Strong Fermi-Level Pinning at Intact Metal/Si Interface Formed with Graphene Diffusion Barrier

We report the systematic experimental studies demonstrating that a graphene layer inserted at Metal/n-Si(001) interface can protect the Schottky junction efficiently from unwanted changes in electrical properties. High-resolution transmission electron microscopy (HRTEM) images support the conjecture of the inserted graphene layer preventing the atomic inter-diffusion at interface. Especially, the reverse-bias leakage current of Metal/Graphene/n-Si(001) junction is found to be noticeably smaller than that of Metal/n-Si(001) junction, strongly supporting the role of graphene insertion layer as an efficient diffusion barrier. The internal photoemission (IPE) measurements show unambiguously that the Schottky barrier of Metal/Graphene/n-Si(001) junction is almost independent of metal work-function, implying very strong Fermi-level pinning at interface. The atomically-impermeable and electronically-transparent aspects of the graphene insertion layer can provide a reliable experimental method to form an intact Schottky contact for all semiconductors in general.