Graphene and 2D Materials for Transistor, Memristor, Synaptic and Light-Stimulated Devices

Abstract: Graphene and two-dimensional material based electronic applications has been proposed and experimentally demonstrated, including transistors, memristors, and artificial synapses. Graphene is the very attractive material taking advantages of its unique lattice structure. The high carrier mobility alleviates the RC delay issue in circuit level and its weak surface van der Waals interaction enables ultra-low energy consumption in a memristor device architecture. Moreover, those surface properties lead graphene into neuromorphic devices as demonstrated in current study. A novel graphene based insulator, fluorographene, is firstly applied as gate dielectric in a field effect transistor. To identify the dielectric quality, dielectric constant, breakdown electric field and thermal stability are investigated. The scalable and one-step fabrication of single atomic-layer transistors is demonstrated by the selective fluorination of graphene using a low-damage CF4 plasma treatment, where the generated F-radicals preferentially fluorinated the graphene at low temperature (less than 200 °C) while defect formation was suppressed by screening out the effect of ion damage. The fluorographe was also used as decoupling for graphene as its substrate and mobility was improved much. Graphene nanodiscs (GNDs), functionalized using NH3 plasma, as charge trapping sites (CTSs) for non-volatile memory applications have been investigated. Moreover, the graphene based memristor exhibits high reliability and robustness. Inspired by its internal ion migration, a state-of-art neuromorphic operations was demonstrated to mimic human brain functions. The weak van der Waal interaction of graphene interface, graphene based neuromorphic memristor exhibit ultra-low spiking energy consumption and also demonstrate a programmable metaplasticity fashion. A fluorographene based synaptic transistor was demonstrated also. Finally, a new two-dimensional (2D) material, Bi2O2Se, and graphene have the characteristics of positive and negative light-stimulated photocurrent, respectively. Based on these properties, the light-stimulated synaptic device can be realized by a proper operation in measurement. The modulation of the light pulse on the device simulated the excitation and inhibition behavior similar as in biological synapses. A circuit level based on graphene and 2D material-electronic is the good candidate to be developed in future and combining with the concept of artificial neuron network (ANN).

Keywords: Fluorographene; memristors; artificial synapse; Bi2O2Se; light-stimulate.