Formation of Ge nanoparticles in SiO_xN_y by ion implantation and thermal annealing

Germanium nanoparticles embedded within dielectric matrices hold much promise for applications in optoelectronic and electronic devices. Here we investigate the formation of Ge nanoparticles in amorphous SiO_1.67N_0.14 as a function of implanted atom concentration and thermal annealing temperature. Using x-ray absorption spectroscopy and other complementary techniques, we show Ge nanoparticles exhibit significant finite-size effects such that the coordination number decreases and structural disorder increases as the nanoparticle size decreases. While the composition of SiO_1.67N_0.14 is close to that of SiO₂, we demonstrate that the addition of this small fraction of N yields a much reduced nanoparticle size relative to those formed in SiO₂ under comparable implantation and annealing conditions. We attribute this difference to an increase in an atomic density and a much reduced diffusivity of Ge in the oxynitride matrix. These results demonstrate the potential for tailoring Ge nanoparticle sizes and structural properties in the SiO_xN_y matrices by controlling the oxynitride stoichiometry.