Tuning the optoelectronic properties of the rGO-AuNPs hybrid film by pre-decoration and AuNPs-assisted thermal reduction

Abstract

Reduced graphene oxide (rGO) decorated with plasmonic gold nanoparticles (AuNPs) is a versatile hybrid material from both aspects of processing and functionality for building the novel optoelectronic and sensor devices. This article presents an alternative way to prepare and tune the optoelectronic properties of the rGO-AuNPs hybrid film by pre-decoration and AuNPs-assisted thermal reduction of graphene oxide (GO). Au was sputtered on GO film for the varied duration before subjected to medium-temperature (MT) reduction of 700 °C and high-temperature (HT) reduction of 1,000 °C. The surface of rGO-MT was decorated by ball AuNPs, while rGO-HT was populated by wire AuNPs and patches of Au thin film after solid-state dewetting. Decoration of AuNPs enhanced the reduction of GO and increased the carrier mobility of rGO-AuNPs hybrid film. The effect was intense for the HT reduction, where the highest hole mobility of 159 ± 5.4 cm2/Vs and the lowest sheet resistance of 325.82 ± 0.32 Ω/sq were measured for the rGO-HT film with 30 s pre-sputtered Au. Without pre-decoration of AuNPs, the reduction results in increased optical constants of the rGO film. This is well expected as the optical absorption of GO within UV–visible–NIR increased due to thermal reduction, resembling the graphene. Remarkably, we found the optical constants of rGO lowered for a longer duration of Au pre-sputtering. The AuNPs directly enhanced the electrical conduction while at the same time tuned the optical constants of rGO more towards GO by incomplete reduction of the embedded layer. The combination of electrically and optically conducting rGO film with the presence of localized surface plasmon resonance from AuNPs in the visible range is prospective for various target applications.