Meso-silica/Erbium-doped ceria binary particles as functionalized abrasives for photochemical mechanical polishing (PCMP)

We report the design and synthesis of meso-silica/ceria binary composite particles and their usage as functionalized abrasives for photochemical mechanical polishing (PCMP). Meso-silica nanospheres were uniformly coated with (Er3+-doped) ceria nanoparticles via an environmentally friendly precipitation approach. The resulting products were characterized by XRD, FESEM, HRTEM, HADDF-STEM, EDX mapping, UV?vis, Raman, XPS, PL, and nitrogen adsorption?desorption measurements. High-resolution AFM analyses revealed that the binary abrasives contributed to mechanical damage and scratch eliminations, and finally achieved ultra-smooth surfaces with an average root-mean-square roughness of less than 0.2 nm. Owing to the increased oxygen vacancy and Ce3+ ion contents, the Er3+-doped abrasives in oxide-PCMP exhibited superior removal rates derived from the improved photocatalytic and tribochemical activities, thus leading to a 160% increment of removal rates compared to the undoped ones in oxide-CMP. The topographical variations of the surfaces after PCMP with Er3+-doped composites significantly reduced from ?3.1 nm to ?0.39 nm. High-quality and high-efficiency polishing can be achieved by the dynamical balance between the photocatalytic surface modification and the tribochemical material removal of the chemically soft layers. Furthermore, the synergistic roles of elastic mesosilica supports and active ceria components of the binary abrasives in material removal processes were also discussed.