Impact of Atomic Defects on Ceria Surfaces on Chemical Mechanical Polishing of Silica Glass Surfaces

This study investigates the impact
of atomic defects,
such as oxygen
vacancies and Ce3+ ions, on cerium oxide (ceria) surfaces
during chemical mechanical polishing (CMP) for silica glass finishing.
Using density functional theory (DFT) and reactive molecular dynamics
simulations, the interaction of orthosilicic molecules and silica
glass with dry and wet ceria surfaces is explored. Defects alter the
surface reactivity, leading to the dissociation of orthosilicic acid
on oxygen vacancies, forming a strong Si–O–Ce bond.
Hydroxylated surfaces exhibit easier oxygen vacancy formation and
thermodynamically favored substitution of hydroxyl groups with orthosilicic
acid. A new ReaxFF library for silica/ceria interfaces with defects
is validated using DFT outcomes. Reactive MD simulations demonstrate
that ceria surfaces with 30% Ce3+ ions on (111) planes
exhibit higher polishing efficiency, attributed to increased Si–O–Ce
bond formation. The simultaneous presence of oxygen vacancies and
various acidic and basic sites on ceria surfaces enhances the polishing
efficiency, involving acid–base reactions with silica. Defective
surfaces show superior efficiency by removing silicate chains, contrasting
with nondefective surfaces removing isolated orthosilicate units.
This study provides insights into optimizing CMP processes for high-precision
glass industry surface finishing.