Synthesis of self-assembled Ge nanocrystals employing reactive RF sputtering

This work presents the results of a simple methodology able to control crystal size, dispersion and spatial distribution of germanium nanocrystals (Ge-NCs). It takes advantage of a self-assembled process taken place during the deposit of the system SiO2/Ge/SiO2 by reactive RF sputtering. Nanoparticles formation is controlled mainly by the roughness of the first SiO2 layer but the ulterior interaction of the interlayer with the top layer also play a role. Structural quality of germanium nanocrystals increases with roughness and the interlayer thickness. The tetragonal phase of germanium is produced and its crystallographic quality improves with interlayer thickness and oxygen partial pressure. Room temperature photoluminescence emission without a post growth thermal annealing process indicates that our methodology produces a low density of non-radiative traps.