Fiber texturing in nano-crystalline TiO2 thin films deposited at 150 degrees C by dc-reactive sputtering on fiber-textured [0001] ZnO:Al substrates

TiO2 thin films were deposited at an effective surface temperature of 150 degrees C by dc-reactive magnetron sputtering on ZnO : Al oriented substrates having a fiber texture along the [0 0 0 1] axis, and studied by transmission electron microscopy and x-ray diffraction analyses. The substrate texturing was used to tailor the TiO2 structure in such a way that a porous matrix made of anatase nano-grains (10 nm in diameter) is formed instead of an amorphous layer (as observed at 150 degrees C on glass). Additionally, we demonstrate that, by adding an ex situ 200 degrees C annealing, the anatase domains also gain a fiber texture with the axes aligned to that of the substrate. The TiO2/AZO structural coupling is expected to play a crucial role for the carrier transport through the interface as required in dye-sensitized solar cells. Moreover, the low temperatures used render the process compatible with commonly used plastics substrates.