Ion implantation enhancing the mechanical properties of diamond

This study aims to reveal the underlying mechanism of the mechanical property reinforcement of diamond after ion implantation. Molecular dynamics simulation for ion implantation into diamond surface is carried out along with nanoindentation experiment on the modified diamond surface. The findings suggest that the hardness and Young's modulus of the modified diamond are influenced by the implantation dose. The strengthening mechanisms of the modified diamond involve the coupling effect of phase transformation strengthening and dislocation strengthening. Dislocation loops formed by gallium ions implantation are initially pinned by point defects. The shear stress generated during nanoindentation provides the necessary energy for unpinning, triggering extensive dislocation propagation and slip. The multiplied dislocations significantly enhance diamond hardness by impeding lattice slip and atomic diffusion pathways. The size mismatch between gallium ions and carbon atoms induces lattice distortion, creating localized high-pressure zones within the implanted layer, which serves as the necessary driving force for phase transformation from cubic diamond to hexagonal diamond. The high-pressure shear strain field during nanoindentation further promotes nucleation and growth of the hexagonal phase, thereby enhancing the material strength through transformation hardening. Furthermore, gallium ions implantation increases interatomic bonding strength and induces lattice contraction, leading to an elevated elastic modulus.