Atomistic Interrogation of B-N Co-dopant Structures and Their Electronic Effects in Graphene.
Chemical doping has been demonstrated to be an effective method for producing high-quality, large-area graphene with controlled carrier concentrations and an atomically tailored work function. The emergent optoelectronic properties and surface reactivity of carbon nanostructures are dictated by the microstructure of atomic dopants. Co-doping of graphene with boron and nitrogen offers the possibility to further tune the electronic properties of graphene at the atomic level, potentially creating p- and n-type domains in a single carbon sheet, opening a gap between valence and conduction bands in the 2-D semimetal. Using a suite of high-resolution synchrotron-based X-ray techniques, scanning tunneling microscopy, and density functional theory based computation we visualize and characterize B-N dopant bond structures and their electronic effects at the atomic level in single-layer graphene grown on a copper substrate. We find there is a thermodynamic driving force for B and N atoms to cluster into BNC structures in graphene, rather than randomly distribute into isolated B and N graphitic dopants, although under the present growth conditions, kinetics limit segregation of large B-N domains. We observe that the doping effect of these BNC structures, which open a small band gap in graphene, follows the B:N ratio (B > N, p-type; B < N, n-type; B═N, neutral). We attribute this to the comparable electron-withdrawing and -donating effects, respectively, of individual graphitic B and N dopants, although local electrostatics also play a role in the work function change.
Department of Science and Mathematics, Fashion Institute of Technology/State University of New York , New York, New York 10001, United States.
Theanne
T
Schiros
Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory , Menlo Park, California 94025, United States.
Dennis
D
Nordlund
Lucia
L
Palova
Liuyan
L
Zhao
Chemistry Department, Cornell University , Ithaca, New York 10065, United States.
Mark
M
Levendorf
Materials Measurement Laboratory, National Institute of Standards and Technology , Gaithersburg, Maryland 20899, United States.
Cherno
C
Jaye
David
D
Reichman
Chemistry Department, Cornell University , Ithaca, New York 10065, United States.
Jiwoong
J
Park
Center for Functional Nanomaterials, Brookhaven National Laboratory , Upton, New York 11973, United States.
Mark
M
Hybertsen
Abhay
A
Pasupathy
X-ray spectroscopy; atomic design; chemical bonding; doping; electronic structure; graphene; scanning tunneling microscopy; work function