Graphene field effect transistors with Niobium contacts and asymmetric transfer characteristics

TL;DR

This paper reports on the fabrication and electrical characterization of graphene field effect transistors with Niobium contacts, revealing asymmetric transfer characteristics influenced by Nb/graphene interactions and vacuum conditions.

Contribution

It introduces a novel fabrication of Nb-contacted graphene transistors and explains their asymmetric transfer behavior through interface chemistry and doping effects.

Findings

Asymmetric transfer characteristics observed with a resistance plateau in the n-branch.

Weakly chemisorbed Nb acts as p-dopant on graphene.

Vacuum degassing affects the transistor behavior.

Abstract

We fabricate back-gated field effect transistors using Niobium electrodes on mechanically exfoliated monolayer graphene and perform electrical characterization in the pressure range from atmospheric down to 10-4 mbar. We study the effect of room temperature vacuum degassing and report asymmetric transfer characteristics with a resistance plateau in the n-branch. We show that weakly chemisorbed Nb acts as p-dopant on graphene and explain the transistor characteristics by Nb/graphene interaction with unpinned Fermi level at the interface.