A Comparative Investigation of Chemically Reduced Graphene Oxide Thin Films Deposited via Spray Pyrolysis

We present a comparative investigation between thin films of graphene oxide (GO) and chemically reduced graphene oxide (rGO) deposited onto glass substrates via spray pyrolysis. Two reduction techniques are investigated: (1) the exposition of a sprayed layer of GO to vapors of hydrazine hydrate to produce rGO_V and (2) the addition of liquid hydrazine hydrate to a suspended GO solution, which is then sprayed onto a substrate to produce rGO_L. Three different spectroscopy techniques, Raman, Fourier transform infrared, and UV-Vis-NIR, show that the two reduced samples have less lattice disorder in comparison to GO, with rGO_L having the highest degree of reduction. Interestingly, topography characterization by atomic force microscopy reveals a morphological change occurring during the exposure to hydrazine hydrate vapors, resulting in a thickness of 110 nm for the rGO_V film, which is a factor of 16 larger than rGO_L and GO. Finally, I-V measurements show a significant decrease of the GO's resistivity after the reduction process, where rGO_L features a resistivity 90 times lower than rGO_V, confirming that rGO_L has the highest degree of reduction. Our results indicate that the reduction process for rGO_V is susceptible to introducing intercalated water molecules in the material while the fabrication technique for rGO_L is a suitable route to obtain a material with minimal lattice disorder and properties approaching those of graphene.