Micro-arc oxidized S-TiO2 nanoporous layers: Cationic or anionic doping?

S-doped TiO2 layers were grown on titanium substrates by MAO process. SEM results revealed a porous morphology with a pore size of 40-100 am. Our XRD analysis showed that the anatase relative content reached its maximum value at the voltage of 500 V. The existence of sulfur in the states of S4+ and S6+ which substituted Ti4+ in the titania crystalline lattice was confirmed by XPS results; meanwhile, no S2- was detected. That is, a cationic doping was observed. EDS results showed that sulfur concentration ill the layers increased with the voltage. The band gap energy was also calculated as 2.29 eV employing a UV-Vis spectrophotometer. (C) 2010 Elsevier B.V. All rights reserved.