Photoresponse in the visible range from Cr doped TiO2 nanotubes

Layers of TiO2 nanotubes have been fabricated by electrochemical anodization of Ti. After annealing the tubes to an anatase structure Cr doping was carried out by ion implantation at an energy of 60 keV and at two nominal fluences, 5x1015 cm-2 and 5x1016 cm-2. XRD measurements reveal that the anatase structure shows a certain degree of amorphization after ion implantation. However, this effect can be reversed by subsequent thermal annealing. Photoelectrochemical measurements show a visible photoresponse for the Cr+ implanted tubes. Reannealing the tubes, leads to an increase in the photoresponce magnitude in the visible range of the solar spectrum.