Theoretical Approach to Analysis of X-Ray Grazing-Incidence Diffraction from 2D Crystals
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Theoretical Approach to Analysis of X-Ray Grazing-Incidence Diffraction from 2D Crystals M. A. Chueva, G. V. Prutskovb, N. N. Novikovab,*, E. M. Pashaevb, O. V. Konovalovc, N. D. Stepinad, A. V. Rogachevb, and S. N. Yakuninb a Valiev
Institute of Physics and Technology, Russian Academy of Sciences, Moscow, 117218 Russia b National Research Centre “Kurchatov Institute,” Moscow, 123182 Russia c European Synchrotron Radiation Facility (ESRF), Grenoble, 38043 France d Shubnikov Institute of Crystallography, Federal Scientific Research Centre “Crystallography and Photonics,” Russian Academy of Sciences, Moscow, 119333 Russia *e-mail: [email protected] Received April 27, 2020; revised April 27, 2020; accepted May 12, 2020
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. DOI: 10.1134/S1063774520050041
INTRODUCTION The unique properties of synchrotron radiation (primarily, high intensity and coherence) allow to increase significantly the spatial resolution, sensitivity, and accuracy of X-ray studies. Modern surface-sensitive methods provide wide opportunities to obtain the structural data on the interfaces and surfaces of individual nanoobjects and to monitor the kinetics of the structure-formation processes in two-dimensional ensembles of various nature. These studies not only increase significantly the knowledge of the structure of nanoscale systems but also facilitate onrush of technological progress (because interfaces and ultrathin layers become key elements of promising functional materials and nanodevices). Two-dimensional ensembles at liquid interfaces are of peculiar interest due to the high mobility of nearsurface ions, molecules, and nanoparticles in these structures. Using self-assembly principles, one can grow complex ultrathin films on a liquid surface and control the nanoarchitecture of these systems at the molecular level. One can modify parameters of these films in a wide range by changing the chemical and physical characteristics of the liquid subphase, which makes it possible to create in a controlled manner radically new bioorganic nanomaterials that are absent in nature. The main functional properties of these materials (optical, electrical, magnetic, etc.) are deter-
mined by collective molecular dynamics at the interface; therefore, determination of hierarchical relationships between the molecular c
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