Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)In-plane strain anisotropy was clearly observed by the X-ray Bragg-surface diffract ion technique in the silicon lattice surrounded by nanoparticles that were synthesized by in ion-beam-induced epitaxial recrystallization process of Fe-implanted amorphous Si layer. High resolution transmission electron microscopy images have shown the occurrence of metallic spherical and plate-like gamma-FeSi2 nanoparticles in the implanted/recrystallized region. These were found in different orientations within the sample, being responsible for the strain anisotropy detected. The striking anisotropy effect. due to mainly the plate-like nanoparticles in the recrystallized region, appears when comparing two (-6.04 degrees and 83.96 degrees) (002) rocking curves at Bragg-surface diffraction exact condition. Furthermore, the mappings of the (111) Bragg-surface diffraction reflections show an evident anisotropy between phi = -6.04 degrees and 83.96 degrees mappings and also a marked broadening of the implanted sample profile as compared to that of the Si (matrix). Reciprocal space maps obtained for both perpendicular directions clearly exhibit this anisotropic effect in the as direction, thus confirming the Bragg-surface diffraction results.101043634369Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)LNLSConselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)FAPESP [07/08609-3]