title: Local diffusion induced roughening in cobalt phthalocyanine thin film growth.
abstract: We have studied the kinetic roughening in the growth of cobalt phthalocyanine (CoPc) thin films grown on SiO2/Si(001) surfaces as a function of the deposition time and the growth temperature using atomic force microscopy (AFM). We have observed that the growth exhibits the formation of irregular islands, which grow laterally as well as vertically with coverage of CoPc molecules, resulting rough film formation. Our analysis further disclosed that such formation is due to an instability in the growth induced by local diffusion of the molecules following an anomalous scaling behavior. The instability relates the (ln(t))(1/2), with t as deposition time, dependence of the local surface slope as described in nonequilibrium film growth. The roughening has been characterized by calculating different scaling exponents α, β, and 1/z determined from the height fluctuations obtained from AFM images. We obtained an average roughness exponent α = 0.78 ± 0.04. The interface width (W) increases following a power law as W ∼ t(β), with growth exponent β = 0.37 ± 0.05 and lateral correlation length (ξ) grows as ξ ∼ t(1/z) with dynamic exponent 1/z = 0.23 ± 0.06. The exponents revealed that the growth belongs to a different class of universality.
authors.affiliation: Department of Physics and §Center for Nanotechnology, Indian Institute of Technology Guwahati , Guwahati 781039, India.
authors.forename: Murali
authors.initials: M
authors.lastname: Gedda
authors.forename: Nimmakayala V V
authors.initials: NV
authors.lastname: Subbarao
authors.forename: Dipak K
authors.initials: DK
authors.lastname: Goswami