Achieving highly hydrophobic or hydrophilic HfNx-Ag films surfaces by controlling the existing forms of Ag

Abstract

Increasing demands for robust hydrophobic or hydrophilic surfaces in harsh conditions such as erosion, abrasion and high temperature, have stimulated the development of intrinsically hydrophobic or hydrophilic ceramics (or metals). Despite tremendous efforts, realizing robust highly hydrophobic or hydrophilic ceramics surfaces using a simple method remains a great challenge. In this letter, we report that HfNx-Ag films with two different existing forms of Ag: (1) Solute Ag and (II) Precipitate Ag, were deposited using co-sputtering system by setting deposition temperature at room temperature (RT) and 400°C, respectively, further achieving highly hydrophobic (water contact angle (WCA)∼120°) or hydrophilic (WCA∼55°) surfaces by controlling the content of solute Ag or precipitate Ag. Solute Ag provides the hydrophobic Ag2O groups with coordinative saturation though surface self-oxidation, which inhibits hydrogen bonding with interfacial water molecules, whereas hydrophilic precipitate Ag acts as Lewis acid, which interacts strongly with water.