Effect of sputtering gas on structural, optical and hydrophobic properties of DC-sputtered hafnium oxide thin films

The outdoor ceramic insulators of power transmission lines and transformers are suffering from the problem of contamination due to which surface flashover phenomenon is frequent. The main objective of this work was to prepare hydrophobic hafnium oxide (HfO2) thin films to mitigate contamination problem. The hafnium oxide coatings were deposited on glass substrates by DC reactive magnetron sputtering from a pure hafnium target. The depositions of HfO2 films were carried out in O2 + Ar and O2 + He atmosphere. The structural, optical and hydrophobic properties were examined by varying O2/Inert gas ratio. The prepared samples were characterized by X-ray diffraction, EDS, AFM, UV-vis-NIR spectrophotometer and contact angle goniometer. The coatings were found to be crystalline, transparent and hydrophobic for all samples. The deposition rate, hydrophobicity, transparency, band gap and particle size are better for the films deposited in argon atmosphere in comparison to helium. The hydrophobicity was found to be dependent on roughness of the film. The roughness (5.06 nm) and the water contact angle (102.25°) were found maximum for the film deposited at O2/Ar ratio equals to 0.5. The transmittance was also found ~ 90% at this particular ratio. The band gap of the film deposited at above mentioned ratio was found to be 5.41 eV ensuring insulating nature of the film.