Generation and removal mechanisms of modified structures in single crystal diamond by nitrogen plasma-assisted polishing

CX Wang and JQ Wan and YH Huang and L Pan and ZM Chai and J Cheng and YJ Dai and Y Zou and YH Liu, SURFACES AND INTERFACES, 73, 107457 (2025).

DOI: 10.1016/j.surfin.2025.107457

Single crystal diamond (SCD) holds great potential for next-generation integrated circuits. However, its high hardness and chemical inertness present significant challenges to polishing with high material removal rates and ultra-smooth surfaces. This study investigates the generation and removal mechanisms in nitrogen plasma-assisted polishing of SCD through ReaxFF molecular dynamics simulations and polishing experiments. Simulation results reveal that sp(2) hybridized modified structures form on the SCD surface at an optimal plasma temperature of 2000-3000 K. These structures facilitate atom removal, reducing the surface friction coefficient by 28.74%. After polishing, the nitrogen content on the SCD surface returned to its original level, indicating that the modified surface layer was easily removed. Nitrogen plasma-assisted polishing transforms the stable sp(3) hybridized structure of SCD into a more easily removable sp(2) hybridized form. A selective conjugated bond- breaking effect is proposed to explain the removal mechanism, in the modified structure, certain bonds within the conjugated rings exhibit a bond order of 1, making them more susceptible to breakage. The resulting carbon dangling bonds readily bond with abrasive particles, thereby facilitating material removal. The proposed mechanism offers a new perspective for enhancing both efficiency and surface quality in diamond polishing processes.

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