International audienceThe X-ray scattering of partially transformed 3C-SiC single crystals is considered in detail. Extended diffuse scattering streaks, originating from stacking faults (SFs) lying in the {111} planes, are clearly observed in the widerange reciprocal-space maps. The intensity distribution along the diffuse streaks is simulated with a model including the contributions of the diffuse scattering originating from the SFs [based on the pioneering theoretical description given by Kabra, Pandey & Lele (1986). J. Mater. Sci. 21, 1654–1666], the coherent scattering emanating from untransformed areas of the crystals and all -dependent terms that affect the scattered intensity (the layer structure factor, the irradiated volume and the polarization of the beam). The quantitative simulation of the diffuse streaks reveals that the transformation occurs through the glide of partial dislocations and allows one to derive the transformation level. It is shown that the 3C polytype is indeed unstable at high temperature. However, it is further shown that defect-free 3C-SiC single crystals remain stable at temperatures where 3C-SiC is known to be usually unstable (2173 K). The origin of this apparent stability is very likely of kinetic nature, i.e. the lack of crystalline defects inhibits the transformation

International audienceThe 3C-6H polytypic transition in SiC single crystals is studied by means of diffuse x-ray scattering. Based on numerical simulations of the diffuse scattering intensity distribution we unambiguously prove that the 3C-6H transition in SiC occurs through the glide of partial dislocations and not by the "layer displacement" mechanism i.e., local diffusional rearrangement of the Si and C atoms. The technique is extremely sensitive and can be used as a nondestructive mean to obtain statistically relevant values of the transition level down to 0.05%

We applied a picosecond dynamic grating technique for studies of nonequilibrium carrier dynamics in a 0.8 mm thick bulk 3C-SiC crystal grown by the continuous feed physical vapor transport (CF-PVT) on 6H-SiC (0001) substrate. Investigation of carrier dynamics at surface or bulk excitation conditions was performed for excess carrier density in range from ~ 1017 cm-3 to ~ 1020 cm3 using for excitation weakly or strongly absorbed illumination. In DPBs free domains, the bipolar diffusion coefficient and carrier lifetime value at 300K were found gradually increasing with carrier density. The bipolar mobility vs. temperature dependence, μ. ~ T -k, provided a value k = 1.2 - 2 in range T < 100 K, thus indicating a negligible scattering by point and extended defects. These data indicated strong contribution of the carrier-density dependent but not defect-density governed scattering mechanisms, thus indicating high quality of the CF-PVT grown bulk cubic SiC. These studies were found in good correlation with the structural and photoluminescence characterization of the given crystal.