High-resolution diffuse X-ray scattering study from nearly perfect silicon single crystals

High-resolution measurements of diffuse X-ray scattering (DXS) have been made at and above room temperature around 111, 333, 444 and 555 reciprocal lattice points (relps) using highly collimated Mo Kα₁ and Cu Kα₁ radiations with the specimen set in (1, -1, 1) symmetrical Bragg geometry. The distribution of DXS intensity around different relps has shown that at temperatures up to at least 573 K the contribution of thermal DXS to the observed DXS is very small. This is apparently due to the high value of the Debye temperature (640 K) of silicon. A remarkable feature of these results is that for the same value of the scattering vector |K*| the DXS intensity is different for the parallel and antiparallel orientations of K* relative to R*. The amount of anisotropy varied from sample to sample and depended on the thermal history of the specimen. This and the other features show that the observed DXS is predominantly due to point defects and their aggregates. A typical size parameter for the aggregates is 3000 to 10 000 Å.