Voltage-Gated Switching of Moiré Patterns in Epitaxial Molecular Crystals.

Studying molecular materials at the nanoscale allows us to gain a deeper understanding of supramolecular structure formation and serves as the basis for rationally controlling the resulting interfacial properties. Here, we describe the formation of extended Moiré patterns resulting from the assembly of dipolar π-conjugated molecules on highly oriented pyrolytic graphite at the liquid-solid interface as characterized by scanning tunneling microscopy (STM). By switching the bias of the sample and thus the orientation of the external electric field in the vicinity of the STM junction, structural reorganization of the molecular building blocks and the resulting organic 2D crystal is induced and can conveniently be monitored by the appearance and disappearance of the Moiré patterns. Importantly, the formation and loss of the Moiré patterns are fully reversible, providing exquisite control over epitaxial molecular crystals. Our approach provides fundamental insights into the supramolecular organization and resulting superstructure formation of incommensurable 2D lattices upon applying an electric field and enables the rational tuning of Moiré patterns as a key step toward the potential integration of organic 2D crystals in molecular nanodevices.