Periodically Modulated Electronic Properties of the Epitaxial Monolayer Graphene on Ru(0001)

Abstract

The local structural and electronic properties of the epitaxial monolayer graphene (MG) on Ru(0001) surface were investigated by using scanning tunneling microscopy/spectroscopy (STM/STS) and first-principles calculations. High resolution STM images and STS spectra measured in a large bias voltage range indicated both geometric and electronic corrugation of the MG. The local work function (LWF) of the MG/Ru(0001) surface was obtained to be around 3.5 eV by two separate methods based on the experimental dz/dV and I–z curves respectively. We also found a considerable LWF difference (about 100 to 200 meV) between different sites within a unit cell of the moiré pattern of MG/Ru(0001). Furthermore, noticeable bias-polarity-dependence of the local barrier height (LBH) of MG on Ru(0001) surface was observed, supporting the existence of the Smoluchowski smoothing effect due to the presence of surface dipole moment in consequence of strong MG–Ru interactions. These findings indicate that MG/Ru(0001) can be used as an ideal template for periodic nanostructures with various applications.