Thickness dependent wetting properties and surface free energy of HfO2 thin films

• Published in: Applied physics letters Vol. 108; no. 23
• Main Authors: Zenkin, Sergei, Belosludtsev, Alexandr, Kos, Šimon, Čerstvý, Radomír, Haviar, Stanislav, Netrvalová, Marie
• Format: Journal Article
• Language: English
• Published: Melville American Institute of Physics 06.06.2016
• Subjects: Adhesion; Applied physics; Contact angle; Dependence; Film thickness; Free energy; Hafnium oxide; Hydrophobicity; Magnetron sputtering; Properties (attributes); Surface energy; Thin films; Water drops; Wetting
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/1.4953262

We show here that intrinsic hydrophobicity of HfO2 thin films can be easily tuned by the variation of film thickness. We used the reactive high-power impulse magnetron sputtering for preparation of high-quality HfO2 films with smooth topography and well-controlled thickness. Results show a strong dependence of wetting properties on the thickness of the film in the range of 50–250 nm due to the dominance of the electrostatic Lifshitz-van der Waals component of the surface free energy. We have found the water droplet contact angle ranging from ≈120° for the thickness of 50 nm to ≈100° for the thickness of 2300 nm. At the same time the surface free energy grows from ≈25 mJ/m2 for the thickness of 50 nm to ≈33 mJ/m2 for the thickness of 2300 nm. We propose two explanations for the observed thickness dependence of the wetting properties: influence of the non-dominant texture and/or non-monotonic size dependence of the particle surface energy.