Oriented Metallic Nano-Objects on Crystalline Surfaces by Solution Epitaxial Growth

Chemical methods offer the possibility to synthesize a large panel of nanostructures of various materials with promising properties. One of the main limitations to a mass market development of nanostructure based devices is the integration at a moderate cost of nano-objects into smart architectures. Here we develop a general approach by adapting the seed-mediated solution phase synthesis of nanocrystals in order to directly grow them on crystalline thin films. Using a Co precursor, single-crystalline Co nanowires are directly grown on metallic films and present different spatial orientations depending on the crystalline symmetry of the film used as a 2D seed for Co nucleation. Using films exposing 6-fold symmetry surfaces such as Pt(111), Au(111), and Co(0001), the Co heterogeneous nucleation and epitaxial growth leads to vertical nanowires self-organized in dense and large scale arrays. On the other hand, using films presenting 4-fold symmetry surfaces such as Pt(001) and Cu(001), the Co growth leads to slanted wires in discrete directions. The generality of the concept is demonstrated with the use of a Fe precursor which results in Fe nanostructures on metallic films with different growth orientations which depend on the 6-fold/4-fold symmetry of the film. This approach of solution epitaxial growth combines the advantages of chemistry in solution in producing shape-controlled and monodisperse metallic nanocrystals, and of seeded growth on an ad hoc metallic film that efficiently controls orientation through epitaxy. It opens attractive opportunities for the integration of nanocrystals in planar devices.