery after photobleaching, FRAP, measurement, the phospholipid bilayers were found to follow the contours of the nano wires as continuous and fluid, locally curved bilayers. However these data do not reveal the coverage, composition and the dimensions of the bilayer. In this project we aim to revel this using grazing incident small angle neutron scattering (GISANS). For this purpose we have performed GISANS experiments at the KSW-1 at FRM II (Germany), VSANS at NIST (USA) and SANS2D at ISIS (UK) with phospholipid covered nanowires. The nanowires were covered with a phospholipid bilayer obtained from deposition from vesicular dispersion of mixture of 20mol% DOPE in DOPC. In these experiments we have successfully shown the formation of a lipid bilayer and the subsequent binding of membrane protein. These results shows that nanowire supported lipid bilayer is an excellent way to study biding membrane protein to curved lipid interfaces.

Design of W/Si supermirror by block method

In X ray region, the supermirror can provide better optical performance than metal substrate or two-layer mirror. W/Si supermirrors are designed in 0.2–10 keV by block method. These mirrors have big grazing incidence angles of 1.0, 1.4, and 1.7 degrees, which is the most important characteristic in our job. Compared with two-layer mirror, our design provides a significant improvement of reflectance in 5–10 keV, and it also gives a good initial one for further optimization by other algorithms. Our job has a potential application in X ray astronomical imaging detection missions.

Investigation of the potential sputtering process on the solid Ne surfaces induced by grazing incidence of slow Ar q+

SynopsisFor the quantitative investigation of the potential sputtering process on the surface of noble gas solid, we have performed the coincidence measurement of the ions desorbed and projectiles scattered from solid Ne surfaces, due to 3 keV Ar6+ impacts at grazing incidence angles. The dependence of desorption on the charge state of the scattered Ar projectiles is found.

Evolution of crystallographic structure and ferroelectricity of Hf0.5Zr0.5O2 films with different deposition rate

Hf0.5Zr0.5O2 films are one of the most attractive HfO2-based ferroelectric films because of good ferroelectricity, extreme thinness, and excellent compatibility with silicon devices. The origin of the ferroelectricity of Hf0.5Zr0.5O2 films is the noncentrosymmetric orthorhombic phase (space group Pca21). The effects of process temperature, annealing temperature, thickness, and doping to increase the portion of the orthorhombic phase, which contributes to ferroelectricity, have been studied extensively. However, although most studies have used atomic layer deposition, no study has been reported on the effect of the deposition rate on the ferroelectricity of Hf0.5Zr0.5O2 films. In this work, the influences of the deposition rate on the ferroelectricity and crystal structure of Hf0.5Zr0.5O2 films were examined. In order to conduct systematic and quantitative analysis, measurements of switching transient current, ferroelectric P-E curve, dielectric constant, deconvolution of grazing angle incidence X-ray diffraction, and piezoresponse force microscopy were performed. Hf0.5Zr0.5O2 films with a deposition rate of 1.1 Å/cycle have a more ideal hysteresis curve shape, higher remanent polarization (initial state: 16 μC/cm2, wake up state: 22 μC/cm2), and a higher orthorhombic phase portion than other deposition rates.

Adsorption and desorption phenomena on thermally annealed multi-walled carbon nanotubes by XANES study

The multi-walled carbon nanotubes (MWCNTs) studied in this work were synthesized by the catalytic chemical vapor deposition (CCVD) process, and were thermally annealed by the hot filament plasma enhanced (HF PE) method at 550 °C for two hours. The x-ray absorption near edge structure (XANES) technique was used to investigate the adsorption and desorption phenomena of the MWCNTs at normal and grazing incidence angles. The adsorbates were found to have different sensitivities to the thermal annealing. The geometry of the incident beam consistently gave information about the adsorption and desorption phenomena. In addition, the adsorption of non-intrinsic potassium quantitatively affected the intrinsic adsorbates and contributed to increase the conductivity of the MWCNTs. The desorption of potassium was almost 70% greater after the thermal annealing. The potassium non-intrinsic adsorbates are from a physisorption mechanism whereas the intrinsic adsorbates result from chemisorption.

Design and Analysis of Hard X-Ray Microscope Employing Toroidal Mirrors Working at Grazing-Incidence

A high resolution microscope is designed for plasma hard X-ray (10–20[Formula: see text]keV) imaging diagnosis. This system consists of two toroidal mirrors, which are nearly parallel, with an angle twice that of the grazing incidence angle and a plane mirror for spectral selection and correction of optical axis offset. The imaging characteristics of single toroidal mirror and double mirrors are analyzed in detail by the optical path function. The optical design, parameter optimization, image quality simulation and analysis of the microscope are carried out. The optimized hard X-ray microscope has a resolution better than 5[Formula: see text][Formula: see text]m at 1[Formula: see text]mm object field of view. The experimental data shows that the variation of the resolution is smaller in the direction of incident angle decrease than that in the increasing direction.

Performance of Si/PEDOT:PSS Solar Cell Controlled by Dipole Moment of Additives

Solar cells composed of silicon (Si) and polymer films have attracted much attention because of their high performance and facile preparation using aqueous solutions. Although a large amount of research has been carried out to further improve their performance, the factors required to achieve this are not yet fully understood from the perspective of physical chemistry. Here, we show the effect of additives on the performance of Si/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) solar cells using six different additives. The relationships among the solar cell performance, electrical properties, and the structure of the polymer film are examined by changing the additive and conducting cyclic voltammetry, electric conductivity, and two-dimensional grazing incidence angle X-ray diffraction measurements. The dipole moment of the additive molecule was determined to be a key factor for improving the performance of Si/PEDOT:PSS solar cells. In particular, an additive with a higher dipole momen...

New Opportunities for in Situ and Operando Characterization of Electrochemical Systems at I07

The range of material systems and architectures used in electrochemical research is vast, spanning from solid-solid electrolyte interfaces for solid state batteries to nano-sized particles systems for electrocatalytic materials in fuel cells. Despite the physical differences among these systems the possibility of establishing relationships between structure and activity is a common key aspect for understanding interfacial electrochemical processes. I07 is the surface and interface x-ray diffraction beamline at the Diamond synchrotron (Didcot,UK). The beamline exploits a high brilliance 3rd generation synchrotron source to allow the characterization of a wide array of possible sample types, opening up experimental possibilities which are not feasible using standard lab based x-ray sources. The use of grazing incidence angle techniques available on I07 not only allows reduction of background signal from the bulk enabling measurements of signals from the top layers of a sample, but it also enables investigation of the relationship between nano-scale structural changes and reactivity during time-resolved experiments. The current capabilities of beamline I07 will be outlined regarding in-situ and operando measurements of material systems for applications in energy storage. Also opportunities for investigating novel solid-state electrolyte material interfaces will be detailed. Experimental techniques discussed will include surface x-ray diffraction, x-ray reflectivity, grazing incidence small angle x-ray scattering, grazing incidence wide angle x-ray scattering, and liquid surface x-ray scattering.

Effects of deposition temperature on the properties of sputtered yttrium-doped hafnium oxide thin films

Yttrium-doped HfO2 (Y:HfO2) thin films with different deposition temperature were deposited on p-type (100) silicon substrates. The composition and chemical states of each element in the films were investigated by x-ray photoelectron spectroscopy (XPS). The grazing angle incidence x-ray diffraction (GIXRD) patterns suggested the phase transformation of Y:HfO2 thin films as the increase of deposition temperature. The thickness and density of the thin films were calculated by fitting x-ray reflectivity (XRR) data. Root mean square (RMS) roughness was obtained from atomic force microscopy (AFM) images. As the deposition temperature increased, a transition from linear dielectric to ferroelectric behavior happened. Lower leakage current density was obtained by increasing the deposition temperature.

Development of an adjustable Kirkpatrick-Baez microscope for laser driven x-ray sources.

A prototype of a highly adjustable Kirkpatrick-Baez (KB) microscope has been designed, built, and tested in a number of laser driven x-ray experiments using the high power (200 TW) VEGA-2 laser system of the Spanish Centre for Pulsed Lasers (CLPU). The presented KB version consists of two, perpendicularly mounted, 500 μm thick silicon wafers, coated with a layer of platinum, a few tens of nanometers thick. Unlike the usual millimeter thick glass substrate, this design allows for a larger bending flexibility and large adjustment range. According to simulations, this KB microscope offers broadband multikiloelectron volt reflection spectra (1 eV-20 keV), allowing more spectral tunability than conventional Bragg crystals. In addition to be vacuum compatible, this prototype is characterized by a relatively small size (21 cm × 31 cm × 27 cm) and permits remote control and modification both of the radii of curvature (down to 10 m) and of the grazing incidence angle (up to 60 mrad). A few examples of focusing performance tests and experimental results are discussed.

System for coincidence measurements of the ions desorbed and projectiles scattered from noble gas solid surfaces by slow multiply charged ion impacts

We have developed a new experimental apparatus for performing coincidence measurements of the ions desorbed and projectiles scattered from the surfaces of noble gas solids by slow multiply charged ion impacts at grazing incidence angles. This simultaneously measures the desorbed ions' flight times and the scattered projectiles' charge states. We also conduct experiments on 6 keV Ar6+ impacts onto a solid Ne surface using the device.