Influence of defects on the thickness dependence of integral reflectivity of dislocation-free silicon crystals

Abstract

The influence of large dislocation loops and clusters (with radius rd of the order of extinction length Λ) in dislocation-free silicon crystals grown by the Czochralsky-method on the thickness dependence of the total integral reflectivity Ri as well as on its Bragg's RB and diffuse RD components is investigated by variation of the X-ray wavelength (MoK, CuK-radiation) and of the order of Laue diffraction. For such defects diffuse scattering is concentrated near the reciprocal lattice point (RLP). Integral intensities are measured by means of the Bragg-Laue double crystal spectrometer in the positions (n, −n) and (n, −2n). The components RB and RD are determined using the formula of the dynamical theory of X-ray scattering in crystals with homogeneously distributed defects and the values of diffraction parameters i.e. the static Debye-Waller's factor L, and coefficient absorption due to diffuse scattering μds measured under conditions of weak absorption where the interfere influence of dynamical effects is negligible. The sensitivity of Ri to large defects is shown to increase at the expence of growing of the relative contribution of the RD component by transition to reflection of higher orders as well as by using of harder short-wavelength radiation. The ratio RD/Ri does not depend on the crystal thickness under conditions of strong absorption what conforms the arising of the dynamical regime for the diffuse component. This effect is absent for small (rd ≫ Λ) defects. The parameter L is shown to be more sensitive to the presence of large defects than μds. [Russian Text Ignored].