  Strains strongly affect the properties of low-dimensional materials, such as
graphene. By combining in situ, in operando, reflection high energy electron
diffraction experiments with first-principles calculations, we show that large
strains, above 2%, are present in graphene during its growth by chemical vapor
deposition on Ir(111) and when it is subjected to oxygen etching and ion
bombardment. Our results unravel the microscopic relationship between point
defects and strains in epitaxial graphene and suggest new avenues for graphene
nanostructuring and engineering its properties through introduction of defects
and intercalation of atoms and molecules between graphene and its metal
substrate.
