On the wettability and optical properties of nanocrystalline CeO2 thin films

Abstract

Cerium oxide (CeO₂) is an inexpensive material and has many applications due to its excellent wetting and optical properties. However, deposition of CeO₂ thin films of desired wettability (hydrophobic/hydrophilic) and with high refractive index (n) and large band gap (E_g) is a challenging task. In the present study, wettability and optical properties of E-beam evaporated CeO₂ thin films have been reported in the substrate temperature range RT-700 °C. All the evaporated CeO₂ thin films showed only hydrophobic nature, as revealed by contact angle measurements. Further, the maximum values of n (2.38) and E_g (3.21 eV) of CeO₂ thin film are obtained at 700 °C as determined by spectroscopic ellipsometer. Our earlier reported results of sputtered CeO₂ thin films show that it is possible to achieve both hydrophilic and hydrophobic nature and also high n (2.62) and large E_g (3.43 eV) values simply by varying the substrate temperature and this phenomenon has been attributed to the occurrence of energetic ion bombardment of depositing films. These results indicate that the wettable and optical properties of CeO₂ thin films depend on the deposition technique and the associated process parameters.