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Microstructure and strength of AlN–SiC interface studied by synchrotron X-rays
Argunova, T. S.,Gutkin, M. Y.,Shcherbachev, K. D.,Je, J. H.,Lim, J. H.,Kazarova, O. P.,Mokhov, E. N. Springer Science + Business Media 2017 JOURNAL OF MATERIALS SCIENCE - Vol.52 No.8
<P>Bulk AlN crystals grown by sublimation on SiC substrates exhibit relatively high dislocation densities. The kind of defect formation at early growth stages influences the structural quality of the grown crystals. In this work, the dislocation distribution near to the interface is understood through investigation of thin (<= 1.5 mm) continuous (non-cracked) freestanding crystals obtained in one process with the evaporation of the substrates. TheAlN specimens were characterized using synchrotron radiation imaging techniques. We revealed by triple-axis X-ray diffraction study that, near to the former interface, randomly distributed dislocations configured to form boundaries between similar to 0.02 degrees misoriented sub-grains (from [0001] direction). Threading dislocation structure similar to that in epitaxial GaN films was not detected. To explain these observations, a theoretical model of misfit stress relaxation near the interface is suggested.</P>
Argunova, Tatiana S.,Gutkin, Mikhail Yu.,Kazarova, O.P.,Mokhov, E.N.,Nagalyuk, Sergey S.,Je, Jung H. Trans Tech Publications, Ltd. 2015 Materials science forum Vol.821 No.-
<P>We report on the growth method and the structural characterization of freestanding AlN crystals. An AlN layer is grown on a gradually decomposing SiC substrate yielding a freestanding crack free 2H single crystal with dislocation density 5×10<SUP>4</SUP>cm<SUP>-2</SUP>and without grain boundaries as confirmed by synchrotron radiation phase contrast imaging and topography data. Wafers of 600-1000 μm thick and up to 15 mm in diameter are obtained. The thermal stress distribution in a conventional AlN/SiC structure is discussed. Theoretical estimates show that cracking of AlN layers is a natural result of their growth on undecomposed SiC substrates.</P>
Elliptical micropipes in SiC revealed by computer simulating phase contrast images
Argunova, Tatiana,Kohn, Victor,Jung, Ji-Won,Je, Jung-Ho WILEY-VCH Verlag 2009 Physica status solidi. PSS. A, Applications and ma Vol.206 No.8
<P>The elliptical micropipes in SiC are studied using computer simulation of the phase contrast images. The experimental measurements of “white beam” images are performed at third-generation synchrotron radiation source in Pohang, Korea. We reveal that the transmitted X-ray spectrum of a high brilliance with a pronounced maximum at 16 keV enables to form partially coherent images even for transparent objects. The computer simulation allows one to automatically determine the diameters of elliptical cross-sections based on best matches between calculated and experimental intensity profiles. We show that the micropipes studied here have extended elliptical cross-sections, sometimes rotating around the micropipe axis.</P>
Argunova, T S,Jung, J W,Je, J H,Abrosimov, N V,Grekhov, I V,Kostina, L S,Rozhkov, A V,Sorokin, L M,Zabrodskii, A G Institute of Physics [etc.] 2009 Journal of Physics. D, Applied Physics Vol.42 No.8
<P>Dislocations in p-type Si<SUB>1−<I>x</I></SUB>Ge<SUB><I>x</I></SUB> single crystals (2–8 at% Ge) grown with the Czochralski technique are investigated by synchrotron white beam topography in transmission geometry. As the Ge concentration increases, the dislocation structure evolves from individual dislocations to slip bands and sub-grain boundaries, and the dislocation density increases from <10<SUP>2</SUP> cm<SUP>−2</SUP> to 10<SUP>5</SUP>–10<SUP>6</SUP> cm<SUP>−2</SUP> at 8 at%. We discuss the effect of dislocations on the electrical characteristics such as resistivity ρ<SUB><I>v</I></SUB>, Hall hole mobility μ<SUB>p</SUB>, carrier lifetime τ<SUB>e</SUB> and <I>I</I>–<I>V</I> characteristics. Here τ<SUB>e</SUB> and <I>I</I>–<I>V</I> characteristics are measured from the diodes fabricated by bonding the p-Si<SUB>1−<I>x</I></SUB>Ge<SUB><I>x</I></SUB> to n-Si wafers. <I>I</I>–<I>V</I> characteristics are not deteriorated in spite of a five times decrease in τ<SUB>e</SUB> with the Ge concentration.</P>
Argunova, T. S.,Yi, J. M.,Jung, J. W.,Je, J. H.,Sorokin, L. M.,Gutkin, M. Yu.,Belyakova, E. I.,Kostina, L. S.,Zabrodskii, A. G.,Abrosimov, N. V. WILEY-VCH Verlag 2007 Physica status solidi. PSS. A, Applications and ma Vol.204 No.8
<P>The defect structure of Si<SUB>1–x </SUB>Ge<SUB>x </SUB> wafers with 4% of germanium and their interfaces with Si wafers were studied using white radiation topography and phase-sensitive radiography. The heterostructures were manufactured by direct bonding of Si<SUB>1–x </SUB>Ge<SUB>x </SUB> and Si crystalline wafers made of bulk crystals that were grown by the Czochralski technique. In Si<SUB>1–x </SUB>Ge<SUB>x </SUB> crystals, the segregations of Ge act as dislocation nucleation sites. In Si<SUB>1–x </SUB>Ge<SUB>x </SUB>/Si bonded structures, the segregation of Ge as well as the accumulation of dislocations induce elastic strain and plastic deformation during high-temperature bonding annealing. With the topography–radiography combination, we are able not only to detect microcracks, indicating nonbonded areas, by radiography, but also to reveal dislocations and long-range strain fields by topography at the same time. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)</P>
Argunova, Anastasiia G.,Petrova, Pavlina N.,Okhlopkova, Aitalina A.,Shadrinov, Nikolay V.,Gogoleva, Olga V.,Cho, Jin-Ho Korean Chemical Society 2015 대한화학회지 Vol.59 No.3
The effect of ultrasonication on PTFE and its composites with zeolite and fluoroplast F-4NTD-2 was studied. Ultrasonication was found to cause changes in the supramolecular structure, and consequently, the tensile strength, relative elongation, and mass wear rate. Changes in the topology of the materials following ultrasonication were investigated by scanning electron microscopy. The optimum enhancement of the desired properties was found in the PTFE composite containing 2% activated zeolite.