Large Effective Work-function Increase in Al/SiO2/Si Junction with Graphene Interlayer at Al/SiO2 Interface

Abstract

We report the significant change of the effective work-function from ~3.31 to ~4.35 eV of Al electrode when the graphene interlayer is inserted at the Al/SiO2 interface in Al/SiO2/n-Si junction, confirmed by capacitance-voltage (C-V) measurements. This effective work-function increase is considered to originate from the formation of electric dipole layer reflecting the electron orbital overlapping between Al and graphene (interaction dipole layer). According to the electrostatic analysis of solving Poisson equation for the flat-band conditions, the interaction dipole has its negative side toward the graphene layer, inducing a potential increase across the Al/graphene interface. A similar electrostatic effect of interaction dipole layer is also observed when using a Pt electrode with relatively high work-function. Differently from the Al electrode, the effective work-function of Pt electrode is measured to decrease from ~4.85 to ~4.68 eV, implying that the polarity of interaction dipole layer has its positive side toward the graphene layer. Based on such large effective work-function tuning (~1.04 eV) comparable to the Si band gap (~1.12 eV), the Al electrode accompanied by the partially-transferred graphene interlayer can be used for controlling both n-MOS and p-MOS systems.

*NRF-2020M3F3A2A02082437, NRF-2018H1A2A1062406