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Self-nanostructured ZnO:Al conductive layers consisting of [112̅0] oriented domains were coated by a conformal TiO2 thin film and sensitized by 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin (TCPP) to be used as transparent conductive electrodes in dye-sensitized solar cells. In addition to the higher surface availability due to the nanopatterning, the TCPP surface density increases by 330% (UV−vis) with respect to a flat conventional substrate thanks to a more dense molecular arrangement, as evidenced by combining high-resolution X-ray photoelectron spectroscopy and atomic force microscopy. Furthermore, the presence of zinc atoms in the TiO2 overlayer (Ti(:Zn)O2) crucially influences the electronic properties of the assembled TCPP. As a consequence of the orbitals' rearrangement attributed to the presence of zinc, a significant quenching of luminescence is observed in the emission spectra of TCPP-sensitized Ti(:Zn)O2, suggesting that electrons could be more effectively injected from the molecular orbitals to the conduction band of the semiconductor.

In a system consisting of two different lattices, the structural stability is ensured when an epitaxial relationship occurs between them and allows the system to retain the stress, avoiding the formation of a polycristalline film. The phenomenon occurs if the film thickness does not exceed a critical value. Here we show that, in spite of its orthorombic structure, a 14nm-thick NiSi layer can threedimensionally (3D) adapt to the cubic Si lattice by forming transrotational domains. Each domain arises by the continuous bending of the NiSi lattice, maintaining a close relationship with the substrate structure. The presence of transrotational domains does not cause a roughening of the layer but instead it improves the structural and electrical stability of the silicide in comparison with a 24nm-thick layer formed using the same annealing process. These results have relevant implications on thickness scaling of NiSi layers currently used as metallizations of electronic devices.Correspondence should be addressed to : Alessandra Alberti ( Alessandra.Alberti@imm.cnr.it) Acta Crystallographica B, 61, 486-491 (2005) 2

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