Microscopic insights into hydrophobicity of cerium oxide: effects of crystal orientation and lattice constant

Abstract Cerium oxide possesses intrinsic hydrophobic properties ascribed to the unique electronic structure. However, the relationship between the crystal structure and hydrophobicity of cerium oxide has not been systematically studied. Herein, it is experimentally and theoretically demonstrated that the water contact angle (105.9°) of the (111) surface is higher than that (91.7°) of the (220) surface, associated with the lower surface free energy (28.44 mN/m) of (111) surface than that (38.48 mN/m) of (220) surface. Furthermore, cerium oxide films with (111)-terminated surface are annealed at 300 °C and 600 °C for 1 h, respectively. The lattice constant increases (5.4594 A 300 °C > the as-deposited), leading to the increased water contact angle (96.7°