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1
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X-Ray Topographic Investigation of Cellular Structure and its Relation to another Defects in Various Types of GaAs Single-Crystals

100%
Wierzchowski W., Mazur K.
Acta Physica Polonica A
|
1993
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vol. 84
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issue 4
789-794
EN
The defect patterns in GaAs crystal grown using liquid encapsulated Czochralski and gradient freeze methods with various types of doping were characterized using complementary X-ray topographic methods. It was found that the cellular structure occurring in the low doped crystal is developed independently from the actual growth surface. The occurrence of the cellular structure is connected with significant lattice deformation, and some results point that significant stress can influence its formation. The high doping prevents formation of the cellular structure, but at higher doping the phenomenon of "cellular growth" can occur due to instabilities of the growth surface. The present results point that defect pattern in GaAs crystals is more affected by the type of doping than by the choice of the growth method.
2
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High Quality (100) and (001) Oriented Substrates Prepared from Czochralski Grown SrLaGaO_{4} and SrLaAlO_{4} Single Crystals

81%
Berkowski M., Fink-Finowicki J., Sass J., Mazur K.
Acta Physica Polonica A
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1997
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vol. 92
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issue 1
201-204
EN
The growth of SrLaGaO_{4} and SrLaAlO_{4} crystals on ⟨100⟩ and ⟨001⟩ oriented seeds was investigated. Various defects, which appeared in crystals grown on these two orientations, were observed in polarized light and by X-ray diffraction topography. It was found that to obtain a substrate of the best quality, the crystal should be cut along the growth directions. Therefore, crystals pulled along ⟨100⟩ direction are utilized for preparation of (001) substrates, whereas (100) substrates are better to cut from crystals grown on ⟨001⟩ seed. The quality of the prepared substrates was determined by high resolution X-ray diffraction study in terms of rocking curve and mean mosaic angle.
3
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Defects in Detwinned LaGaO_{3} Substrates

81%
Mazur K., Fink-Finowicki J., Berkowski M., Schell N.
Acta Physica Polonica A
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1997
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vol. 92
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issue 1
205-208
EN
Single crystals of lanthanum gallate would be the suitable substrate for YBaCuO films except for the phase transition and the tendency to twinning existing in this material. However, by appropriate choice of growth conditions in the Czochralski method, it is possible to grow single crystal of LaGaO_{3} with low density of twin boundaries. Special stress and temperature treatment can then be applied to such materials to remove majority of existing twins. The substrates were examined by X-ray topography before and after detwinning and the surface was scanned with a profilometer.
4
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Investigation of Misfit Dislocation Sources in GaAs Epitaxial Layers

71%
Wierzchowski W., Mazur K., Strupiński W., Wieteska K., Graeff W.
Acta Physica Polonica A
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1996
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vol. 89
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issue 3
341-346
EN
The formation of misfit dislocation was studied in GaAs homoepitaxial layers on the substrates containing considerable amount of isoelectronic indium. The layers were grown with metal-oxide chemical vapour deposition and chemical vapour deposition methods including low temperature process with tertiarbutylarsine arsenic source. The critical conditions of misfit dislocation formation were exceeded up to 5×. The samples were examined before and after epitaxial process with a number of different X-ray topographic and diffractometric methods, including high resolution synchrotron white beam topography. The crystallographic identification of the defects was supported by the numerical simulation of topographic images. It was found that a number of threading dislocations, continuing in the epitaxial layer from those existing in the substrate, did not take part in the formation of misfit dislocations despite a suitable slip system. On the other hand, the formation of misfit dislocations from small imperfections of epitaxial deposit was proved in many cases. A reasonable good quality of the layers was confirmed by the resolution of individual defects and only small broadening of rocking curves.
5
Content available remote

X-Ray Diffraction Investigations of NdGaO_{3} Single Crystal

71%
Mazur K., Sass J., Giersz W., Reiche P., Schell N.
Acta Physica Polonica A
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1997
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vol. 92
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issue 1
226-230
EN
Neodymium gallium perovskite single crystals grown with the Czochralski method were examined with several complementary X-ray methods. By means of X-ray diffraction topography and reciprocal space diagram the structural perfection and crystal homogeneity of the studied wafers were determined. Additionally, the results of the X-ray reflectometry investigations of the surface perfection after the mechanochemical treatment are presented.
6
Content available remote

Topographic and Reflectometric Investigation of Crystallographic Defects and Surface Roughness in 4H Silicon Carbide Homoepitaxial Layers Deposited at Various Growth Rates

61%
Wierzchowski W., Wieteska K., Mazur K., Kościewicz K., Balcer T., Strupiński W., Paulmann C.
Acta Physica Polonica A
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2012
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vol. 121
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issue 4
915-919
EN
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.
7
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Influence of SiC Surface Preparation on Homoepitaxial Growth; X-ray Reflectometric Studies

52%
Mazur K., Wierzchowski W., Wieteska K., Hofman W., Sakowska H., Kościewicz K., Strupiński W., Graeff W.
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issue 2
272-276
EN
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.
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