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Abstract
Fractal analysis recognises that the concepts of length and area for irregular objects are not absolute, but depend on the measurement scale. In the present work, three-dimensional topography of different surfaces has been measured by scanning tunnelling microscopy (STM) and atomic force microscopy (AFM) tech niques. In particular, gold and aluminium thin films grown by evaporation techniques on silicon substrates have been studied. Fractal analysis by the frequency method was used to characterise the quality of the surfaces. The films were prepared with thickness from 30 up to 2000 nm. It was observed that the low and high frequency components of the roughness depend strongly on film thickness. Moreover, at small thickness two different fractal components in the surface roughness can be observed, which implies that low thickness coatings follow a dynamic completely different from that for high thickness. In conclusion, it has been established that fractal analysis can be used to characterise thin film surface coatings and to determine the coating type obtained.