Fractal features of titanium oxide surfaces

The fractal characteristics of TiO2 nanocrystalline films were studied and related to the efficiency of light absorption. The fractal dimension of the film surface was computed using atomic force microscopy and we found Df=2.33±0.02. Since the absorbed light energy Qa, and therefore the resulting photocurrent I, are proportional to the effective film area S, we concluded that I∼Qa∼S∼RDf, where R is the linear size of the rectangular film surface. This conclusion points to a new photoelectrochemical method for the observation of the surface roughness and for the calculation of the fractal dimension in semiconducting films.