Direct measurement of Dirac point and Fermi level at graphene/oxide interface by internal photoemission

We report the first direct measurement of the Dirac point, the Fermi level, and the work function of single layer gapless graphene by using photoemission threshold spectroscopy. Since the pioneering work of Novoselov et al in 2004, [1] graphene has attracted an immense amount of interest from all disciplines. [2] The knowledge of the physics of graphene-based devices has grown dramatically. Along with the recent success of large area chemical vapor deposition (CVD) growth of graphene, [3] it seems the industrial applications such as transparent electrodes, [4] field effect transistors, [5] and quantum well devices [6] are becoming more promising. However, the precise position of the Dirac point and Fermi level at the graphene/oxide interface has yet to be investigated; despite their importance in the design and modeling of graphene-based devices. In this paper, we present the study of a semi-transparent metal/high-k/graphene/SiO2/Si structure, and focus our study on the photoemission phenomena at the graphene/SiO2 interface. As a result, a complete electronic band alignment of the graphene/SiO2/Si system is accurately constructed for the first time.