  We induced periodic biaxial tensile strain in polycrystalline graphene by
wrapping it over a substrate with repeating pillar-like structures with a
periodicity of 600 nm. Using Raman spectroscopy, we determined to have
introduced biaxial strains in graphene in the range of 0.4% to 0.7%. Its band
structure was characterized using photoemission from valance bands, shifts in
the secondary electron emission, and x-ray absorption from the carbon 1s levels
to the unoccupied graphene conduction bands. It was observed that relative to
unstrained graphene, strained graphene had a higher work function and higher
density of states in the valence and conduction bands. We measured the
conductivity of the strained and unstrained graphene in response to a gate
voltage and correlated the changes in their behavior to the changes in the
electronic structure. From these sets of data, we propose a simple band diagram
representing graphene with periodic biaxial strain.
