Atomic-scale analysis of nanoindentation behavior on cylindrical silicon mirrors with different crystal orientations

JH Li and HG Li and XP Wu and XG Guo and S Gao, MATERIALS TODAY COMMUNICATIONS, 49, 114018 (2025).

DOI: 10.1016/j.mtcomm.2025.114018

Single-crystal silicon cylindrical mirrors are widely used in focusing optical systems, typically fabricated through ultra-precision grinding and polishing. Considering the curvature effects of these mirrors, the crystallographic anisotropy of silicon along the arc-shaped profile leads to variations in mechanical behavior and damage formation during machining. To elucidate the anisotropic nano-mechanical behavior under different crystal orientations, this study integrates nanoindentation experiments with molecular dynamics (MD) simulations. The results demonstrated that as the crystal orientation transitions from 100 to 110 along the cylindrical surface, the material hardness increases, while the elastic modulus and elastic recovery decrease. The orientation 100 exhibits low hardness and high modulus, which promote elastic recovery and uniform dislocation glide. This combination effectively mitigates severe surface and subsurface damage. In contrast, the orientation 110 shows higher hardness but lower modulus, resulting in restricted recovery, localized dislocation activity, and frequent Lomer- Cottrell lock formation. These mechanisms ultimately lead to deeper amorphous zones. Intermediate orientations such as 520 and 530 exhibit behavior transitional between 100 and 110. This work establishes a fundamental correlation between mechanical properties, dislocation mechanisms, and damage evolution, offering valuable insights for optimizing ultra-precision grinding and polishing processes to achieve high-quality optical surfaces.

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