engleski

Potentiostatic vs. galvanostatic approach for growth of the titania nanostructured arrays via electrochemical etching of titanium films deposited by magnetron sputtering

High-end performance of light-absorbers and adjacent charge transfer layers in the state-of- the-art thin-film photovoltaics can be heavily improved, by preparing constituting films in configurations of homogeneously ordered vertical arrays of nanoformations such as nanotubes. Nowadays the efforts of upgrading the nanostructured films focus in finding preparation routes that can facilitate larger area films with better reproducibility while maintaining satisfactory properties. Semiconducting titania nanotubes suitable for solar cell application are commonly derived by an electrochemical etching of titanium (deposited on ITO by RF magnetron sputtering) in fluorine rich electrolyte via intermediate titanium hexafluorite and subsequent thermal treatment. Having in mind the complexity of the process it is obvious the yield nanotubes heavily depend on many parameters. Here we try to identify the parameters responsible for variance in the properties of the nanotubes or even outcome of the synthesis and take it out of the equation. With many of the parameters that are commonly not controlled brought under constant value, we refer to the electrochemical etching as the facile upgrading tool. In a nutshell, we have previously shown that the successful electrochemical etching is a combination of overlapping contributions, which significantly change during the process. It is our goal to see how applying potentiostatic or galvanostatic conditions correlates to beneficial distribution of etching conditions during the whole duration of the process. To investigate the yield titania nanotube arrays, we refer to broad structural analysis (GIXRD), electron microscopy analysis (SEM, EDS), atomic force microscopy (AFM), solid-state dielectric spectroscopy (SS-IS), and various transmittance are reflectance spectroscopies (UV-VIS, Raman, FTIR). It was shown that it was possible to stabilize the etching process and observe the effect of the potentiostatic or galvanostatic contributions individually. The mechanisms of etching are somewhat different but it was not possible to generally discriminate between the two approaches. Specific requirements preclude the selection of the route.

titania nanotubes ; magnetron sputtering ; anodization

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