Facile approach for in situ measurement of anode temperature during the growth of self-ordered nanoporous anodic alumina thin films: Influence of Joule heating on pore microstructure

Anodic aluminium oxide (AAO) thin films, containing hexagonally ordered nanopores, are widely used as templates for fabricating a large number of zero and one- dimensional functional nanostructures such as nanodots, nanowires and nanotubes. The localized pore temperature developed due to the heat generation phenomenon during anodization plays a key role in the growth morphology of the nanoporous structure. The influence of temperature on the electrochemical process of anodization is generally evaluated by considering the electrolyte temperature, while little importance is given to the localized electrode temperature. In the present work, nanoporous alumina templates were prepared using a two step anodization process with oxalic acid as electrolyte under different bath temperatures and voltages. We report a novel approach to measure the in situ anode temperature during the anodization process that uses a Pt thin film RTD sensor which is deposited on partially fabricated alumina through anodization. The in-situ anode temperature has been recorded at different anodization conditions and their contribution to the rise in the anode temperature is presented. Our results indicate that Joule heating is the major source of heat developed during the anodization