Self-assembled growth of Ni nanoparticles in amorphous alumina matrix

We present the formation of ordered 3D lattice of Ni nanocrystals/nanoparticles in amorphous alumina matrix achieved by a self-assembly process during a single-step magnetron sputtering deposition of Ni/Al₂O₃ multilayer at room temperature. The structure of the films was analyzed using Grazing Incidence Small and Wide Angle X-ray Scattering, Transmission Electron Microscopy, Atomic Force Microscopy, Grazing Incidence Wide Angle X-ray Scattering, and Time-of-Flight Elastic Recoil Detection Analysis measurements. The self-assembly is driven by surface morphology effects and it results in a body-centered tetragonal (BCT) lattice of Ni particles with crystalline face-centered cubic (FCC) internal structure in amorphous Al₂O₃ matrix. The size distribution of Ni NPs is narrow, and the material has good mechanical properties due to the alumina matrix. We show that the NP sizes and separations can be easily tuned by a suitable choice of the deposition conditions. The quality of the ordering achieved in the alumina matrix is found to be significantly better than the ordering of Ni particles in silica. The obtained results are important for the understanding of the self-assembly process of metallic particles in amorphous matrices and the applications of such materials. The prepared materials are potentially interesting for spintronic applications.