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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, 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>
Far-field x-ray phase contrast imaging has no detailed information on the object
Kohn, V G,Argunova, T S,Je, J H Institute of Physics [etc.] 2010 Journal of Physics. D, Applied Physics Vol.43 No.44
<P>We show that x-ray phase contrast images of some objects with a small cross-section diameter <I>d</I> satisfy a condition for a far-field approximation <I>d</I> ≪ <I>r</I><SUB>1</SUB> where <I>r</I><SUB>1</SUB> = (λ<I>z</I>)<SUP>1/2</SUP>, λ is the x-ray wavelength, <I>z</I> is the distance from the object to the detector. In this case the size of the image does not match the size of the object contrary to the edge detection technique. Moreover, the structure of the central fringes of the image is universal, i.e. it is independent of the object cross-section structure. Therefore, these images have no detailed information on the object.</P>