Unraveling the Structural and Electronic Properties of Graphene/Ge(110).

The direct growth of graphene on a semiconducting substrate opens a new avenue for future graphene-based applications. Understanding the structural and electronic properties of the graphene on a semiconducting surface is key for realizing such structures; however, these properties are poorly understood thus far. Here, we provide insight into the structural and electronic properties of graphene grown directly on a Ge(110) substrate. Our scanning tunneling microscopy (STM) study reveals that overlaying graphene on Ge(110) promotes the formation of a new Ge surface reconstruction, i.e., a (6 x 2) superstructure, which has been never observed for a bare Ge(110) surface. The electronic properties of the system exhibit the characteristics of both graphene and Ge. The differential conductance (dI/dV) spectrum from a scanning tunneling spectroscopy (STS) study bears a parabolic structure, corresponding to a reduction in the graphene Fermi velocity, exhibiting additional peaks stemming from the p-orbitals of Ge. The density functional theory (DFT) calculations confirm the existence of surface states due to the p-orbitals of Ge.