Papers by Keyword: In Situ Studies

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Authors: Yu Yang, Jian Qiu Guo, Balaji Raghothamachar, Michael Dudley, Swetlana Weit, Andreas N. Danilewsky, Patrick J. McNally, Brian R. Tanner
Abstract: We present in-situ observations of the dynamical operation of multiple double-ended Frank-Read dislocation sources in a PVT-grown 4H-SiC wafer under thermal gradient stresses. The nucleation of these sources is facilitated by a specific configuration consisting of one basal plane dislocation (BPD) segment pinned by two threading edge dislocations (TEDs). This configuration is formed during PVT crystal growth by deflection of TEDs on to the basal planes by macrosteps and re-deflection of resulting BPDs back into TEDs. Under the influence of thermal gradient stresses induced by heating inside a double ellipsoidal mirror furnace, the pinned BPD segment glides and activates dislocation multiplication by the double Frank-Read source mechanism. A more intricate mechanism of swapping of TED pinning points between Frank-Read sources lying on same basal plane is identified, enabling one dislocation loop to effectively “pass through” the other dislocations on same basal plane.
Authors: S.M. Clark, Robert J. Cernik, A. Grant, S. York, P.A. Atkinson, A. Gallagher, D.G. Stokes, S.R. Gregory, N. Harris, W. Smith, M.H. Hancock, M.C. Miller, K. Ackroyd, R. Farrow, R. Frances, D. O'Hare
Authors: Andrew N. Fitch
Abstract: The highly-collimated, intense X-rays produced by a synchrotron radiation source can be harnessed to build high-resolution powder diffraction instruments with a wide variety of applications. The general advantages of using synchrotron radiation for powder diffraction are discussed and illustrated with reference to the structural characterisation of crystalline materials, atomic PDF analysis, in-situ and high-throughput studies where the structure is evolving between successive scans, and the measurement of residual strain in engineering components.
Authors: A.F. Gualtieri, E. Mazzucato, C.C. Tang, Robert J. Cernik
Authors: Nuno Franco, Eduardo Alves, Nuno P. Barradas
Abstract: The Hotbird is a state of the art X-ray laboratory for advanced materials characterisation, installed at ITN since 1999. Several major improvements in its capabilities have been implemented. On the one hand, new hardware developments have extended the applications that can be studied and on the other hand, new software has enabled both enhanced automated control of the system, and improved data analysis that leads to extraction of further precise information from the data. One improvement was the implementation of the x-ray reflectometry (XRR) technique, which is a major expansion of the Hotbird capabilities. XRR is well-suited to characterise film thickness and roughness with high resolution. Furthermore, several optics improvements, such as a Göbel mirror and monochromators were introduced. The combination of this optics allows one to use either a higher intensity beam (orders of magnitude better) or a higher resolution beam configuration. A new high-temperature chamber was developed, which allows one to perform in-situ experiments with excellent temperature control up to 800 °C, in all possible configurations. Data simulation/fitting analysis software for XRR was developed. Also, to control the diffractometer and perform experiments, a new user-friendly software package was developed. In order to illustrate the Hotbird capabilities improvements, several experimental examples will be described.
Authors: B. Fortin, A.F. Gualtieri, Matteo Leoni, M. Prudenziati, C.C. Tang
Authors: Thomas Wroblewski, Adeline Buffet
Abstract: X-ray diffraction imaging allows the investigation of a large area of a polycrystalline specimen in a single shot. Dynamic processes like recystallization can, therefore, be studied without prior knowledge of where they occur. Even early stages of nucleation can be traced back using the information from images taken from the fully recrystallized specimen. Experiments performed at HASYLAB beamline G3 on cold rolled Cu and Al showed nucleation and growth behaviour that cannot be explained by classical models.
Authors: Pavel Strunz, Debashis Mukherji, Ralph Gilles, Joachim Rösler, A. Wiedenmann
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