The influence of the nanostructure design on the corrosion behaviour of TiN thin films prepared by glancing angle deposition

This study reports on the influence of nanostructure design on the corrosion behaviour of titanium nitride (TiN) thin films, prepared by DC reactive magnetron sputtering, using the Glancing Angle Deposition (GLAD) technique. The primary objective was to explore how modifying the deposition geometry affects the growth design and surface features of TiN films (keeping roughly constant the N/Ti ratio) and compare these effects with those produced by changing the chemical composition within the same thin film system (N/Ti increasing ratios). For this, two groups of samples were prepared: Group 1 – the samples were prepared in the conventional geometry (normal growth) with varied nitrogen content (stoichiometric and non-stoichiometric films) and; Group 2 – the samples were prepared with modified growth geometries (inclined and zigzag, with increasing incidence angles), keeping an almost unchanged stoichiometry. The results revealed increased surface porosity and roughness for Group 2 films compared to Group 1, demonstrating that deposition geometry can affect more significantly the surface characteristics than the composition variations. Corrosion studies indicated that the films prepared within Group 2, despite having higher porosity, showed a more stable open circuit potential (OCP) and nobler values than the reference close-stoichiometric TiN_0.92 film (reference sample) from Group 1. However, potentiodynamic polarization curves suggested higher corrosion kinetics for Group 2 films, most likely due to their increased surface heterogeneities. Electrochemical impedance spectroscopy (EIS) confirmed these findings, showing lower corrosion resistance for films prepared with inclined and zigzag geometries, if compared to the films prepared in conventional geometry (Group 1 samples).

This study advances the current state of the art on this film's responses, by demonstrating that tailoring nanostructure design through deposition geometry offers a promising approach to optimize the corrosion behaviour of TiN_x without the need to change its composition.