We determined the band alignment of a graphene-oxide-silicon structure using internal photoemission spectroscopy. From the flatband voltage and Dirac voltage we infer a 4.3 10e11 cm-2 negative extrinsic charge present on the graphene surface. Also, we extract the graphene work function to be 4.56 eV, in an excellent agreement with the theoretical and experimental values in literature. The electron and hole injections from heavily doped p-type silicon (Si) are both observed. The barrier height from the top of valence band of Si to the bottom of conduction band of silicon dioxide (SiO2) is found to be 4.3 eV. The weak electron injection from the graphene enables us to observe hole injection from Si to graphene. The barrier height for holes escaping from the bottom of Si conduction band to the top of SiO2 valence band is found to be 4.6 eV.
Citation: Applied Physics Letters
Pub Type: Journals
graphene, internal photoemission spectroscopy, band alignment, workfunction