Anatase/Rutile nucleation and growth on (0002) and (11-20) oriented ZnO:Al/glass substrates at 150 degrees C

TiO2/ZnO:Al (AZO) bilayers were grown by DC reactive sputtering at temperature below 200 degrees C. The AZO structure was tuned in such a way that (0002) and (11-20) preferentially oriented and fiber textured domains were formed. The TiO2 layers grown at 150 degrees C on those two kinds of substrates are partially crystalline (and not amorphous as expected) in a composition which is substrate-dependent. Anatase was selectively formed on (0002) oriented AZO substrates after deposition, and maintained for annealing temperatures up to 650 degrees C. A mixture of anatase and rutile has instead nucleated and grown on the (11-20) oriented AZO substrate, with their relative amount changing by increasing the annealing temperature. Anatase selectivity and also its nucleation at low temperature are promising issues to realise flexible dye sensitised solar cells. (C) 2013 Elsevier B.V. All rights reserved.