Nanoporous Aluminum Oxide Thin Films on Si Substrate: Structural Changes as a Function of Interfacial Stress

This paper reports the effect of Al 2 O 3 −SiO 2 interfacial stress on porous anodic alumina (PAA) structures formed by anodizing 150 nm thick aluminum thin films (ATF) deposited on silicon (Si) and glass substrates. The increase in the interfacial stress was achieved by growing thicker SiO 2 layers by anodizing the substrate after complete ATF oxidation. Thicker SiO 2 layers induced structural changes on the PAA. The nanopore diameter and interpore distance increased from 50 to 80 nm and 90 to 150 nm, respectively, and the nanopore density decreased from 60 to 43 nanopores μm −2 . The modifications of the PAA structure are related to the expansion of the SiO 2 layer, which exerts a bottom-up pressure on the PAA film to minimize the stress generated on the Al 2 O 3 −SiO 2 interface.