Morphological image interpretation of organic nickel(II) phthalocyanine-tetrasulfonic acid tetrasodium film using fractal analysis

Surface morphologies are often used to characterize various interface processes including charge transfer and surface contact between layers in thin films. In fractal surface analysis, Hurst exponent is used as descriptor of surface roughness and the spectral exponent as long-range correlation between two spatially separated points. In this paper, an alternative surface model known as generalized Cauchy process (GCP) is introduced to provide dual description of fractal and long-range correlation properties simultaneously. The GCP model is used to characterize surface morphologies of organic nickel(II) phthalocyanine-tetrasulfonic acid tetrasodium thin film. The fractal and correlation exponents estimated from the AFM images of the thin film are then used to explain the variation in the electrical conductivity of thin films treated with solvent for different time durations that modified the surface properties. Higher electric conductivity is observed for thin films with higher fractal dimension but also enhanced when there exists spatially correlated morphologies in the form of network enhances charge transport at interfaces.