Graphene Complementary Logic Inverter Fabricated with Thin Film Over-layer for Nondestructive Doping

Abstract

Due to the outstanding charge carrier transport properties, graphene has been considered as a candidate material for next-generation nanoelectronic devices. Graphene composed of a single atomic layer can be easily doped by a contact material, which is a great advantage in fabricating complementary logic devices. Here, we introduce the stable complementary inverter fabricated by doping graphene selectively with metal and oxide thin over-coating films. Ti, Al, and SiO 2 thin films were deposited on the surface of hydrophobic and chemically-inert graphene for doping and also as seed layers to deposit a uniform Al 2 O 3 protective layer. The graphene doping with those metal and oxide thin films was confirmed by measuring the Raman spectra of graphene channels and the electrical properties of fabricated field effect transistors. For the Ti and Al films, the doping type was found to be n-type. Meanwhile, the SiO2 film was found to dope graphene to be p-type. The fabricated inverter showed stable operation for a wide range of drain voltage from 0.5 V to 20 V with clear voltage inversion. With a ~100 nm thick SiO2 gate insulator, the voltage gain was measured to be ~0.93 and ~0.86 for the Al-SiO2 and Ti-SiO2 doping combination, respectively.