RESUMEN
The tuneability of oxygen containing groups in graphene oxide (GO) that controls physicochemical properties is highly desirable for device applications. In this context, the thermally reduced graphene oxide (r-GO) powders and spin coated thin films with varying sp2/sp3 carbon network have been prepared using highly exfoliated GO (synthesized using modified Hummer's method with an innovative conjunction of lyophilisation). The additional step of lyophilisation results in the formation of highly exfoliated and monodispersed GO nanosheets as evidenced from FESEM, TEM, XRD, and Raman, FT-IR and UV-Vis spectroscopy. Spectroscopic analysis revealed the systematic evolution of r-GO with tuneable structural, optical and electrical properties as results of varying annealing temperatures (100-400 °C), due to restoration of sp2 conducting carbon network i.e., the formation of new -CâC- network and Stones-Wales defect. The tuneability of physical properties is further corroborated by change in the resistance values, as evidenced through the current-voltage characteristics in GO thin film based lateral device structures with Ag and Al top contacts. Controlling physicochemical properties at relatively low processing temperature warrants the utilization of GO and r-GO in various electronic and optoelectronic devices.
RESUMEN
The bipolar resistive switching (BRS) between a metallic low resistance state (LRS) and an insulating high resistance state (HRS) is demonstrated for annealed graphene oxide (GO) thin film-based device structures with aluminum (Al) as one of the contact electrodes. An optimal switching of â¼104 order is recorded for Al/GO (200 °C)/indium tin oxide (ITO) among the device structures in metal (M2)/GO (T)/metal (M1) configurations (M1 = Al, Au, or ITO and M2 = Au or Al), fabricated using GO (T)/metal (M1), annealed at different temperatures, T = 100, 200, 300, and 400 °C. The initial Ohmic conduction for electronic transport and the presence of metal contents through GO thin films in the X-ray photoelectron spectroscopy support the physical evidence of Al filament formation between the two electrodes as imaged by the high-resolution transmission electron microscopy. The speculated mechanism for BRS in repeated voltage sweep cycles is attributed to the current triggered breaking of metal filaments because of the combined effect of Joule's heating and Peltier heat generation at LRS â HRS transition, and electric field induced migration of metal atoms, leading to the formation of metal filaments through the GO film at the HRS â LRS transition. The higher switching ratio exhibited in the current study could be translated to engineer simple and low-cost resistive memory devices.