Nucleation and growth of water ice on oxide surfaces: the influence of a precursor to water dissociation

Abstract

We have investigated how nucleation and growth processes of ice are influenced by interfacial molecular interactions on some oxide surfaces, such as rutile TiO₂(110), TiO₂(100), MgO(100), and Al₂O₃(0001), based on the diffraction patterns of electrons transmitted through ice crystallites under the experimental configuration of reflection high energy electron diffraction (RHEED). The cubic ice Ic grows on the TiO₂(110) surface with the epitaxial relationship of (110)_Ic//(110)_TiO2 and [001]_Ic//[10]_TiO2. The epitaxial ice growth tends to be disturbed on the TiO₂(110) surface under the presence of oxygen vacancies and adatoms. The result is not simply ascribable to small misfit values between TiO₂ and ice Ic lattices (∼2%) because ice grains are formed randomly on TiO₂(100). No template effects are identified during ice nucleation on the pristine MgO(100) and Al₂O₃(0001) surfaces either. The water molecules are chemisorbed weakly on these surfaces as a precursor to dissociation via the acid–base interaction. Such anchored water species act as an inhibitor of epitaxial ice growth because the orientation flexibility of physisorbed water during nucleation is hampered at the interface by the preferential formation of hydrogen bonds.