Observation of Pull-In Instability in Graphene Membranes
under Interfacial Forces
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Abstract
We
present a unique experimental configuration that allows us to determine
the interfacial forces on nearly parallel plates made from the thinnest
possible mechanical structures, single and few layer graphene membranes.
Our approach consists of using a pressure difference across a graphene
membrane to bring the membrane to within ∼10–20 nm above
a circular post covered with SiO<sub><i>x</i></sub> or Au
until a critical point is reached whereby the membrane snaps into
adhesive contact with the post. Continuous measurements of the deforming
membrane with an AFM coupled with a theoretical model allow us to
deduce the magnitude of the interfacial forces between graphene and
SiO<sub><i>x</i></sub> and graphene and Au. The nature of
the interfacial forces at ∼10–20 nm separation is consistent
with an inverse fourth power distance dependence, implying that the
interfacial forces are dominated by van der Waals interactions. Furthermore,
the strength of the interactions is found to increase linearly with
the number of graphene layers. The experimental approach can be used
to measure the strength of the interfacial forces for other atomically
thin two-dimensional materials and help guide the development of nanomechanical
devices such as switches, resonators, and sensors