Effect of diffuse scattering in the strain profile determination by double crystal X-ray diffraction

Double-crystal X-ray diffraction is used to determine the depth-profile of the lattice strain in silicon single crystals after self-ion implantation and electron beam irradiation. A 1 × 1014 cm−2 dose and 60 keV energy for the implantation is chosen so that the annealing process can lead to the formation of a thin deformed surface layer (≈ 100 nm) characterized by a low deformation (≈ 10−4). The strain profile is calculated through computer simulation of the experimentally obtained rocking curve, by application of the dynamical theory of diffraction for imperfect crystals. It is shown that for crystalline systems like the one investigated here, when weak intensity signals have to be reproduced, attention has to be paid to the physical factors which affect the simulation of the diffraction profile. In particular, neglecting diffuse (thermal, Compton) scattering can lead to an incorrect determination of the strain profile. A simple expression relating this scattered intensity to dynamical Bragg diffraction gives a strain distribution consistent with the one directly observed by cross-section transmission electron microscopy.