The Concentration and Spinning Rate Effect

Deposition of organic material by spin-coating has been done for almost a century [114]. Solution flow dynamics [115-117], film surface topography [118-120], and evaporate effects [121-123] has been explored both theoretically and experimentally. The two main parameters that control the amount of polyelectrolyte adsorbed onto the substrate are solute concentration and spin rate. These have been shown to directly influence the thickness of monolayer films [125, 126]. Dubas and Schlenoff have fabricated multiplayer poly-electrolyte films by immersing spinning substrate into poly-electrolyte solution. Peter and Malkiat investigated those variables in multiplayer polyelectrolyte films that are spin-assembled by dropping a solution onto a spinning substrate [113]. The materials used include the polyanion PAZO and polycation PEI. The thickness of a film of a single polyelec-trolyte can be easily controlled by varying the concentration of polyelctrolyte and spin rates. Higher concentrations of PEI most likely lead to a greater amount of adsorbed PEI, and therefore lead to greater amounts of PAZO deposited on the film.

At faster spin rates, the films experience increased mechanical forces, which lead to shorter contact time between the polyelectrolyte [115]. The forces acting on a spinning film have been studied in detail [127, 128]. The effects of spin rate on both monolayer thickness [124, 125] and multiplayer thickness [113] have been studied.

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