Bipolar Resistive Switching Mechanism Research Articles

Conduction and switching behavior of e-beam deposited polycrystalline Nb2O5 based nano-ionic memristor for non-volatile memory applications

Investigation has been done of bipolar resistive switching mechanism of Pt/Nb2O5/Pt and Bare conductive paint (BCP)/ Nb2O5/Pt memristive devices with orthorhombic phase prepared by e-beam evaporation method. The device exhibits reproducible switching with a ratio of (Roff/Ron) of 20 or higher which is good enough in read out for practical memory devices. The device exhibits reversible switching and better consistency during the switching from a high resistance state to a low resistance state and vice versa under a low operational voltage (<±1 V) due to its controlled formation and/or annihilation of conduction path. Switching mechanism is elucidated using a model invoking drift and diffusion of oxygen vacancies for the formation and rupture of conduction path during the Set and Reset process. The as deposited Nb2O5 thin film shows itself as amorphous in nature and transferred to orthorhombic phase by post annealing at 600 °C/30 min in O2 ambient. The reliability test of memristive device stack structures has been investigated by observing the retention of 600 min and reproducible switching through endurance test of over 1000 cycles which is better than the reported structures employing single layer of Nb2O5. The device does not show any performance degradation during the test.

Direct growth of FeS2 on paper: A flexible, multifunctional platform for ultra-low cost, low power memristor and wearable non-contact breath sensor for activity detection

This is the first demonstration of direct growth of iron pyrite (FeS2) via a single step hydrothermal route on low cost, biodegradable, flexible cellulose paper substrate which is further explored as a versatile multifunctional platform for memristor (with top and bottom electrodes) and wearable breath sensor (with planar contacts) which exhibits excellent switching and response respectively. XRD, EDAX studies confirmed the formation of crystalline pyrite FeS2. Memristor device exhibits excellent bipolar resistive switching mechanism at very low set, reset voltages i.e. +0.25 V, −0.5 V with a very low power consumption in the range of few micro to nano watts, decent switching ratio of 4 × 102, good data retention up to 2 × 104 s and excellent switching endurance up to 500 cycles. Furthermore, FeS2 grown on paper displayed excellent response towards exhaled breath exhibiting distinguished response towards oral and nasal breath. The sensor was employed in monitoring the exhaled breath pattern during dynamic movements like walking, running and jumping. The mechanism of sensing can be attributed to the conductivity and hydrophilic nature of sensor aiding in adsorption and desorption of the water molecules from the exhaled breath on to the FeS2 microspheres. The strategy outlined here, presents a low cost approach using iron and its pyrites which are abundant, non-toxic and also cost effective based flexible devices for multifunctional electronic applications.

Prediction of the Current-Voltage Characteristics and the Bipolar Resistive Switching Mechanism in Polymer-Based Sandwiched Structures

The prediction of the current-voltage (IV) characteristics of resistive switching devices has remained a challenge before their physical realization. This research work addresses the prediction of the IV characteristics and the bipolar switching mechanism of polymer-based resistive switches by examining their structures before their fabrication. The research was carried out through an analytical study of the device structure, thereby correlating the predicted IV curve to the in-situ IV characteristics of the device. Different types of the device structures were considered, depending upon the work function of the top and the bottom electrodes and the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) levels of the sandwiched layer. We concluded that the defects/traps within the sandwiched layer lead to the interface effect being the dominant switching mechanism driving the polymer-based resistive switches. Furthermore, we also found that the devices following the interface effect are driven from trap-limited space-charge-limited current (SCLC) conduction to trap-free SCLC conduction as their current conduction mechanisms.

Mechanism of electron transport and bipolar resistive switching in lead oxide thin films

In this paper, we report a model that interprets the mechanism of bipolar resistive switching in thin metal oxide layers as a purely electronic process. Based on the experimental results, we find that the main transport mechanism in our compensated highly resistive semiconductor is related to space-charge-limited current traps. The S-shaped I–V characteristics of the structure layers of Pt/PbO/Pt with stable bipolar resistive switching demonstrate filamentary charge carrier injection in the bulk of the film. This leads to the formation of conductive filamentary areas in the metal-oxide film. We associate the transition from the high resistive state to the low resistive state (SET process) with the trap-filling limit being reached in the local conductive filamentary area, accompanied by the transition of this area to a state with a high degree of degeneracy. The stability of the conductive filament is provided by the potential barrier formed on the border with the main volume of the lead oxide compensated semiconductor film. The return to the initial state (RESET process) occurs at the injection of opposite charge carriers into the degenerate semiconductor in the local filamentary area, followed by the charge carrier recombination and transformation of this area into a highly resistive compensated semiconductor.

Bipolar resistive switching behavior of an amorphous Ge₂Sb₂Te₅ thin films with a Te layer.

The mechanism of bipolar resistive switching (BRS) of amorphous Ge2Sb2Te5 (GST) thin films sandwiched between inert electrodes (Ti and Pt) was examined. Typical bipolar resistive switching behavior with a high resistance ratio (∼10(3)) and reliable switching characteristics was achieved. High-resolution transmission electron microscopy revealed the presence of a conductive Te-filament bridging between the top and bottom electrodes through an amorphous GST matrix. The conduction mechanism analysis showed that the low-resistance state was semiconducting and dominated by band transport, whereas Poole-Frenkel conduction governed the carrier transport in the high-resistance state. Thus, the BRS behavior can be attributed to the formation and rupture of the semiconducting conductive Te bridge through the migration of the Te ions in the amorphous GST matrix under a high electric field. The Te ions are provided by the thin (∼5 nm) Te-rich layer formed at the bottom electrode interface.

Bipolar and unipolar resistive switching effects in an Al/DLC/W structure

In this paper, nonvolatile bipolar resistive switching (BRS) as well as unipolar resistive switching (URS) effects are observed in diamond-like carbon (DLC) thin films prepared by the filtered cathodic vacuum arc technique. By controlling the current compliance, either bipolar or unipolar switching is obtained. The fabricated Al/DLC/W structure showing BRS exhibits good performance with a low operation voltage (<1.0 V) and a data retention time of >105 s. The mechanism of BRS is fitted by ohmic and SCLC laws in the low resistance state and high resistance state scenarios. Fuse and antifuse effects are proposed to be the principle for the URS behaviour.