A Study of Phase Transition Mechanisms in Vanadium Dioxide Thin Films for Flat Panel Display Appliciations PDF Download

Author: Scott H. Beasor
Publisher:
ISBN:
Category : Metal-insulator transitions
Languages : en
Pages : 190

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Author: Joyeeta Nag
Publisher:
ISBN:
Category : Electronic dissertations
Languages : en
Pages : 192

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Author: Jaime Monzon Reyes
Publisher:
ISBN:
Category : Electric conductivity
Languages : en
Pages : 456

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Author:
Publisher:
ISBN:
Category : Dissertations, Academic
Languages : en
Pages : 396

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"Education, arts and social sciences, natural and technical sciences in the United States and Canada".

Author: Raul Torrico
Publisher:
ISBN: 9781321834154
Category : Phase transformations (Statistical physics)
Languages : en
Pages : 491

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Abstract: Vanadium Dioxide (VO2) has been garnering a lot of attention because of its ability to undergo a phase transition from insulator to metal when heated and to switch back to insulator when cooled. Here we use the scattering-type Near-Field Optical Microscope to study the changes caused in the optical properties by the phase transition in near-field regime of VO2 . We observe the growth of metallic VO2 puddles at varying temperatures from room temperature up to a critical temperature around 358 K. The insulator to metal transition causes the optical constants in VO2 to drastically change. Taking advantage of the change, coupling VO2 with plasmonic structures has the interesting effect of combining to form optical metamaterials. These man-made materials exhibit behaviors not found in nature. Using the Lumerical Solutions software, it is possible to model and simulate those optical behaviors for different types of noble metal plasmonic structures using insulating and metallic VO2 at different light sources. These metamaterials can be categorized as hybrid-tunable metamaterials which can be designed to filter certain resonance frequencies without having to change plasmonic structure.

Author: W. E. Case
Publisher:
ISBN:
Category :
Languages : en
Pages : 355

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A number of application concepts have emerged based on the idea that a phase transition thin film such as vanadium dioxide provides a high resolution, two-dimensional format for switching, recording, and processing optical signals. These applications range from high density optical disk recording systems and optical data processing to laser protection devices, infrared FLIRS and seekers, laser radar systems and IR scene simulators. All application candidates have a potential for providing either a totally new capability, an improved performance, a lower cost, or combinations of the three. Probably of greatest significance is the emergence of agile sensor concepts arising out of some of the film's special properties. These are represented by the above FLIRs, seekers and laser radar systems. A three year research program has been completed to advance the state-of-the-art in the preparation and charaterization of selected thin film phase transition materials. The objectives of the program were: a) to expand the data base and improve operational characteristics of Vought prepared vanadium dioxide thin films, b) to evolve process chemistry and subsequently characterize several new program materials, including rare-earth chalcogenides, organic semiconductor charge complexes, alloys of transition metal oxides, and metal-insulator cermets, and c) to spin-off new applications and concepts.

Author: J.G. Dash
Publisher: Springer Science & Business Media
ISBN: 1461330572
Category : Science
Languages : en
Pages : 369

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The Advanced Study Institute on Phase Transitions in Surface Films was held at the Ettore Majorana Centre for Scientific Cul ture in Erice, Sicily, during June 11 to June 25, 1979. This Institute was the second course of the International School of Low Temperature Physics which was established at the Centre in 1977, with the guidance and inspiration of T. Regge and A. Zichichi. The 1979 course selected a topic on one of the most rapidly advancing fields of condensed matter physics in the late 70's. The program of topics and speakers was developed with the advice of the Organizing Committee, composed of J. Friedel, N. D. Mermin, R. E. Peierls, T. Regge and J. Wheatley. These two weeks were memorable for the range and depth of the lectures and seminars, and the sustained high interest of the students and faculty through a damanding schedule of over 5 hours a day of formal sessions. A large fraction of the leading researchers in the field were there. It would have been impossible to gather such a large group five years earlier, for the field itself is hardly 10 years old. Although the foundations of the thermodynamics of surface films were laid down by Gibbs about 100 years ago, and experiments on oil/water monolayers were carried out by Pockels and Rayleigh at about the same time, the beginnings of the modern field were much more recent.

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: Felipe Rivera
Publisher:
ISBN:
Category : Crystallization
Languages : en
Pages : 95

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Crystalline films of vanadium dioxide were obtained through thermal annealing of amorphous vanadium dioxide thin films sputtered on silicon dioxide. An annealing process was found that yielded polycrystalline vanadium dioxide thin films, semi-continuous thin films, and films of isolated single-crystal particles. Orientation Imaging Microscopy (OIM) was used to characterize and study the phase and the orientation of the vanadium dioxide crystals obtained, as well as to differentiate them from other vanadium oxide stoichiometries that may have formed during the annealing process. There was no evidence of any other vanadium oxides present in the prepared samples. Indexing of the crystals for the orientation study was performed with the Kikuchi patterns for the tetragonal phase of vanadium dioxide, since it was observed that the Kikuchi patterns for the monoclinic and tetragonal phases of vanadium dioxide are indistinguishable by OIM. It was found that a particle size of 100 nm was in the lower limit of particles that could be reliably characterized with this technique. It was also found that all VO2 crystals large enough to be indexed by OIM had a preferred orientation with the C axis of the tetragonal phase parallel to the plane of the specimen.

Author: Ilya Valmianski
Publisher:
ISBN:
Category :
Languages : en
Pages : 92

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Vanadium oxides are a prototypical family of highly correlated oxides. In his dissertation, I present the study of two vanadium oxides in particular, V2O3 and VO2, which undergo simultaneously both a structural phase transition and a metal to insulator transition. While traditionally these phase transitions were studied in equilibrium, bulk, or in meso/macro-scale devices, in my work I focused on different modalities: fast, small, and strained. In my work on fast time scales during photoexcitation of V2O3 we found a novel meta-stable intermediate state that appears due to symmetry change in the monoclinic phase. This change occurs in the proximity of high temperature rhombohedral domains on length scales similar to those of electronic correlation. Our finding shows that the electronic and structural transitions in V2O3 have similar length scales but very different time scales. In VO2 and V2O3 nanoscale devices, we found a length-scale competition between Joule heating and electric field driven current induced metal to insulator transition. We proposed a novel thermoelectric model and performed simulations using finite element methods. Our modeling showed that the transition is highly inhomogeneous and the resulting filaments are surface bound with thermal gradients generating Seebeck electric fields on the order of 1000 V/cm. Finally, we studied pressurized and strained thin films in V2O3 and discovered strong strain relaxation for pressures of up to 500 MPa, which cause a deviation of thin film Pressure-Temperature phase diagram from bulk behavior. This strain relaxation relies on the difference between the structural and morphological length scales, which allows the formation of strain relaxing creases. Once those creases are fully strained, the thin films respond similarly to bulk samples.