Voltage controlled polarity switching of photoresponse in graphene oxide-based memristor

Abstract

The electrical and optoelectrical characteristics of graphene oxide thin film have been studied to establish its potential for various device applications. Symmetric nonlinear hysteresis in a current–voltage space, a typical memristor characteristic, has been observed using a planar metal/insulator/metal configuration. The obtained current–voltage behavior of the device has been visualized based on the voltage-dependent contributions from various charge carriers in the presence of different trap sites in the fabricated thin film. The uniqueness of this device's characteristics is to show a bias voltage-dependent polarity switching of photoresponse under illumination, and this photoswitching occurs through a switching voltage point (∼2 V). The time dynamics of this photocurrent reveal that under a low bias voltage (<2 V), the device shows capacitive memristor characteristics. The exponentially growing photocurrent is additive in nature, and the device shows the photoresponse having a time constant of ∼2 s at +1 V. As bias voltage increases (>2 V), another current appears opposite to the normal photocurrent that depends on the bias voltage and intensity of illumination. A detailed analysis of the time dynamics of photoresponse reveals that the time constant of this current changes from ∼9 s (+2 V) to ∼5 s (+4 V). The observed photoswitching is due to different time constants of these counter-interacting currents, resulting in polarity switching. Here, we attempt to shed light on the fundamental mechanisms that connect the nonlinear, nonzero crossing hysteresis observed in the electrical characteristics with its voltage-dependent photoswitching that can be judicially exploited for conceptualizing graphene oxide-based photonic devices.