Publications by authors named "Thomas Ratcliff"
Article Synopsis
- The resistive switching characteristics of metal/oxide/metal devices are influenced by the stoichiometry of their oxide layers, which can be controlled through the use of reactive metal electrodes.
- This study analyzes how thermal annealing at various temperatures affects the composition and structure of Nb/NbO bilayers, utilizing techniques like Rutherford backscattering spectrometry and X-ray diffraction.
- Results indicate that interdiffusion leads to changes in the stoichiometry of Nb and NbO layers until crystallization occurs, enhancing device reliability and performance after the oxide films crystallize, with observed effects on switching characteristics and capacitance.
Article Synopsis
- Oxides that can switch between insulating and metallic states are promising for creating efficient relaxation oscillators in neural networks, but few have transition temperatures above room temperature.
- The study focuses on vanadium oxide (V O) thin films, demonstrating their potential in metal/oxide/metal relaxation oscillators with stable performance and unique electrical properties.
- Research reveals that the conduction in V O is concentrated in narrow paths, with non-linear dynamics in coupled oscillators, marking a significant step towards using V O as a functional material for next-generation neuromorphic computing.
Article Synopsis
- This study explores temperature mapping using scanning thermal microscopy (SThM) to analyze NbO-based memristive devices, focusing on their thermal behavior during switching phenomena.
- SThM offers a high spatial resolution of around 100 nm and does not require specific material coatings, making it an effective alternative to traditional techniques like thermoreflectance thermal imaging (TRTI).
- Results indicate that SThM successfully reproduces current redistribution patterns seen in previous studies and suggests that thermal boundary resistance significantly affects heat transfer between the active components and the top electrodes of the devices.
Metal-oxide-metal (MOM) devices based on niobium oxide exhibit threshold switching (or current-controlled negative differential resistance) due to thermally induced conductivity changes produced by Joule heating. A detailed understanding of the device characteristics therefore relies on an understanding of the thermal properties of the niobium oxide film and the MOM device structure. In this study, we use time-domain thermoreflectance to determine the thermal conductivity of amorphous NbO films as a function of film composition and temperature.
View Article and Find Full Text PDFEngineering the Threshold Switching Response of NbO-Based Memristors by Ti Doping.
ACS Appl Mater Interfaces
January 2021
Two terminal metal-oxide-metal devices based on niobium oxide thin films exhibit a wide range of non-linear electrical characteristics that have applications in hardware-based neuromorphic computing. In this study, we compare the threshold-switching and current-controlled negative differential resistance (NDR) characteristics of cross-point devices fabricated from undoped NbO and Ti-doped NbO and show that doping offers an effective means of engineering the device response for particular applications. In particular, doping is shown to improve the device reliability and to provide a means of tuning the threshold and hold voltages, the hysteresis window, and the magnitude of the negative differential resistance.
View Article and Find Full Text PDFElectric Field- and Current-Induced Electroforming Modes in NbO.
ACS Appl Mater Interfaces
February 2020
Electroforming is used to initiate the memristive response in metal/oxide/metal devices by creating a filamentary conduction path in the oxide film. Here, we use a simple photoresist-based detection technique to map the spatial distribution of conductive filaments formed in Nb/NbO/Pt devices, and correlate these with current-voltage characteristics and in situ thermoreflectance measurements to identify distinct modes of electroforming in low- and high-conductivity NbO films. In low-conductivity films, the filaments are randomly distributed within the oxide film, consistent with a field-induced weakest-link mechanism, while in high-conductivity films they are concentrated in the center of the film.
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