Fractal analysis of field induced effects on thin films of nickel

Thin films of nickel deposited on mica substrates have been investigated using scanning tunneling microscopy (STM). The STM topograph represents a clear microscopically repeated structure on the nickel thin film surfaces. When a voltage pulse was applied normal to the film surface, large clusters which were present on the virgin sample fragmented into smaller similarly looking clusters. This surface topographic data analysis was carried out in terms of fractal dimension (D), which is a single parameter quantification (surface roughness) over many orders of magnitude. It is observed that the application of voltage pulse changes surface morphology quite drastically and restoration takes place in a few minutes. The present analysis in terms of fractal dimension of the surface is in good agreement with expected changes in surface morphology.