Concerted Chemical-Mechanical Reaction in Catalyzed Growth of Confined Graphene Layers into Hexagonal Disks

Abstract

Graphene and graphite synthesis of uniform films is becoming routine, so now efforts are turning to grow specific patterns or complex structures. More research is needed with regard to the practical aspects of the growth of graphene layers, especially as it relates to self-assembled structures. We used gallium-catalyzed thermal decomposition of silicon carbide to understand spatially confined growth. Growing graphene layers push on a large step in hard silicon carbide (SiC) with significant force, as observed by high-resolution transmission electron microscopy of film cross sections. Alternatively multiple graphitic layers can grow into disks embedded in silicon carbide if the crystal is heated above the transition to plastic deformation. Euler buckling appears to limit the size and deformation of the silicon carbide crystal to produce graphitic flakes with an oriented hexagonal shape. These results illustrate the effect of the mechanical force of growing graphene in confined spaces: the growing graphene can be redirected, graphene can deform the confining barrier, or growth of graphene can be limited. This also provides a route for fabrication of masses of homogeneous, hexagonal disks of graphite with dimensions that are tuned by directed self-assembly