Polishing of polycrystalline diamond using synergies between chemical and mechanical inputs: A review of mechanisms and processes

Polycrystalline diamond (PCD) deposited as a thin film is an attractive material, both technologically and from a scientific viewpoint, due to its unique combination of properties. However, because many applications require the PCD to have a high quality surface finish, efficient and cost-effective polishing has become a critical and limiting step in advancing the more widespread use of PCD. The most widely-used processes for the polishing of PCD make use of synergies that can be achieved through applying a combination of chemical and mechanical inputs. This paper reviews the current state-of-the-art of such processes, which are mainly represented by chemical mechanical polishing (CMP) technology, for the polishing of polycrystalline diamond. An in-depth and informative literature survey is presented of the effects of the PCD characteristics and process-dependent factors such as polishing slurry composition, polishing pad/plate material, and polishing parameters, on the polishing/material removal rate and surface quality. Particular attention is given to the underlying mechanisms governing the material removal during polishing, which are complex and vary depending on the process, and are still unclear. Three main routes to material removal during the polishing of diamond are identified and summarized based on experimental results, chemical characterizations and computational simulations: interfacial mechanochemical removal, chemically-stimulated mechanical removal, and mechanochemical transformation of diamond. Finally, more recently developed polishing methods that make use of ultraviolet and plasma irradiations are introduced, and the limitations of existing research and future research directions are discussed.