Synergistic Experimental and Molecular Dynamics Study on the Si Ion Irradiation-Induced Mechanical Degradation in SiC Nanowires

Investigating irradiation-induced mechanical degradation in silicon carbide (SiC) nanowires (NWs) remains challenging. Here, we combine in situ tensile testing within a scanning electron microscope (SEM) and molecular dynamics (MD) simulations to systematically investigate damage evolution in 3C-SiC NWs under Si⁺ irradiation. Experiments reveal a pronounced reduction in Young's modulus and fracture strength even at low doses (<0.2 dpa). MD simulations reveal distinct degradation mechanisms: strength is governed by surface-defect-induced stress concentration, whereas modulus decay results from the synergistic effects of surface amorphization and internal defect accumulation. A Tensile Core-Shell Model is established to quantify this evolution, revealing that interface-driven defect recombination thickens a mechanically ineffective shell while preserving the crystalline core. Notably, SiC NWs maintain brittle fracture across all doses and exhibit superior amorphization resistance. These findings link atomic-scale defects to macroscopic stiffness decay, providing a robust framework for predictive modeling and radiation-tolerant design of nanodevices.