Silicon (I 11) and (100) substrates converted into silicon carbide under molecular beam epitaxy (MBE) and rapid thermal chemical vapour conditions (RTCVD) were studied by transmission electron microscopy (TEM). The investigations revealed for both conversion technologies the existence of good structural quality and well aligned (I 11) and (001) beta-SiC layers. For the layers formed by RTCVD deposition the grain misorientation stays generally below about +/-3degrees, whereas in the MBE case the diffraction arcs related to the 3C-SiC diffraction spots are more extended. This indicates a stronger rotational spread between the individual grains. The maximum rotation was observed to be around 15degrees. Furthermore diffraction features related to highly oriented hexagonal inclusions within the thin 3C-SiC layer formed under MBE conditions are more pronounced than in the case of the RTCVD samples. A dislocation distribution analysis carried out by high resolution electron microscopy revealed misfit dislocation inside the SiC layer and also at the SiC/Si interface. Plan-view selected area electron diffraction evidences compositional and structural homogeneity. Defects present in the carbonized layers were determined. The results obtained indicate the formation of a suitable large area pseudosubstrate under both formation conditions.