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

2D Materials. 2019. Vol. 6. No. 4. P. 045021-1–045021-10.

Kovaleva N. N., Chvostova D., Potůčhek Z., Cho H. D., Fu X., Fekete L., Pokorny J., Bryknar Z., Kugel K., Dejneka A., Kang T. W., Panin G. N., Kusmartsev F. V.

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 twodimensional
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 single- and 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.

Keywords: graphene, графен, plasma treatment, плазменная обработка, optical spectra, оптические спектры