Filamentary Resistive Switching Localized at Cathode Interface in NiO Thin Films

Abstract

This study examined the resistance switching mechanism of the W tip/40 nm NiO/Ir and Pt/40 nm NiO/Ir structures in a voltage sweep mode. The results showed that the conducting filaments propagate from the anode interface, and resistance switching is induced by the rupture and recovery of the conducting filaments in the localized regions near the cathode. This is in contrast to what is observed in TiO 2 ͓Kim et al., Appl. Phys. Lett., 91, 012907 ͑2007͔͒, where the filamentary switching occurs at the anode interface. NiO is a p-type electrical conduction material. Localized hole injection at the anode interface induced the removal of oxygen ions from NiO to the anode ͑or atmosphere͒ by the Joule heating-assisted electromigration. This eventually leads to the metallic Ni filament formation extending from the anode interface to the cathode interface. The weaker Ni filament near the cathode interface induced a larger local heat generation for the given switching currents, which leads to the cathode interface localized switching.Reliable resistance switching has been reported in many metal oxide systems and may have potential applications in future nonvolatile semiconductor memory devices. Among the range of resistance switching metal/binary oxide/metal systems, NiO and TiO 2 are perhaps the most widely studied resistance-switching materials, 1-5 where the electrode material is typically a noble metal. Resistance switching in these systems has been reported to be closely related to the formation and rupture of conducting filaments. 1-5 It is reasonable to assume that the filaments are formed by the percolation of defects, such as oxygen vacancies ͑V O ͒ in TiO 2 and Ni interstitial ions ͑Ni i ͒ in NiO, which may contribute to electrical conduction. 6,7 It was recently reported that the rupture and recovery of filaments, corresponding to the RESET ͓switching from the low resistance state ͑LRS͒ to high resistance state ͑HRS͔͒ and SET switching ͑switching from the HRS to LRS͒, respectively, in a 40 nm thick TiO 2 film occur in a localized region ͑3-10 nm thick͒ near the anode interface in a unipolar resistive switching mode through the unidirectional electromigration of oxygen ions. 8 The current flow through these tiny filaments heats the filament area to high temperatures ͑a few hundred degrees͒, 9 which means that the electromigration of defects is thermally assisted. Therefore, the temperature distribution is another key factor governing the switching behavior. 10 Considering the different types of electrical carriers in TiO 2 ͑electron͒ and NiO ͑hole͒, local rupture and recovery can occur in a region near the cathode interface in a metal/NiO/metal. Under the given bias condition, O 2− ions move to the anode ͑or even to the atmosphere͒, which results in an oxygen-deficient TiO 2−x in TiO 2 and nickel-excess Ni 1+x O in NiO. As the electromigration of O 2− ions in both materials is a thermally activated process, achieving a local high temperature, due to the electrical carrier injection at a localized point at the elec...

Collective Motion of Conducting Filaments in Pt/n‐Type TiO2/p‐Type NiO/Pt Stacked Resistance Switching Memory

“…[ 20 ] The growth direction of such CFs depend on the majority carrier type of the oxides, e.g., the CFs in n-type TiO 2 and p-type NiO have an opposite growth direction and consequently are ruptured near the anode and cathode, respectively. [16][17][18] Interestingly, when these two types of fi lms were stacked, a peculiar bias polarity-dependent RS behaviour and approximately 10 3 times shorter reset time, which accompanies a smaller reset power, were observed. It is expected that this extraordinary fi nding will shed new light on understanding the RS mechanism in these materials.…”

Oxygen-concentration effect on p-type CuAlOx resistive switching behaviors and the nature of conducting filaments

“…This is probably because the available p-type oxides are relatively limited, and the CFs' nature for p-type oxides has not yet been clearly elucidated. 5,[7][8][9][10][11] For instance, the oxygen-deficient CFs model is not always suitable to explain some of the opposing RS behaviors observed in p-type oxides, such as the bias polarity dependence and the switching location. 7,10 Therefore, it is necessary to take a deeper insight into the RS mechanism of p-type oxides, with special focus on the CFs' nature.…”

Conduction mechanism of resistance switching in fully transparent MgO-based memory devices

“…When a large forming voltage is applied across the films, the oxygen-deficient regions emerge due to the movement of oxygen ions and even runaway of oxygen element at the anode interface. 29,30 Under the external electrical field, the oxygen-deficient regions propagate toward the other electrode. When the percolation threshold is passed, the filamentary conducting paths will be formed, as shown in Fig.…”

“…However, with the limit of compliance current, the loss of the oxygen element is not so serious that the HRS can be recovered through the redistribution of oxygen vacancies locally (absorbing oxygen ions in the nearby regions). 30,31 After the forming, the original HRS of the devices was switched to the LRS. Subsequently, as voltage is applied, the I-V behaviors exhibit Ohmic conduction in the LRS until the filament path was ruptured by the Joule heating effect.…”