A novel Si nanoparticle (SNP) system of spatially coherent distribution was created by low energy oxygen ion implantation during Si molecular beam epitaxy. Highly oriented Si nanoparticles embedded in an SiO2 matrix of dimensions d of 4-100 nm with log-normal size distribution are demonstrated. The single-crystal character of the SNPs is revealed by transmission electron microscopy and the preferred crystalline axis is oriented to the substrate normal, [100], retaining the epitaxial character compared with dispersive SNPs. The morphology of individual nanoparticles is significantly faceted towards [100] and [111] as opposed to regular polyhedra with the crystal habit of [311], [111] characteristic of thermodynamically stabilized dispersive SNPs, Visible luminescence bands are observed at room temperature.