Effective Work-Function of Au Electrode Modulated by Graphene Interlayer at Au/Al2O3 Interface in Au/Al2O3/n-Si Junction

Abstract

The effective work-function of metal electrode is one of the major factors to determine the threshold voltage of metal/oxide/semiconductor (MOS) junction. Here, we report that the effective work-function of Au electrode increases by ~0.4 eV with a graphene interlayer inserted at Au/Al2O3 interface in Au/Al2O3/n-Si junction. The effective work-function of metal electrode in Au/Graphene/Al2O3/n-Si junction is compared directly with that in Au/Al2O3/n-Si junction without the graphene interlayer both of which are extracted from capacitance-voltage (C-V) measurements. Additionally, the C-V measurements of both Au/Graphene/Al2O3/n-Si and Au/Al2O3/n-Si junctions show the hysteretic behaviors for a complete round of sweeping the gate voltage applied on the metal electrode. In the case of Au/Al2O3/n-Si junction, the flat-band voltage for the gate voltage increasing (VFB+) is lower by ~0.4 V than that for the gate voltage decreasing (VFB-). This clockwise hysteretic behavior in C-V curve is known to be due to the delayed response of interface-trap charges on the semiconductor surface. Meanwhile, the difference between VFB+and VFB- is reduced significantly to ~0.15 V for the Au/Graphene/Al2O3/n-Si junction. We propose a plausible model for explaining the reduction of hysteretic behavior associated with the graphene interlayer.