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Aleksandra Baron-Wiecheć – Guangdong Technion – Israel Institute of Technology, China
The functional properties of thin anodic oxide films are closely linked to strategic research topics such as nanoscale ferromagnetism in semiconductors, aqueous proton-ion batteries, and wearable electronics. Under specific anodization conditions, it is possible to form regular arrays of nanometric pores with varied morphology and properties, including dielectric, optical, or hydrophobic characteristics. However, due to the complexity and overlapping phenomena involved in the formation of self-regulated pores within the primary barrier-type oxide film, the underlying mechanisms remain a subject of considerable debate.
This presentation aims to clarify certain aspects of the theories regarding the initiation and growth of anodic films through the use of isotopic labelling. The oxygen isotope ¹⁸O was employed to trace oxygen ion movements during the formation of porosity in amorphous films produced by anodization in an acidic environment. By combining particle accelerator-based techniques, namely ion-induced nuclear reactions (Nuclear Reaction Analysis, NRA) and ion scattering (Rutherford Backscattering Spectrometry, RBS), significant differences were observed in the formation of embryo pores, oxygen migration, and electrolyte ion incorporation during anodization under similar galvanostatic parameters.
It is highly probable that a peculiar space charge distribution, arising from the presence of hydrogen and other doping ions from the electrolyte, exerts a dual effect: it retards the ejection of Al³⁺ ions while also hindering the inward migration of O²⁻ ions, despite the presence of a strong electric field during anodization. Nevertheless, the presence of hydrogen in anodic films and its role in the growth mechanism remain unconfirmed and largely unexplored, despite their potential significance. Consequently, the final part of the talk will introduce a new research line currently being established at the SAFIR platform, specifically Elastic Recoil Detection Analysis (ERDA), which promises to be an invaluable tool for the qualitative and quantitative assessment of hydrogen in thin films, extending beyond anodic oxides.
