Inherent stochasticity during insulator–metal transition in VO2

2021 ◽  
Vol 118 (37) ◽  
pp. e2105895118
Author(s):  
Shaobo Cheng ◽  
Min-Han Lee ◽  
Richard Tran ◽  
Yin Shi ◽  
Xing Li ◽  
...  
Keyword(s):  
Phase Transition ◽  
Resistive Switching ◽  
Structural Phase ◽  
Ex Situ ◽  
Structural Anisotropy ◽  
Neuromorphic Computing ◽  
Monoclinic Crystal ◽  
Transmission Electron ◽  
Insulator Metal Transition ◽  
Microscopic Studies

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.

Structural Phase Transition of Tungsten-Doped Vanadium Dioxide Nanopowders Prepared by Thermolysis

2008 ◽  
Vol 8 (3) ◽  
pp. 1417-1421 ◽  
Author(s):  
Zifei Peng ◽  
Wei Jiang ◽  
Heng Liu
Keyword(s):  
Phase Transition ◽  
Differential Scanning Calorimetry ◽  
Transition Temperature ◽  
Vanadium Dioxide ◽  
Structural Phase ◽  
Hysteresis Loops ◽  
Tungstic Acid ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Transmission Electron

Tungsten-doped vanadium dioxide (VO2) nanopowders were prepared by thermolysis of (NH4)5[(VO)6(CO3)4(OH)9] · 10H2O at low temperature, with active white powdery tungstic acid used as a substitutional dopant. The composition and microstructure of the powders were examined by X-ray diffraction, transmission electron microscope, and differential scanning calorimetry. The change in electrical resistance due to the S–M transition was measured from 0 to 150 °C by the four-probe method. Hysteresis loops and differential scanning calorimetry analysis of the samples indicated that the phase-transition temperature of VO2 nanopowders was 67.15 °C. For tungstendoped VO2 nanopowders, the temperature was reduced to 26.46 °C. After sintering the nanopowders, Tc rose from 26.46 °C to 34.85 °C with the sizes increasing to the bulk. A significant direct correlation between particle size and Tc was confirmed. The results indicated that white powdery tungstic acid is exceptionally effective as a dopant for reducing transition temperature.

scholarly journals Strain-controlled insulator–metal transition in YTiO3/SrTiO3 superlattices: effect of interfacial reconstruction

2017 ◽  
Vol 5 (38) ◽  
pp. 9898-9902 ◽  
Author(s):  
Xue-Jing Zhang ◽  
Peng Chen ◽  
Bang-Gui Liu
Keyword(s):  
Phase Transition ◽  
Structural Phase Transition ◽  
Structural Phase ◽  
Insulator Metal Transition

Strain-controlled insulator–metal transition and structural phase transition in YTiO3/SrTiO3 superlattices due to interfacial reconstruction.

The Structural Phase Transition in Individual Vanadium Dioxide Nanoparticles

2009 ◽  
Vol 1184 ◽  
Author(s):  
Felipe Rivera ◽  
Robert C. Davis ◽  
Richard Vanfleet
Keyword(s):  
Thin Films ◽  
Phase Transition ◽  
Vanadium Dioxide ◽  
Structural Phase ◽  
Polycrystalline Thin Films ◽  
Transmission Electron ◽  
Order Of Magnitude ◽  
Insulator Phase Transition ◽  
Means Of Transmission ◽  
Individual Particles

AbstractVanadium dioxide (VO2) single crystals undergo a structural first-order metal to insulator phase transition at approximately 68°C. This phase transition exhibits a resistivity change of up to 5 orders of magnitude in bulk specimens. We observe a 2-3 order of magnitude change in thin films of VO2. Individual particles with sizes ranging from 50 to 250 nm were studied by means of Transmission Electron Microscopy (TEM). The structural transition for individual particles was observed as a function of temperature. Furthermore, the interface between grains was also studied. We present our current progress in understanding this phase transition for polycrystalline thin films of VO2 from the view of individual particles.

scholarly journals Operando characterization of conductive filaments during resistive switching in Mott VO2

2021 ◽  
Vol 118 (9) ◽  
pp. e2013676118
Author(s):  
Shaobo Cheng ◽  
Min-Han Lee ◽  
Xing Li ◽  
Lorenzo Fratino ◽  
Federico Tesler ◽  
...  
Keyword(s):  
Resistive Switching ◽  
Vanadium Dioxide ◽  
Electrical Transport ◽  
Insulator Transition ◽  
Metal Insulator Transition ◽  
Neuromorphic Computing ◽  
Metal Insulator ◽  
Transmission Electron

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.

scholarly journals Giant nonvolatile resistive switching in a Mott oxide and ferroelectric hybrid

2019 ◽  
Vol 116 (18) ◽  
pp. 8798-8802 ◽  
Author(s):  
Pavel Salev ◽  
Javier del Valle ◽  
Yoav Kalcheim ◽  
Ivan K. Schuller
Keyword(s):  
Phase Transition ◽  
Electronic Properties ◽  
Real Time ◽  
Resistive Switching ◽  
Structural Phase ◽  
Metal Insulator Transition ◽  
Metal Insulator ◽  
Practical Applications ◽  
New Class ◽  
Order Of Magnitude

Controlling the electronic properties of oxides that feature a metal–insulator transition (MIT) is a key requirement for developing a new class of electronics often referred to as “Mottronics.” A simple, controllable method to switch the MIT properties in real time is needed for practical applications. Here we report a giant, nonvolatile resistive switching (ΔR/R > 1,000%) and strong modulation of the MIT temperature (ΔTc > 30 K) in a voltage-actuated V2O3/PMN-PT [Pb(Mg,Nb)O3-PbTiO3] heterostructure. This resistive switching is an order of magnitude larger than ever encountered in any other similar systems. The control of the V2O3 electronic properties is achieved using the transfer of switchable ferroelastic strain from the PMN-PT substrate into the epitaxially grown V2O3 film. Strain can reversibly promote/hinder the structural phase transition in the V2O3, thus advancing/suppressing the associated MIT. The giant resistive switching and strong Tc modulation could enable practical implementations of voltage-controlled Mott devices and provide a platform for exploring fundamental electronic properties of V2O3.

scholarly journals Phase Transition and Metallization of Orpiment by Raman Spectroscopy, Electrical Conductivity and Theoretical Calculation under High Pressure

Materials ◽  
2019 ◽  
Vol 12 (5) ◽  
pp. 784 ◽  
Author(s):  
Kaixiang Liu ◽  
Lidong Dai ◽  
Heping Li ◽  
Haiying Hu ◽  
Linfei Yang ◽  
...  
Keyword(s):  
Phase Transition ◽  
Electrical Conductivity ◽  
Raman Spectroscopy ◽  
High Pressure ◽  
First Principles ◽  
Theoretical Calculations ◽  
Structural Phase ◽  
Theoretical Research ◽  
Continuous Change ◽  
Transmission Electron

The structural, vibrational, and electronic characteristics in orpiment were performed in the diamond anvil cell (DAC), combined with a series of experimental and theoretical research, including Raman spectroscopy, impedance spectroscopy, atomic force microscopy (AFM), high-resolution transmission electron microscopy (HRTEM), and first-principles theoretical calculations. The isostructural phase transition at ~25.0 GPa was manifested as noticeable changes in the compressibility, bond lengths, and slope of the conductivity, as well as in a continuous change in the pressure dependence of the unit cell volume. Furthermore, a pressure-induced metallization occurred at ~42.0 GPa, accompanied by reversible electrical conductivity. We also determined the metallicity of orpiment at 45.0 GPa by first-principles theoretical calculations, and the results were in good agreement with the results of the temperature-dependent conductivity measurements. The HRTEM and AFM images of the recovered sample confirmed that orpiment remains in the crystalline phase with an intact layered structure and available crystal-shaped clusters. These high-pressure behaviors of orpiment present some crucial information on the structural phase transition, metallization, amorphization and superconductivity for the A2B3-type of engineering materials at high pressure.

Size and Interface Coherency Dependent Phase Transformation of Niobium Nanoparticles Embedded in Copper Matrix by Mechanical Alloying

2012 ◽  
Vol 602-604 ◽  
pp. 243-248
Author(s):  
Ruo Shan Lei ◽  
Shi Qing Xu ◽  
Ming Pu Wang ◽  
Ye Jun Li ◽  
Wei Hong Qi
Keyword(s):  
Phase Transition ◽  
Size Effects ◽  
Structural Phase ◽  
Sufficient Conditions ◽  
Copper Matrix ◽  
Transmission Electron Microscopy Observation ◽  
X Ray Diffraction ◽  
Microscopy Observation ◽  
X Ray ◽  
Transmission Electron

The object of this work is to investigate the interface and size effects on the structural phase transition of Nb nanoparticles (NPs) embedded in Cu matrix. By means of X-ray diffraction analysis and high-resolution transmission electron microscopy observation, it is found that higher coherency of the Cu/Nb interface benefits the occurrence of phase transition in Nb NPs with larger sizes. The sufficient conditions for the transition are: (1) the size of Nb NPs should be smaller than 8 nm; (2) the Cu/Nb interfaces should be semi-coherent or coherent. The experimental results are consistent with the predictions of Bond Energy model.

Characterization of phase-transition-induced micro-domain structures in vanadium dioxide

2014 ◽  
Vol 47 (2) ◽  
pp. 732-738
Author(s):  
Ping Lu ◽  
Jiadong Zhou ◽  
Xinling Liu ◽  
Zongtao Zhang ◽  
Fangfang Xu ◽  
...  
Keyword(s):  
Phase Transition ◽  
Vanadium Dioxide ◽  
Structural Phase ◽  
Group Method ◽  
M1 Phase ◽  
Domain Structures ◽  
Transmission Electron ◽  
First Order Transition ◽  
Antiphase Domains

The displacive structural phase transition of vanadium dioxide (VO2) from the high-temperature tetragonal rutile (R) phase to the low-temperature monoclinic M1 or M2 phase may induce the formation of a variety of domain structures. Here, all possible types of phase-transition-induced domain structures of the M1 and M2 phases have been theoretically formulated by using a general space group method. The predicted domain structures of the M1 phase, including mirror or rotation twins and antiphase domains, have been confirmed by transmission electron microscopy observation of VO2powders and films, while the antiphase domains have never been involved in previous studies. The changes undergone by domain structures during a thermal or electron-beam-induced phase transition have been investigated. These results may suggest the potential influence of domain structures on the nucleation and progress of phase transitions, which unambiguously affect the hysteresis behavior of the first-order transition of VO2.

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