  The effective work-function of metal electrode is one of the major factors to
determine the threshold voltage of metal/oxide/semiconductor junction. In this
work, we demonstrate experimentally that the effective work-function of
Aluminum (Al) electrode in Al/SiO$_2$/n-Si junction increases significantly by
$\sim$1.04 eV with the graphene interlayer inserted at Al/SiO$_2$ interface. We
also provide the device-physical analysis of solving Poisson equation when the
flat-band voltage is applied to the junction, supporting that the wide tuning
of Al effective work-function originates from the electrical dipole layer
formed by the overlap of electron orbitals between Al and graphene layer. Our
work suggests the feasibility of constructing the dual-metal gate CMOS
circuitry just by using Al electrodes with area-specific underlying graphene
interlayer.
