Spin-Coating Self-Assembly for Micropatterning of Ultrathin Multilayer Films
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Spin-Coating Self-Assembly for Micropatterning of Ultrathin Multilayer Films Hongseok Jang, Sangcheol Kim, and Kookheon Char School of Chemical Engineering, Seoul National University, San 56-1, Shinlim-dong, Kwanak-gu, Seoul 151-744, Korea ABSTRACT A new approach to create layer-by-layer assembled multilayer ultrathin films with welldefined micropatterns in a short process time is introduced. To achieve such micropatterns with high line resolution in organic multilayer films, microfluidic channels were combined with the convective self-assembly process employing both hydrogen bonding and electrostatic intermolecular interactions. The channels were initially filled with polymer solution by capillary pressure and the residual solution was then removed by spinning process. The micropatterns with distinct line boundaries were obtained and the small ridges were also observed at the edges of the patterned lines. Spin self-assembled vertical heterostructural multilayer patterning using (PVP/PAA)5 micropatterns, which were prepared with microfluidic channels, as a template was also investigated. INTRODUCTION Since the ionic layer-by-layer assembly technique was first introduced for the fabrication of polyelectrolyte multilayers, this self-assembling technique has been extended to conducting polymer composites, nonlinear optical dyes, and the assembly of biomolecular systems [1-4]. Furthermore, other driving forces such as hydrogen and chemical bonding for the self-assembly have been explored [5]. For the applications of organic or organic/inorganic hybrid multilayer thin films to high performance devices, the internal structure of individual layers in the films should be in high order and the ability to pattern with a feature of micrometer or less on the films are also required. Recently, several methods for the multilayer patterning have been reported [69]. In these methods, however, chemically patterned templates should be prepared on the substrates because the adsorption process is based on the self-diffusion and the rearrangement due to the interactions between adsorbing molecules and templates [6-8]. To achieve the selective deposition, the alternating regions of chemically different functionality should be realized on a surface: one region promotes the adsorption and the other effectively resists the adsorption of polyions on the surface. Also, Yang et al. recently applied the conventional photolithography to the patterning of multilayer films [9]. According to the recent work demonstrated by Cho et al., the multilayer films with highly ordered internal structure could be easily prepared by the spin self-assembly (SA) process although it is much simpler and faster in preparation than the conventional dip self-assembly process [10]. In recent study, we developed a new approach to produce well-defined micropatterns of multilayer ultrathin films in a short process time. Microfluidic channels were used to achieve such micropatterns with high line resolution, combining with the convective SA process (i.e., the sel
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