Molecular Dynamics of Self-Assembled Monolayer Formation in Soft Nanolithgoraphy

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Molecular dynamics simulation is performed to study the growth mechanism of self-assembled monolayer in the AFM tip-assisted soft nanolithography such as in dip-pen nanolithography [1]. We investigate how the droplet created around the tip spreads out to become a monolayer on the substrate eventually. In contrast to the previous diffusion model [2], our molecular simulation shows that a molecule on top pushes out a molecule below it and the molecule just pushed out in turn pushes out a molecule next to it. The monolayer grows when such a serial pushing propagates to its periphery. For a relatively weak adsorbate-substrate binding, the monolayer has irregular branches. As the adsorbate-substrate binding strengthens, the monolayer becomes a compact hexagon due to the substrate anisotropy. An extremely strong molecule-substrate binding gives a circular monolayer. The monolayer periphery shows an initial diffusional growth in its time dependence followed by a slow subdiffusional expansion. The rates of self-assembled monolayer growth exhibit a turn-over behavior with increase of the attractive force between the molecule and substrate. References 1.C. A. Mirkin, ACS Nano 1, 79 (2007). 2. J. Jang, S. Hong, G. C. Schatz, and M. A. Ratner, J. Chem. Phys. 115, 2721 (2001)

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Journal: TechConnect Briefs
Volume: 1, Nanotechnology 2008: Materials, Fabrication, Particles, and Characterization – Technical Proceedings of the 2008 NSTI Nanotechnology Conference and Trade Show, Volume 1
Published: June 1, 2008
Pages: 360 - 363
Industry sector: Advanced Materials & Manufacturing
Topics: Composite Materials
ISBN: 978-1-4200-8503-7