Stress-strain in electron-beam activated polymeric micro-actuators

Actuation of thin polymeric films via electron irradiation is a promising avenue to realize devices based on strain engineered two-dimensional 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 a 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.