Thermal and Plasma-Enhanced Atomic Layer Deposition of Yttrium Oxide Films and the Properties of Water Wettability

The atomic layer deposition (ALD) of yttrium oxide (Y2O3) is investigated using the liquid precursor Y(EtCp)2(iPr-amd) as the yttrium source with thermal (H2O) and plasma-enhanced (H2O plasma and O2 plasma) processes, respectively. Saturation is confirmed for the growth of the Y2O3 films with each investigated reactant with a similar ALD window from 150 to 300 °C, albeit with a different growth rate. All of the as-deposited Y2O3 films are pure and smooth and have a polycrystalline cubic structure. The as-deposited Y2O3 films are hydrophobic with water contact angles >90°. The water contact angle gradually increased and the surface free energy gradually decreased as the film thickness increased, reaching a saturated value at a Y2O3 film thickness of ∼20 nm. The hydrophobicity was retained during post-ALD annealed at 500 °C in static air for 2 h. Exposure to polar and nonpolar solvents influences the Y2O3 water contact angle. The reported ALD process for Y2O3 films may find potential applications in the field of hydrophobic coatings.