Influence of top electrode on resistive switching effect of chitosan thin films
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culty of Materials Science and Technology, University of Science, Vietnam National University, Ho Chi Minh 70000, Vietnam Address all correspondence to this author. e-mail: [email protected]
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Received: 17 August 2019; accepted: 1 November 2019
Chitosan has attracted significant attention in the past decade because of its potential applications in water engineering, the food and nutrition technology, the textile and paper industries, and drug delivery. Recently, a particularly interesting application of chitosan has been proposed in transparent flexible electronic devices, including memristors and transistors. In this work, the resistive switching (RS) effect of chitosan thin films in a capacitor-like structure with Ag and Al as alternative top electrodes was studied. Both the devices showed a bistable RS effect under an external electric field with a high endurance of 102. The electrical conduction and RS mechanisms of chitosan-based devices were investigated. The trap-controlled space charge–limited current was responsible for electrical transport at the low-resistance state of both devices, while direct tunneling and Schottky emission at the high-resistance state were related to Ag/chitosan/fluorine-doped tin oxide (FTO) and Al/chitosan/FTO, respectively. The RS mechanism of the Ag/chitosan/FTO device was attributed to the formation and dissociation of Ag filaments through the dielectric layer, whereas the change in the barrier height at the Al and chitosan interface under an external electric field could control the RS mechanism of the Al/chitosan/FTO device.
Introduction With the rapid development of technologies involved in data storage devices, the innovative memory with simple fabricated process, high usability and environmentally-friendly characteristics have become essential demands [1, 2]. Resistive random access memory (RRAM), which is expected to replace the entrenched incumbent technologies, has been investigated in detail using a variety of materials in efforts to improve the capacity, density, and write/erase speed of digital memories [3]. Among numerous kinds of switching layer materials, RRAMs based on polymer thin films are preferred because of their polymeric networks, which are very versatile when applied in flexible devices [4, 5]. Chitosan, a biopolymer, is derived from chitin, which can be extracted from cell waste of shrimps, lobsters, krill, and crab [6]. These sources are available in nature and inexpensive and will thus be an ideal direction for industrial-scale production. The low conductivity and mechanical strength of chitosan make it particularly suitable for the insulator layer in an RRAM structure. In recent years, a few reports of chitosan film–based memory devices have been
ª Materials Research Society 2019
made by Hosseini et al. [4, 7, 8, 9], in which chitosan was doped with Ag or mixed with another polymer to form a composite. Some other authors reported the use of a chitosan electrolyte as the gate dielectric in transistors [10, 11]. Employing nanoparticle incorporation and a
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