Samsung Advanced Institute of Technology

Ge(110) is a peerless substrate for the growth of large scale graphene monolayers due to its anisotropic twofold symmetry to control the unidirectional alignment of the initial graphene islands. However, in spite of efforts to unveil the growth mechanism of graphene on Ge(110), the initial stage of the growth is not unraveled completely. Herein, we study the initial growth properties of graphene on Ge(110) which were synthesized with ethylene precursor gases, via in situ cryogenic scanning tunneling microscopy (STM) and spectroscopy (STS). The STM results confirm the unidirectional growth of the graphene nanoribbons (GNRs) initiated from carbon cluster seeds on terraces in the early stage of graphene growth. Subsequent growth transformed those GNRs to graphene nanoislands (GNIs) which eventually coalesce to form single crystalline monolayer graphene. STS measurements demonstrated that the GNIs have small bandgaps induced by the confinement effect of graphene. This study can provide the in-depth understanding on the graphene growth on Ge(110) in various synthesis conditions, as well as a new recipe for the graphene growth on Ge(110).