Spyros Stathopoulos

Interface Asymmetry Induced by Symmetric Electrodes on Metal–Al:TiO

Emerging memory technologies have sparked great interest in studying a variety of materials that can be employed in metal–insulator–metal topologies to support resistive switching. While the majority of reports focus on identifying appropriate materials that can be used as active core layers, the selection of electrodes also impacts the performance of such memory devices. Here, both the top and the bottom interfaces of symmetric Metal–Al:TiO

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–Metal Structures

–Metal structures have been investigated by the analysis of their current versus voltage characteristics in the temperature range of 300–350 K. Three different metals were utilized as electrodes, Nb, Au, and Pt, for covering a wide range of work function and electronegativity values. Despite their symmetric structure, the devices were found to exhibit asymmetric performance with respect to the applied bias polarity. Clear signature plots indicating thermionic emission over the interface Schottky barriers have been obtained. The asymmetry between the top and the bottom interfaces was further evaluated by the values of the potential barrier heights and by the barrier lowering factors, both calculated from the experimental data. This study highlights the importance of the interface effects and proves that in addition to film doping, proper (top/bottom) metal selection, and interface engineering should also be exploited for developing thin film metal oxide based devices with tailored electrical characteristics.

A TiO2 ReRAM parameter extraction method

In this work, we present a parameter extraction method for TiO2 memristive devices that applies on a resistive switching rate model which embodies only four parameters for each voltage biasing polarity. The simple form of the model functions allows the derivation of a predictive analytical resistive state response expression under constant bias voltage. By employing corresponding experimental testing on the devices, we fit such constant bias responses exhibited by physical memristor samples on this analytical expression. Next, we apply a simple algorithm that extracts the suitable model parameters that capture the switching rate behavior of the characterized device in its voltage range of operation.

Conduction mechanisms at distinct resistive levels of Pt/TiO 2-x /Pt memristors

Resistive random access memories (RRAMs) are considered as key enabling components for a variety of emerging applications due to their capacity to support multiple resistive states. Deciphering the underlying mechanisms that support resistive switching remains to date a topic of debate, particularly for metal-oxide technologies, and is very much needed for optimizing their performance. This work aims to identify the dominant conduction mechanisms during switching operation of Pt/TiO2-x/Pt stacks, which is without a doubt one of the most celebrated ones. A number of identical devices were accordingly electroformed for acquiring distinct resistive levels through a pulsing-based and compliance-free protocol. For each obtained level, the switching current-voltage (I-V) characteristics were recorded and analyzed in the temperature range of 300 K–350 K. This allowed the extraction of the corresponding signature plots revealing the dominant transport mechanism for each of the I-V branches. Gradual (analogue) switching was obtained for all cases, and two major regimes were identified. For the higher resistance regime, the transport at both the high and low resistive states was found to be interface controlled due to Schottky emission. As the resistance of devices reduces to lower levels, the dominant conduction changes from an interface to the core-material controlled mechanism. This study overall supports that engineering the metal-oxide/metal electrode interface can lead to tailored barrier modifications for controlling the switching characteristics of TiO2 RRAM.Resistive random access memories (RRAMs) are considered as key enabling components for a variety of emerging applications due to their capacity to support multiple resistive states. Deciphering the underlying mechanisms that support resistive switching remains to date a topic of debate, particularly for metal-oxide technologies, and is very much needed for optimizing their performance. This work aims to identify the dominant conduction mechanisms during switching operation of Pt/TiO2-x/Pt stacks, which is without a doubt one of the most celebrated ones. A number of identical devices were accordingly electroformed for acquiring distinct resistive levels through a pulsing-based and compliance-free protocol. For each obtained level, the switching current-voltage (I-V) characteristics were recorded and analyzed in the temperature range of 300 K–350 K. This allowed the extraction of the corresponding signature plots revealing the dominant transport mechanism for each of the I-V branches. Gradual (analogue) swi...

Live demonstration: A TiO2 ReRAM parameter extraction method

We demonstrate a desktop platform which has the ability of modeling ReRAM TiO2 samples in a highly automated manner. The system consists of a bespoke RRAM characterization instrument that hosts packaged RRAM devices and is operated via a PC. The systems python-based software includes a module that automatically applies strategically chosen sequences of pulses to a test device and then extracts the suitable parameter values for a resistive switching model from the elicited response.