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Seminar organised by EMAT
Subject : Quantitative analysis on chemical inhomogeneity in a superconducting Fe1+y(Se0.28Te0.72 )1-xsingle crystal using HRTEM
Speaker: Ta-Kun Chen, EMAT, Universiteit Antwerpen
Abstract:
The recently discovered high-transition-temperature (Tc)
iron-based superconductors have drawn considerable attention [1-3]. To
date, however,
no complete theory for them but some experimental facts remains
difficult to answer and to reconcile with one another [4]. From the
first report of superconductivity with
Tc = 26 K in oxypnictides (LaFeAsO1-xFx) [3], another chalcogen-based subfamily, FeSe, was found later having a lower
Tc (8.5 K) [5]. This compound not only characterizes
in simplest layer structure among all iron-based superconductors. The
chalcogen-based iron superconductors are considered to be
superconducting as they are nearly stoichiometric, with controversial
point of view that small amount of defects exist either in the form of
iron interstitials or chalcogen vacancies. We demonstrate a quantitative
structural and chemical analysis of a superconducting
Fe1+y(Se0.28Te0.72 )1-x single
crystal using a high resolution transmission electron microscope
(HRTEM). The structure was quantitatively analyzed from the modulus of
reconstructed exit wave using simulated thermal annealing method. A good
estimation of defect concentration and the types
of point defects, iron interstitials or Se/Te vacancies, are presented.
References
[1] H. Takahashi et al., Nature 453, 376 (2008).
[2] C. Day, Physics Today 62, 36 (2009).
[3] Y. Kamihara et al., Journal of the American Chemical Society 130, 3296 (2008).
[4] I. I. Mazin, Nature 464, 183 (2010).
[5] F. C. Hsu et al., Proceedings of the National Academy of Sciences of the United States of America 105, 14262 (2008).
When and where: Wednesday, October 26, 2011 at 15.00 h in room U.241, Campus Groenenborger
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