How Much N-Doping Can Graphene Sustain?
Doped, substituted, or alloyed graphene is an attractive candidate for use as a tunable element of future nanomechanical and optoelectronic devices. Here we use the density functional theory, density functional tight binding, cluster expansion, and molecular dynamics to investigate the thermal stability and electronic properties of a binary 2D alloy of graphitic carbon and nitrogen (C(1-x)N(x)). The stability range naturally begins from graphene and must end before x = 1, where pure nitrogen rather forms molecular gas. This poses a compelling question of what highest x < 1 still permits stable 2D hexagonal lattice. Such upper limit on the nitrogen concentration that is achievable in a stable alloy can be found based on the phonon and molecular dynamics calculations. The stability switchover is predicted to between x = 1/3 (33.3%) and x = 3/8 (37.5%), and no stable hexagonal lattice two-dimensional CN alloys can exist at the N concentration of x = 3/8 (37.5%) and higher.
†The State Key Laboratory of Theoretical and Computational Chemistry, Institute of Theoretical Chemistry, Jilin University, Changchun 130023, People's Republic of China.|‡Department of Materials Science and Nanoengineering, Rice University, Houston, Texas 77005, United States.
Zhiming
Z
Shi
‡Department of Materials Science and Nanoengineering, Rice University, Houston, Texas 77005, United States.
Alex
A
Kutana
‡Department of Materials Science and Nanoengineering, Rice University, Houston, Texas 77005, United States.|§Department of Chemistry, Rice University, Houston, Texas 77005, United States.
Boris I
BI
Yakobson
CN alloy; maximum N concentration; phonon spectrum and molecular dynamics; stability