The Control of Metal-insulator Transition in Vanadium Dioxide PDF Download

Author: Naga Phani B. Aetukuri
Publisher:
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Category :
Languages : en
Pages :

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The external control of the conductivity of correlated oxides is one of the most promising avenues towards realizing energy-efficient electronic devices. One of the prime candidates for such devices, vanadium dioxide (VO2), undergoes a temperature-driven metal-insulator transition (MIT) near room temperature (~340 K) with a concomitant change in crystal symmetry. First, using epitaxial strain provided by a variable thickness RuO2 buffer layer, we vary the MIT transition temperature of VO2 (001) films continuously from ~285 to ~345 K. We show, using strain-, polarization- and temperature-dependent x-ray absorption spectroscopy, in conjunction with x-ray diffraction and electrical transport measurements, that the transition temperature (TMIT) of VO2 is controlled by the orbital occupancy in its metallic state. Our results furthermore indicate that the magnitude of the structural distortion across the transition is also directly related to the orbital occupation in the metallic state. This work opens up the possibility of controlling the nature of the conducting state in atomically thin VO2 layers by manipulating the orbital occupancy by, for example, hetero-structural engineering. In a related study, we have used a combination of electron-beam and optical lithography to fabricate lateral two-terminal nano-devices from VO2 films deposited on TiO2 (001) substrates without RuO2 buffer layers. In these devices, we show that the transition can also be engendered by the application of modest electric fields, several orders of magnitude below the electric breakdown field, making this phenomenon potentially useful for two or three terminal switches. The delay time before switching is found to decrease with increasing electric field and temperature. We discuss whether these results indicate the transition is dominated by electronic or by Joule heating effects. These results demonstrate the possibility of triggering an MIT at low voltages and, therefore, at low energies, which is essential for device applications. Finally, we also discuss MIT in VO2-TiO2 based hetero-structures. We show that the temperature-driven MIT persists in VO2 films as thin as 1.8 nm.

Author: Xuefei Li
Publisher:
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Languages : en
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Nanomaterials provide exciting opportunities for the understanding and realization of their distinctive properties derived from the nanoscale dimensions. Vanadium dioxide (VO2) materials that exhibit metal-insulator transition (MIT) properties, with coupled structural transformations and abrupt changes in electrical and optical properties, serve as an example of such materials with unique fundamental dynamics and distinct properties at reduced dimensions.To illustrate the fundamental transition mechanisms on the nanoscale, and to construct switchable building blocks that can be integrated into nanoelectronic and nano-optical devices, advancements of synthesis routes to nanoscale VO2 materials need to be developed by overcoming intrinsic synthetic challenges associated with the stoichiometry and phase control. In this dissertation, I present such strategies for synthesizing VO2 nanostructures.This dissertation starts with an overview of nanomaterials syntheses in chapter 1, with emphasis on the synthesis of nanoscale heterostructures, post-synthetic composition and phase engineering of nanostructures via cation exchange processes, and the metal-insulator transition properties of the VO2 nanostructures. In chapter 2, I demonstrate a pathway to synthesize complex heterostructures enabled by Ag-Au-S reactive synthons, utilizing the phase segregation and cation exchange based methods introduced in chapter 1. The following chapters focus on strategies for the solution-based synthesis of VO2 nanostructures. Chapter 3 demonstrates a seeded approach for synthesizing VO2-TiO2-VO2 heterostructures, where VO2 domains nucleate and grow epitaxially on TiO2 nanorod seeds. The metal-insulator transition properties of the VO2 domains can be modulated by controlling the VO2 domain sizes as well as the TiO2-VO2 interfacial features. Chapter 4 describes a ZnO-templated synthesis of amorphous, morphologically pre-defined VO2 nanostructures, which can be thermally converted to crystalline VO2 nanostructures exhibiting metal-insulator transition properties. Chapter 5 demonstrates the synthesis of Mo-doped VO2 nanorod structures that are seeded by epitaxial MoO2 nanostructures, with controlled metal-insulator transition temperature as a function of Mo dopant distribution and concentration. This dissertation is summarized by Chapter 6, which provides insights into emerging fields of study enabled by expanded capabilities for synthesizing VO2 nanostructures.

Author: Shriram Ramanathan
Publisher: Springer Science & Business Media
ISBN: 1441906649
Category : Technology & Engineering
Languages : en
Pages : 344

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Thin Film Metal-Oxides provides a representative account of the fundamental structure-property relations in oxide thin films. Functional properties of thin film oxides are discussed in the context of applications in emerging electronics and renewable energy technologies. Readers will find a detailed description of deposition and characterization of metal oxide thin films, theoretical treatment of select properties and their functional performance in solid state devices, from leading researchers. Scientists and engineers involved with oxide semiconductors, electronic materials and alternative energy will find Thin Film Metal-Oxides a useful reference.

Author: Paolo Bettotti
Publisher: Springer
ISBN: 3319530356
Category : Technology & Engineering
Languages : en
Pages : 351

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This book covers the latest research on porous materials at the submicron scale and inspires readers to better understand the porosity of materials, as well as to develop innovative new materials. A comprehensive range of materials are covered, including carbon-based and organic-based porous materials, porous anodic alumina, silica, and titania-based sol-gel materials. The fabrication, characterization, and applications of these materials are all explored, with applications ranging from sensors, thermoelectrics, catalysis, energy storage, to photovoltaics. Also of practical use for readers are chapters that describe the basics of porous silicon fabrication and its use in optical sensing and drug delivery applications; how thermal transport is affected in porous materials; how to model diffusion in porous materials; and a unique chapter on an innovative spectroscopic technique used to characterize materials' porosity. This is an ideal book for graduate students, researchers, and professionals who work with porous materials.

Author: Theodor Schneller
Publisher: Springer Science & Business Media
ISBN: 3211993118
Category : Technology & Engineering
Languages : en
Pages : 801

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This is the first text to cover all aspects of solution processed functional oxide thin-films. Chemical Solution Deposition (CSD) comprises all solution based thin- film deposition techniques, which involve chemical reactions of precursors during the formation of the oxide films, i. e. sol-gel type routes, metallo-organic decomposition routes, hybrid routes, etc. While the development of sol-gel type processes for optical coatings on glass by silicon dioxide and titanium dioxide dates from the mid-20th century, the first CSD derived electronic oxide thin films, such as lead zirconate titanate, were prepared in the 1980’s. Since then CSD has emerged as a highly flexible and cost-effective technique for the fabrication of a very wide variety of functional oxide thin films. Application areas include, for example, integrated dielectric capacitors, ferroelectric random access memories, pyroelectric infrared detectors, piezoelectric micro-electromechanical systems, antireflective coatings, optical filters, conducting-, transparent conducting-, and superconducting layers, luminescent coatings, gas sensors, thin film solid-oxide fuel cells, and photoelectrocatalytic solar cells. In the appendix detailed “cooking recipes” for selected material systems are offered.

Author: Joseph Woicik
Publisher: Springer
ISBN: 3319240439
Category : Science
Languages : en
Pages : 576

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This book provides the first complete and up-to-date summary of the state of the art in HAXPES and motivates readers to harness its powerful capabilities in their own research. The chapters are written by experts. They include historical work, modern instrumentation, theory and applications. This book spans from physics to chemistry and materials science and engineering. In consideration of the rapid development of the technique, several chapters include highlights illustrating future opportunities as well.

Author: Tyler J. Huffman
Publisher:
ISBN:
Category : Physics
Languages : en
Pages :

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The salient feature of the familiar structural transition accompanying the thermally-driven metal-insulator transition in bulk vanadium dioxide (VO2) is a pairing of all the vanadium ions in the monoclinic M¬1 insulating phase. Whether this pairing (unit cell doubling) alone is sufficient to open the energy gap has been the central question of a classic debate which has continued for almost sixty years. Interestingly, there are two less familiar insulating states, monoclinic M2 and triclinic, which are accessible via strain or chemical doping. These phases are noteworthy in that they exhibit distinctly different V-V pairing. With infrared and optical photon spectroscopy, we investigate how the changes in crystal structure affect the electronic structure. We find that the energy gap and optical inter-band transitions are insensitive to changes in the vanadium-vanadium pairing. This result is confirmed by DFT+U and HSE calculations. Hence, our work conclusively establishes that intra-atomic Coulomb repulsion between electrons provides the dominant contribution to the energy gap in all insulating phases of VO2. VO2 is a candidate material for novel technologies, including ultrafast data storage, memristors, photonic switches, smart windows, and transistors which move beyond the limitations of silicon. The attractiveness of correlated materials for technological application is due to their novel properties that can be tuned by external factors such as strain, chemical doping, and applied fields. For advances in fundamental physics and applications, it is imperative that these properties be measured over a wide range of regimes. Towards this end, we study a single domain VO2 crystal with polarized light to characterize the anisotropy of the optical properties. In addition, we study the effects of compressive strain in a VO2 thin film in which we observe remarkable changes in electronic structure and transition temperature. Furthermore, we find evidence that electronic correlations are active in the metallic rutile phase as well. VO2 films exhibit phase coexistence in the vicinity of the metal-insulator transition. Using scanning near-field infrared microscopy, we have studied the patterns of phase coexistence in the same area on repeated heating and cooling cycles. We find that the pattern formation is reproducible each time. This is an unexpected result from the viewpoint of classical nucleation theory that anticipates some degree of randomness. The completely deterministic nature of nucleation and growth of domains in a VO2 film with imperfections is a fundamental finding. This result also holds promise for producing reliable nanoscale VO2 devices.

Author: Yi Long
Publisher: CRC Press
ISBN: 1000393577
Category : Science
Languages : en
Pages : 416

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The usage of building energy accounts for 30–40% of total energy consumption in developed countries, exceeding the amount for industry or transportation. Around 50% energy for building services is contributed by heating, ventilation, and air-conditioning (HVAC) systems. More importantly, both building and HVAC energy consumptions are predicted to increase in the next two decades. Windows are considered as the least energy-efficient components of buildings. Therefore, smart windows are becoming increasingly important as they are capable of reducing HVAC energy usage by tuning the transmitted sunlight in a smart and favoured way: blocking solar irradiation on hot days, while letting it pass through on cold days. Compared with other type of smart windows, thermochromic windows have the unique advantages of cost-effectiveness, rational stimulus, and passive response. This book covers fabrication of vanadium dioxide–based smart windows, discusses various strategies to enhance their performance, and shares perspectives from the top scientists in this particular field.

Author: Pandurang Ashrit
Publisher: Elsevier
ISBN: 0081017480
Category : Technology & Engineering
Languages : en
Pages : 378

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The phase transition and the reversible optical and electrical switching that occur in chromogenic materials under the influence of external forces such as heat, light, and electric field are topics of enormous scientific interest. Transition Metal Oxide Thin Film–Based Chromogenics and Devices discusses experimental and theoretical developments in the field of chromogenics based on the transition metal oxide (TMO) thin films. Understanding the relationship between the switching properties of TMO materials and their nanostructure is of paramount importance in developing efficient chromogenic devices. The tailoring of these switching behaviors is afforded detailed coverage in this book, alongside in-depth discussion of a range of chromogenic materials and devices, including photochromics, thermochromics, and electrochromics. Transition Metal Oxide Thin Film–Based Chromogenics and Devices covers both the theoretical aspects of TMO thin film–based chromogenics and their engineering applications in device construction. Academics and professionals in the fields of materials science and optics will find this book to be a key resource, whether their focus is low-dimension materials, light-materials interactions, or device development. - Enables researchers to keep up with developments in thin film–based chromogenics - Provides detailed coverage of the switching mechanism of the various TMO thin films to assist readers in developing more efficient devices - Offers in-depth discussion of a range of chromogenic materials and devices, including thermochromics, photochromics, and electrochromics

Author: Mengkun Liu
Publisher:
ISBN:
Category :
Languages : en
Pages : 316

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Abstract: The metal insulator transition in vanadates has been studied for decades and yet new discoveries still spring up revealing new physics, especially among two of the most studied members: Vanadium sesquioxide (V2 0 3 ) and Vanadium dioxide (VO2 ). Although subtleties abound, both of the materials have first order insulator to metal phase transitions that are considered to be related to strong electron-electron (e-e) correlation. Further, ultrafast spectroscopy of strongly correlated materials has generated great interest in the field given the potential to dynamically distinguish the difference between electronic (spin) response versus lattice responses due to the associated characteristic energy and time scales.In this thesis, I mainly focus on utilizing ultrafast optical and THz spectroscopy to study phase transition dynamics in high quality V2 0 3 and VO2 thin films epitaxially grown on different substrates. The main findings of the thesis are:(1) Despite the fact that the insulator to metal transition (IMT) in V2 03 is electron-correlation driven, lattice distortion plays an important role. Coherent oscillations in the far-infrared conductivity are observed resulting from coherent acoustic phonon modulation of the bandwidth W. The same order of lattice distortion induces less of an effect on the electron transport in VO 2 in comparison to V2 03 . This is directly related to the difference in latent heat of the phase transitions in VO2 and V2 03 .(2) It is possible for the IMT to occur with very little structural change in epitaxial strained VO2 films, like in the case of Cr doped or strained V2 03 . However, in V02 , this necessitates a large strain which is only possible by clamping to a substrate with larger c axis parameter through epitaxial growth. This is demonstrated for VO 2 films on TiO2 substrates.(3) Initiating an ultrafast photo-induced insulator-to-metal transition (IMT) is not only possible with above bandgap excitation, but also possible with high-field far-infrared excitation. With the help of the field enhancement in metamaterial split ring resonator gaps, we obtain picosecond THz electric field transients of several MV/cm which is sufficient to drive the insulator to metal transition in V0 2 .