Fractal Theory And Application In Thin Film Microstructure

This thesis introduces fractal theory and the progress and present status of the applications of fractal theory in charactering quantitatively microstructure of thin films at first. Then apply this theory to character the microstructure of two sorts of nonaparticle films.In chapter one, we review the progress and present status of the applications of fractal theory in thin film study, and suggest that fractal is an effective method to character quantitatively microstructure of thin films. Several basic concepts, such as fractal, fractal dimension and multifractal, are introduced in chapter two.Chapter three focuses on the fractal study of thin film. We obtain the TEM micrographs of Au-MgF2 composite nanoparticle films and semicontinuous Ag films. We study the micrographs of Au-MgF2 composite nanoparticle films with Au volume fraction from 6.0% to 62.6%. The outcomes show that the distribution density of the particles increases simultaneously with the metal grain growth, and the film transits from discrete state to network state, with increasing the Au volume fraction. We find that the fractal dimension of the samples increases from 1.5516 to1.7671 with increasing the Au volume fraction. Multifractal spectra f(a)~ashow that the spectrum width Aα increases with increasing the Au volume fraction at first, and decreases later. It indicates that the inhomogeneous space distribution of Au particles also increase at first, and decrease later. Size distribution of Au particles transits from Au particles of minimum volume playing important roles to Au particle of maximum volume playing important roles when Au volume fraction goes beyond a certain critical value (between 26.5% and 38.2%). We also study the micrographs of semicontinuous Ag films with thickness of 1.5nm, 12nm, 67nm and 98nm by means of fractal theory. The results show that the fractal dimension of the samples increases from 1.4051 to 1.7428 with increasing the thin film thickness. Multifractal spectra f(a)~a show that the spectrum widthAα increased with increasing the thin film thickness. It indicates that the inhomogeneous space distribution of Ag islands also increase. Size distribution ofAg islands transits from Ag islands of minimum volume playing important roles to Ag islands of maximum volume playing important roles when the thickness of semicontinuous Ag film goes beyond a certain critical value (between 12nm and 67nm).