Ligand-performance relationships of surface-modified CeO2 in chemical mechanical polishing: A case of coordination number

Abstract

Surface modification represents one of the most effective methods for tailoring the properties of CeO₂ particles in chemical mechanical polishing. Although numerous studies have demonstrated preliminary evidence that ligand structure plays an important role in determining the performance of modified CeO₂, fundamental insights into the structure-property relationships between ligand coordination number and polishing performance remain lacking in the literature. By comparing the polishing performance of CeO₂ slurries modified by a series of phosphorus ligands with varying numbers of coordination sites-including H₃PO₄, aminotrimethylene phosphonic acid (ATMP), and diethylenetriaminepenta(methylenephosphonic acid) (DTPMP)-we demonstrate that ligands with more chelating sites yield superior modification effects. Specifically, optimal performance in terms of suspension stability, material removal rate, and surface quality was observed for slurries modified with DTPMP. Mechanistic investigation through density functional theory calculations reveals that both the coordination strengths and ligand densities on the CeO₂ surface are correlated with their coordination number, which results in distinct performance characteristics of the prepared slurries. This work not only elucidates the fundamental relationships between ligand coordination number and the polishing performance of CeO₂ slurries but also provides a practical strategy for developing high-performance slurries required for chemical mechanical polishing.