Thickness-dependent morphology, microstructure, adsorption and surface free energy of sputtered CeO2 films

Abstract

Thickness plays a key role in determining the surface morphology, microstructure and properties of films. Herein, CeO2 films with different thickness were deposited onto silicon substrates by magnetron sputtering. Prepared films exhibited preferred crystal orientation of (111) plane, which had the smallest surface energy compared to other crystal orientations. Film thickness affected the surface morphology, microstructure, surface chemistry, as well as wetting properties of CeO2 films. With increasing film thickness, the grain size became larger and the root-mean-square (RMS) roughness increased. More oxygen vacancies were detected for the thicker film, which enhanced the hydrocarbon adsorption and reduced the wetting, the water contact angle could reach 101.8°. In addition, surface free energy calculations showed that the interaction between water and film surface was mainly electrostatic and surface free energy decreased when the film became thicker. Such films with varying thickness and controllable wettability could find various practical applications.