Thermal and plasma-enhanced atomic layer deposition of yttrium oxide films and the properties of water wettability.

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) process, respectively. Saturation is confirmed for growth of the Y2O3 films with each investigated reactant with a similar ALD window from 150 to 300 ˚C, albeit with the different growth rate. All the as-deposited Y2O3 films are pure, smooth and with a polycrystalline cubic structure. The as-deposited Y2O3 films are hydrophobic with water contact angles over 90°. The water contact angle gradually increased and the surface free energy gradually decreased as film thickness increased, reaching a saturated value at Y2O3 film thickness of about 20nm. The hydrophobicity was retained during post-ALD annealed at 500 °C in static air for 2 h. Exposure to polar and non-polar solvents influences the Y2O3 water contact angle. The reported ALD process for Y2O3 films may find potential applications in the field of hydrophobic coatings.