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Observation of the long-range distortion field between parallel dislocations with opposite Burgers vectors

Single crystals of silicon carbide are grown industrially for high-power electronic applications. Defects can negatively affect the device s performance. It is therefore of interest to accurately characterise such defects in order to optimise the growth process.

Bragg diffraction (in particular, rocking curve imaging, with a spatial resolution in the sub-micron range and an angular resolution in the µ-radian range) was employed at beamline BM05 to image the distortion fields around dislocations. It is well known that, due to the interaction of their distortion fields, parallel dislocations with opposite Burgers vectors can attract each other. This weak distortion

field was characterised, and it was shown that when the movement of the dislocations is not possible, the distortion field between the dislocations is not simply the superposition of the individual distortion fields. When the distance D between dislocations is ~ 50 - 250 µm, these deviations are in the micro-radian range.

Figure 145 shows a peak position map of a region of the sample, indicative of the local misorientation relative to the crystal matrix. It can be observed that the distortion between parallel dislocations with opposite Burgers vectors does not decay to zero but towards a constant value α. A simple phenomenological model is proposed for the total energy of the pair of dislocations. This total energy is reduced by having this region with a constant misorientation α, where α should roughly vary as 1/D. This appears to be in agreement with the experimental data.

Fig. 145: a) Peak position map. Individual dislocations show a typical red/blue dipole-like signature corresponding to the opposite sign of the strain on either side of the dislocation core. Inverting the sign of the Burgers vector inverts the strain (i.e., changes a red/blue dipole into a blue/red dipole). b) In the region between a dislocation with opposite Burgers vector, separated by a small distance D ~ 50 - 250 µm, the strain field does not decay to zero but seems to stabilise at a small value α.

PRINCIPAL PUBLICATION AND AUTHORS

Rocking Curve Imaging Investigation of the Long-Range Distortion Field between Parallel Dislocations with Opposite Burgers Vectors, T.N. Tran Caliste (a), A. Drouin (b), D. Caliste (c), C. Detlefs (a), J. Baruchel (a), Appl. Sci. 11, 9054 (2021); https:/doi.org/10.3390/ app11199054 (a) ESRF (b) SOITEC, Bernin (France) (c) UGA-CEA, Grenoble (France)