  Actuation of thin polymeric films via electron irradiation is a promising
avenue to realize devices based on strain engineered two dimensional (2D)
materials. Complex strain profiles demand a deep understanding of the mechanics
of the polymeric layer under electron irradiation; in this article we report a
detailed investigation on electron-induced stress on poly-methyl-methacrylate
(PMMA) thin film material. After an assessment of stress values using a method
based on dielectric cantilevers, we directly investigate the lateral shrinkage
of PMMA patterns on epitaxial graphene, which reveals a universal behavior,
independent of the electron acceleration energy. By knowing the stress-strain
curve, we finally estimate an effective Young's modulus of PMMA on top of
graphene which is a relevant parameter for PMMA based electron-beam lithography
and strain engineering applications.
