  2D crystals, such as graphene, exhibit the higher strength and stiffness of
any other known man-made or natural material. So far, this assertion has been
primarily based on modelling predictions and on bending experiments in
combination with pertinent modelling. True uniaxial loading of suspended
graphene is not easy to accomplish; however such an experiment is of paramount
importance in order to assess the intrinsic properties of graphene without the
influence of an underlying substrate. In this work we report on uniaxial
tension of graphene up to moderate strains of 0.8% ca.. This has been made
possible by sandwiching the graphene flake between two polymethylmethacrylate
(PMMA) layers and by suspending its central part by the removal of a section of
PMMA with e-beam lithography. True uniaxial deformation is confirmed by the
measured large phonon shifts with strain by Raman spectroscopy and the
indication of lateral buckling (similar to what is observed for thin
macroscopic membranes under tension). Finally, we also report on how the stress
is transferred to the suspended specimen through the adhesive grips and
determine the value of interfacial shear stress that is required for efficient
axial loading in such a system.
