Modeling Vapor Deposition Polymerization: Kinetic Monte Carlo Approach

A Kinetic Monte Carlo method is employed to model vapor deposition of growing, linear-polymer thin films which have applications ranging from microelectronic interconnects to biotechnology. Our 1+1 dimensional lattice model [1] implements various dynamical processes that occur during the film-growth, including random-angle deposition, monomer adsorption, free-monomer diffusion, and polymer-end flips. The temperature ($T$) is parametrized using the diffusion coefficient $(D=\exp(-\Delta E_a/k_BT))$, where $\Delta E_a$ is the activation energy for surface diffusion. The diffusion coefficient ($D$) and the deposition rate ($F$) play an important role in the growth process through the ratio $G$ ($=D/F$). We study the polymer chain length distribution, average polymer-chain length, film density, film height, surface-width, and radius of gyration as a function of $G$, system size ($L$), and time. Since polymers have much more complicated structures and interactions than those of organic materials, we find novel behaviors that are different from inorganic thin film growth. [1] W. Bowie and Y.-P. Zhao, \emph{Surf.\ Sci.\ Lett.} \textbf{563}, L245 (2004).