Preparation of Silica-On-Titania Patterns with a Wettability Contrast

Author(s): Kanta, A., R. Sedev, John Ralston

Journal: Langmuir (2005) 21: 5790-5794.

Abstract:
The preparation of patterned inorganic surfaces consisting of silica (SiO₂) and titania (TiO₂) is described. The approach is based on a combination of standard photolithography and plasma-enhanced chemical vapor deposition. Silicon wafers coated with a titania layer (40 nm) were patterned by use of a positive photoresist and then a thin silica layer (10-40 nm) was plasma-deposited. The photoresist was removed by decomposition at 800 °C. The inorganic patterned surfaces possessed excellent high-temperature resistance. Since the silica patches were effectively dehydroxylated during the thermal treatment, the patterns consisted of moderately hydrophobic (silica) and hydrophilic (titania) domains with a significant wettability contrast (40° for water). The surface was further hydrophobized with a self-assembled monolayer of fluoroalkylsilane (FAS) and exposed to UV light. The FAS layer was locally oxidized on the TiO₂ patches and the wettability contrast was maximized to 120° (the highest possible value on smooth surfaces).