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Inkjet-printed Polyvinyl Alcohol Multilayers

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University of Warwick

De Montfort University

Large attention has recently been given to a novel technology named memristor, for having the potential of becoming the new electronic device standard. Yet, its manifestation as the fourth missing element is rather controversial among scientists. Here we demonstrate that TiO2-based metal-insulator-metal devices are more than just a memory-resistor. They possess resistive, capacitive and inductive components that can concurrently be programmed; essentially exhibiting a convolution of memristive, memcapacitive and meminductive effects. We show how non-zero crossing current-voltage hysteresis loops can appear and we experimentally demonstrate their frequency response as memcapacitive and meminductive effects become dominant.

Memory impedance in TiO2 based metal-insulator-metal devices.

In this work, we show that identical TiO2-based memristive devices that possess the same initial resistive states are only phenomenologically similar as their internal structures may vary significantly, which could render quite dissimilar switching dynamics. We experimentally demonstrated that the resistive switching of practical devices with similar initial states could occur at different programming stimuli cycles. We argue that similar memory states can be transcribed via numerous distinct active core states through the dissimilar reduced TiO2-x filamentary distributions. Our hypothesis was finally verified via simulated results of the memory state evolution, by taking into account dissimilar initial filamentary distribution.

Stochastic switching of TiO2-based memristive devices with identical initial memory states.

This work exploits the coexistence of both resistance and capacitance memory effects in TiO2-based two-terminal cells. Our Pt/TiO2/TiO x /Pt devices exhibit an interesting combination of hysteresis and non-zero crossing in their current-voltage (I-V) characteristic that indicates the presence of capacitive states. Our experimental results demonstrate that both resistance and capacitance states can be simultaneously set via either voltage cycling and/or voltage pulses. We argue that these state modulations occur due to bias-induced reduction of the TiO x active layer via the displacement of ionic species.

Coexistence of memory resistance and memory capacitance in TiO2 solid-state devices.

The next generation of nonvolatile memory storage may well be based on resistive switching in metal oxides. TiO2 as transition metal oxide has been widely used as active layer for the fabrication of a variety of multistate memory nanostructure devices. However, progress in their technological development has been inhibited by the lack of a thorough understanding of the underlying switching mechanisms. Here, we employed high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) combined with two-dimensional energy dispersive X-ray spectroscopy (2D EDX) to provide a novel, nanoscale view of the mechanisms involved. Our results suggest that the switching mechanism involves redistribution of both Ti and O ions within the active layer combined with an overall loss of oxygen that effectively render conductive filaments. Our study shows evidence of titanium movement in a 10 nm TiO2 thin-film through direct EDX mapping that provides a viable starting point for the improvement of the robustness and lifetime of TiO2-based resistive random access memory (RRAM).

ArticleTotal : 2	Year
Publication title Cited by 7	2016
Publication title Cited by 4	2017

Article	Year
Memory impedance in TiO2 based metal-insulator-metal devices. Scientific reports\| PubMed ID: 24682245	2014
Stochastic switching of TiO2-based memristive devices with identical initial memory states. Nanoscale research letters\| PubMed ID: 24994953	2014
Coexistence of memory resistance and memory capacitance in TiO2 solid-state devices. Nanoscale research letters\| PubMed ID: 25298759	2014
Investigation of the Switching Mechanism in TiO2-Based RRAM: A Two-Dimensional EDX Approach. ACS applied materials & interfaces\| PubMed ID: 27409358	2016

Iulia Salaoru

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