Authors: M.V. Diamanti, T. Souier, M. Chiesa, MP. Pedeferri
Affilation: Politecnico di Milano, Italy
Pages: 117 - 120
Keywords: anodizing, C-AFM, titanium oxide, nanostructure, heterogeneity
The anodic oxidation of titanium allows the obtaining of an oxide layer with thickness, color, homogeneity and insulating properties that depend on the process parameters. TiO2 thin films have been studied mostly to derive information on the oxidation kinetics of the metal. Still, a deeper understanding of oxide properties is vital to engineered applications of TiO2 nanostructured films, such as in the most recent field of memristive devices, where a precise control of oxide thickness and its electrical properties is required. Conductive Atomic Force Microscopy (C-AFM) is the ideal technique to investigate the electrical properties of thin oxide layers with high spatial resolution, as it provides information on the presence of heterogeneities (e.g. thickness variations, amorphous/crystalline domains). In this work, C-AFM measurements were performed on TiO2 oxides obtained by anodizing titanium in diluted sulfuric acid, with cell voltage ranging from 0 to 10 V, to understand the oxide coverage of the metal surface and to detect crystal domains. Oxide thickness was estimated by coulometric and spectrophotometric measurements. The findings highlighted a multifaceted heterogeneous nature of anodic oxides: a fine tuning of their electrical properties is possible by modulating anodizing parameters and cross-checking the obtained characteristics through the non-destructive techniques proposed.