The high-speed three-dimensional movement dynamic friction polishing (3DM-DFP) has been recognized as an efficient approach for ultra-smoothing single crystal diamond (SCD) surface. Continuing from the previous works focusing on the subsurface cleavage of diamond after 3DM-DFP, process optimization and surface reaction evolution mechanism as a fundamental building block is investigated, for the first time, for comprehensively understanding this fast-smoothing manner. By systematically adjusting the controlling factor, stronger load (0.3 MPa) and appropriate duration (0.5 h) as well as moderate sliding speed (in the range of 30 to 45 m s⁻¹) is found to be able to obtain the smooth surface of SCD without uncontacted traces or break-surface cleavage. Subtle residual clues on SCD surface as a function of progressive DFP procedure indicate that Fe catalytic oxidation mainly produce Fe₂O₃ and partial intermediate oxides Fe_1-yO. Meanwhile, the activated oxygen inserts sp³ CC bonds could form CO or CO and C-O-V (vacancy) at existing reactive surface sites. The (100) favorable CO bonds can be rebuilt if (100) surface is reformed, although the CO bonds associated with non-(100) rough surface would replace them during DFP procedure. The formed COC and concomitant C-O-V as well as the oxidized graphite give rise to the increase of CO proportion, and finally the covered defective graphitic phase has an approximate CO/CO ratio of 1.25. All these are endowed potential value for future upgrading of DFP technique for diamond surface smoothing.

The high-speed three-dimensional movement dynamic friction polishing (3DM-DFP) has been recognized as an efficient approach for ultra-smoothing single crystal diamond (SCD) surface. Continuing from the previous works focusing on the subsurface cleavage of diamond after 3DM-DFP, process optimization and surface reaction evolution mechanism as a fundamental building block is investigated, for the first time, for comprehensively understanding this fast-smoothing manner. By systematically adjusting the controlling factor, stronger load (0.3 MPa) and appropriate duration (0.5 h) as well as moderate sliding speed (in the range of 30 to 45 m s⁻¹) is found to be able to obtain the smooth surface of SCD without uncontacted traces or break-surface cleavage. Subtle residual clues on SCD surface as a function of progressive DFP procedure indicate that Fe catalytic oxidation mainly produce Fe₂O₃ and partial intermediate oxides Fe_1-yO. Meanwhile, the activated oxygen inserts sp³ CC bonds could form CO or CO and C-O-V (vacancy) at existing reactive surface sites. The (100) favorable CO bonds can be rebuilt if (100) surface is reformed, although the CO bonds associated with non-(100) rough surface would replace them during DFP procedure. The formed COC和伴随的COV以及被氧化的石墨会导致C O比例的增加，最终被覆的缺陷石墨相的C O / C O比率约为1.25。所有这些都为将来升级DFP技术用于钻石表面平滑化提供了潜在的价值。