X-ray structural analysis at the Department of Condensed Matter Physics

Milan Dopita, Radomír Kužel, Václav Holý, Lukáš Horák, Stanislav Daniš

Department of Condensed Matter Physics, Faculty of Mathematics and Physics, Charles University, Ke Karlovu 5, 121 16, Prague 2, Czech Republic

milan.dopita@matfyz.cuni.cz

The Group of Structure Analysis at the Department of Condensed Matter Physics, Faculty of Mathematics and Physics, Charles University has a long term tradition going back to the beginning of the Faculty of Mathematics and Physics (founded in 1951). For several decades the group scientists focus to the research of the structure of materials using X-ray diffraction, neutron scattering or synchrotron radiation [1]. The main directions of research include structural analysis and analysis of the real structure of polycrystalline materials, thin layers, multilayers, two-dimensional surface structures, ferroelectrics, semiconductors, magnetic materials, quantum dots, liquid crystals, fullerenes, ultra-fine grained and nanocrystalline materials with the aim to find the relationships between the structure and properties of materials [2].

Recently the group consist of Stanislav Daniš, Petr Doležal, Milan Dopita (head of the group), Václav Holý, Lukáš Horák (head of the X-ray laboratory), Radomír Kužel and Tereza Košutová. It is worth to mention that the past and recent scientific focus of the group was significantly formed by former group members, at the field of crystallography, X-ray scattering and materials science well known personalities as are or were Josef Šedivý, Václav Valvoda, Pavla Čapková, Ludmila Dobiášová, Radovan Černý, Jan Ilavský, David Rafaja, Zdeněk Matěj, Daniel Šimek.

Besides of the top level own research, awarded by high number of national and international grants, the members of the group are intensively involved in education, teaching and training activities at the faculty, consisting of lecturing and guaranty of courses, exercises and lectures, supervising Bc., Mgr. and PhD students and programs. Additionally the members of the group were and are historically active in CSCA (past scientific secretaries V. Valvoda and R. Černý and recent scientific secretary R. Kužel), and are involved in organization of national and international scientific meetings, crystallographic conferences and workshops.

In past few years the X-ray laboratory, underwent significant instrumental upgrade. Several modern – top class laboratory instruments, substantially broadening the instrumental possibilities and available scattering techniques of the laboratory, were commissioned [3]. Namely i) the general purpose X-ray diffractometer equipped with a high flux rotation anode X-ray source and goniometer allowing both, coplanar and non-coplanar (in-plane) diffraction; ii) high energy X-ray diffractometer equipped with unique X-ray optical elements, operating with various X-ray energies (6.9 – 22 keV); and iii) apparatus dedicated to a small angle X-ray scattering (SAXS) and small angle X-ray scattering in non-coplanar geometry (GISAXS) measurements. All machines are equipped with modern 2D hybrid pixel, single photon counting, low noise, detectors.

This unique combination of X-ray diffractometers offers measurements covering a wide range of reciprocal space between q of 0.003 to 21 1/Å (q is a magnitude of reciprocal space vector), which allows the fundamental studies of materials properties in ranges from 0.03 up to 200 nm, in real space. The equipment represents a unique collection of instruments allowing nearly any type of laboratory accessible X-ray scattering experiment - measurements of single crystals, polycrystalline bulk and powder materials, nanocrystalline samples, thin films, multilayers and epitaxial layers.

Figure 1. List of X-ray diffractometers available in the X-ray laboratory at the Department of Condensed Matter Physics, Faculty of Mathematics and Physics, Charles University. From left upper corner: Seifert XRD7, Bruker D8, Photonics Science Laue diffractometer, Panalytical MPD, Panalytical MRD, Rigaku Rapid II, left bottom corner: refurbished low temperature diffractometer Dicont based on Siemens D500, Rigaku SmartLab, Malvern-Panalytical Empyrean II, Xenocs Xeuss 2.0 SAXS/WAXS diffractometer.

The instruments can operate with various X-ray wavelengths (Co, Cu, Mo and Ag), and in different geometries: Bragg-Brentano geometry, medium resolution parallel beam setting, high resolution geometry, with monochromatic Kα₁ radiation and in coplanar and non-coplanar (in-plane) mode. Various sample environments, low and high temperature chambers, deformation (tensile and compression) stage, reaction chamber are available for individual diffractometers. Methodologically the laboratory offers the structure solution and refinement, qualitative and quantitative phase analysis, the real structure of material studies: preferred orientation of crystallites – texture measurements, residual stress measurements, reflectivity measurements, rocking curve measurements, reciprocal space mapping, pair distribution function – total scattering measurements, small angle x-ray scattering and grazing-incidence small angle x-ray scattering.

Figure 2. List of non-ambient conditions chambers and stages available in the X-ray laboratory at the Department of Condensed Matter Physics. From left upper corner: Linkam TS 1000, Linkam THMS 600, Anton Paar DHS 1100, MRI HT-1600 high temperature chambers, Anton Paar XRK 900 reactor chamber, left bottom corner: Oxford Cryosystems Cryostream 800 cooler, Cold Edge closed cycle He Cryostat, MRI compression / tensile stage, Almax easyLab diamond anvil cell.

[1] V. Valvoda, MaterialsStructure, vol. 8, number 2, (2001), 104.

[2] R. Kužel, V. Holý, S. Daniš, Materials Structure, vol. 17, no. 2a, (2010), k68

[3] https://kfkl.mff.cuni.cz/en/xray