Mechanical Properties of Suspended Graphene Drums under Ultra-High Vacuum Electron Irradiation

We investigate the mechanical properties of suspended monolayer graphene drums subjected to ultra-high vacuum electron irradiation using atomic force microscopy nanoindentation. Electron irradiation is widely used for graphene modification and device fabrication, yet its mechanical impact remains unclear. Irradiation was performed at dosages from 1×10¹⁶ to 6×10¹⁶ e⁻/cm² at 1.5 KeV to prevent contamination and isolate electron-induced effects, which are believed to cause lattice modification such as hydrogenation. Nanoindentation before and after irradiation was analyzed using a membrane deflection model. The results reveal two distinct regimes. For pristine graphene, the stiffness was 265 N/m; after low-dose irradiation, it increased to 421 N/m, while high doses caused softening due to lattice damage, reducing it to 228 N/m. In the first stage, the stiffness rose from 277 N/m before irradiation to 335 N/m after irradiation. Post-irradiation annealing at 250 °C restored the elastic modulus to 248 N/m. A similar trend was observed in the second stage, along with enhanced fracture strength, indicating effective lattice healing. These findings reveal tunable mechanical behavior in graphene and are significant for its application in robust nanomechanical and energy storage devices.