Lattice strain distribution resolved by X-ray Bragg-surface diffraction in an Si matrix distorted by embedded FeSi₂ nanoparticles

Out-of-plane and primarily in-plane lattice strain distributions, along the two perpendicular crystallographic directions on the subsurface of a silicon layer with embedded FeSi₂ nanoparticles, were analyzed and resolved as a function of the synchrotron X-ray beam energy by using ω:φ mappings of the () and (111) Bragg-surface diffraction peaks. The nanoparticles, synthesized by ion-beam-induced epitaxial crystallization of Fe⁺-implanted Si(001), were observed to have different orientations and morphologies (sphere- and plate-like nanoparticles) within the implanted/recrystallized region. The results show that the shape of the synthesized material singularly affects the surrounding Si lattice. The lattice strain distribution elucidated by the nonconventional X-ray Bragg-surface diffraction technique clearly exhibits an anisotropic effect, predominantly caused by plate-shaped nanoparticles. This type of refined detection reflects a key application of the method, which could be used to allow discrimination of strains in distorted semiconductor substrate layers.