  We use the tip of the scanning tunneling microscope (STM) to manipulate
single weakly bound nanometer-sized sheets on the the highly oriented pyrolytic
graphite (HOPG) surface through artifically increasing the tip and sample
interaction in humid environment. By this means it is possible to tear apart a
graphite sheet againt a step and fold this part onto the HOPG surface and thus
generate the gaphene superlattices with hexagonal symmetry. The tip and sample
surface interactions, including the van der Waals force, eletrostatic force and
capillary attraction force originating from the Laplace pressure due to the
formation of a highly curved fluid meniscus connecting the tip and sample, are
discussed in details to understand the fromation mechnism of graphen
superlattice induced by the STM tip. Especially, the capillary force is the key
role in manipulating the graphite surface sheet in the hunmidity condition. Our
approach may provides a simple and feasible route to prepare the controllable
superlattices and graphene nanoribbons but also replenish and find down the
theory of generation of graphene superlattice on HOPG surface by the tip.

Chemical Physics;Materials Science