Germanium nanocrystals (Ge-NCs) have been obtained by low energy ion beam synthesis in a SiNx/HfO2 stack layer. The effect of the Ge implanted dose variations on structural characteristics (size, position, chemical bonding) of Ge-NCs have been investigated by Transmission Electron Microscopy and Raman spectroscopy. Our results show that several processes (damage, diffusion, oxidation.) that depend on the Ge implanted dose, take place during the synthesis and complicate the expected behavior of the ion beam synthesized system. However, significant memory windows with good retention properties have been observed in these stack structures, indicating their feasibility for low operating voltage, non-volatile memory devices. (C) 2013 Elsevier B.V. All rights reserved.