The synthesis of two-dimensional arrays of Si nanocrystals in an HfO2 matrix has been achieved by deposition of HfO2/SiO/HfO2 multilayer structures followed by high temperature (1100 degrees C) thermal treatment in nitrogen atmosphere. Silicon out-diffusion from the SiO layer through the HfO2 films has been shown to be the limiting factor in the formation of the Si nanocrystals. Suitable strategies have been identified in order to overcome this limitation. Si nanocrystal formation has been achieved by properly adjusting the thickness of the SiO layer.