Structural Study of Copper Doped Single-Crystal Silicon by Diffusion

The paper presents the results of a structural study of single-crystal silicon doped with copper by thermodiffusion at 1423K. The object of the study was n-Si crystals grown by the Czochralski method, containing SiO2 oxygen precipitates. Structural analysis was performed on an X-ray diffractometer with an improved optical scheme, which made it possible to detect weak additional reflections and changes in lattice parameters. It was established that copper doping leads to the appearance of elastic stresses in the surface layers of the crystal, a change in the interplanar distance (111) and a redistribution of the intensities of reflections (222) and (333). Diffuse scattering and additional selective reflections were detected, indicating the formation of new phases. For the first time, a direct structural method has shown the formation of CuO nanocrystals with a monoclinic structure and an average size of 14–14.5 nm and Cu2O nanocrystals with a cubic structure and an average size of about 17 nm. Their lattice parameters were measured experimentally and are slightly different from the standard reference values, which shows that the silicon matrix and internal stresses affect their structure. It has been shown that SiO2 oxygen precipitates create local elastic fields that promote diffusion, nucleation, and separation of copper in the form of oxide nanophases. The results obtained clarify the mechanism of structural transformations in copper-doped silicon.

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