Efficient green emission from edge states in graphene perforated by nitrogen plasma treatment

Abstract

Plasma functionalization of graphene is one of the facile ways to tune its doping level without the need for wet chemicals making graphene photoluminescent. Microscopic corrugations in the two-dimensional structure of bilayer CVD graphene having a quasi-free-suspended top layer, such as graphene ripples, nanodomes, and bubbles, may significantly enhance local reactivity leading to etching effects on exposure to plasma. Here, we discovered that bilayer CVD graphene treated with nitrogen plasma exhibits efficient UV-green-red emission, where the excitation at 250 nm leads to photoluminescence with the peaks at 390, 470, and 620 nm, respectively. By using Raman scattering and spectroscopic ellipsometry, we investigated doping effects induced by oxygen or nitrogen plasma on the optical properties of singleand bilayer CVD graphene. The surface morphology of the samples was studied by atomic force microscopy. It is revealed that the top sheet of bilayer graphene becomes perforated after the treatment by nitrogen plasma. Our comprehensive study indicates that the dominant green emission is associated with the edge defect structure of perforated graphene filled with nitrogen. The discovered efficient emission appearing in nitrogen plasma treated perforated graphene may have a significant potential for the development of advanced optoelectronic materials. arXiv:1911.08351v1 [cond-mat.mtrl-sci]

Raman Spectroscopy Imaging of Exceptional Electronic Properties in Epitaxial Graphene Grown on SiC

“…Similar phenomena have been reported in bilayer CVD graphene perforated by Nitrogen (N 2 ) plasma [ 162 ]. Here, the bilayer has a quasi-free-standing nature, that is, suspended above a substrate, as demonstrated by Raman analysis.…”

“…Other forms of the lattice strain exist in graphene and graphene-related materials, such as: 1-epitaxial triangular nano-prisms [ 152 ] and 2-nano holes induced in CVD graphene bilayers with plasma etching [ 162 ] 3-epitaxial graphene-SiC intercalation [ 163 ]. It was also shown theoretically that reshaping graphene layer with the kirigami (cut-and-fold Japanese art) method provides another source of lattice strain due to a redistribution of the infinite gaussian curvature from conical points [ 15 ].…”

“…The nano-prisms appear during the epitaxial growth process. Their shape and distribution are controllable by the Argon flow in the chamber [ 162 ]. The resulting deformed monolayer graphene contains regions of high strain in the vicinity of the nano-prisms.…”

“…In perforated CVD graphene [ 162 ], local lattice distortions arising near perforated edges, may induce incredibly large pseudo-magnetic field which will have a sign variation in space [ 15 ]. As a result, the obtained zero energy Landau level will be extremely stable [ 170 ].…”

“…Thus, perforated CVD graphene may be a highly promising candidate material to host MFs even at room temperature. To confirm this premise, recent observations of photoluminescence (PL) in perforated CVD graphene have shown three principal broad lines [ 162 ]. We may speculate that the discovered broad band PL emissions can be attributed to the optical transitions between numerous Landau levels induced by fluctuating pseudo-magnetic fields.…”