k68      Struktura 2010 - Lectures                                    Materials Structure, vol. 17, no. 2a (2010)


                                 Radomír Kužel, Stanislav Daniš, Václav Holý
      Department of Condensed Matter Physics, Faculty of Mathematics and Physics, Charles University in
                                 Prague, 121 16 Prague 2, Ke Karlovu 5

Some details from the X-ray group history can be found in        terns. The system is also useful for the analysis of samples
[1]. X-ray analysis was one of the main activities of the De-    containing large grains.
partment of Solid State Physics from the very beginning of           There are several directions of the research nowadays.
the Faculty of Mathematics and Physics (founded 1951).           The X-ray lab participates in an European project on mag-
The X-ray group was headed by Doc. Josef Šedivý                  netic semiconductors, the investigation of structure of di-
(1951-1985) and then by Prof. Václav Valvoda who was             luted magnetic semiconductors (GaMnAs, GeMn, GaFe
also active in the CSCA as a scientific secretary. In the six-   N). In the case of GaMnAs in particular we determine the
ties and seventies, the main focus was given to carbides and     concentration of magnetic Mn ions in various lattice posi-
nitrides and lattice vibrations studies. Since 1985 intensive    tions (substitutional, interstitial) by anomalous X-ray dif-
studies of nitride thin films, in particular TiN, were per-      fraction and X-ray stading wave method. We study also
formed. Then different streams were followed by individ-         strain relaxation in laterally patterned magnetic epitaxial
ual members - magnetic multilayers, materials deformed           layers by high-resolution X-ray diffraction. Another inter-
by severe plastic deformation, diffusion studied by XRD,         national project deals with in-situ investigation of epitaxial
quarternary intermetallic compounds, materials with func-        layers of GaN during deposition. Our task is to develop a
tional gradient of composition, intercalates, high-tempera-      method for the determination of densities of various types
ture superconductors, nanocomposites, ferroelectrics etc.        of threading dislocations by X-ray reciprocal space map-
    During the last decade, significant update of X-ray in-      ping of diffuse scattering. In the field of nanophysics, we
struments was achieved. The laboratory has several new           study of structure of semiconductor nanoparticles embed-
systems - modern complex diffractometer for investigation        ded in amorphous matrix by grazing-incidence small angle
of thin films - MRD X’Pert Pro (Philips) equipped with sev-      scattering and diffraction during magnetron deposition and
eral optical modules for measurements in different resolu-       post-growth annealing. We use the DAFS method for the
tion: parabolic Goebel mirror, two four-crystal mono-            investigation of local chemical composition of semicon-
chromators, parallel plate collimator, graphite monochro-        ductor quantum dots (GeSi, InGaN).
mator, triple axis germanium monochromator. The sample               Other directions follow past investigations and method-
holder is placed on the large Eulerian cradle for measure-       ological development. In collaboration with other depart-
ment of stress and texture using also polycapillary optics .     ments of the faculty and TU Freiberg, microstructural
    Vertical q-q Panalytical diffractometer X’Pert Pro has       studies of submicrocrystalline materials obtained by severe
several options. For room temperature measurements, the          plastic deformation are performed by several complemen-
specimen is placed on the xyz table with j-rotation and in-      tary methods – XRD line profile analysis, TEM, positron
clinations. For conventional symmetric scans, variable slits     annihilation spectroscopy, mechanical testing and EBSD.
are used to keep the analyzed specimen area fixed. In the        Anotother stream consists in complex XRD characteriza-
diffracted beam either point detector with monochromator         tion of thin polycrystalline films of different type. The
or linear position detector PIXCel can be used. The latter is    main attention has been given to TiO2 films, stress analysis,
applied for fast data collection, in particular at non-ambient   time and thickness dependence of crystallization by in-situ
temperatures and also for line profile analysis requiring        measurements high-temperature studies.
low-noise data. Combined parallel-focusing geometry in               Many studies of different nanocrystalline powders are
double-mirror setup is useful for rough surfaces or non-flat     performed as well. Successful testing of possibility of mea-
specimen. MRI high-temperature chamber with both direct          surement of pair distribution function of nanocrystalline
and radiant heating can replace the table.                       powders in laboratory conditions was done recently. A
    Bruker D8 Avance diffractometer is used for standard         new software MStruct for whole pattern fitting suitable for
powder diffraction and it is equipped with variable slits        the above analysis (nanomaterials, thin films) was devel-
and Sol-X solid state detector for supression of fluorescent     oped by Z. Matìj.
background.                                                          The X-ray lab is frequently used by our colleagues from
    HZG-4 goniometer from Freiberger Präzisionsmecha-            the group of magnetic properties of the department for sev-
nik is now used for collection of full patterns with Mo radi-    eral tasks - single crystal quality assesment and orienta-
ation.                                                           tion, phase analysis and Rietveld analysis of different
    A new Rigaku Rapid II system with a cylindrical 2D im-       intermetallic compounds with interesting magnetic proper-
age plate detector is designed for collection of single crys-    ties.
tal data and structure determination but also for microdi        1. V. Valvoda, Materials Structure, 8 (2001) 104-105.
ffraction and very fast collection of Debye-Scherrer pat-
                                                                         full contribution will be published in next issue

                                             Ó Krystalografická spoleènost

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