Capillary force-induced superlattice variation atop a nanometer-wide graphene flake and its moire origin studied by STM

Abstract

We present strong experimental evidence for the moire origin of superlattices on graphite by imaging a live transition from one superlattice to another with concurrent and direct measurement of the orientation angle before and after rotation using scanning tunneling microscopy (STM). This has been possible due to a fortuitous observation of a superlattice on a nanometer-sized graphene flake wherein we have induced a further rotation of the flake utilizing the capillary forces at play at a solid-liquid interface using STM tip motion. We propose a more ``realistic'' tip-surface meniscus relevant to STM at solid-liquid interfaces and show that the capillary force is sufficient to account for the total expenditure of energy involved in the process.