Controlling Molecular Growth between Fractals and Crystals on Surfaces
Résumé
Recent studies demonstrate that simple functional molecules, which usually form two-dimensional (2D) crystal structures when adsorbed on solid substrates, are also able to self-assemble into ordered openwork fractal aggregates. To direct and control the growth of such fractal supramolecules, it is necessary to explore the conditions under which both fractal and crystalline patterns develop and coexist. In this contribution, we study the coexistence of Sierpiński triangle (ST) fractals and 2D molecular crystals that were formed by 4,4″-dihydroxy-1,1′:3′,1″-terphenyl molecules on Au(111) in ultrahigh vacuum. Growth competition between the STs and 2D crystals was realized by tuning substrate and molecular surface coverage and changing the functional groups of the molecular building block. Density functional theory calculations and Monte Carlo simulations are used to characterize the process. Both experimental and theoretical results demonstrate the possibility of steering the surface self-assembly to generate fractal and nonfractal structures made up of the same molecular building block.
Mots clés
Density functional theory
Surface self-assembly
Functional molecules
Hydrogen bonds
Molecular crystals
Molecules
Monte Carlo methods
Growth competition
Self assembly
Scanning tunneling microscopy
Intelligent systems
Fractals
Two-dimensional (2D) crystals
Substrates
Crystalline patterns
Molecular building blocks
self-assebly
Molecular surfaces