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Determination of Atomic Positions in SiC 4H Using Quantitative Convergent Beam Refinements

Published online by Cambridge University Press:  02 July 2020

R. Holmestad ,
J.-P. Morniroli ,
J.M. Zuo  and
J.C.H. Spence
R. Holmestad
Affiliation:
Dept. of Physics, University of Trondheim, NTNU, N-7034, Trondheim, Norway Dept. of Physics and Astronomy, ASU, Tempe, AZ, 85287-1504, USA
J.-P. Morniroli
Affiliation:
Physical Metallurgy, URA CNRS 234, University of Lille I, 59655 Villeneuve d'Ascq., France
J.M. Zuo
Affiliation:
Dept. of Physics and Astronomy, ASU, Tempe, AZ, 85287-1504, USA
J.C.H. Spence
Affiliation:
Dept. of Physics and Astronomy, ASU, Tempe, AZ, 85287-1504, USA
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Silicon carbide (SiC) is a widely used ceramic material, with many structural and electronic applications. It exists in many polytypes, differing from one another only by the stacking sequence of close packed double layers of Si and C atoms. The polytype called 4H has the hexagonal structure shown in figure 1. The double layers here have a stacking sequence of ABACABAC.. The distance z between the Si and the C layers (shown in figure 1) is an adjustable parameter, which is not exactly known. The aim of this work is to determine the atomic positions in the c-direction by quantitative convergent beam electron diffraction (QCBED). The goal is to develop a general refinement approach for structure determination by electron diffraction. Many newly synthesized materials are available in only very small quantities in the single crystal form and/or mixed with other phases, making X-ray diffraction methods difficult. SiC is often full of stacking faults. For these types of materials, the CBED method is ideal because of the small probe that can be used; areas of less than 100 Å can be studied.

Type
Electron Crystallography; the Electron Phase Problem
Information
Microscopy and Microanalysis , Volume 3 , Issue S2: Proceedings: Microscopy & Microanalysis '97, Microscopy Society of America 55th Annual Meeting, Microbeam Analysis Society 31st Annual Meeting, Histochemical Society 48th Annual Meeting, Cleveland, Ohio, August 10-14, 1997 , August 1997 , pp. 1051 - 1052
Copyright
Copyright © Microscopy Society of America 1997

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References

1. See i.e. Spencer, M.G.et al. Silicon Carbide and related Materials, (1993) IOP conf. ser. 137.Google Scholar
2.Spence, J.C.H. and Zuo, J.M.Electron microdiffraction (1992) Plenum Press.10.1007/978-1-4899-2353-0CrossRefGoogle Scholar
3.Pirouz, P. and Yang, J.W.Ultramicroscopy 51 (1993) 189.10.1016/0304-3991(93)90146-OCrossRefGoogle Scholar
4.Zuo, J.M. Ultramicroscopy (1997) in print.Google Scholar
5.Zuo, J.M. This proc. (1997).Google Scholar
6. RH is supported by the Norwegian Research Council. JMZ and JCHS are supported by NSF grant DMR 9412146. The authors acknowledge P. Pirouz for providing the SiC single crystal.Google Scholar