Effect of nitrogen-doping on the surface chemistry and corrosion stability of TiO2 films

TiO2 and N-doped TiO2 films were grown on AISI 316 stainless steel substrates and on Si (100) by metallorganic chemical vapor deposition (MOCVD) at 400°C and 500°C. X-ray photoelectron spectroscopy, scanning electron microscopy, and contact angle techniques were used to characterize de films. The corrosion behavior was assessed by monitoring the open circuit potential, electrochemical impedance spectroscopy and potentiodynamic polarization tests in 3.5wt% NaCl solution at room temperature. The results show that 6.18 at% of nitrogen was introduced in the films grown at 400°C and 8.23 at% at 500°C, and that besides TiO2, nitrogen phases were identified. All the films are hydrophilic and the contact angles varied from 48° to 72°. The films presented good homogeneity, low porosity and rounded grains in the range of 40–90nm. The RMS roughness varied between 5.5 and 18.5nm. Titanium dioxide films grown at 400°C showed better corrosion resistance than those grown at 500°C due to its compact morphology. Nitrogen-doping was not efficient to protect the substrate from corrosion.