Master of Science
Michael G. Cottam
Recently, Giovannetti et al. successfully demonstrated that some metals (such as Cu and Au) only have weak van der waals interaction with graphene and thus can only form weak bonding without severely shifting graphene’s band structure, which describes the energies range of the electrons in the material. Therefore, this opens up windows for graphene enhancement without greatly changing its properties. Furthermore, Zhou et al. later suggested the possibility of self-assembling periodic arrays of alkali atoms on graphene. In our group, graphene thin films fabricated in a cost effective way using solution-processed methods have been used extensively, including decorating graphene thin films with metallic nanoparticles for optical enhancement. Motivated by these experiments, our study reports a facile fabrication method for copper nanoparticle (Cu-np) superlattice, which is a periodic structure of copper-nanoparticle lines. This fabrication is based on thermal evaporation of ultrathin layers of copper. These copper layers are deposited on solution-processed thin films formed by few-layer graphene platelets. We show that the annealing of these systems in nitrogen without previous exposure to air prompts the heterogeneous nucleation of the Cu layer into nanoparticle superlattices. And these nanoparticles self-assemble along specific crystallographic directions of graphene. Theoretical calculations suggest the lowest formation energy for Cu-nanoparticle arrays forming along armchair directions, indicating that their self-assembly is energetically more favorable. The possibility of using these superlattices in evanescent waveguiding devices is explored by scanning near-field optical microscopy. The light-confining properties of our systems in the near field indicate that our nanoparticle superlattices are poised to satisfy the technological demands required by nanophotonics devices.
Ouyang, Tianhao, "Self-assembled copper nanoparticle superlattices on graphene thin films" (2016). Electronic Thesis and Dissertation Repository. 3940.