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

Abstract

Memristive devices based on the resistive switching mechanism are continuously attracting attention in the framework of neuromorphic computing and next-generation memories. Here, we report on a comprehensive analysis of resistive...

Effect of electrode materials on resistive switching behaviour of NbOx-based memristive devices

“…1 a in which it can be appreciated the compactness of the NbO x layer and the smoothness of the BE interface due to the anodic oxidation process, as confirmed also by Transmission Electron Microscopy (TEM) analysis reported in our previous work 25 . Note that a detailed chemical and structural analysis revealed that the NbO x is amorphous and is characterised by the presence of Nb(+ 5) oxidation state on the top of the anodized film and Nb(+ 2) oxidation state at the interface with the common Nb BE, as investigated in our previous work 25 . Note that while the same oxidation states are then found after the deposition with the Au TE 25 , chemical properties at the metal/NbO x interface with the TE may locally slightly vary the oxide stoichiometry due to the interaction with the TE metal.…”

“…An example of the cross-section of the device structure can be found in Fig. 1 a in which it can be appreciated the compactness of the NbO x layer and the smoothness of the BE interface due to the anodic oxidation process, as confirmed also by Transmission Electron Microscopy (TEM) analysis reported in our previous work 25 . Note that a detailed chemical and structural analysis revealed that the NbO x is amorphous and is characterised by the presence of Nb(+ 5) oxidation state on the top of the anodized film and Nb(+ 2) oxidation state at the interface with the common Nb BE, as investigated in our previous work 25 .…”

“…Note that a detailed chemical and structural analysis revealed that the NbO x is amorphous and is characterised by the presence of Nb(+ 5) oxidation state on the top of the anodized film and Nb(+ 2) oxidation state at the interface with the common Nb BE, as investigated in our previous work 25 . Note that while the same oxidation states are then found after the deposition with the Au TE 25 , chemical properties at the metal/NbO x interface with the TE may locally slightly vary the oxide stoichiometry due to the interaction with the TE metal. To have a comparison between the effect of different TE metals, each type of cell was studied with the same electrical scheme, with the BE grounded and the bias voltage applied to the TE.…”

“…While device-to-device variability of Au-terminated devices was already analysed in our previous work 25 , we have here investigated the device-to-device variability of Pt terminated devices focusing on cells with 30 nm NbO x . Figure 7 a shows a collection of I-V curves representing the medians of the endurance tests for each device under test.…”

“…Among metal oxides, NbO x thin films have recently attracted great attention as insulator layers for the realization of memristive devices 13 – 33 . Besides resistive switching devices have been realized by depositing NbO x thin films by means of radio frequency (RF) sputtering, Atomic Layer Deposition (ALD), Physical Layer Deposition (PLD), and other Complementary Metal Oxide Semiconductor (CMOS) compatible techniques 16 , 18 , 19 , 26 , anodic oxidation has been recently proposed as an alternative grown technique for the realization of NbO x thin films with resistive switching capabilities 21 , 22 , 25 , 34 . While in these works the resistive switching capabilities have been analysed by considering peculiar metal electrode configurations, a relationship in-between the choice of metal electrodes and resistive switching functionalities in NbO x -based devices still have to be established.…”