Simplistic Model for the Dendritic Growth of a Monolayer in Dip Pen Nanolithography

Abstract

This paper presents a simple random-walk (RW) model for monolayer growth in dip pen nanolithography (DPN). The monolayer in the RW model grows via a combination of hopping down and serial pushing of molecules deposited from the tip. The directional coherence in pushing induces branches of a monolayer that grow in preferential directions that are determined by the underlying lattice for the surface. The RW model accurately reproduces a molecular dynamics (MD) simulation for the DPN of nonpolar molecules on goldlike surfaces, indicating that the pushing mechanism accurately describes molecular motions. The molecular deposition in the MD simulation is found to be close to a random Poisson process. The high directional coherence produces self-replicating branches in the monolayer that are characteristic of dendritic growth. With a change in directional coherence, the RW model produces diverse structures such as circles, hexagons, and dendrites.

Thermal Effect on Positive Patterned Self‐Assembled Monolayer Grown from a Droplet of Alkanethiol

“…d), where further adsorption took place with increasing time. At a long time ( t > 10 ns), relevant to an experimental timescale for the growth of SAMs in DPN lithography, there were a tiny droplet of 24 ODT molecules (9% of total), remaining on top of the pile of the SAM island. Noticeably, among these 24 ODT molecules, 11 ODT molecules got adsorb on the surface by a distinct pathway named serial pushing.…”

Classic, liquid, and matrix-assisted dip-pen nanolithography for materials research

“…In the serial pushing model for SAM formation, the alkanethiols dropped from the tip (shaded circles) pushed a molecule on the substrate (open circles) out of its original position, and the alkanethiols on the substrate were in turn pushed to the periphery. Later, to illustrate the dendritic growth of an organic monolayer in classic DPN, Jang and co-workers 82 suggested a simple random-walk model that combined the hopping down model and serial pushing model (Fig. 3).…”

Random Walk Simulation for the Growth of Monolayer in Dip Pen Nanolithography

“…In this respect, theory and modeling have proven to be useful. 4,[7][8][9][10] Central to modeling DPN is how a nascent droplet (deposited from an AFM tip) spreads out to form a SAM afterward. Given that molecules are designed to chemisorb to a substrate, Jang et al 8 proposed a diffusion model of DPN assuming that the molecules are trapped irreversibly once they have reached the chemisorption sites on the substrate.…”