Direct observation of bandgap opening at the metasurface of nano-scale highly oriented pyrolytic graphite

Abstract

By using angle-resolved photoemission spectroscopy (ARPES), we study the electronic structure of highly oriented pyrolytic graphite (HOPG). In contrast to the pristine HOPG, band gap opening of approximately 100 meV is directly observed at the surface of nano-scale HOPG square pattern. Our Raman data and density functional theory calculations suggest that the bandgap opening is likely caused by tensile strain induced from the patterning. We believe that this surface engineering of HOPG will not only be useful for enhancing terahertz devices but also provides a route for modifying other materials/metasurfaces for optoelectronics applications.