AbstractNickel silicide nanocrystals (NCs) were formed by thermally annealing SiO_xN_y films either implanted with Ni or coated with an evaporated Ni film. It is observed that the NCs grow into well-defined single crystalline structures embedded in a SiO_xN_y matrix, and that their size can be directly controlled by adjusting the concentrations of either silicon or nickel in the SiO_xN_y layer. The formation of well-defined NC monolayers was also demonstrated by depositing an ultra-thin Ni layer between two SiO_xN_y layers. These structures are shown to exhibit characteristic capacitance-voltage hysteresis suitable for nonvolatile memory applications.