138 research outputs found
GaN_Dislocations_1 EBSD Example data
No full text<p>EBSD Example data from a GaN sample, measured by Naresh Gunasekar. Data conversion by Aimo Winkelmann.</p>
Diffraction of backscattered electrons at crystal surfaces
No full textElectron backscatter diffraction (EBSD) has developed into a valuable tool for the analysis of materials in the scanning electron microscope (SEM) [1]. Pronounced improvements in applications of the EBSD method can be expected if it is possible to gain access to a quantitative description of not only the total number of backscattered electrons, but also to the fine-scale angular variations observed as diffraction patterns of these electrons. A complete simulation of the observed intensities, however, is only possible by applying electron diffraction theories that can properly include the multiple (dynamical) scattering of keV electrons in crystals [2,3].
I will discuss the application of many-beam dynamical theory to the simulation of experimental diffraction patterns of backscattered electrons. By energy-resolved measurements, the correlation between the energy loss of the scattered electrons and their diffraction effects can be investigated. First experimental results of corresponding angle-resolved reflection electron energy loss measurements are presented [4]. It is shown that under certain conditions, inelastically backscattered electrons can show more pronounced diffraction effects than the elastic electrons.
1. A.J. Schwartz, M. Kumar, B.L. Adams, D. P. Field (Eds.), Electron Backscatter Diffraction in Materials Science, 2nd edition, Springer, Berlin, 2009
2. A. Winkelmann, C. Trager-Cowan, F. Sweeney, A. P. Day, P. Parbrook, Ultramicroscopy 107, 414 (2007)
3. A. Winkelmann, Ultramicroscopy 108, 1546 (2008)
4. M. R. Went, A. Winkelmann, M. Vos, Ultramicroscopy 109, 1211 (2009
GaN Stripes EBSD
No full text<p>Raw EBSD Data for a GaN thin film sample with changing polarities and crystal structures as published in:</p>
<p>Point-Group Sensitive Orientation Mapping Using EBSD. Winkelmann A., Nolze G., Himmerlich M., Lebedev V., Reichmann A. (2016) In: Holm E.A. et al. (eds) Proceedings of the 6th International Conference on Recrystallization and Grain Growth (ReX&GG 2016). Springer. The data was measured by G.Nolze, the sample was provided by V. Lebedev and M. Himmerlich<br>
<a href="https://doi.org/10.1007/978-3-319-48770-0_41">https://doi.org/10.1007/978-3-319-48770-0_41</a></p>
<p>The data in <a href="https://zenodo.org/api/files/0f9f0014-75e7-4f63-bf8d-1636448101a8/static_bam_ef.txt?versionId=9ca597c9-edd1-486d-b542-00a5dd1edf72">static_bam_ef.txt </a> is a static EBSD background image (taken from a different experiment with the same detector)</p>
Nichtlineare Photoemission an Metalloberflächen unter Einfluss der Spin-Bahn-Kopplung
No full textDiese Arbeit beschäftigt sich mit der Untersuchung des Einflusses der Spin-Bahn-Wechselwirkung in der optischen Mehrphotonenanregung von spin-polarisierten Photoelektronen an nichtmagnetischen und magnetischen Metalloberflächen. In nichtlinearen Photoemissionsprozessen spielen die optisch angeregten Zwischenzustände eine große Rolle. Mehrphotonen-Photoemission bietet einen einzigartigen Zugang zu diesen Zuständen. Eine Vielzahl von Effekten in aktuell relevanten Forschungsrichtungen der Festkörperphysik wird direkt oder indirekt vom Elektronenspin beeinflusst. Dies macht die Wichtigkeit eines experimentellen Zugangs zum Elektronenspin in Festkörpern deutlich. Über die Kopplung des Spins eines Elektrons mit seiner Bahnbewegung im Mechanismus der Spin-Bahn-Kopplung kann ein indirekter Zugriff auf den Spinfreiheitsgrad über die Anregung der Elektronenorbitale erfolgen. Mittels zirkular polarisierter Strahlung können die Dipol-Auswahlregeln für optische Übergänge zwischen verschiedenen Elektronenzuständen genutzt werden, um gezielt Elektronen mit einer bestimmten Spinausrichtung aus einem insgesamt unpolarisierten Ensemble anzuregen.von Aimo Winkelman
Il confine della bellezza: «Venise sauvée» di Simone Weil.
No full textLa tragedia incompiuta Venise sauvée è un enigma e, insieme, un cristallo geometricamente perfetto. Oggetto di scarso interesse fino a oggi all’interno degli studi weiliani, la pièce concentra in versi e immagini il pensiero assoluto dell’autrice permettendo di approfondirne luci e ombre. Al tempo stesso quest’opera consente di avvicinare riscritture novecentesche poco conosciute del teatro tragico e di metterne alla prova forme e contenuti attraverso occhi femminili, appassionati di perfezione: occhi “imperdonabili”. Obiettivo precipuo di questo saggio è analizzare la genesi, la struttura drammaturgica e i principali nodi teorici che scaturiscono dal testo drammatico al fine di investigare il conflitto e, insieme, l’insospettabile rimozione, che li caratterizza. Più nello specifico, attraverso l’intersezione della pièce con altre opere della stessa autrice o prese da lei a modello, si vuole mostrare come la bellezza – concetto chiave del pensiero weiliano – finisca per tradire la trama stessa della realtà da cui trae origine – e di cui si offre quale accesso privilegiato – se tende ad annullarne la contraddizione. Il tragico non è negoziabile o redimibile e il bello scaturisce soltanto da ogni aporia consumata fino in fondo: è confine sottile e in continua oscillazione tra opposti inconciliabili che chiede di essere abitato.The unfinished tragedy Venise sauvée is an enigma and, at the same time, a geometrically perfect crystal. Subject of little interest, to this date, within the weilian studies, the play gathers in verses and pictures the absoluteness of thought of the author, allowing to deepen its shadows and highlights. At the same time, this play allow as well to bring little-known twentieth-century rewritings of tragedy in light, and testing its forms and contents through the eyes of women, lovers of perfection: eyes which are “unforgivable”. Primary objective of this paper is thus to analize the genesis, the dramatic structure and the main theoretical points arising from the dramatic text in order to investigate the conflict and, together, the unexpected displacement which characterizes them. More specifically, through the intersection of the play with other works by the same author or with works taken by the author as model works, we want to show how beauty, which stands as a key concept of the weilian thought, ends up betraying the very fabric of the reality from which it originates (and to which it offers itself as a privileged way of access) when it tends to cancel contradictions. The tragic is not negotiable or redeemable, and beauty springs only from all aporia which are worn down to the bottom: thin line it is, and in constant oscillation between irreconcilable opposites which just ask to be lived
EBSD Kikuchi Pattern Analysis, Silicon 15kV
No full textSupplementary Data and Images for Si EBSD pattern analysis as presented in
A. Winkelmann, T.B. Britton, G. Nolze "Constraints on the effective electron energy spectrum in backscatter Kikuchi diffraction", Physical Review B (2019
Corpo danza creazione. Sasha Waltz & Guests
No full textUn viaggio nel corpo attraverso la danza. Si parte dall’analisi di alcune opere di Sasha Waltz, coreografa e regista tedesca che grazie a vent’anni di ricerca con e sul corpo accompagna nel suo labirinto. Intrecciando sguardi, linguaggi e discipline differenti l’autrice propone una lettura originale della coreutica dell’artista e attraverso di essa fornisce mappe e strumenti per orientarsi nel tempio corporeo. Il fine è mostrarne le molteplici dimensioni e possibilità, il valore euristico del simbolo e dell’immaginazione e la capacità dell’arte di Tersicore non solo di diagnosticare l’odierna mistificazione del corpo, ma anche di offrirsi come canale di guarigione attraverso nuove - o forse solo dimenticate - parole, immagini e pratiche creative. Si arriva infine a una storia, una storia di rinascita attraverso il corpo, la danza e la creazione, che vede l’autrice scoprirsi e portarsi in scena per invitare il lettore a fare lo stesso: a riconoscere e abitare il proprio corpo, a scrivere il suo racconto, a proseguire il viaggio.A journey into the body through dance. It starts with the analysis of some works by Sasha Waltz, a German choreographer and director who, thanks to a wave of research with and on the body, accompanies in its labyrinth. Interweaving different looks, languages and disciplines, the author proposes an original reading of the artist's choreutics and through it she provides maps and tools to orientate oneself in the "body temple". The aim is to show the different dimensions and possibilities of the body, the heuristic value of the symbol and the imagination and the ability of Terpsichore's art not only to diagnose today's mystification of the body, but also to offer itself as a healing channel through new - or maybe just forget - words, images and creative practices. Finally, we come to a story, a story of rebirth through the body, dance and creation, which sees the author discovering herself and inviting the reader to do the same: to recognize and live in one's own body, to write own story, to continue the journey.  
The Kikuchi bandlet method for the intensity analysis of the electron backscatter Kikuchi diffraction patterns
No full textThe present dissertation attempts to extend the application fields of the Electron Backscatter Kikuchi Diffraction technique (EBSD) by enabling the analysis of the intensity of the Electron Backscatter Kikuchi Diffraction patterns (EBSPs). It also presents an error analysis for the conventional method that retrieves the crystallographic orientation from an EBSP. The error analysis is performed on simulated patterns. An analytical, inferential statistics-based method for estimating the accuracy of a retrieved orientation and a retrieved misorientation of a real pattern is validated. The second part of this work introduces a method, which deconvolutes and reconstructs the individual Kikuchi bands, and thus, enables an accurate and automatic analysis of their intensity profiles. The method is termed the Kikuchi bandlet method. Two of this method's exemplary applications are also presented: (1) the quantification of the stored crystalline defects and (2) the improvement of the accuracy of the retrieved crystal orientation and the retrieved projection parameters of an EBSP. The method proposed for quantifying the stored defects through quantifying the individual Kikuchi band's sharpness is applied to a controlled experimental case of bending a micro-cantilever. It is shown that, using this method, for each reflector, the deviation of the atomic positions from equilibrium can be retrieved through the band sharpness, which, in effect, measures the incoherency of the diffracted beams. Linking the band sharpness to the underlying crystal structure is performed through the simulation of Kikuchi patterns resulting from a crystal structure containing a known defect, and subsequently, analysing the pattern with the Kikuchi bandlet method. The results shows that the dislocation is clearly visible on the planes that fulfil the criterion of diffraction, with being the dislocation's Burgers vector and being the reciprocal space vector of the reflector. They also show that the retrieved band sharpness correlates with the value.The intensity profile analysis of a reconstructed K-band reveals its characteristic hyperbolic features. Using these curves increases the accuracy of the estimated orientation and projection center. This is presented as the second application of the Kikuchi bandlet method. In the case studied here, for simulated pattern, an order of magnitude improvement in orientation accuracy and times improvement in projection center accuracy is achieved
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