Diffuse x-ray scattering from thermal donors in Czochralski-grown silicon

The diffuse x-ray (Cu K alpha(1)) scattering from Czochralski-grown (Cz) silicon crystals after annealing at 450 degrees C for 24 h has been investigated. The x-ray measurements have been made near the (400) and (311) Bragg reflections in directions parallel and perpendicular to the scattering vector. All the characteristic features have been predicted by the theory fur scattering from defect clusters with weak displacement fields (Huang scattering). It is shown that the long-range part of their displacement fields has an orthorhombic symmetry and the defects are the interstitial type. Furthermore, by comparing the symmetry of the diffuse scattering intensities with that of displacement fields around the thermal donor models in Cz Si, it is found that an NL8 or IO2 (self-interstitial and two oxygens) model is reasonable as a core structure of thermal donors.