Multi-physical field coupling polishing of diamond for atomic-scale damage-free surface

Diamond is renowned for its high stability in extreme environments, such as high temperatures, high pressures, and strong corrosive conditions, which makes it demonstrate irreplaceable superior performance in quantum devices, high-power optical systems, and ultra-high-frequency electronic devices. Nevertheless, its intrinsic brittleness, difficulty in material removal, and vulnerability to damage caused by processing severely limit its practical application. The inherently rough surface of as-grown diamond necessitates precision polishing to obtain ultra-smooth, damage-free surface with nanometer-scale roughness, sub-micrometer form accuracy, and minimal subsurface damage. This paper provides a systematic review of state-of-the-art diamond polishing technologies, addressing the challenge of achieving sub-nanometer roughness and damage-free surface, with particular emphasis on the need for atomic-level surface integrity. The discussion covers laser polishing (LP), mechanical polishing (MP), ion beam polishing (IBP), gas cluster ion beam polishing (GCIBP), plasma polishing, dynamic friction polishing (DFP), chemical mechanical polishing (CMP), ultraviolet-assisted polishing (UVAP), plasma-assisted polishing (PAP), laser-assisted polishing (LAP), ultrasonic-assisted polishing (UAP), and other major techniques. By deconstructing these technological approaches, four fundamental material removal mechanisms, i.e., microfracture, graphitization, oxidation, physical sputtering and chemical etching, are identified. This highlights that hybrid, multi-physics polishing strategies can effectively balance the material removal rate (up to several μm·h^-1) and surface quality (down to sub-nanometer scale), outperforming conventional single-field techniques. Finally, the review outlines future directions, emphasizing innovations in multi-physics coupling mechanisms and intelligent control of atomic-scale manufacturing processes, thereby providing theoretical guidance and technical pathways to overcome the coupled challenges of atomic precision, efficiency, and extreme service conditions.