Low temperature chemical treatment of graphene films made by double self-assembly process to improve sheet resistance

Abstract

In this study, a low temperature hydro iodic acid (HI) vapor treatment of the self-assembled graphene films has been developed, and the electrical, optical, structural and morphological properties were investigated by four point probe, UV-Visible spectroscopy, Raman spectroscopy and scanning electron microscopy (SEM). Mono-, doubleand triple-layer of graphene flakes were deposited on glass substrates by using the Double Self-Assembly (DSA) process. The self-assembled graphene films were treated with HI vapors at 40 degrees C for different time intervals between 1 and 24 h. In addition, graphene deposition and HI-vapor treatment (at 40 degrees C for 1 h) was enforced three times to the same substrate. The optical transparency values of the self-assembled mono- (MGFs), double- (DGFs) and triple-layer graphene flakes (TGFs) were measured as 91, 85 and 80%, respectively (values at 550 nm). Due to the HI-vapor treatment, the sheet resistance of MGFs significantly reduced from 1.1 x 10(7) Omega omega square(-1) to 2.9 x 10(4) omega square(-1), the transparency of the graphene films slightly reduced by 2-5%, the I-D/I-G ratio of the DGFs decreased from 1.01 to 0.81, while the I-2D/I-G ratio increased from 0.43 to 0.48 in the Raman spectrum. Thanks to its impressive reducing effect on sheet resistance, HI-vapor treatment can be a suitable method to improve the conductivity of low-cost large area graphene films.