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 Cu(111) surface, which shows an unexpected remarkably sharp and strong emission near 3.16 eV (full-width at half-maximum ≤ 3meV) and multiple emissions around 3.18 eV. As temperature increases, these emissions blue-shift, showing the characteristic negative thermal coefficient of graphene. Observed PLs originate from significantly suppressed dispersion of excited electrons in graphene caused by hybridization of graphene π and Cu d orbitals of the 1st and 2nd Cu layers at a shifted saddle point 0.525(M+K) of Brillouin zone. This finding provides a new pathway to engineering novel optoelectronic graphene devices, whilst maintaining the outstanding electrical properties of graphene.
@article{arxiv.1610.08630,
title = {Two-dimensional Excitonic Photoluminescence in Graphene on Cu surface},
author = {Youngsin Park and Yoo S. Kim and Chang Woo Myung and Robert A. Taylor and Christopher C. S. Chan and Benjamin P. L. Reid and Timothy J. Puchtler and Robin J. Nicholas and Tomba S. Laishram and Geunsik Lee and Chan C. Hwang and Chong Yun Park and Kwang S. Kim},
journal= {arXiv preprint arXiv:1610.08630},
year = {2016}
}