Temat: 61.72.Ff - Prolib Integro

Skocz do pozycji: 1.

Tytuł:: Synchrotron Diffraction topography in Studying of the Defect Structure in Crystals Grown by the Czochralski Method
Autorzy:: Wierzchowski, W.
Wieteska, K.
Malinowska, A.
Wierzbicka, E.
Lefeld-Sosnowska, M.
Świrkowicz, M.
Łukasiewicz, T.
Pajączkowska, A.
Paulmann, C.
Tematy:: 61.72.Ff; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1399483.pdf Link otwiera się w nowym oknie
Opis:: The synchrotron diffraction topography had been widely used for investigation of the structural defects in crystals grown by the Czochralski method. Similarly as conventional diffraction topography, the synchrotron topography consists in recording with high spatial resolution of the beam formed by the Bragg reflection from the crystal. The advantages of synchrotron sources come from the possibilities of using the wavelength from a wide spectral range, improved high spatial resolution and collimation of the beam as well as from shortening the time necessary for the investigation. The synchrotron diffraction topography includes experimentally simpler white beam topography and more complicated monochromatic beam (multicrystal) topography, where the beam is formed by monochromators. In the case of Czochralski-grown crystals the synchrotron diffraction topography can be used for studying of the individual dislocations and their complexes such as glide bands or sub-grain boundaries, individual blocks, twinning, the domain structure and various segregation effects negatively affecting crystal properties. In addition, the topographical investigation can provide information concerning the reasons for the generation of defects, useful in the improving of the technology. In the present paper the possibilities of the synchrotron diffraction topography are discussed on the basis of several investigations of the Czochralski-grown oxide and semiconductor crystals, performed by the authors at HASYLAB. The majority of the results concern the oxide crystals grown at the Institute of Electronic Materials Technology, in particular garnets, orthovanadates, mixed calcium barium and strontium niobates as well as praseodymium lanthanum aluminates.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 2.

Tytuł:: X-Ray Topographic Studies of Defect Structure in $YVO_4$ Crystals
Autorzy:: Wieteska, K.
Wierzchowski, W.
Łukasiewicz, T.
Wierzbicka, E.
Malinowska, A.
Lefeld-Sosnowska, M.
Graeff, W.
Tematy:: 61.72.Ff; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1812259.pdf Link otwiera się w nowym oknie
Opis:: The perfection of $YVO_4$ crystals, which are predicted to replace formerly used YAG garnets due to higher quantum efficiency and lower excitation level, was studied. The investigations of Czochralski grown undoped $YVO_4$ single crystals were performed mainly by means of X-ray topographic methods. Both synchrotron and conventional X-ray sources were used. The study revealed relatively high density of weak point-like contrasts which can be most probably interpreted as dislocation outcrops. In regions of the crystal close to its boundary we observed glide bands. It was also found that in some regions the dislocations form local subgrain boundaries. The white beam back reflection and monochromatic beam topography allowed to evaluate a local misorientation which not exceeded several angular minutes. No segregation fringes were observed proving a good homogeneity of chemical composition.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 3.

Tytuł:: Defect Structure Formed at Different Stages οf Growth Process in Erbium, Calcium and Holmium Doped $YVO_{4}$ Crystals
Autorzy:: Malinowska, A.
Wierzbicka, E.
Lefeld-Sosnowska, M.
Wieteska, K.
Wierzchowski, W.
Łukasiewicz, T.
Świrkowicz, M.
Graeff, W.
Tematy:: 61.72.Ff; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1538950.pdf Link otwiera się w nowym oknie
Opis:: The defect structure of $YVO_{4}$ single crystals doped with $Er^{3+},$ $Ho^{3+}$ and $Ca^{2+}$ were studied by X-ray diffraction topographic methods, using laboratory and synchrotron radiation sources. Variously developed block structure was the dominating imperfection of the investigated crystals observed both in conventional Lang and synchrotron topographs. The evaluation of block misorientation was realised by means of superimposed projection and section white beam synchrotron radiation topographs. More possibilities of following the mutual rotation of blocks were provided by means of white beam synchrotron radiation WBSR projection topographs exposed through the fine mesh.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 4.

Tytuł:: X-ray Diffraction Topography - Investigation of Single Crystals Grown by the Czochralski Method
Autorzy:: Lefeld-Sosnowska, M.
Malinowska, A.
Tematy:: 61.72.Ff; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1399485.pdf Link otwiera się w nowym oknie
Opis:: X-ray diffraction topography is one of basic diagnostics tools serving for visualisation of single crystal lattice defects. Defects of various kinds can be observed. The present study is a review of topographic results obtained in the X-ray laboratory of the Institute of Experimental Physics, University of Warsaw, for three families of single crystals grown by the Czochralski method: (i) silicon (Si) and $Si_{1-x}Ge_{x}$, (ii) selected binary REVO_4 oxides and (iii) selected ternary $ABCO_4$ oxides. The effect of chemical composition, growth conditions and post growth thermal annealing on the defect appearing in crystals is discussed. Various defects are revealed: the growth dislocations (some early Si crystals), the composition-gradient-induced lattice deformation $(Si_{1-x}Ge_{x}$, solid solutions $Ca_{x}Sr_{1-x}NdAlO_4)$, defects generated in Si after the post growth thermal processes, oriented elongated rod-like macro-defects tending to form networks within the crystal core, cellular structure in the outer shell $(SrLaGaO_4)$, and variously developed block structure (in selected binary $\text{REVO}_4$ crystals).
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 5.

Tytuł:: Characterisation of the Defect Structure in Gadolinum Orthovanadate Single Crystals Grown by the Czochralski Method
Autorzy:: Wierzbicka, E.
Malinowska, A.
Wieteska, K.
Wierzchowski, W.
Lefeld-Sosnowska, M.
Świrkowicz, M.
Łukasiewicz, T.
Paulmann, C.
Tematy:: 61.72.Ff; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1431600.pdf Link otwiera się w nowym oknie
Opis:: The $GdVO_4$ single crystals, both undoped and doped with erbium or thulium, were studied by means of X-ray diffraction topographic methods exploring laboratory and synchrotron radiation sources. Variously developed block structure, caused probably by thermal stresses, was revealed. The highest crystallographic perfection was observed in the crystal doped with 4 at.% of thulium, which was free of the grain boundaries in the end part. Contrary to that, the differences in structural perfection between samples cut out from various regions of the crystal and for different kinds of doping, were less distinct in other crystals. The diffraction topographic methods enabled the statement that the misorientation between various blocks is in the range of several arc minutes.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 6.

Tytuł:: Interference Fringes in the Plane Wave Topographic Images of Growth Bands in Si:Ge
Autorzy:: Wieteska, K.
Wierzchowski, W.
Graeff, W.
Lefeld-Sosnowska, M.
Regulska, M.
Tematy:: 61.72.Ff; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/2030662.pdf Link otwiera się w nowym oknie
Opis:: An Si:Ge crystal with approximately 3% of germanium was studied with strongly collimated short-wavelength monochromatic synchrotron beam (beamline E2 at HASYLAB). The topographs obtained in the asymmetric 224 reflection revealed the presence of interference fringes related to growth bands caused by segregation of germanium. The fringes, observed for the first time, were strongly dependent on the angular setting and it was possible to distinguish at least three systems of fringes. A number of features of the existing strain field, which may be important for the formation of the fringes, was determined using other topographic methods, especially the Bragg-case section topography.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 7.

Tytuł:: The Simulation of Bragg-Case Section Images οf Dislocations and Inclusions in Aspect of Identification of Defects in SiC Crystals
Autorzy:: Balcer, T.
Wierzchowski, W.
Wieteska, K.
Tematy:: 61.72.Ff
61.72.up; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1538998.pdf Link otwiera się w nowym oknie
Opis:: The numerical simulation has been applied for studying of Bragg-case section topographic images of dislocation and rod-like inclusions. The validity of simple approximation of extinction contrast was confirmed in the case of screw dislocations in silicon carbide crystals. A procedure for approximate calculation of the strain field of rod-like inclusion was constructed, consisting of adding the contributions from a very large number of point-like inclusions uniformly distributed inside the assumed volume of the inclusion. The procedure ensured a reasonable similarity between the simulated topographs and experimental Bragg-case section topographic images of some pipe-formed cavities in silicon carbide crystals. The method is useful for some other materials, e.g. it enabled to compute realistic simulation of plane-wave topographs of the rod-like inclusions in YAG.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 8.

Tytuł:: 3D Reconstruction of Dislocation Structures in $Fe-Al_{28,40}$
Autorzy:: Veselý, J.
Kopeček, J.
Tematy:: 68.37.Lp
61.72.Ff; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1402157.pdf Link otwiera się w nowym oknie
Opis:: Some of the experimental problems faced when attempting dislocation tomography are discussed. A method of 3D reconstruction of straight line segments with much lower experimental requirements than tomography is proposed. This method is applied to dislocation structures found in two iron aluminium alloys (28 and 40 at.% Al). Resulting information on statistical distribution of dislocation segment lengths and orientations is presented.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 9.

Tytuł:: Influence of SiC Surface Preparation on Homoepitaxial Growth; X-ray Reflectometric Studies
Autorzy:: Mazur, K.
Wierzchowski, W.
Wieteska, K.
Hofman, W.
Sakowska, H.
Kościewicz, K.
Strupiński, W.
Graeff, W.
Tematy:: 61.05.cm
61.72.Ff
61.72.up; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1538812.pdf Link otwiera się w nowym oknie
Opis:: X-ray reflectometric and diffraction topographic methods were applied for examination of 4H and 6H silicon carbide substrates finished with various regimes, as well as, silicon carbide epitaxial layers. The investigations indicated a very good quality of the substrate surfaces finished with the process established at the Institute of Electronic Materials Technology, which provided the surface roughness σ = 0.55 ± 0.07 nm for 4H-SiC wafers. These values were better than those of substrate wafers offered by many commercial producers. The surface roughness was decreased during the initial high temperature etching to σ = 0.22 ± 0.07 nm. A relatively good structural quality was confirmed in the case of 4H epitaxial wafers deposited on the substrates prepared from the crystals manufactured at the IEMT, with the 8° off-cut from the main (001) plane.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 10.

Tytuł:: Topographic and Reflectometric Investigation of Crystallographic Defects and Surface Roughness in 4H Silicon Carbide Homoepitaxial Layers Deposited at Various Growth Rates
Autorzy:: Wierzchowski, W.
Wieteska, K.
Mazur, K.
Kościewicz, K.
Balcer, T.
Strupiński, W.
Paulmann, C.
Tematy:: 61.05.cm
61.72.Ff
61.72.up; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1431659.pdf Link otwiera się w nowym oknie
Opis:: Undoped 4H silicon carbide epitaxial layers were deposited by means of CVD method with growth rates of 2 μm/h, 5 μm/h and 11 μm/h at 1540°C on n-doped 8°, 4° and 0° off-cut 4H-SiC (00·1) substrates. The structural defects were studied before and after growth of the epitaxial layers by means of conventional Lang topography, synchrotron white beam and monochromatic beam topography and by means of X-ray specular reflectometry. The topographic investigations confirmed the continuation of the dislocations in the epitaxial deposit on the 8° and 4° off-cut substrates without new extended defects. The important difference occurred in the surface roughness of the epitaxial layers, which increased for higher growth rates. The epitaxial layers grown on 0° off-cut substrates at analogous condition contained usually other SiC polytypes, but the influence of the growth rate on the distribution of the polytypes was observed.
Dostawca treści:: Biblioteka Nauki

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