The self-assembly of colloidal particles into 2D arrays
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As the feature size of new devices continues to decrease so too does the feasibility of top-down methods of patterning them. In many cases bottom-up methods are replacing the existing methods of assembly, as having building blocks self-organize into the desired structure appears, in many cases, to be a much more advantageous route. Self-assembled nanoparticulate films have a wide range of potential applications; high-density magnetic media, sensing arrays, meta-materials and as seeds for 3D photonic crystals to name a few. Thus, it is critical that we understand the fundamental dynamics of pattern formation on the nanoparticulate and colloidal scale so that we may have better control over the formation and final quality of these structures. We study computationally the self-organization of colloidal particles in 2D using both Monte Carlo and dynamic simulation We present 3 studies employing Monte Carlo simulation. In the first study, Monte Carlo simulations were used to understand the experimental observation of highlyordered 2D arrays of bidisperse, stabilized gold nanoparticles. It was shown that the LS lattice forms with the addition of interparticle forces and a simple compressive force, revealing that bidisperse lattice formation is, in fact, a dynamic process. It was evident that the LS lattice forms in large part because the particles within the lattice reside in their respective interparticle potential wells. In the second Monte Carlo study, this information was used to predict size-ratios and surface coverages for novel lattice structures. These predictions are intended to guide experimentalists in their search for these exciting new structures. In the third study it was shown that polydisperse amounts of amorphous-silicon nanoparticles could form 2D clusters exhibiting long-range orientational order even in the absence of translational order. Monte Carlo simulations were performed, which included lateral capillary forces and a simple stabilizing repulsion, resulting in structures that were strikingly similar to the experimentally observed In the fourth study we used dynamic simulation to study the hydrodynamicallyassisted self-organization of DNA-functionalized colloids in 2D. It was shown that hydrodynamic forces allow a more thorough sampling of phase space than through thermal or Brownian forces alone.