  Sub-wavelength laser induced periodic surface structures (LIPSS-Sticks)
created by ultrashort pulsed laser irradiation on the surface of titanium are
used for the first time to template the electrochemical growth of titanium
dioxide nanotube arrays. This is an example of a double self-organized process,
as both LIPSS formation and electrochemical anodization involve spontaneous
generation of order from initially non-ordered precursors. LIPSS-Sticks have a
2x greater visible to near infrared light (400 - 1400 nm) collection efficiency
compared to flat titanium dioxide due to the enhanced light scattering from
grating-like structures. The growth of nanostructures with time was modelled
electrostatically to explain the features of a templated anodization process
that differ from the usual anodization of flat surfaces. This new templated
growth method is general and can also be applied to Cu, W, Fe, Ti alloys and Al
for the fabrication of hierarchically nanostructured surfaces using two
complementary fabrication techniques: ultrashort pulsed laser ablation and
electrochemical anodization.
