Tunable Dielectric Characteristics of the Nanocomposite Diode Based on Functionalized Graphene Quantum Dots with and without Gadolinium

Due to the excellent properties of gadolinium (Gd), a rare earth element, in fluorescence and magnetic resonance imaging (MRI), solutions of Gd-free and Gddoped polyethyleneimine (PEI)-functionalized graphene quantum dots (GQDs) have been separately synthesized and characterized. In the present study, the dielectric properties of Gd-free/doped nanocomposite-based diodes have been compared using impedance spectroscopy (IS) in the frequency range from 1 kHz to 500 kHz and voltage range from -3 V to +5 V at 300 K. From our experimental results, the Gd-free diode was found to have a negative dielectric constant (ε). In contrast, the Gd-doped nanocomposite diode exhibited positive ε. The ε of the Gd-free diode is -80, while the ε of the Gd-doped diode is 35 at 5 V for 1 kHz. The experimental results showed that the dielectric properties of both structures were strongly dependent on the applied voltage and frequency. The Gd doping in the interface has prevented the domination of loss mechanisms within the structure, eliminated negative dielectric at lower frequencies, and conferred a unique micro-capacitor characteristic to the structure. All these efforts will contribute to the development of functional carbon-based materials and the creation of new electronic devices and tunable dielectric properties.