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Nandi SK, Nath SK, Das SK, Murdoch BJ, Ratcliff T, McCulloch DG, Elliman RG. Effect of Interdiffusion and Crystallization on Threshold Switching Characteristics of Nb/Nb 2O 5/Pt Memristors. ACS APPLIED MATERIALS & INTERFACES 2023; 15:58613-58622. [PMID: 38051757 DOI: 10.1021/acsami.3c14431] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/07/2023]
Abstract
The resistive switching response of two terminal metal/oxide/metal devices depends on the stoichiometry of the oxide film, and this is commonly controlled by using a reactive metal electrode to reduce the oxide layer. Here, we investigate compositional and structural changes induced in Nb/Nb2O5 bilayers by thermal annealing at temperatures in the range of 573-973 K and its effect on the volatile threshold switching characteristics of Nb/Nb2O5/Pt devices. Changes in the stoichiometry of the Nb and Nb2O5 films are determined by Rutherford backscattering spectrometry and energy-dispersive X-ray (EDX) mapping of sample cross sections, while the structure of the films is determined by X-ray diffraction, Raman spectroscopy, and transmission electron microscopy (TEM). Such analysis shows that the composition of the Nb and Nb2O5 layers is homogenized by interdiffusion at temperatures less than the crystallization temperature (i.e., >773 K) but that this effectively ceases once the films crystallize. This is explained by comparison with the predictions of a simple diffusion model which shows that the compositional changes are dominated by oxygen diffusion in the amorphous oxide, which is much faster than that in the crystalline phases. We further show that these compositional and structural changes have a significant effect on the electroforming and threshold switching characteristics of the devices, the most significant being a marked increase in their reliability and endurance after crystallization of the oxide films. Finally, we examine the effect of annealing on the quasistatic negative differential resistance characteristics and oscillator dynamics of devices and use a lumped element model to show that this is dominated by changes in the device capacitance resulting from interdiffusion.
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Affiliation(s)
- Sanjoy Kumar Nandi
- Research School of Physics, Australian National University, Canberra, Australian Capital Territory 2601, Australia
| | - Shimul Kanti Nath
- Research School of Physics, Australian National University, Canberra, Australian Capital Territory 2601, Australia
- School of Photovoltaic and Renewable Energy Engineering, University of New South Wales (UNSW Sydney), Kensington, New South Wales 2052, Australia
| | - Sujan Kumar Das
- Research School of Physics, Australian National University, Canberra, Australian Capital Territory 2601, Australia
| | - Billy J Murdoch
- School of Science, RMIT University, Melbourne, Victoria 3001, Australia
| | - Thomas Ratcliff
- Research School of Physics, Australian National University, Canberra, Australian Capital Territory 2601, Australia
| | | | - Robert G Elliman
- Research School of Physics, Australian National University, Canberra, Australian Capital Territory 2601, Australia
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2
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Li X, Zhong Y, Chen H, Tang J, Zheng X, Sun W, Li Y, Wu D, Gao B, Hu X, Qian H, Wu H. A Memristors-Based Dendritic Neuron for High-Efficiency Spatial-Temporal Information Processing. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023; 35:e2203684. [PMID: 35735048 DOI: 10.1002/adma.202203684] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2022] [Revised: 06/06/2022] [Indexed: 06/15/2023]
Abstract
Diverse microscopic ionic dynamics help mediate the ability of a biological neural network to handle complex tasks with low energy consumption. Thus, rich internal ionic dynamics in memristors based on transition metal oxide are expected to provide a unique and useful platform for implementing energy-efficient neuromorphic computing. To this end, a titanium oxide (TiOx )-based interface-type dynamic memristor and an niobium oxide (NbOx )-based Mott memristor are integrated as an artificial dendrite and spike-firing soma, respectively, to construct a dendritic neuron unit for realizing high-efficiency spatial-temporal information processing. Further, a dendritic neural network is hardware-implemented for spatial-temporal information processing to highlight the computational advantages achieved by incorporating dendritic functions in the network. Human motion recognition is demonstrated using the Nanyang Technological University-Red Green Blue (NTU-RGB) dataset as a benchmark spatial-temporal task; it shows a nearly 20% improvement in accuracy for the memristors-based hardware incorporating dendrites and a 1000× advantage in power efficiency compared to that of the graphics processing unit (GPU). The dendritic neuron developed in this study can be considered a critical building block for implementing more bio-plausible neural networks that can manage complex spatial-temporal tasks with high efficiency.
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Affiliation(s)
- Xinyi Li
- School of Integrated Circuits, Beijing National Research Center for Information Science and Technology (BNRist), Tsinghua University, Beijing, 100084, China
- Beijing Innovation Center for Future Chips (ICFC), Tsinghua University, Beijing, 100084, China
| | - Yanan Zhong
- Institute of Functional Nano & Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Soochow University, Suzhou, Jiangsu, 215123, China
| | - Hang Chen
- Department of Computer Science and Technology, Tsinghua University, Beijing, 100084, China
| | - Jianshi Tang
- School of Integrated Circuits, Beijing National Research Center for Information Science and Technology (BNRist), Tsinghua University, Beijing, 100084, China
- Beijing Innovation Center for Future Chips (ICFC), Tsinghua University, Beijing, 100084, China
| | - Xiaojian Zheng
- School of Integrated Circuits, Beijing National Research Center for Information Science and Technology (BNRist), Tsinghua University, Beijing, 100084, China
- Beijing Innovation Center for Future Chips (ICFC), Tsinghua University, Beijing, 100084, China
| | - Wen Sun
- School of Integrated Circuits, Beijing National Research Center for Information Science and Technology (BNRist), Tsinghua University, Beijing, 100084, China
- Beijing Innovation Center for Future Chips (ICFC), Tsinghua University, Beijing, 100084, China
| | - Yang Li
- Department of Internet of Things Technology and Application, China Mobile Research Institute, Beijing, 100053, China
| | - Dong Wu
- School of Integrated Circuits, Beijing National Research Center for Information Science and Technology (BNRist), Tsinghua University, Beijing, 100084, China
- Beijing Innovation Center for Future Chips (ICFC), Tsinghua University, Beijing, 100084, China
| | - Bin Gao
- School of Integrated Circuits, Beijing National Research Center for Information Science and Technology (BNRist), Tsinghua University, Beijing, 100084, China
- Beijing Innovation Center for Future Chips (ICFC), Tsinghua University, Beijing, 100084, China
| | - Xiaolin Hu
- Department of Computer Science and Technology, Tsinghua University, Beijing, 100084, China
| | - He Qian
- School of Integrated Circuits, Beijing National Research Center for Information Science and Technology (BNRist), Tsinghua University, Beijing, 100084, China
- Beijing Innovation Center for Future Chips (ICFC), Tsinghua University, Beijing, 100084, China
| | - Huaqiang Wu
- School of Integrated Circuits, Beijing National Research Center for Information Science and Technology (BNRist), Tsinghua University, Beijing, 100084, China
- Beijing Innovation Center for Future Chips (ICFC), Tsinghua University, Beijing, 100084, China
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Park W, Kim G, In JH, Rhee H, Song H, Park J, Martinez A, Kim KM. High Amplitude Spike Generator in Au Nanodot-Incorporated NbO x Mott Memristor. NANO LETTERS 2023; 23:5399-5407. [PMID: 36930534 DOI: 10.1021/acs.nanolett.2c04599] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
NbOx-based Mott memristors exhibit fast threshold switching behaviors, making them suitable for spike generators in neuromorphic computing and stochastic clock generators in security devices. In these applications, a high output spike amplitude is necessary for threshold level control and accurate signal detection. Here, we propose a materialwise solution to obtain the high amplitude spikes by inserting Au nanodots into the NbOx device. The Au nanodots enable increasing the threshold voltage by modulating the oxygen contents at the electrode-oxide interface, providing a higher ON current compared to nanodot-free NbOx devices. Also, the reduction of the local switching region volume decreases the thermal capacitance of the system, allowing the maximum spike amplitude generation. Consequently, the Au nanodot incorporation increases the spike amplitude of the NbOx device by 6 times, without any additional external circuit elements. The results are systematically supported by both a numerical model and a finite-element-method-based multiphysics model.
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Affiliation(s)
- Woojoon Park
- Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Republic of Korea
| | - Gwangmin Kim
- Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Republic of Korea
| | - Jae Hyun In
- Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Republic of Korea
| | - Hakseung Rhee
- Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Republic of Korea
| | - Hanchan Song
- Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Republic of Korea
| | - Juseong Park
- Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Republic of Korea
| | - Alba Martinez
- Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Republic of Korea
| | - Kyung Min Kim
- Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Republic of Korea
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Nath SK, Nandi SK, Das SK, Liang Y, Elliman RG. Thermal transport in metal-NbO x-metal cross-point devices and its effect on threshold switching characteristics. NANOSCALE 2023; 15:7559-7565. [PMID: 37038892 DOI: 10.1039/d3nr00173c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
Volatile threshold switching and current-controlled negative differential resistance (NDR) in metal-oxide-metal (MOM) devices result from thermally driven conductivity changes induced by local Joule heating and are therefore influenced by the thermal properties of the device-structure. In this study, we investigate the effect of the metal electrodes on the threshold switching response of NbOx-based cross-point devices. The electroforming and switching characteristics are shown to be strongly influenced by the thickness and thermal conductivity of the top-electrode due to its effect on heat loss from the NbOx film. Specifically, we demonstrate a 40% reduction in threshold voltage and a 75% reduction in threshold power as the thickness of the top Au electrode is reduced from 125 nm to 25 nm, and a 24% reduction in threshold voltage and 64% reduction in threshold power when the Au electrode is replaced by a Pt electrode of the same thickness of NbOx film, due to its lower thermal conductivity. Lumped element and finite element modelling of the devices show that these improvements are due to a reduction in heat loss to the electrodes, which is dominated by lateral heat flow within the electrode. These results clearly demonstrate the importance of the electrodes in determining the electroforming and threshold switching characteristics of MOM cross point devices.
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Affiliation(s)
- Shimul Kanti Nath
- Department of Electronic Materials Engineering, Research School of Physics, The Australian National, University, Canberra, ACT 2601, Australia.
- Department of Electrical, Electronic and Computer Engineering, The University of Western Australia, 35 Stirling Highway, Perth 6009, Australia
| | - Sanjoy Kumar Nandi
- Department of Electronic Materials Engineering, Research School of Physics, The Australian National, University, Canberra, ACT 2601, Australia.
| | - Sujan Kumar Das
- Department of Electronic Materials Engineering, Research School of Physics, The Australian National, University, Canberra, ACT 2601, Australia.
| | - Yan Liang
- School of Electronic and Information, Hangzhou Dianzi University, Hangzhou, 310018, China
| | - Robert G Elliman
- Department of Electronic Materials Engineering, Research School of Physics, The Australian National, University, Canberra, ACT 2601, Australia.
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Zrinski I, Zavašnik J, Duchoslav J, Hassel AW, Mardare AI. Threshold Switching in Forming-Free Anodic Memristors Grown on Hf-Nb Combinatorial Thin-Film Alloys. NANOMATERIALS (BASEL, SWITZERLAND) 2022; 12:3944. [PMID: 36432230 PMCID: PMC9697845 DOI: 10.3390/nano12223944] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/22/2022] [Revised: 11/03/2022] [Accepted: 11/05/2022] [Indexed: 06/16/2023]
Abstract
The development of novel materials with coexisting volatile threshold and non-volatile memristive switching is crucial for neuromorphic applications. Hence, the aim of this work was to investigate the memristive properties of oxides in a Hf-Nb thin-film combinatorial system deposited by sputtering on Si substrates. The active layer was grown anodically on each Hf-Nb alloy from the library, whereas Pt electrodes were deposited as the top electrodes. The devices grown on Hf-45 at.% Nb alloys showed improved memristive performances reaching resistive state ratios up to a few orders of magnitude and achieving multi-level switching behavior while consuming low power in comparison with memristors grown on pure metals. The coexistence of threshold and resistive switching is dependent upon the current compliance regime applied during memristive studies. Such behaviors were explained by the structure of the mixed oxides investigated by TEM and XPS. The mixed oxides, with HfO2 crystallites embedded in quasi amorphous and stoichiometrically non-uniform Nb oxide regions, were found to be favorable for the formation of conductive filaments as a necessary step toward memristive behavior. Finally, metal-insulator-metal structures grown on the respective alloys can be considered as relevant candidates for the future fabrication of anodic high-density in-memory computing systems for neuromorphic applications.
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Affiliation(s)
- Ivana Zrinski
- Institute of Chemical Technology of Inorganic Materials, Johannes Kepler University Linz, Altenberger Street, 69, 4040 Linz, Austria
| | - Janez Zavašnik
- Jožef Stefan Institute, Jamova Cesta 39, 1000 Ljubljana, Slovenia
| | - Jiri Duchoslav
- Center for Surface and Nanoanalytics, Johannes Kepler University Linz, Altenberger Street, 69, 4040 Linz, Austria
| | - Achim Walter Hassel
- Institute of Chemical Technology of Inorganic Materials, Johannes Kepler University Linz, Altenberger Street, 69, 4040 Linz, Austria
- Danube Private University, Steiner Landstrasse 124, 3500 Krems-Stein, Austria
| | - Andrei Ionut Mardare
- Institute of Chemical Technology of Inorganic Materials, Johannes Kepler University Linz, Altenberger Street, 69, 4040 Linz, Austria
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Nandi SK, Puyoo E, Nath SK, Albertini D, Baboux N, Das SK, Ratcliff T, Elliman RG. High Spatial Resolution Thermal Mapping of Volatile Switching in NbO x-Based Memristor Using In Situ Scanning Thermal Microscopy. ACS APPLIED MATERIALS & INTERFACES 2022; 14:29025-29031. [PMID: 35700145 DOI: 10.1021/acsami.2c06870] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Temperature mapping by in situ thermoreflectance thermal imaging (TRTI) or midwave infrared spectroscopy has played an important role in understanding the origins of threshold switching and the effect of insulator-metal transitions in oxide-based memrsitive devices. In this study, we use scanning thermal microscopy (SThM) as an alternative thermal mapping technique that offers high spatial resolution imaging (∼100 nm) and is independent of material. Specifically, SThM is used to map the temperature distribution in NbOx-based cross-bar and nanovia devices with Pt top electrodes. The measurements on cross-bar devices reproduce the current redistribution and confinement processes previously observed by TRTI but without the need to coat the electrodes with a material of high thermo-reflectance coefficient (e.g., Au), while those on the nanovia devices highlight the spatial resolution of the technique. The measured temperature distributions are compared with those obtained from physics-based finite-element simulations and suggest that thermal boundary resistance plays an important role in heat transfer between the active device volume and the top electrode.
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Affiliation(s)
- Sanjoy Kumar Nandi
- Department of Electronic Materials Engineering, Research School of Physics, Australian National University, Canberra, Australian Capital Territory 2601, Australia
| | - Etienne Puyoo
- Université Lyon, INSA Lyon, CNRS, Ecole Centrale de Lyon, Université Claude Bernard Lyon 1, CPE Lyon, INL, UMR5270, 69621 Villeurbanne, France
| | - Shimul Kanti Nath
- Department of Electronic Materials Engineering, Research School of Physics, Australian National University, Canberra, Australian Capital Territory 2601, Australia
- Department of Electrical, Electronic and Computer Engineering, The University of Western Australia, Crawley, Western Australia 6009, Australia
| | - David Albertini
- Université Lyon, INSA Lyon, CNRS, Ecole Centrale de Lyon, Université Claude Bernard Lyon 1, CPE Lyon, INL, UMR5270, 69621 Villeurbanne, France
| | - Nicolas Baboux
- Université Lyon, INSA Lyon, CNRS, Ecole Centrale de Lyon, Université Claude Bernard Lyon 1, CPE Lyon, INL, UMR5270, 69621 Villeurbanne, France
| | - Sujan Kumar Das
- Department of Electronic Materials Engineering, Research School of Physics, Australian National University, Canberra, Australian Capital Territory 2601, Australia
- Department of Physics, Jahangirnagar University, Dhaka 1342, Bangladesh
| | - Thomas Ratcliff
- Department of Electronic Materials Engineering, Research School of Physics, Australian National University, Canberra, Australian Capital Territory 2601, Australia
| | - Robert G Elliman
- Department of Electronic Materials Engineering, Research School of Physics, Australian National University, Canberra, Australian Capital Territory 2601, Australia
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Nath SK, Nandi SK, Ratcliff T, Elliman RG. Engineering the Threshold Switching Response of Nb 2O 5-Based Memristors by Ti Doping. ACS APPLIED MATERIALS & INTERFACES 2021; 13:2845-2852. [PMID: 33406833 DOI: 10.1021/acsami.0c19544] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
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 Nb2O5 and Ti-doped Nb2O5 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. Based on temperature-dependent current-voltage characteristics and lumped-element modelling, these effects are attributed to doping-induced reductions in the device resistance and its rate of change with temperature (i.e., the effective thermal activation energy for conduction). Significantly, these studies also show that a critical activation energy is required for devices to exhibit NDR, with doping providing an effective means of engineering the current-voltage characteristics. These results afford an improved understanding of the physical mechanisms responsible for threshold switching and provide new insights for designing devices for specific applications.
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Affiliation(s)
- Shimul Kanti Nath
- Department of Electronic Materials Engineering, Research School of Physics, The Australian National University, Canberra, Australian Capital Territory 2601, Australia
| | - Sanjoy Kumar Nandi
- Department of Electronic Materials Engineering, Research School of Physics, The Australian National University, Canberra, Australian Capital Territory 2601, Australia
| | - Thomas Ratcliff
- Department of Electronic Materials Engineering, Research School of Physics, The Australian National University, Canberra, Australian Capital Territory 2601, Australia
| | - Robert Glen Elliman
- Department of Electronic Materials Engineering, Research School of Physics, The Australian National University, Canberra, Australian Capital Territory 2601, Australia
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