Measuring and Modeling the Mechanical Properties of Suspended Graphene Drums after Electron Irradiation.*

This study explores the mechanical behaviors of suspended monolayer graphene drums subjected to controlled electron irradiation under ultra-high vacuum (UHV) conditions, using atomic force microscopy (AFM) nanoindentation. Graphene samples were irradiated using an electron gun at dosages ranging from 1×10¹⁶ to 6×10¹⁶ e⁻/cm². The acquired force–deflection data were analyzed using a nonlinear membrane deflection model to extract key mechanical parameters, including the elastic modulus and intrinsic pre-stress. Our findings reveal a non-monotonic trend in the elastic modulus: an initial enhancement at lower irradiation dosages, attributed to defect-induced lattice stiffening, followed by a degradation at higher doses due to increased defect density and lattice disorder. Furthermore, we investigated the fracture strength of the graphene membranes before irradiation, post-irradiation, and after temperature annealing at 250 °C. Post-annealing measurements demonstrated a partial recovery of fracture strength, indicating defect healing and structural reordering. These results underscore the tunability of graphene's mechanical properties via defect engineering and thermal treatment, offering valuable insights for its integration into flexible and high-performance devices.