Electronic and geometric corrugation of periodically rippled, self-nanostructured graphene epitaxially grown on Ru(0001)

Abstract

Graphene epitaxially grown on Ru(0001) displays a remarkably ordered pattern\nof hills and valleys in Scanning Tunneling Microscopy (STM) images. To which\nextent the observed "ripples" are structural or electronic in origin have been\nmuch disputed recently. A combination of ultrahigh resolution STM images and\nHelium Atom diffraction data shows that i) the graphene lattice is rotated with\nrespect to the lattice of Ru and ii) the structural corrugation as determined\nfrom He diffraction is substantially smaller (0.015 nm) than predicted (0.15\nnm) or reported from X-Ray Diffraction or Low Energy Electron Diffraction. The\nelectronic corrugation, on the contrary, is strong enough to invert the\ncontrast between hills and valleys above +2.6 V as new, spatially localized\nelectronic states enter the energy window of the STM. The large electronic\ncorrugation results in a nanostructured periodic landscape of electron and\nholes pockets.\n