1 research outputs found
Self-Assembly and Photopolymerization of Sub‑2 nm One-Dimensional Organic Nanostructures on Graphene
While graphene has attracted significant attention from
the research
community due to its high charge carrier mobility, important issues
remain unresolved that prevent its widespread use in technologically
significant applications such as digital electronics. For example,
the chemical inertness of graphene hinders integration with other
materials, and the lack of a bandgap implies poor switching characteristics
in transistors. The formation of ordered organic monolayers on graphene
has the potential to address each of these challenges. In particular,
functional groups incorporated into the constituent molecules enable
tailored chemical reactivity, while molecular-scale ordering within
the monolayer provides sub-2 nm templates with the potential to tune
the electronic band structure of graphene via quantum confinement
effects. Toward these ends, we report here the formation of well-defined
one-dimensional organic nanostructures on epitaxial graphene via the
self-assembly of 10,12-pentacosadiynoic acid (PCDA) in ultrahigh vacuum
(UHV). Molecular resolution UHV scanning tunneling microscopy (STM)
images confirm the one-dimensional ordering of the as-deposited PCDA
monolayer and show domain boundaries with symmetry consistent with
the underlying graphene lattice. In an effort to further stabilize
the monolayer, in situ ultraviolet photopolymerization induces covalent
bonding between neighboring PCDA molecules in a manner that maintains
one-dimensional ordering as verified by UHV STM and ambient atomic
force microscopy (AFM). Further quantitative insights into these experimental
observations are provided by semiempirical quantum chemistry calculations
that compare the molecular structure before and after photopolymerization