A large angle convergent beam electron diffraction study of the core nature of dislocations in 3 C -SiC
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A large angle convergent beam electron diffraction study of the core nature of dislocations in 3C-SiC X. J. Ning and P. Pirouz Department of Materials Science and Engineering, Case Western Reserve University, Cleveland, Ohio 44106-7204 (Received 31 July 1995; accepted 18 December 1995)
Dislocations produced by 1300 ±C indentation of the silicon-terminated (111) face of 3C-SiC were investigated by transmission electron microscopy. They were all found to be either widely separated partial dislocation pairs, or else, arrays of single partial dislocation half-loops on neighboring parallel slip planes and having the same Burgers vector. It was concluded that in the latter case, each array consisted of leading partial dislocations which had nucleated without accompanying trailing partial dislocations. The core nature of both dissociated dislocations and arrays of single partial dislocations has been determined by the technique of large angle convergent beam electron diffraction. The results indicate that the core of all single partial dislocation half-loops constituting an array consists of silicon atoms. It is concluded that, with the present deformation geometry, the Si-core partial dislocations are preferentially nucleated before the C-core partial dislocations. In the case of a dissociated dislocation, when a pair of partials was present, electron microscopy observations revealed that the morphology of the two partial dislocations was very different; while the Si-core partials were smooth, the C-core partial dislocations had a zig-zag morphology.
I. INTRODUCTION
Many properties of dislocations in semiconductors depend on their core structure. In a binary compound semiconductor, such as SiC, the core of partial dislocations consists of only one atomic species, Si or C for SiC. In addition, the cores are often reconstructed, thus eliminating the dangling bonds that may otherwise exist. Thus, the dynamical properties of the partial dislocations, in say SiC, may depend on the reconstructed Si–Si or C–C bonds in their cores. Experiments have also shown that the morphology of the dislocations often depends on the nature of the core. It is therefore important to know the atomic species at the core of partial dislocations. This paper is concerned with the determination of the core structure of partial dislocations in SiC where the core consists of either Si atoms or C atoms. A. Structure of SiC
SiC is a tetrahedrally coordinated wide-band gap semiconductor suitable for the manufacture of hightemperature electronic devices, as well as a refractory ceramic with numerous applications in structural composites. SiC is a material that shows polytypism, i.e., occurs in different crystal structures all consisting of different stacks of identical double layers of carbon and silicon (for a review, see Ref. 1). However, the stacking sequence of these double layers along a direction normal to the layer planes is different in each polytype. In general, this stacking direction is taken as t
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