Polymer/TiO2 Nanorod Nanocomposite Optical Memristor Device

Abstract

Modulation of resistive switching memory by light opens the route to new optoelectronic devices that can be controlled both optically and electronically. Applications include integrated circuits with memory elements switchable by light and neuromorphic computing with optically reconfigurable and tunable synaptic circuits. We report on a unique nanocomposite resistive switching material and device made from a low concentration (∼0.1% by mass) of titanium dioxide nanorods (TiO2-NRs) embedded within the azobenzene polymer, poly(disperse red 1 acrylate, PDR1A). The device exhibits both reversible electronic memristor switching and reversible polarization-dependent optical switching. Optical irradiation by circularly polarized light causes a trans-cis photochemical isomerization that modifies the conformation and orientation of the photoactive azo-unit within the polymer. The resulting expansion of the composite (PDR1A/TiO2-NR) polymer film modifies the conduction pathway, facilitated by the presence of the TiO2-NRs, as a semiconductor material, through the (PDR1A/TiO2-NR) polymer film, which provides a sensitive means to control resistive switching in the device. The effect is reversible by changing the polarization state of the incident light. A charge-flux memristor model successfully reproduces the current-voltage hysteresis loops and threshold switching properties of the device, as well as the effect of the illumination on the electrical characteristics.