Optical characterization of reduced graphene Based composite thin films: Left- Handed Materials (Metamaterials)

Negative index material is a type of metamaterial with negative refractive index; being an artificial material, its fabrication is quite difficult, scaling up the production to meet the commercial demand is a challenge and the strong energy dissipation by metals poses another difficulty. This study employed a low cost, scalable technique (Electrodeposition) to synthesis Al and Ca doped NiO-ZnO-rGO thin films on fluorine doped tin oxide (FTO) without any complexing agents. The thin films were optically characterized using double Spectrophotometer within 300-1000 nm wavelength. Results reveal low absorption for all films but high transmittance of max. 78 % for luminum doped thin films. The incorporation of Al3+ and Ca2+ indicate the optical band gap of NiO-ZnO-rGO shifted to low energy (2.0 eV) and high energy (2.20 eV) respectively. All the composite thin films have unique features; negative refractive indexes, negative imaginary dielectric constant, and negative optical conductivity. These optical results of the films show they are novel left handed materials suitable for wider applications such as telemedicine, internet of things, transmission lines, energy storage devices, bio sensing, wearable devices etc.