Figure 1

AFM images and photoemission spectra. (A) AFM images of reference and nanostructured samples. Reference samples: a) coverslip (1 x 1 μm²), rms roughness is 0.343 ± 0.004 nm; b) Poly-L-Lysine coated coverslip (1 x 1 μm²), rms roughness 0.271 ± 0.020 nm; c) flat TiO₂ (2 x 1 μm²), rms roughness of 0.229 ± 0.004 nm. The vertical color scales range between 0 and 10 nm. Nanostructured samples: d) and e) high resolution SEM images and f) and g) AFM topographies (2 x 1 μm²) of 50 nm and 200 nm thick nanostructured TiO₂, respectively. The roughness of the thinner film has been evaluated 20.2 ± 0.5 nm, whereas of the thicker film 29.1 ± 1 nm. The ns-TiO₂ films clearly appear to have a fine raster of nanometer-sized grains with porosity at the subnanometer scale and with the thicker film showing larger height fluctuations. (B). O1s and Ti 2p photoemission spectra before and after thermal annealing of flat and ns-TiO₂ films. Ti 2p_1/2 and Ti 2p_3/2 peaks fall at 465.3 eV and 459.6 eV respectively (Ti(IV) bound to oxygen) and O 1 s peak shows two components one at 531.1 eV (oxygen bound to Ti(IV)) and the other at 533.5 eV (oxygen bound to contaminants).