Atomically Thin Epitaxial Template for Organic Crystal Growth Using Graphene with Controlled Surface Wettability

A two-dimensional epitaxial growth template for organic semiconductors was developed using a new method for transferring clean graphene sheets onto a substrate with controlled surface wettability. The introduction of a sacrificial graphene layer between a patterned polymeric supporting layer and a monolayer graphene sheet enabled the crack-free and residue-free transfer of free-standing monolayer graphene onto arbitrary substrates. The clean graphene template clearly induced the quasi-epitaxial growth of crystalline organic semiconductors with lying-down molecular orientation while maintaining the “wetting transparency”, which allowed the transmission of the interaction between organic molecules and the underlying substrate. Consequently, the growth mode and corresponding morphology of the organic semiconductors on graphene templates exhibited distinctive dependence on the substrate hydrophobicity with clear transition from lateral to vertical growth mode on hydrophilic substrates, which originated from t...