Electronic structure of MoO3−x/graphene interface

The interfacial electronic structure of MoO3−x/graphene has been investigated using photoemission spectroscopy. The experimental data showed that upon deposition of MoO3−x, the Fermi level of graphene shifts downward gradually from its Dirac point due to the p-type doping effect. From the Fermi level shift of −0.28 eV, the hole density of graphene was estimated to be 5.44 × 1012 cm−2. The formation of surface negative dipole due to electron transfer from graphene to the deposited MoO3−x films increased the sample′s work function. The existence of gap states in MoO3−x induced by oxygen vacancies greatly reduced the hole injection barrier at the MoO3−x/graphene interface.