Graphene field effect transistors with Niobium contacts and asymmetric transfer characteristics

Antonio Di Bartolomeo, Filippo Giubileo, Francesco Romeo, Paolo Sabatino, Giovanni Carapella, Laura Iemmo, Thomas Schroeder, Grzegorz Lupina

Published 2015-08-04Version 1

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.