Advances and challenges in mechanical, chemical and energy-field-assisted polishing techniques for single-crystal and polycrystalline diamonds: a comprehensive review

• A comprehensive overview of precision polishing technologies for single-crystal and polycrystalline diamonds was provided. • The latest progress, characteristics, mechanisms and key influencing factors of different polishing methods were critically reviewed. • Emerging energy-field-assisted polishing techniques were systematically summarized and discussed. Diamond has been extensively applied in optics and semiconductor industries owing to its exceptional physical and chemical properties. For industrial applications, diamond surfaces often demand high precision and minimal damage. However, its extreme hardness and chemical inertness pose significant challenges for surface processing. To address this, various polishing techniques have been developed; this article provides a systematic review of the principal methods for polishing single-crystal and polycrystalline diamonds, including mechanical polishing, mechanochemical polishing thermochemical polishing, chemical–mechanical polishing, and dynamic friction polishing. The polishing quality, material removal rate, and underlying material removal mechanisms of these techniques are comparatively analyzed. While some methods can achieve ultra-low surface roughness and others offer high material removal rates, no single technique fully satisfies all processing requirements. In recent years, plasma-assisted polishing technology and laser-assisted polishing technology have greatly improved polishing quality through the innovative combination of ion or laser-induced chemical modification and mechanical removal. The ultrasound-assisted polishing technology and electrical discharge machining technology have also greatly improved the material removal rate through high-frequency ultrasound energy field and discharge effect. Low-temperature-assisted polishing can process single crystal diamond wafers with sub nanometer surface quality. These emerging technologies are showing great potential in the field of diamond polishing.