Multifractal Approach For A Description Of Properties Of Polycrystalline Thin Films
MULTIFRACTAL APPROACH FOR A DESCRIPTION OF PROPERTIES OF POLYCRYSTALLINE THIN FILMS
V. V. Serebrij 1, B. A. Snopok2, S. I. Lysenko2,
P. E. Strizhak1
1L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, pr. Nauki, 31, Kiev, Ukraine, 252039
e-mail: pstrizhak@hotmail.com
2Institute of Semiconductor Physics, National Academy of Sciences of Ukraine, pr. Nauki, 45, Kiev, Ukraine, 252650
Multifractal analysis is performed for description of the surface topography of thin polycrystalline gold film. The film was obtained by thermal evaporation in vacuum. Its structure was modified by annealing at different temperatures in the range 20¸200 oC. All films were imaged by Atomic Force Microscopy. Image was analyzed as a collection of layers taken parallel to the mean surface. Fractal subsets with different scaling properties were described by multifractal divergence (e.g. the difference between maximal and minimal values of the f (a) spectrum). This allowed us to highlight the effect of the temperature of film annealing on the surface structure. We found that fractal diversity jumps down in the temperature range 130¸140 oC. Therefore, phase transition occurs in the system. Below the temperature of the phase transition the surface topography is characterized by high roughness and existence of small-scale irregularities. At critical temperature the surface structure undergoes morphological transition caused by melting of small-scale irregularities. The melting also results in a decrease of the surface roughness due to the flowing down of gold crystallites. We also illustrate that surface transformation under low-temperature annealing changes the power spectral density and probability distribution of height functions. We show a correspondence between multifractal properties of annealed polycrystalline thin gold films and their abilities to absorb various gases.
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