Abstract
The discovery of resistance switching memristors marks a paradigm shift in the search for alternative non-volatile memory components in the semiconductor industry. Normally a dielectric in these bistable memory cells changes its resistance with an applied electric field or current, albeit retaining the resistive state based on the history of the applied field. Despite showing immense potential, sustainable growth of this new memory technology is bogged down by several factors including cost, intricacies of design, lack of efficient tunability, and issues with scalability and eco-friendliness. Here, we demonstrate a simple arrangement wherein an ethanol-adsorbed ZnO thin film exhibits orders of magnitude change in resistance when activated by visible light. We show that there exists two stable ohmic states, one in the dark and the other in the illuminated regime, as well as a significant delay in the transition between these saturated states. We also demonstrate that visible light acts as a non-invasive tuning parameter for the bistable resistive states. Furthermore, a pinched hysteresis I-V response observed in these devices indicate what seems to be a new type of memristive behaviour.
Highlights
Adsorbed oxygen molecules in these ethanol sensors are believed to reduce the mobility of the free electron gas, thereby increasing overall resistance of the sample[32]
In this paper we present a novel experimental result wherein a thin film made from zinc oxide particles dispersed in ethanol exhibits orders of magnitude resistive switching induced by visible light at room temperature
The transition time between the low and high resistive states depends on the size or morphology of ZnO particles, same characteristic switching behavior is observed in all thin films made of regular ZnO powder, nanopowder or nanowires
Summary
Adsorbed oxygen molecules in these ethanol sensors are believed to reduce the mobility of the free electron gas, thereby increasing overall resistance of the sample[32]. Unlike memristors in MIM configuration, our ZnO thin film is deposited on a glass substrate using sol-gel method and the top surface is exposed to the ambient environment Resistive switching in this configuration is observed irrespective of the size or morphology of ZnO particles, i.e., with ZnO powder, nanopowder or nanowires, when deposited on a plain uncoated glass substrate from a suspension in ethanol. We trace the origin of this resistive switching behaviour to the surface characteristics of the thin films by using plasma-facilitated surface modifications, characterizing the surface modification by FTIR analysis and by measuring the switching behaviour as a function of the wave length of the incident light We propose that this switching phenomenon arises from the displacement of adsorbed oxygen from the ZnO surface upon exposure to light
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