Статті в журналах: "Metal-Insulator Transition devices"

1

Lee, D., B. Chung, Y. Shi, G. Y. Kim, N. Campbell, F. Xue, K. Song, et al. "Isostructural metal-insulator transition in VO2." Science 362, no. 6418 (November 29, 2018): 1037–40. http://dx.doi.org/10.1126/science.aam9189.

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The metal-insulator transition in correlated materials is usually coupled to a symmetry-lowering structural phase transition. This coupling not only complicates the understanding of the basic mechanism of this phenomenon but also limits the speed and endurance of prospective electronic devices. We demonstrate an isostructural, purely electronically driven metal-insulator transition in epitaxial heterostructures of an archetypal correlated material, vanadium dioxide. A combination of thin-film synthesis, structural and electrical characterizations, and theoretical modeling reveals that an interface interaction suppresses the electronic correlations without changing the crystal structure in this otherwise correlated insulator. This interaction stabilizes a nonequilibrium metallic phase and leads to an isostructural metal-insulator transition. This discovery will provide insights into phase transitions of correlated materials and may aid the design of device functionalities.

2

Li, Dasheng, Jonathan M. Goodwill, James A. Bain, and Marek Skowronski. "Scaling behavior of oxide-based electrothermal threshold switching devices." Nanoscale 9, no. 37 (2017): 14139–48. http://dx.doi.org/10.1039/c7nr03865h.

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Materials exhibiting insulator to metal transition (IMT) and transition metal oxides showing threshold switching behavior are considered as promising candidates for selector devices for crossbar non-volatile memory application.

3

Wang, Qi, Kai Liang Zhang, Fang Wang, Kai Song, and Zhi Xiang Hu. "Investigation on the Electric-Field-Induced Metal-Insulator Transition in Vo_X-Based Devices." Applied Mechanics and Materials 130-134 (October 2011): 1–4. http://dx.doi.org/10.4028/www.scientific.net/amm.130-134.1.

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A sandwich device structure of MIM (metal/insulator/metal) is designed and its metal-insulator transition induced by an external electric field is investigated. VOxfilms were deposited on several different substrates by dc magnetic sputtering at room temperature. The device of Pt/VOx/Cu/Ti/SiO2/Si exhibited steady bipolar resistance switching behaviors between high resistive state (HRS) and low resistive state (LRS) with-0.4V/0.3V operation voltage (SET/RESET), while the devices of Pt/VOx/V/Cu/Ti/SiO2/Si, Pt/VOx/Al/Ti/SiO2/Si and Pt/VOx/Pt/Ti/SiO2/Si didn’t show this steady characteristic. From the comparison of these devices based on different substrates, the Schottky Emission model was quoted to explain this resistance switching characteristic in Pt/VOx/Cu/Ti/SiO2/Si device.

4

Polak, Paweł, Jan Jamroz, and Tomasz K. Pietrzak. "Observation of Metal–Insulator Transition (MIT) in Vanadium Oxides V2O3 and VO2 in XRD, DSC and DC Experiments." Crystals 13, no. 9 (August 23, 2023): 1299. http://dx.doi.org/10.3390/cryst13091299.

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Due to metal–insulator transitions occurring in those compounds, materials and devices based on vanadium (III) and (IV) oxides draw increasing scientific attention. In this paper, we observed the transitions in both oxides using contemporary laboratory equipment. Changes in the crystallographic structure were precisely investigated as a function of the temperature with a step of 2 °C. Thermal effects during transitions were observed using differential scanning calorimetry. The DC conductivity of the materials was measured quasi-continuously as a function of the temperature. All the experiments were consistent and showed considerable hysteresis of the metal–insulator transition in both vanadium oxides.

5

Cheng, Shaobo, Min-Han Lee, Richard Tran, Yin Shi, Xing Li, Henry Navarro, Coline Adda, et al. "Inherent stochasticity during insulator–metal transition in VO2." Proceedings of the National Academy of Sciences 118, no. 37 (September 7, 2021): e2105895118. http://dx.doi.org/10.1073/pnas.2105895118.

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Vanadium dioxide (VO2), which exhibits a near-room-temperature insulator–metal transition, has great potential in applications of neuromorphic computing devices. Although its volatile switching property, which could emulate neuron spiking, has been studied widely, nanoscale studies of the structural stochasticity across the phase transition are still lacking. In this study, using in situ transmission electron microscopy and ex situ resistive switching measurement, we successfully characterized the structural phase transition between monoclinic and rutile VO2 at local areas in planar VO2/TiO2 device configuration under external biasing. After each resistive switching, different VO2 monoclinic crystal orientations are observed, forming different equilibrium states. We have evaluated a statistical cycle-to-cycle variation, demonstrated a stochastic nature of the volatile resistive switching, and presented an approach to study in-plane structural anisotropy. Our microscopic studies move a big step forward toward understanding the volatile switching mechanisms and the related applications of VO2 as the key material of neuromorphic computing.

6

Hong, Woong-Ki, SeungNam Cha, Jung Inn Sohn, and Jong Min Kim. "Metal-Insulator Phase Transition in Quasi-One-Dimensional VO2Structures." Journal of Nanomaterials 2015 (2015): 1–15. http://dx.doi.org/10.1155/2015/538954.

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The metal-insulator transition (MIT) in strongly correlated oxides has attracted considerable attention from both theoretical and experimental researchers. Among the strongly correlated oxides, vanadium dioxide (VO2) has been extensively studied in the last decade because of a sharp, reversible change in its optical, electrical, and magnetic properties at approximately 341 K, which would be possible and promising to develop functional devices with advanced technology by utilizing MITs. However, taking the step towards successful commercialization requires the comprehensive understanding of MIT mechanisms, enabling us to manipulate the nature of transitions. In this regard, recently, quasi-one-dimensional (quasi-1D) VO2structures have been intensively investigated due to their attractive geometry and unique physical properties to observe new aspects of transitions compared with their bulk counterparts. Thus, in this review, we will address recent research progress in the development of various approaches for the modification of MITs in quasi-1D VO2structures. Furthermore, we will review recent studies on realizing novel functional devices based on quasi-1D VO2structures for a wide range of applications, such as a gas sensor, a flexible strain sensor, an electrical switch, a thermal memory, and a nonvolatile electrical memory with multiple resistance.

7

Wei, Na, Xiang Ding, Shifan Gao, Wenhao Wu, and Yi Zhao. "HfOx/Ge RRAM with High ON/OFF Ratio and Good Endurance." Electronics 11, no. 22 (November 20, 2022): 3820. http://dx.doi.org/10.3390/electronics11223820.

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A trade-off between the memory window and the endurance exists for transition-metal-oxide RRAM. In this work, we demonstrated that HfOx/Ge-based metal-insulator-semiconductor RRAM devices possess both a larger memory window and longer endurance compared with metal-insulator-metal (MIM) RRAM devices. Under DC cycling, HfOx/Ge devices exhibit a 100× larger memory window compared to HfOx MIM devices, and a DC sweep of up to 20,000 cycles was achieved with the devices. The devices also realize low static power down to 1 nW as FPGA’s pull-up/pull-down resistors. Thus, HfOx/Ge devices act as a promising candidates for various applications such as FPGA or compute-in-memory, in which both a high ON/OFF ratio and decent endurance are required.

8

Huang, Tiantian, Rui Zhang, Lepeng Zhang, Peiran Xu, Yunkai Shao, Wanli Yang, Zhimin Chen, Xin Chen, and Ning Dai. "Energy-adaptive resistive switching with controllable thresholds in insulator–metal transition." RSC Advances 12, no. 55 (2022): 35579–86. http://dx.doi.org/10.1039/d2ra06866d.

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9

Weidemann, Sebastian, Mark Kremer, Stefano Longhi, and Alexander Szameit. "Topological triple phase transition in non-Hermitian Floquet quasicrystals." Nature 601, no. 7893 (January 19, 2022): 354–59. http://dx.doi.org/10.1038/s41586-021-04253-0.

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AbstractPhase transitions connect different states of matter and are often concomitant with the spontaneous breaking of symmetries. An important category of phase transitions is mobility transitions, among which is the well known Anderson localization1, where increasing the randomness induces a metal–insulator transition. The introduction of topology in condensed-matter physics2–4 lead to the discovery of topological phase transitions and materials as topological insulators5. Phase transitions in the symmetry of non-Hermitian systems describe the transition to on-average conserved energy6 and new topological phases7–9. Bulk conductivity, topology and non-Hermitian symmetry breaking seemingly emerge from different physics and, thus, may appear as separable phenomena. However, in non-Hermitian quasicrystals, such transitions can be mutually interlinked by forming a triple phase transition10. Here we report the experimental observation of a triple phase transition, where changing a single parameter simultaneously gives rise to a localization (metal–insulator), a topological and parity–time symmetry-breaking (energy) phase transition. The physics is manifested in a temporally driven (Floquet) dissipative quasicrystal. We implement our ideas via photonic quantum walks in coupled optical fibre loops11. Our study highlights the intertwinement of topology, symmetry breaking and mobility phase transitions in non-Hermitian quasicrystalline synthetic matter. Our results may be applied in phase-change devices, in which the bulk and edge transport and the energy or particle exchange with the environment can be predicted and controlled.

10

Heo, Jinseong, Heejeong Jeong, Yeonchoo Cho, Jaeho Lee, Kiyoung Lee, Seunggeol Nam, Eun-Kyu Lee, et al. "Reconfigurable van der Waals Heterostructured Devices with Metal–Insulator Transition." Nano Letters 16, no. 11 (October 5, 2016): 6746–54. http://dx.doi.org/10.1021/acs.nanolett.6b02199.

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11

McGee, Ryan, Ankur Goswami, Rosmi Abraham, Syed Bukhari, and Thomas Thundat. "Phase transformation induced modulation of the resonance frequency of VO2/tio2 coated microcantilevers." MRS Advances 3, no. 6-7 (2018): 359–64. http://dx.doi.org/10.1557/adv.2018.140.

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AbstractHere we present an investigation into the phase change mechanism and detection methods of the metal-insulator transition of vanadium dioxide (VO2). We are able to detect the onset of the phase transition, and track it to completion using both the mechanical and electrical response by depositing VO2/TiO2 layers onto microcantilever devices by pulsed laser deposition. The resonance frequency of v-shaped cantilevers was shown to increase by up to 41 % upon deposition of VO2 as detected by laser Doppler vibrometry. Such a large increase in resonance frequency is ascribed to high tensile stress imparted onto the cantilever during the deposition process. The insulator-metal transition manifested as a 5 % increase in the resonance frequency as a result of lattice compression, resulting in additional tensile stress in the more ordered metallic phase. Electrically, the transition was confirmed by over three orders magnitude decrease in resistance upon heating past the transition. The metal-insulator transition was measured with an accuracy of a few °C when comparing the two methods, however, the transition was much sharper in the mechanical response.

12

Calhoun, Seth, Rachel Evans, Cameron Nickle, Isaiah O. Oladeji, Justin Cleary, Evan M. Smith, Sayan Chandra, Debashis Chanda, and Robert E. Peale. "Vanadium Oxide Thin Film by Aqueous Spray Deposition." MRS Advances 3, no. 45-46 (2018): 2777–82. http://dx.doi.org/10.1557/adv.2018.512.

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ABSTRACTVanadium Oxide has application to infrared bolometers due to high temperature coefficient of resistivity (TCR). It has attracted interest for switchable plasmonic devices due to its metal to insulator transition near room temperature. We report here the properties of vanadium oxide deposited by an aqueous spray process. The films have a ropy surface morphology with ∼70 nm surface roughness. The polycrystalline phase depends on annealing conditions. The films have TCR of ∼2%/deg, which compares well with sputtered films. Only weak evidence is found for an insulator-metal phase transition in these films.

13

Ma, Chung T., Salinporn Kittiwatanakul, Apiprach Sittipongpittaya, Yuhan Wang, Md Golam Morshed, Avik W. Ghosh, and S. Joseph Poon. "Phase Change-Induced Magnetic Switching through Metal–Insulator Transition in VO2/TbFeCo Films." Nanomaterials 13, no. 21 (October 27, 2023): 2848. http://dx.doi.org/10.3390/nano13212848.

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The ability to manipulate spins in magnetic materials is essential in designing spintronics devices. One method for magnetic switching is through strain. In VO2 on TiO2 thin films, while VO2 remains rutile across the metal–insulator transition, the in-plane lattice area expands going from a low-temperature insulating phase to a high-temperature conducting phase. In a VO2/TbFeCo bilayer, the expansion of the VO2 lattice area exerts tension on the amorphous TbFeCo layer. Through the strain effect, magnetic properties, including the magnetic anisotropy and magnetization, of TbFeCo can be changed. In this work, the changes in magnetic properties of TbFeCo on VO2/TiO2(011) are demonstrated using anomalous Hall effect measurements. Across the metal–insulator transition, TbFeCo loses perpendicular magnetic anisotropy, and the magnetization in TbFeCo turns from out-of-plane to in-plane. Using atomistic simulations, we confirm these tunable magnetic properties originating from the metal–insulator transition of VO2. This study provides the groundwork for controlling magnetic properties through a phase transition.

14

Walls, Brian, Oisín Murtagh, Sergey I. Bozhko, Andrei Ionov, Andrey A. Mazilkin, Daragh Mullarkey, Ainur Zhussupbekova, et al. "VOx Phase Mixture of Reduced Single Crystalline V2O5: VO2 Resistive Switching." Materials 15, no. 21 (October 31, 2022): 7652. http://dx.doi.org/10.3390/ma15217652.

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The strongly correlated electron material, vanadium dioxide (VO2), has seen considerable attention and research application in metal-oxide electronics due to its metal-to-insulator transition close to room temperature. Vacuum annealing a V2O5(010) single crystal results in Wadsley phases (VnO2n+1, n > 1) and VO2. The resistance changes by a factor of 20 at 342 K, corresponding to the metal-to-insulator phase transition of VO2. Macroscopic voltage-current measurements with a probe separation on the millimetre scale result in Joule heating-induced resistive switching at extremely low voltages of under a volt. This can reduce the hysteresis and facilitate low temperature operation of VO2 devices, of potential benefit for switching speed and device stability. This is correlated to the low resistance of the system at temperatures below the transition. High-resolution transmission electron microscopy measurements reveal a complex structural relationship between V2O5, VO2 and V6O13 crystallites. Percolation paths incorporating both VO2 and metallic V6O13 are revealed, which can reduce the resistance below the transition and result in exceptionally low voltage resistive switching.

15

Kwon, Osung, Hongmin Lee, and Sungjun Kim. "Effects of Oxygen Flow Rate on Metal-to-Insulator Transition Characteristics in NbOx-Based Selectors." Materials 15, no. 23 (December 1, 2022): 8575. http://dx.doi.org/10.3390/ma15238575.

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In this work, NbOx-based selector devices were fabricated by sputtering deposition systems. Metal-to-insulator transition characteristics of the device samples were investigated depending on the oxygen flow rate (3.5, 4.5, and 5.5 sccm) and the deposition time. The device stack was scanned by transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS). The yields, including MIT, nonlinear, and Ohmic, in working devices with different deposition conditions were also evaluated. Moreover, we observed the trend in yield values as a function of selectivity. In addition, the current–voltage (I–V) curves were characterized in terms of DC and pulse endurance. Finally, the switching speed and operating energies were obtained by applying a triangular pulse on the devices, and the recovery time and drift-free characteristics were obtained by the paired pulses.

16

Druzhinin, Anatoly, Igor Ostrovskii, Yuriy Khoverko, and Sergij Yatsukhnenko. "Magnetic Properties of Doped Si<B,Ni> Whiskers for Spintronics." Journal of Nano Research 39 (February 2016): 43–54. http://dx.doi.org/10.4028/www.scientific.net/jnanor.39.43.

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Study the magnetic properties of Si<B,Ni> whiskers, the concentration of which corresponds to a dielectric and metal side of metal-insulator transition, is performed. Percolation laws of the magnetic clusters formation, that is important for development of spintronic devices, are considered.

17

Xu, Zhen, Ayrton A. Bernussi, and Zhaoyang Fan. "Voltage Pulse Driven VO2 Volatile Resistive Transition Devices as Leaky Integrate-and-Fire Artificial Neurons." Electronics 11, no. 4 (February 9, 2022): 516. http://dx.doi.org/10.3390/electronics11040516.

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In a hardware-based neuromorphic computation system, using emerging nonvolatile memory devices as artificial synapses, which have an inelastic memory characteristic, has attracted considerable interest. In contrast, the elastic artificial neurons have received much less attention. An ideal material system that is suitable for mimicking biological neurons is the one with volatile (or mono-stable) resistive change property. Vanadium dioxide (VO2) is a well-known material that exhibits an abrupt and volatile insulator-to-metal transition property. In this work, we experimentally demonstrate that pulse-driven two-terminal VO2 devices behave in a leaky integrate-and-fire (LIF) manner, and they elastically relax back to their initial value after firing, thus, mimicking the behavior of biological neurons. The VO2 device with a channel length of 20 µm can be driven to fire by a single long-duration pulse (>83 µs) or multiple short-duration pulses. We further model the VO2 devices as resistive networks based on their granular domain structure, with resistivities corresponding to the insulator or metallic states. Simulation results confirm that the volatile resistive transition under voltage pulse driving is caused by the formation of a metallic filament in an avalanche-like process, while this volatile metallic filament will relax back to the insulating state at the end of driving pulses. The simulation offers a microscopic view of the dynamic and abrupt filament formation process to explain the experimentally observed LIF behavior. These results suggest that VO2 insulator–metal transition could be exploited for artificial neurons.

18

Parihar, Abhinav, Nikhil Shukla, Matthew Jerry, Suman Datta, and Arijit Raychowdhury. "Computing with dynamical systems based on insulator-metal-transition oscillators." Nanophotonics 6, no. 3 (April 19, 2017): 601–11. http://dx.doi.org/10.1515/nanoph-2016-0144.

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AbstractIn this paper, we review recent work on novel computing paradigms using coupled oscillatory dynamical systems. We explore systems of relaxation oscillators based on linear state transitioning devices, which switch between two discrete states with hysteresis. By harnessing the dynamics of complex, connected systems, we embrace the philosophy of “let physics do the computing” and demonstrate how complex phase and frequency dynamics of such systems can be controlled, programmed, and observed to solve computationally hard problems. Although our discussion in this paper is limited to insulator-to-metallic state transition devices, the general philosophy of such computing paradigms can be translated to other mediums including optical systems. We present the necessary mathematical treatments necessary to understand the time evolution of these systems and demonstrate through recent experimental results the potential of such computational primitives.

19

Lu, Chang, Qingjian Lu, Min Gao, and Yuan Lin. "Dynamic Manipulation of THz Waves Enabled by Phase-Transition VO2 Thin Film." Nanomaterials 11, no. 1 (January 6, 2021): 114. http://dx.doi.org/10.3390/nano11010114.

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The reversible and multi-stimuli responsive insulator-metal transition of VO2, which enables dynamic modulation over the terahertz (THz) regime, has attracted plenty of attention for its potential applications in versatile active THz devices. Moreover, the investigation into the growth mechanism of VO2 films has led to improved film processing, more capable modulation and enhanced device compatibility into diverse THz applications. THz devices with VO2 as the key components exhibit remarkable response to external stimuli, which is not only applicable in THz modulators but also in rewritable optical memories by virtue of the intrinsic hysteresis behaviour of VO2. Depending on the predesigned device structure, the insulator-metal transition (IMT) of VO2 component can be controlled through thermal, electrical or optical methods. Recent research has paid special attention to the ultrafast modulation phenomenon observed in the photoinduced IMT, enabled by an intense femtosecond laser (fs laser) which supports “quasi-simultaneous” IMT within 1 ps. This progress report reviews the current state of the field, focusing on the material nature that gives rise to the modulation-allowed IMT for THz applications. An overview is presented of numerous IMT stimuli approaches with special emphasis on the underlying physical mechanisms. Subsequently, active manipulation of THz waves through pure VO2 film and VO2 hybrid metamaterials is surveyed, highlighting that VO2 can provide active modulation for a wide variety of applications. Finally, the common characteristics and future development directions of VO2-based tuneable THz devices are discussed.

20

Gim, Hyeongyu, and Kootak Hong. "Nonvolatile Control of Metal-Insulator Transition in VO2 and Its Applications." Ceramist 26, no. 1 (March 31, 2023): 3–16. http://dx.doi.org/10.31613/ceramist.2023.26.1.01.

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With the advent of the 4th industrial revolution era, there has been a high demand for high-performance electronic devices capable of collecting, storing, and calculating vast amounts of data. Vanadium dioxide (VO2) is considered an attractive candidate for next-generation electronic devices as a prototypical strongly correlated material exhibiting a metal-insulator transition (MIT) accompanied by huge electrical resistivity changes in a few nanoseconds. The nonvolatile control of the MIT in VO2 has recently been the subject of intensive research. In this report, we review recent advancements in the field of nonvolatile control of MIT in VO2, using electrochemical redox reactions, inverse piezoelectric effect, and ferroelectric polarization, and their potential to develop high-performance next-generation electronic devices.

21

Wei, Guodong, Xiaofei Fan, Yiang Xiong, Chen Lv, Shen Li, and Xiaoyang Lin. "Highly disordered VO₂ films: appearance of electronic glass transition and potential for device-level overheat protection." Applied Physics Express 15, no. 4 (April 1, 2022): 043002. http://dx.doi.org/10.35848/1882-0786/ac605d.

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Abstract In this work, the phase transition of a highly disordered amorphous VO2 film is studied. It is found that the electronic transport behavior follows the Arrhenius or Vogel–Tammann–Fulcher model, showing different thermal sensitivity under different thicknesses. Based on it, the concept of a prototype device with overheating protection capability is demonstrated. The results, reflecting the relationship between phase transition and structural disorder, open up a unique pathway to understand the metal insulator transition in strongly correlated electronic systems and to its functionality in electronic devices.

22

Lin, Jianqiang, Shriram Ramanathan, and Supratik Guha. "Electrically Driven Insulator–Metal Transition-Based Devices—Part II: Transient Characteristics." IEEE Transactions on Electron Devices 65, no. 9 (September 2018): 3989–95. http://dx.doi.org/10.1109/ted.2018.2859188.

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23

Li, Dasheng, Abhishek A. Sharma, Darshil K. Gala, Nikhil Shukla, Hanjong Paik, Suman Datta, Darrell G. Schlom, James A. Bain, and Marek Skowronski. "Joule Heating-Induced Metal–Insulator Transition in Epitaxial VO2/TiO2 Devices." ACS Applied Materials & Interfaces 8, no. 20 (May 10, 2016): 12908–14. http://dx.doi.org/10.1021/acsami.6b03501.

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Makino, Kotaro, Kosaku Kato, Yuta Saito, Paul Fons, Alexander V. Kolobov, Junji Tominaga, Takashi Nakano, and Makoto Nakajima. "Terahertz spectroscopic characterization of Ge2Sb2Te5 phase change materials for photonics applications." Journal of Materials Chemistry C 7, no. 27 (2019): 8209–15. http://dx.doi.org/10.1039/c9tc01456j.

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Ge–Sb–Te (GST) phase change materials exhibit a metal-to-insulator transition and therefore are expected to be useful for a variety of terahertz wave applications in addition to their primary application in optical and electrical memory devices.

25

García, Héctor, Jonathan Boo, Guillermo Vinuesa, Óscar G. Ossorio, Benjamín Sahelices, Salvador Dueñas, Helena Castán, Mireia B. González, and Francesca Campabadal. "Influences of the Temperature on the Electrical Properties of HfO2-Based Resistive Switching Devices." Electronics 10, no. 22 (November 17, 2021): 2816. http://dx.doi.org/10.3390/electronics10222816.

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In the attempt to understand the behavior of HfO2-based resistive switching devices at low temperatures, TiN/Ti/HfO2/W metal–insulator–metal devices were fabricated; the atomic layer deposition technique was used to grow the high-k layer. After performing an electroforming process at room temperature, the device was cooled in a cryostat to carry out 100 current–voltage cycles at several temperatures ranging from the “liquid nitrogen temperature” to 350 K. The measurements showed a semiconducting behavior in high and low resistance states. In the low resistance state, a hopping conduction mechanism was obtained. The set and reset voltages increased when temperature decreased because the thermal energies for oxygen vacancies and ions were reduced. However, the temperature did not influence the power absorbed in the reset transition, indicating the local temperature in the filament controls the transition. The set transition turned from gradual to abrupt when decreasing the temperature, due to a positive feedback between the current increase and the Joule heating at low temperatures.

26

Darwish, Mahmoud, and László Pohl. "Insulator Metal Transition-Based Selector in Crossbar Memory Arrays." Electronic Materials 5, no. 1 (February 23, 2024): 17–29. http://dx.doi.org/10.3390/electronicmat5010002.

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This article investigates resistive random access memory (ReRAM) crossbar memory arrays, which is a notable development in non-volatile memory technology. We highlight ReRAM’s competitive edge over NAND, NOR Flash, and phase-change memory (PCM), particularly in terms of endurance, speed, and energy efficiency. This paper focuses on the architecture of crossbar arrays, where memristive devices are positioned at intersecting metal wires. We emphasize the unique resistive switching mechanisms of memristors and the challenges of sneak path currents and delve into the roles and configurations of selectors, particularly focusing on the one-selector one-resistor (1S1R) architecture with an insulator–metal transition (IMT) based selector. We use SPICE simulations based on defined models to examine a 3 × 3 1S1R ReRAM array with vanadium dioxide selectors and titanium dioxide film memristors, assessing the impact of ambient temperature and critical IMT temperatures on array performance. We highlight the operational regions of low resistive state (LRS) and high resistive state (HRS), providing insights into the electrical behavior of these components under various conditions. Lastly, we demonstrate the impact of selector presence on sneak path currents. This research contributes to the overall understanding of ReRAM crossbar arrays integrated with IMT material-based selectors.

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Lee, Su Yeon, Hyun Kyu Seo, Se Yeon Jeong, and Min Kyu Yang. "Improved Electrical Characteristics of Field Effect Transistors with GeSeTe-Based Ovonic Threshold Switching Devices." Materials 16, no. 12 (June 11, 2023): 4315. http://dx.doi.org/10.3390/ma16124315.

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Hyper-field effect transistors (hyper-FETs) are crucial in the development of low-power logic devices. With the increasing significance of power consumption and energy efficiency, conventional logic devices can no longer achieve the required performance and low-power operation. Next-generation logic devices are designed based on complementary metal-oxide-semiconductor circuits, and the subthreshold swing of existing metal-oxide semiconductor field effect transistors (MOSFETs) cannot be reduced below 60 mV/dec at room temperature owing to the thermionic carrier injection mechanism in the source region. Therefore, new devices must be developed to overcome these limitations. In this study, we present a novel threshold switch (TS) material, which can be applied to logic devices by employing ovonic threshold switch (OTS) materials, failure control of insulator–metal transition materials, and structural optimization. The proposed TS material is connected to a FET device to evaluate its performance. The results demonstrate that commercial transistors connected in series with GeSeTe-based OTS devices exhibit significantly lower subthreshold swing values, high on/off current ratios, and high durability of up to 108.

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Cardarilli, Gian Carlo, Gaurav Mani Khanal, Luca Di Nunzio, Marco Re, Rocco Fazzolari, and Raj Kumar. "Memristive and Memory Impedance Behavior in a Photo-Annealed ZnO–rGO Thin-Film Device." Electronics 9, no. 2 (February 7, 2020): 287. http://dx.doi.org/10.3390/electronics9020287.

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An oxygen-rich ZnO-reduced graphene oxide (rGO) thin film was synthesized using a photo-annealing technique from zinc precursor (ZnO)–graphene oxide (GO) sol–gel solution. X-ray diffraction (XRD) results show a clear characteristic peak corresponding to rGO. The scanning electron microscope (SEM) image of the prepared thin film shows an evenly distributed wrinkled surface structure. Transition Metal Oxide (TMO)-based memristive devices are nominees for beyond CMOS Non-Volatile Memory (NVRAM) devices. The two-terminal Metal–TMO (Insulator)–Metal (MIM) memristive device is fabricated using a synthesized ZnO–rGO as an active layer on fluorine-doped tin oxide (FTO)-coated glass substrate. Aluminum (Al) is deposited as a top metal contact on the ZnO–rGO active layer to complete the device. Photo annealing was used to reduce the GO to rGO to make the proposed method suitable for fabricating ZnO–rGO thin-film devices on flexible substrates. The electrical characterization of the Al–ZnO–rGO–FTO device confirms the coexistence of memristive and memimpedance characteristics. The coexistence of memory resistance and memory impedance in the same device could be valuable for developing novel programmable analog filters and self-resonating circuits and systems.

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Basyooni, Mohamed A., Mawaheb Al-Dossari, Shrouk E. Zaki, Yasin Ramazan Eker, Mucahit Yilmaz, and Mohamed Shaban. "Tuning the Metal–Insulator Transition Properties of VO2 Thin Films with the Synergetic Combination of Oxygen Vacancies, Strain Engineering, and Tungsten Doping." Nanomaterials 12, no. 9 (April 26, 2022): 1470. http://dx.doi.org/10.3390/nano12091470.

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Vanadium oxide (VO2) is considered a Peierls–Mott insulator with a metal–insulator transition (MIT) at Tc = 68° C. The tuning of MIT parameters is a crucial point to use VO2 within thermoelectric, electrochromic, or thermochromic applications. In this study, the effect of oxygen deficiencies, strain engineering, and metal tungsten doping are combined to tune the MIT with a low phase transition of 20 °C in the air without capsulation. Narrow hysteresis phase transition devices based on multilayer VO2, WO3, Mo0.2W0.8O3, and/or MoO3 oxide thin films deposited through a high vacuum sputtering are investigated. The deposited films are structurally, chemically, electrically, and optically characterized. Different conductivity behaviour was observed, with the highest value towards VO1.75/WO2.94 and the lowest VO1.75 on FTO glass. VO1.75/WO2.94 showed a narrow hysteresis curve with a single-phase transition. Thanks to the role of oxygen vacancies, the MIT temperature decreased to 35 °C, while the lowest value (Tc = 20 °C) was reached with Mo0.2W0.8O3/VO2/MoO3 structure. In this former sample, Mo0.2W0.8O3 was used for the first time as an anti-reflective and anti-oxidative layer. The results showed that the MoO3 bottom layer is more suitable than WO3 to enhance the electrical properties of VO2 thin films. This work is applied to fast phase transition devices.

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Zhang, Shenli, Hien Vo, and Giulia Galli. "Predicting the Onset of Metal–Insulator Transitions in Transition Metal Oxides—A First Step in Designing Neuromorphic Devices." Chemistry of Materials 33, no. 9 (April 20, 2021): 3187–95. http://dx.doi.org/10.1021/acs.chemmater.1c00061.

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Kim, Jihoon, Sungwook Choi, Seul-Lee Lee, Do Kyung Kim, Min Seok Kim, Bong-Jun Kim, and Yong Wook Lee. "Reversible 100 mA Current Switching in a VO2/Al2O3-Based Two-Terminal Device Using Focused Far-Infrared Laser Pulses." Journal of Nanoscience and Nanotechnology 21, no. 3 (March 1, 2021): 1862–68. http://dx.doi.org/10.1166/jnn.2021.18905.

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In this study, we implemented reversible current switching (RCS) of 100 mA in a two-terminal device based on a vanadium dioxide (VO2) thin film, which could be controlled by far-infrared (FIR) laser pulses. The VO2 thin films used for fabrication of two-terminal devices were grown on sapphire (Al2O3) substrates using a pulsed laser deposition method. An optimal deposition condition was determined by analyzing the resistance-temperature curves of deposited VO2 thin films and the current–voltage characteristics of two-terminal devices based on these films, which were suggested in our previous works. The film surface of the VO2-based device was directly irradiated using focused CO2 laser pulses, and the insulator-metal transition or metal-insulator transition of the VO2 thin film could be triggered depending on laser irradiation. Consequently, RCS of up to 100 mA could be accomplished. This on-state current is close to the upper limit of the current flowing through our VO2 device. The switching contrast, defined as the ratio between on-state and off-state currents, was evaluated and found to be ˜11,962. The average rising and falling times of the switched current were found to be ˜29.2 and ˜71.7 ms, respectively. In comparison with our previous work, the improved heat dissipation structure and the high-quality thin film could maintain the switching contrast at a similar level, although the on-state current was increased by about two times.

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Chen, Yiheng, Wen-Ti Guo, Zi-Si Chen, Suyun Wang, and Jian-Min Zhang. "First-principles study on the heterostructure of twisted graphene/hexagonal boron nitride/graphene sandwich structure." Journal of Physics: Condensed Matter 34, no. 12 (January 7, 2022): 125504. http://dx.doi.org/10.1088/1361-648x/ac45b5.

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Abstract In recent years, the discovery of ‘magic angle’ graphene has given new inspiration to the formation of heterojunctions. Similarly, the use of hexagonal boron nitride, known as white graphene, as a substrate for graphene devices has more aroused great interest in the graphene/hexagonal boron nitride heterostructure system. Based on the first principles method of density functional theory, the band structure, density of states, Mulliken population, and differential charge density of a tightly packed model of twisted graphene/hexagonal boron nitride/graphene sandwich structure have been studied. Through the establishment of heterostructure models twisted bilayer-graphene inserting hBN with different twisted angles, it was found that the band gap, Mulliken population, and charge density, exhibited specific evolution regulars with the rotation angle of the upper graphene, showing novel electronic properties and realizing metal–insulator phase transition. We find that the particular value of the twist angle at which the metal–insulator phase transition occurs and propose a rotational regulation mechanism with angular periodicity. Our results have guiding significance for the practical application of heterojunction electronic devices.

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Shin, Jaemin, Tyafur Pathan, Guanyu Zhou, and Christopher L. Hinkle. "(Invited) Bulk Traps in Layered 2D Gate Dielectrics." ECS Transactions 113, no. 2 (May 17, 2024): 25–33. http://dx.doi.org/10.1149/11302.0025ecst.

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In this work, we synthesize new 2D layered dielectrics and fabricate metal-insulator-metal (MIM) capacitors to determine their viability for scaled gate dielectrics (ZrNCl, HfNCl, BiOCl, and Mg(OH)2) in transition metal dichalcogenide-based transistors. While successful synthesis and fabrication was demonstrated, the properties of the dielectrics were decidedly underwhelming for device applications. The dielectric constants, in most cases, were only marginally better than SiO2 (k = 4-6), the leakage currents were too high due to poor band offsets, and most importantly, the bulk trap density, as seen previously in III-V devices, was very high. Overall, there still is no viable 2D gate dielectric for scaled field effect transistors.

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Sampaio-Silva, Alessandre, Gervásio Protásio dos Santos Cavalcante, Carlos Alberto B. Silva, and Jordan Del Nero. "Design of Molecular Positive Electronic Transition Device." Journal of Computational and Theoretical Nanoscience 18, no. 6 (June 1, 2021): 1714–23. http://dx.doi.org/10.1166/jctn.2021.9729.

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This work presents an investigation on the electronic transport of two devices based on Zigzag Phagraphene Nanoribbons of different widths (ZPGNR1 and ZPGNR2) with Nitrogen-doped edge terminations based on DFT-NEGF methodology using TranSIESTA code. Our results show different transport regimes: (i) ZPGNR1 device exhibits metallic behavior and metal-semiconductor transition when the bias voltage is increased, with symmetry on the eigenchannels (ECs) and the field-effect transistor (FET) signature; and (ii) ZPGNR2 device presents topological insulator (TI) behavior and two operation windows, the first with FET signature characterized by the TI-semiconductor transition and the second with resonant tunnel diode (RTD) signature with broken ECs symmetry due to potential barrier caused by N-doping at the edge and the central region is preferential transport path for the device, inherent to TI systems, generating a negative differential resistance (NDR). Another alternative for ZPGNR2 is to consider a current limiter device Molecular Positive Electronic Transition (MPET)-like.

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Sampaio-Silva, Alessandre, Gervásio Protásio dos Santos Cavalcante, Carlos Alberto B. Silva, and Jordan Del Nero. "Design of Molecular Positive Electronic Transition Device." Journal of Computational and Theoretical Nanoscience 18, no. 6 (June 1, 2021): 1714–23. http://dx.doi.org/10.1166/jctn.2021.9729.

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This work presents an investigation on the electronic transport of two devices based on Zigzag Phagraphene Nanoribbons of different widths (ZPGNR1 and ZPGNR2) with Nitrogen-doped edge terminations based on DFT-NEGF methodology using TranSIESTA code. Our results show different transport regimes: (i) ZPGNR1 device exhibits metallic behavior and metal-semiconductor transition when the bias voltage is increased, with symmetry on the eigenchannels (ECs) and the field-effect transistor (FET) signature; and (ii) ZPGNR2 device presents topological insulator (TI) behavior and two operation windows, the first with FET signature characterized by the TI-semiconductor transition and the second with resonant tunnel diode (RTD) signature with broken ECs symmetry due to potential barrier caused by N-doping at the edge and the central region is preferential transport path for the device, inherent to TI systems, generating a negative differential resistance (NDR). Another alternative for ZPGNR2 is to consider a current limiter device Molecular Positive Electronic Transition (MPET)-like.

36

Wang, Peng-Fei, Qianqian Hu, Tan Zheng, Yu Liu, Xiaofeng Xu, and Jia-Lin Sun. "Optically Monitored Electric-Field-Induced Phase Transition in Vanadium Dioxide Crystal Film." Crystals 10, no. 9 (August 29, 2020): 764. http://dx.doi.org/10.3390/cryst10090764.

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Vanadium dioxide (VO2), due to its electrically induced metal-to-insulator transition with dramatic changes in electrical and optical properties, is considered to be a powerful material for electro-optical devices. However, there are still some controversies about phase transition mechanism under voltage. Here, based on optical characterizations on VO2 crystal nanofilm during the whole process of phase transition, temporal evolution and spatial distribution of changes in electricity, optic and temperature are investigated simultaneously, to explore the mechanism. The variations of Raman spectrum and reflected spectrum, and changes in current and temperature are evidences for occurrence of phase transition, which exhibit different changing behaviors with time and space. These results offer a better understanding of the phase transition mechanism, implying that lattice structure of VO2 changes gradually after applying voltage until the structure is completely converted to metallic structure, which causes a rapid increase in carrier density, resulting in a rapid change in current, reflected spectrum and temperature. Temperature rise before phase transition and applied electric field alone are not enough for triggering metal-insulator transition, but these two factors can act synergistically on structural transformation to induce phase transition.

37

Mizsei, János, Jyrki Lappalainen, and Laszló Pohl. "Active thermal-electronic devices based on heat-sensitive metal-insulator-transition resistor elements." Sensors and Actuators A: Physical 267 (November 2017): 14–20. http://dx.doi.org/10.1016/j.sna.2017.09.052.

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38

Hong, X., A. Posadas, and C. H. Ahn. "Examining the screening limit of field effect devices via the metal-insulator transition." Applied Physics Letters 86, no. 14 (April 4, 2005): 142501. http://dx.doi.org/10.1063/1.1897076.

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39

M, Arunachalam, Thamilmaran P, and Sakthipandi K. "Effect of Sintering Temperature on Metal-Insulator Phase Transition in La1-xCaxMnO3 Perovskites." Frontiers in Advanced Materials Research 2, no. 1 (May 26, 2020): 37–42. http://dx.doi.org/10.34256/famr2014.

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Lanthanum calcium based perovskites are found to be advantageous for the possible applications in magnetic sensors/reading heads, cathodes in solid oxide fuel cells, and frequency switching devices. In the present investigation La0.3Ca0.7MnO3 perovskites were synthesised through solid state reaction and sintered at four different temperatures such as 900, 1000, 1100 and 1200˚ C. X-ray powder diffraction pattern confirms that the prepared La0.3Ca0.7MnO3 perovskites have orthorhombic structure with Pnma space group. Ultrasonic in-situ measurements have been carried out on the La0.3Ca0.7MnO3 perovskites over wide range of temperature and elastic constants such as bulk modulus of the prepared La0.3Ca0.7MnO3 perovskites was obtained as function of temperature. The temperature-dependent bulk modulus has shown an interesting anomaly at the metal-insulator phase transition. The metal insulator transition temperature derived from temperature-dependent bulk modulus increases from temperature 352˚ C to 367˚ C with the increase of sintering temperature from 900 to 1200˚ C.

40

Cheng, Shaobo, Min-Han Lee, Xing Li, Lorenzo Fratino, Federico Tesler, Myung-Geun Han, Javier del Valle, et al. "Operando characterization of conductive filaments during resistive switching in Mott VO2." Proceedings of the National Academy of Sciences 118, no. 9 (February 23, 2021): e2013676118. http://dx.doi.org/10.1073/pnas.2013676118.

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Vanadium dioxide (VO2) has attracted much attention owing to its metal–insulator transition near room temperature and the ability to induce volatile resistive switching, a key feature for developing novel hardware for neuromorphic computing. Despite this interest, the mechanisms for nonvolatile switching functioning as synapse in this oxide remain not understood. In this work, we use in situ transmission electron microscopy, electrical transport measurements, and numerical simulations on Au/VO2/Ge vertical devices to study the electroforming process. We have observed the formation of V5O9 conductive filaments with a pronounced metal–insulator transition and that vacancy diffusion can erase the filament, allowing for the system to “forget.” Thus, both volatile and nonvolatile switching can be achieved in VO2, useful to emulate neuronal and synaptic behaviors, respectively. Our systematic operando study of the filament provides a more comprehensive understanding of resistive switching, key in the development of resistive switching-based neuromorphic computing.

41

Klein, D. R., D. MacNeill, J. L. Lado, D. Soriano, E. Navarro-Moratalla, K. Watanabe, T. Taniguchi, et al. "Probing magnetism in 2D van der Waals crystalline insulators via electron tunneling." Science 360, no. 6394 (May 3, 2018): 1218–22. http://dx.doi.org/10.1126/science.aar3617.

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Magnetic insulators are a key resource for next-generation spintronic and topological devices. The family of layered metal halides promises varied magnetic states, including ultrathin insulating multiferroics, spin liquids, and ferromagnets, but device-oriented characterization methods are needed to unlock their potential. Here, we report tunneling through the layered magnetic insulator CrI3 as a function of temperature and applied magnetic field. We electrically detect the magnetic ground state and interlayer coupling and observe a field-induced metamagnetic transition. The metamagnetic transition results in magnetoresistances of 95, 300, and 550% for bilayer, trilayer, and tetralayer CrI3 barriers, respectively. We further measure inelastic tunneling spectra for our junctions, unveiling a rich spectrum consistent with collective magnetic excitations (magnons) in CrI3.

42

Rakshit, Abhishek, Karimul Islam, Anil Kumar Sinha, and Supratic Chakraborty. "Insulator-to-metal transition of vanadium oxide-based metal-oxide-semiconductor devices at discrete measuring temperatures." Semiconductor Science and Technology 34, no. 5 (April 4, 2019): 055001. http://dx.doi.org/10.1088/1361-6641/ab07d7.

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43

Yu, Wenhao, Luqiu Chen, Yifei Liu, Bobo Tian, Qiuxiang Zhu, and Chungang Duan. "Resistive switching polarity reversal due to ferroelectrically induced phase transition at BiFeO₃/Ca_0.96Ce_0.04MnO₃ heterostructures." Applied Physics Letters 122, no. 2 (January 9, 2023): 022902. http://dx.doi.org/10.1063/5.0132819.

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Ferroelectric resistive switching (RS) devices with functional oxide electrodes allow controlled emergent phenomena at an interface. Here, we demonstrate RS polarity reversal due to ferroelectrically induced phase transition at a doped charge transfer insulator interface. For BiFeO3/Ca0.96Ce0.04MnO3 bilayers grown on a NdAlO3 substrate, by applying voltages to a Ca0.96Ce0.04MnO3 bottom electrode, the resistance changes from a high resistance state (HRS) to a low resistance state (LRS) during a positive voltage cycle (0 → 3 → 0 V), and from a LRS to a HRS during a negative voltage cycle (0 → −3 → 0 V). The RS polarity is completely opposite the expected RS behavior in ferroelectric heterostructures induced by polarization reversal. It is proposed that the unique resistance switching polarity is attributed to the band-filling controlled metal-insulator transition in a Ca0.96Ce0.04MnO3 film, triggered by ferroelectric based electrostatic doping. The results address the importance of ferroelectric field effect on the electronic properties of the interfacial system in ferroelectric/complex oxide-based resistive memory devices.

44

Nishikawa, K., S. Takakura, M. Nakatake, M. Yoshimura, and Y. Watanabe. "Effect of surface modification by Ar⁺ ion irradiation on thermal hysteresis of VO₂." Journal of Applied Physics 133, no. 4 (January 28, 2023): 045305. http://dx.doi.org/10.1063/5.0132957.

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Vanadium dioxide (VO2) undergoes a metal–insulator phase transition at ∼70 °C. As this is a first-order phase transition, VO2 exhibits thermal hysteresis. The reflectivity and electrical resistivity of VO2 drastically change at insulator-to-metal ( TIMT) and metal-to-insulator ( TMIT) transition temperatures during heating and cooling, respectively. For smart glass and thermal memory applications employing VO2, the origin and control factor of thermal hysteresis must be investigated. Additional elemental doping and nano-structuring of VO2 affect the thermal hysteresis width. However, the factors determining TIMT and TMIT remain unclear. TIMT and TMIT can be modified by irradiating Ar+ on the surface of VO2 nanostructures with varying Ar+ irradiation doses ( nAr+) at 1 keV. The temperature-dependent reflectivity against IR light is evaluated. For VO2, TIMT decreases with nAr+ = 3.9 × 1014 cm−2; TMIT increases with nAr+ > 3.9 × 1015 cm−2. Ar+ irradiation decreases the thermal hysteresis width. Because the expected penetration depth of Ar+ at 1 keV into the VO2 surface is <6 nm, the VO2 chemical state at the outermost surface is investigated using x-ray absorption spectroscopy with soft x-ray irradiation. The V L-edge peak energy decreases with increasing nAr+ . Ar+ irradiation reduces V only at the outermost surface state. TIMT is more sensitive than TMIT to the reduction of V. The reduction of only a small fraction at the surface affects the phase transition of the entire VO2. These results are beneficial for understanding the cause of thermal hysteresis width and improving the performance of devices using VO2.

45

Zhang, Yanqing, Weiming Xiong, Weijin Chen, and Yue Zheng. "Recent Progress on Vanadium Dioxide Nanostructures and Devices: Fabrication, Properties, Applications and Perspectives." Nanomaterials 11, no. 2 (January 28, 2021): 338. http://dx.doi.org/10.3390/nano11020338.

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Vanadium dioxide (VO2) is a typical metal-insulator transition (MIT) material, which changes from room-temperature monoclinic insulating phase to high-temperature rutile metallic phase. The phase transition of VO2 is accompanied by sudden changes in conductance and optical transmittance. Due to the excellent phase transition characteristics of VO2, it has been widely studied in the applications of electric and optical devices, smart windows, sensors, actuators, etc. In this review, we provide a summary about several phases of VO2 and their corresponding structural features, the typical fabrication methods of VO2 nanostructures (e.g., thin film and low-dimensional structures (LDSs)) and the properties and related applications of VO2. In addition, the challenges and opportunities for VO2 in future studies and applications are also discussed.

46

Rafiq, Fareenpoornima, Parthipan Govindsamy, and Selvakumar Periyasamy. "Synthesis of a Novel Nanoparticle BaCoO2.6 through Sol-Gel Method and Elucidation of Its Structure and Electrical Properties." Journal of Nanomaterials 2022 (July 19, 2022): 1–15. http://dx.doi.org/10.1155/2022/3877879.

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The physical properties of cobalt oxide with varied oxidation states, and coordination numbers, in the transition series, have numerous applications. The present study explores the physical properties of BaCoO2.6 nanoparticles synthesized through the sol-gel method. The X-ray diffraction figure exhibits a 25 nm crystallite size hexagonal phase. The observational data shows the reduction in the real part of impedance ( Z ’ ), dielectric constant ( ξ ’ ), dielectric loss ( ξ ” ), and a raise in ac conductivity of mixed type of conduction with an elevation in frequency analyzed through impedance spectroscopy. The conductivity due to grain and grain boundaries is shown foremost in the complex impedance analysis. The plot of ∆ V / ∆ T (Seebeck coefficient) in the low-temperature range indicates p-type behavior and the metal-insulator transition in the as-synthesized sample. The sample characteristics suggest applications in optical and switching devices. The Seebeck coefficient is the generation of potential difference when subjected to temperature difference. Thermoelectric materials are associated with the concept of high electrical conductivity like crystals and low thermal conductivity to that of glass. Nanothermoelectric materials can decrease further the thermal conductivity through phonon scattering. Electrical characterization suggests the presence of both NTCR and PTCR behavior in the sample, and hence, it explores the application in thermistor/resistance temperature detector’s (RTD) and low dielectric constant and loss to electro-optical and higher conversion efficiency to storage devices. Additionally, impedance spectroscopy helps in the study of electrochemical systems and solid-state devices wherein the transition of metal-insulator is an add-on to the research.

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Ha, Sieu D., B. Viswanath, and Shriram Ramanathan. "Electrothermal actuation of metal-insulator transition in SmNiO3 thin film devices above room temperature." Journal of Applied Physics 111, no. 12 (June 15, 2012): 124501. http://dx.doi.org/10.1063/1.4729490.

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48

Yoon, Jongwon, Woong-Ki Hong, Yonghun Kim, and Seung-Young Park. "Nanostructured Vanadium Dioxide Materials for Optical Sensing Applications." Sensors 23, no. 15 (July 27, 2023): 6715. http://dx.doi.org/10.3390/s23156715.

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Vanadium dioxide (VO2) is one of the strongly correlated materials exhibiting a reversible insulator–metal phase transition accompanied by a structural transition from a low-temperature monoclinic phase to high-temperature rutile phase near room temperature. Due to the dramatic change in electrical resistance and optical transmittance of VO2, it has attracted considerable attention towards the electronic and optical device applications, such as switching devices, memory devices, memristors, smart windows, sensors, actuators, etc. The present review provides an overview of several methods for the synthesis of nanostructured VO2, such as solution-based chemical approaches (sol-gel process and hydrothermal synthesis) and gas or vapor phase synthesis techniques (pulsed laser deposition, sputtering method, and chemical vapor deposition). This review also presents stoichiometry, strain, and doping engineering as modulation strategies of physical properties for nanostructured VO2. In particular, this review describes ultraviolet-visible-near infrared photodetectors, optical switches, and color modulators as optical sensing applications associated with nanostructured VO2 materials. Finally, current research trends and perspectives are also discussed.

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Rai, R. K., R. B. Ray, G. C. Kaphle, and O. P. Niraula. "A Continuous Time Quantum Monte Carlo as an Impurity Solver for Strongly Correlated System." Journal of Nepal Physical Society 7, no. 3 (December 31, 2021): 14–26. http://dx.doi.org/10.3126/jnphyssoc.v7i3.42185.

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We assess the continuous-time quantum Monte Carlo (CT-QMC) technique with hybridization expansion for solvingthe electronic structure of the strongly correlated system LaxSr1−xVO3 . The impurity solver method implemented here shows the fair agreement with the other available Monte Carlo techniques. From the study, it is found that the CT-QMC technique clearly distinguishes metallic phase, quasiparticle phase and insulating phases of the system depending upon the strength of the correlation. In case of La0.33Sr0.67VO3 system the metal-insulator transition is found to be at U = 4.5 eV for β = 6(eV)−1. The value of U depends with the value of β, and also the value of Hund’s coupling (J) and bandwidth (W). This technique allows the particle to exchange with the reservoir of the particles and the impurity sites, which is accounted numerically to treat the temporal fluctuation of the fermionic systems termed as dynamical mean field theory (DMFT). This theory is used to explain the phenomena of MottHubbard metal insulator transition of the materials which are applicable for designing the Mottronics, Neuromorphic computing, Quantum computing and resistive memory devices.

50

Moon, Jaehyun, Ju-Hun Lee, Kitae Kim, Junho Kim, Soohyung Park, Yeonjin Yi, and Seung-Youl Kang. "Threshold Switching of ALD-NbO_x Films for Neuromorphic Applications." ECS Meeting Abstracts MA2023-02, no. 30 (December 22, 2023): 1558. http://dx.doi.org/10.1149/ma2023-02301558mtgabs.

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Neuromorphic architecture has been suggested as an alternative to the existing von Neumann counterpart. The neuromorphic approach allows massively parallel processing and asynchronous timing schemes with low power consumption. This work presents ALD- NbOx thin films as a potential material for neuromorphic computation. NbO2 shows metal-insulator transition which is the desired property for threshold switching (TS). However, direct forming of NbO2 is rather difficult and deposited NbOx tends predominantly to result in Nb2O5. To obtain NbO2 we used an oxygen scavenger layer of Ti to alter Nb2O5 to NbO2. After a proper electroforming process, the device with a Ti insert showed metal-insulator transition above a specific voltage, i.e., a threshold voltage, and a stable threshold switching characteristics with wide operation range, characteristics not observed in the absence of a Ti insert. The well-defined TS characteristics clearly indicated the Ti role in controlling the oxidation state of NbOx.To verify the oxidation state of NbOx, XPS depth profile analyses were used. The presence of a Ti insertion layer resulted in an increase of 10~30% in Nb4+ states, depending on the total thickness of the NbOx films, while Nb5+ states decreased. Bearing in mind practical applications, we used only CMOS-compatible materials and processes to fabricate TS devices. Our approach suggests a reliable method to fabricate NbO2 neurons. Acknowledgment: This work was supported by Electronics and Telecommunications Research Institute (ETRI) grant funded by the Korean government under grant " Non-CMOS Neuromorphic Device Basic Technology." (22BB1110).

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