Site-Specific Substitutional Boron Doping of Semiconducting Armchair Graphene Nanoribbons

A fundamental
requirement for the development of advanced electronic
device architectures based on graphene nanoribbon (GNR) technology
is the ability to modulate the band structure and charge carrier concentration
by substituting specific carbon atoms in the hexagonal graphene lattice
with p- or n-type dopant heteroatoms. Here we report the atomically
precise introduction of group III dopant atoms into bottom-up fabricated
semiconducting armchair GNRs (AGNRs). Trigonal-planar B atoms along
the backbone of the GNR share an empty p-orbital with the extended
π-band for dopant functionality. Scanning tunneling microscopy
(STM) topography reveals a characteristic modulation of the local
density of states along the backbone of the GNR that is superimposable
with the expected position and concentration of dopant B atoms. First-principles
calculations support the experimental findings and provide additional
insight into the band structure of B-doped 7-AGNRs.