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Two-Dimensional Excitonic Photoluminescence in Graphene on a Cu Surface
Park, Youngsin,Kim, Yooseok,Myung, Chang Woo,Taylor, Robert Anthony,Chan, Christopher C. S.,Reid, Benjamin P. L.,Puchtler, Tim J.,Nicholas, Robin J.,Singh, Laishram Tomba,Lee, Geunsik,Hwang, Chan-Cuk American Chemical Society 2017 ACS NANO Vol.11 No.3
<P>Despite having outstanding electrical properties, graphene is unsuitable for optical devices because of its zero band gap. Here, we report two-dimensional excitonic photoluminescence (PL) from graphene grown on a Cu(111) surface, which shows an unexpected and remarkably sharp strong emission near 3.16 eV (full width at half-maximum <= 3 meV) and multiple emissions around 3.18 eV. As temperature increases, these emissions blue shift, displaying the characteristic negative thermal coefficient of graphene. The observed PL originates from the significantly suppressed dispersion of excited electrons, in graphene caused by hybridization of graphene pi and Cu d orbitals of the first and second Cu layers at a shifted saddle point 0.525(M+K) of the Brillouin zone. This finding provides a pathway to engineering optoelectronic graphene devices, while maintaining the outstanding electrical properties of graphene.</P>