Hydrophilic/hydrophobic surface of Al₂O₃ thin films grown by thermal and plasma-enhanced atomic layer deposition on plasticized polyvinyl chloride (PVC)

Thermal ALD (T-ALD) and plasma-enhanced ALD (PE-ALD) processes were employed to prepare the Al₂O₃ thin films on plasticized polyvinyl chloride (PVC) surfaces at a low deposition temperature of 80 °C. The water contact angle test shows that the T-ALD Al₂O₃ films exhibited a hydrophobic surface, while the PE-ALD Al₂O₃ films were hydrophilic. The difference in the surface hydrophobicity is attributed to the carbon residue in Al₂O₃ films, as revealed by the X-ray photoelectron and Fourier transform infrared spectroscopies. The trend of hydrophobicity follows with the evolution of surface roughness of the T-Al₂O₃ films, indicating that the surface roughness contributed to the hydrophobicity as predicted by the Wenzel's mode. The result indicates that the surface hydrophilicity/hydrophobicity of the Al₂O₃ thin films can be modified and controlled by the deposition conditions of the ALD process.