Visualized Graphene Domains by Aligned Nematic Liquid Crystals

Abstract

Direct visualization of large-area graphene domains is one of the key issues in graphene research, because their electronic, magnetic, chemical and mechanical properties are dominated by their domain size and direction of hexagonally packed carbon matrix. All previous methods used to visualize the domain and boundary of graphene, which include atomic force microscopy, scanning electron microscopy, transmission electron microscopy and raman spectroscopy, are only effective for small area up to several micrometer. This is unable to determine the domain size of the large-area graphene. Here, we demonstrate a very simple method to macroscopically visualize the graphene domains and their boundaries by using nematic liquid crystals on the surface of graphene. Epitaxially aligned nematic liquid crystals on graphene surface are observed using polarized optical microscopy, and obtained textures from liquid crystals are well matched with the domain of graphene. Using this approach, we investigated the effect of domain size and boundary on the quality of graphene in terms of conductance. This method will open a new window for studies on the control of domain, boundary and structure and properties of graphene.