Hierarchical Super-Hydrophilic Aluminum Oxide Architectures on Textured Silicon for Aqueous and Vapor-Phase Interaction

Hierarchical super-hydrophilic surfaces were realized by forming porous anodic aluminum oxide (AAO) and boehmite [AlO(OH)] on micro-textured Si wafers. One-step anodization of e-beam deposited Al followed by controlled pore widening, thermal annealing, or hot water treatment produced oxide architectures exhibiting near-zero water contact angles (aqueous regime) and pronounced H₂O adsorption–desorption responses (vapor regime). Thermogravimetric analysis, moisture isotherms, and FT-IR indicate that increased porosity and anion incorporation (O⁻/O²⁻/oxalate) enrich surface hydroxyl functionality, enhancing affinity to H₂O. The results delineate two complementary regimes—rapid capillary wetting and multilayer vapor adsorption—supporting the use of these oxide/Si hierarchies as interactive water-affine interfaces with potential relevance to moisture gettering and chemosensing.