Structural defects in SiC single crystals studied by small-angle neutron scattering

Growth-induced structural defects such as hollow core super screw dislocation known as micropipes in silicon carbide single crystals grown by sublimation method are investigated. Electron microscopy as well as small-angle neutron scattering (SANS) techniques were used to resolve these defects in sizes. For SANS, scattering signals in the momentum transfer range 0.1-2.2 nm−1 were recorded. This corresponds for the periodic structure to length scale from 3 to 60 nm approximately. Isotropic patterns were analyzed using spherical-shell model. The analyses showed that the small spherical defects are within a volume fraction less than 5% in these crystals. The change in the growth process such as growth rate and atmosphere showed no significant change in the sizes of these defects but has an effect on the distribution of these defects.