Showing papers on "Total external reflection published in 2020"
TL;DR: This work demonstrates how to probe the local structure of two stacked functional layers by means of grazing incidence total X-ray scattering and pair distribution function (PDF) analysis, and highlights the opportunity to develop a detailed understanding of structural evolution during the fabrication of real thin film devices using the PDF technique.
Abstract: Functional thin films are commonly integrated in electronic devices as part of a multi-layer architecture. Metal/oxide/metal structures e.g. in resistive switching memory and piezoelectric microelectrochemical devices are relevant applications. The films are mostly fabricated from the vapour phase or by solution deposition. Processing conditions with a limited thermal budget typically yield nanocrystalline or amorphous layers. For these aperiodic materials, the structure is described in terms of the local atomic order on the length scale of a few chemical bonds up to several nanometres. Previous structural studies of the short-range order in thin films have addressed the simple case of single coatings on amorphous substrates. By contrast, this work demonstrates how to probe the local structure of two stacked functional layers by means of grazing incidence total X-ray scattering and pair distribution function (PDF) analysis. The key to separating the contributions of the individual thin films is the variation of the incidence angle below the critical angle of total external reflection, In this way, structural information was obtained for functional oxides on textured electrodes, i.e. PbZr0.53O0.47O3 on Pt[111] and HfO2 on TiN, as well as HfO2-TiOx bilayers. For these systems, the transformations from disordered phases into periodic structures via thermal teatment are described. These examples highlight the opportunity to develop a detailed understanding of structural evolution during the fabrication of real thin film devices using the PDF technique.
7 citations
TL;DR: It was found that RHEPD plots were similar to RHEED plots if they were compared at Bragg reflections of the same order and multiple scattering effects turned out to be very weak.
Abstract: Azimuthal plots for RHEPD (reflection high-energy positron diffraction) and RHEED (reflection high-energy electron diffraction) were calculated using dynamical diffraction theory and then compared. It was assumed that RHEPD and RHEED azimuthal plots can be collected practically by recording the intensity while rotating the sample around the axis perpendicular to the surface (for the case of X-ray diffraction, such forms of data are called Renninger scans). It was found that RHEPD plots were similar to RHEED plots if they were compared at Bragg reflections of the same order. RHEPD plots can also be determined in the region of total external reflection and for such conditions multiple scattering effects turned out to be very weak. The findings for azimuthal plots are also discussed in the context of the formation mechanisms of Kikuchi patterns.
3 citations
TL;DR: In this article, the internal mechanical stress and the related polarization of the studied dielectrics are determined, and the observed polarization in this single crystal is caused by a large macroscopic dipole moment.
Abstract: Glasslike dielectrics are investigated by methods of plasmon dispersion and asymmetry of the number of localized electrons in the region in which total external reflection of X-rays is formed and excitation of plasmon oscillations takes place. The internal mechanical stress and the related polarization of the studied dielectrics are determined. It is discovered that a lithium fluoride crystal lacks an internal mechanical stress and that the observed polarization in this single crystal is caused by a large macroscopic dipole moment.
1 citations
TL;DR: In this paper, the authors considered the reflection from a random medium of light with short coherence length and found that the second order correlation function of light can have a peak in a direction where the reflection angle is equal to angle of incidence.
Abstract: We consider the reflection from a random medium of light with short coherence length. We found that the second order correlation function of light can have a peak in a direction where the reflection angle is equal to angle of incidence. This occurs when the size of the region, from which light is collected, is larger than the coherence length.
TL;DR: In this paper, a theoretical formalism for quantitative description of X-ray diffraction from Langmuir monolayers under conditions of total external reflection has been developed, based on the distorted-wave approximation.
Abstract: A theoretical formalism for quantitative description of X-ray diffraction from Langmuir monolayers under conditions of total external reflection has been developed. The proposed approach, based on the distorted-wave approximation, allows to consider physical mechanisms for plotting diffraction curves and maps (in the reciprocal space) for real monolayers and describe self-consistently specific features of Bragg peaks. The resulting algorithm can easily be implemented on a personal computer, which provides the opportunities to carry out numerical simulation of experimental two-dimensional diffraction intensity maps and determine reliably both the mean values of structural parameters of layers and their rms deviations.
TL;DR: In this paper, the spectral-angular and angular distributions of parametric X-ray radiation (PXR) and diffracted transition radiation (DTR) are obtained taking into account the multiple scattering of the relativistic electrons by the atoms of the target.
Abstract: The dynamic theory of coherent X-ray radiation, excited in a periodic layered medium by a divergent beam of relativistic electrons in the Bragg scattering geometry, is developed. In framework of the two-wave approximation of the dynamic theory of diffraction, expressions describing the spectral-angular and angular distributions of parametric X-ray radiation (PXR) and diffracted transition radiation (DTR) are obtained taking into account the multiple scattering of the relativistic electrons by the atoms of the target. Based on the expressions obtained, the possibilities of the manifestation of the effects of dynamical diffraction in coherent X-rays were investigated. The influence of the asymmetry of the electron Coulomb field reflection with respect to the target surface (the reflecting layers situate nonparallel to target surface) on the spectral-angular characteristics of the PXR and the DTR under conditions of the electron multiple scattering is estimated. It is shown that at a fixed Bragg angle the width of the PXR spectrum increases when the angle of incidence of the electron on the target decreases, which leads to an increase in the PXR angular density. In the same conditions the width of the frequency domain of total external reflection and the amplitude of the DTR spectrum also increase, which leads to a significant increase in the angular density of the DTR. The obtained analytical expressions can be used to determine the optimal parameters of the experiment on confirmation of the predicted dynamic effects.