Effect of annealing temperature on electrical properties of RGO thin films deposited by Atomized Spray Pyrolysis

Abstract

The modified Hummers method is an ideal method for the bulk production of reduced graphene oxide (RGO) using Sri Lankan natural vein graphite. Deposition of RGO as a thin film (TF) on a substrate is essential for electronic applications in various industries. A novel, improved spray pyrolysis technique called Atomized Spray Pyrolysis deposition method was used to deposit RGO-TFs at a substrate temperature of 150 °C. Thermal annealing (TA) was carried out after deposition of RGO-TFs since post-deposition treatment is essential to enhance its intrinsic properties. Then TA was done for 30 min at different temperatures from 230 to 430 °C. Electrical, morphological and structural characterizations suggested that TA at 330 °C yields optimum intrinsic properties of RGO-TFs. Annealing temperature up to 330 °C is adequate to eliminate most defects such as fabrication residues, residual oxygen functional groups, and folds at edges of RGO flakes. TA at 330 °C retains maximum possible hexagonal lattice structure and carbon to oxygen atomic ratio. However, TA beyond 330 °C exhibits doping of oxygen atoms to vacant carbon atoms at the hexagonal structure of RGO, increasing bandgap since oxygen atoms localize some electrons. At higher annealing temperatures, the formation of buckling, ripples, and wrinkles on the RGO sheets due to induced compressive strain was observed. This results in hindering charge transportation since they behave as scattering sites.