Strong Fermi-Level Pinning at Metal/Si(001) Interface Ensured by Forming Abrupt Schottky Junction with Graphene Insertion Layer

Abstract

We report the experimental studies demonstrating that an impervious graphene layer inserted at metal/n-Si(001) interface is very useful to explore the Fermi-level pinning effect at interface systematically. It is confirmed with High-Resolution Transmission Electron Microscopy (HRTEM) images that the inserted graphene layer prevents the atomic inter-diffusion and an atomically abrupt Schottky junction is formed. The Schottky barrier heights of metal/graphene/Si junctions determined from Internal Photoemission and Current-Voltage measurements show very weak dependence on metal work-function, implying that the Fermi-level of metal electrode is virtually pinned at charge neutrality level close to the valence band edge. The impermeable and electronically transparent properties of graphene would make it possible to form intact Schottky contacts regardless of surface treatment methods used in device fabrication, which provides important information for the Si-based CMOS technology.