## 3 Results  
From the ensemble of images recorded along the rocking curve of our 4H-SiC sample, we produced maps of the local FWHM and peak position. These maps result, as described above, from a Gaussian fit of the rocking curve recorded in each individual pixel. The FWHM map (Figure 2) shows for most pixels a local FWHM that is around 60 \(\upmu\)radians. The width is rather uniform, with a few exceptions that will be discussed later. This value mainly results from the convolution between an \"instrumental\" divergence \(\delta\zeta\) and the local mosaic spread of the crystal. \(\delta\zeta\) includes the divergence of the faintly convergent beam (\(\sim\)40 \(\upmu\)radians) and the width corresponding to the energy bandwidth of the Si (111) monochromator (\(\sim\)30 \(\upmu\)radians). It appears that \(\delta\zeta\) is the dominant term of this convolution and that the mosaic spread corresponding to most of the voxels is smaller (\(<\)30 \(\upmu\)radians), indicating a rather high crystalline quality of the crystal matrix. A few regions exhibit, in Figure 2, a higher FWHM than the matrix. They are associated with the distortion field of crystalline defects. The most visible ones are red-yellow lines located in the upper right corner of the figure, which are probably associated with surface scratches. We also observe a number of red dots surrounded by yellow pixels. These dot-like images are also visible on the peak position map shown in Figure 3, where they display a double-dot shape, the dot on one side exhibiting a higher peak position than the matrix and the one on the other side a lower peak position (see, e.g., the image in the black circle on Figure 3). These FWHM and peak position images are characteristic of dislocations [11], which show up in RCI images as regions of higher FWHM (red-yellow dots in the FWHM map) and exhibit an abrupt change of peak position from one side of the dislocation core to the other, in the peak position map. In both Figures 2 and 3, these dislocation-associated images are \"dot\" shaped, indicating that the dislocation lines are nearly perpendicular to the surface, i.e., nearly parallel to the c-axis. We estimated the dislocation density (-1300/cm\({}^{2}\)) by counting these dot-like images. Figure 3: RCI peak position map. The black circle indicates an isolated dislocation where the peak shift \(\Delta\omega\) has opposite signs on the left and right of the dislocation core. A similar pattern is observed for other isolated dislocations, the sign of \(\Delta\omega\) being reversed (blue-yellow or yellow-blue) as a function of the sign of the Burgers vector of the dislocation. The red arrow indicates the pair of dislocations already pointed out in Figure 2. They display opposite Burgers vectors because the sign of their peak position variation with respect to the matrix is reversed: when going from left to right along the y direction, the change is yellow to blue for the first dislocation and blue to yellow for the second one. Note that the peak shift in the region between the dislocation cores does not decay to the value of the surrounding matrix. Figure 2: RCI peak width (FWHM) map of the 4H-SiC crystal. The red dots are the images of dislocations perpendicular to the surface. The red arrow indicates a pair of dislocations connected by an area exhibiting a higher FWHM than the matrix. The projection of the diffraction vector h, the scale, and the vertical z and horizontal y directions are indicated on the left side. All the observed dot-like images are very similar, suggesting that the crystal displays one type of threading dislocation, having the same direction along the c-axis and the same Burgers vector modulus. The peak position map shows that both signs of the Burgers vector are present because the sign of the angular departure with respect to the matrix average on one (e.g., the right) side of a dislocation is not the same for all dislocations.