Improvement of NbO_x-based threshold switching devices by implementing multilayer stacks

Abstract

In this work the I–V characteristics of a niobium oxide-based threshold switching device were optimized to match the requirements for its application in neuromorphic circuits. Those neuromorphic circuits rely on coupled oscillators utilizing the volatile resistive switching effect of the memristor. A large voltage extension of the negative differential resistance region of the threshold switch enables enhanced signal amplification, and, furthermore, can lead to a better tolerance to device variability. A symmetric switching behavior as well as a high device stability for the operation in both voltage polarities is mandatory to allow the integration in circuits that utilize the connection of several threshold switching devices operated in different polarities. These properties are similarly important for the adoption of the threshold switches as selector devices in bipolar resistive memory arrays. Furthermore, a low forming voltage is desirable because it leads to a better control during the forming step. To meet all those requirements the application of multilayer stacks consisting of niobium and niobium oxide layers is proposed and their optimization is investigated in detail.

Resistive switching and role of interfaces in memristive devices based on amorphous NbOx grown by anodic oxidation

“…10 Memristive devices based on NbO x have been also largely studied for their threshold switching properties, useful as a selector in memory arrays. [11][12][13][14][15][16][17][18][19][20][21][22][23] In all these works, the niobium oxide switching medium is obtained using conventional deposition techniques such as RF sputtering both starting from a NbO x target and from a pure Nb target in an oxygen atmosphere to control its stoichiometry and also by using pulsed laser deposition (PLD), ALD and sol-gel methods. [24][25][26][27][28][29] Recently, anodic oxidation has been proposed as a promising alternative low-cost and easy-to-use technique in the realization of RS devices with high performances.…”

“…10 Memristive devices based on NbO x have been also largely studied for their threshold switching properties, useful as a selector in memory arrays. 11–23 In all these works, the niobium oxide switching medium is obtained using conventional deposition techniques such as RF sputtering both starting from a NbO x target and from a pure Nb target in an oxygen atmosphere to control its stoichiometry and also by using pulsed laser deposition (PLD), ALD and sol–gel methods. 24–29…”

A Memristors‐Based Dendritic Neuron for High‐Efficiency Spatial‐Temporal Information Processing

“…Among niobium oxides, only niobium dioxide (NbO 2 ) shows the desired Mott transition behavior, [32] and therefore, after NbO x device fabrication, an electroforming operation is required to form a Mott transition region in the amorphous NbO x layer which is a mixture of different oxide states. Device engineering, such as doping [33] or stacking multiple layers [34,35] has been employed to control the size and distribution of the Mott transition region for improving the uniformity of the threshold switching process.…”

X-ray reflectivity and X-ray photoelectron spectroscopy studies on reactively sputtered $$\hbox {Nb}_{2}\hbox {O}_{5}$$-based thin-film devices

“…Change in refractive index and deposition stress of sputter-deposited Nb 2 O 5 film has been reported recently by varying deposition pressure and oxygen content in the plasma [15]. In recent times, threshold switching properties of NbO-based metal-insulator-metal (MIM) devices have been presented [16,17]. A multilayer NbO-based MIM structure with fiveorder on/off ratios is also reported [18].…”