Charge-density depinning at metal contacts of graphene field-effect transistors

TL;DR

This paper investigates how charge-density depinning at metal-graphene contacts affects the transfer characteristics of graphene transistors, revealing that certain metal contacts without pinning cause distortions impacting flexible electronics.

Contribution

It demonstrates that using easily-oxidizable metals creates a pinning-free interface, leading to distorted transfer characteristics in graphene transistors, a novel insight into contact effects.

Findings

Distorted transfer characteristics are caused by metal-graphene contact effects.

Pinning-free interfaces are achieved with easily-oxidizable metals.

Charge-density depinning influences device performance in flexible electronics.

Abstract

An anomalous distortion is often observed in the transfer characteristics of graphene field-effect transistors. We fabricate graphene transistors with ferromagnetic metal electrodes, which reproducibly display distorted transfer characteristics, and show that the distortion is caused by metal-graphene contacts with no charge-density pinning effect. The pinning effect, where the gate voltage cannot tune the charge density of graphene at the metal electrodes, has been experimentally observed; however, a pinning-free interface is achieved with easily-oxidizable metals. The distortion should be a serious problem for flexible electronic devices with graphene.