title: Ambipolar to unipolar conversion in graphene field-effect transistors.
abstract: Typical graphene field-effect transistors (GFETs) show ambipolar conduction that is unfavorable for some electronic applications. In this work, we report on the development of unipolar GFETs. We found that the titanium oxide situated on the graphene surface induced significant hole doping. The threshold voltage of the unipolar p-type GFET was tunable by varying the density of the attached titanium oxide through an etching process. An annealing process followed by silicon nitride passivation was found to convert the p-type GFETs to unipolar n-type GFETs. An air-stable complementary inverter integrated from the p- and n-GFETs was also successfully demonstrated. The simple fabrication processes are compatible with the conventional CMOS manufacturing technology.
authors.affiliation: Microelectronics Centre, School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798.
authors.forename: Hong
authors.initials: H
authors.lastname: Li
authors.forename: Qing
authors.initials: Q
authors.lastname: Zhang
authors.forename: Chao
authors.initials: C
authors.lastname: Liu
authors.forename: Shouheng
authors.initials: S
authors.lastname: Xu
authors.forename: Pingqi
authors.initials: P
authors.lastname: Gao