Stability and spectroscopy of single nitrogen dopants in graphene at elevated temperatures.
Single nitrogen (N) dopants in graphene are investigated using atomic-resolution scanning transmission electron microscopy (STEM) combined with electron energy loss spectroscopy (EELS). Using an in situ heating holder at 500 °C provided us with clean graphene surfaces, and we demonstrate that isolated N substitutional atoms remain localized and stable in the graphene lattice even during local sp(2) bond reconstruction. The high stability of isolated N dopants enabled us to acquire 2D EELS maps with simultaneous ADF-STEM images to map out the local bonding variations. We show that a substitutional N dopant causes changes in the EELS of the carbon (C) atoms it is directly bonded to. An upshift in the π* peak of the C K-edge EELS of ∼0.5 eV is resolved and supported by density functional theory simulations.
Department of Materials, University of Oxford , Parks Road, Oxford, OX1 3PH, U.K.
Jamie H
JH
Warner
Yung-Chang
YC
Lin
Kuang
K
He
Masanori
M
Koshino
Kazu
K
Suenaga
EELS; N-doped; STEM; aberration-corrected; graphene; nitrogen