Download or read book A Study of Phase Transition Mechanisms in Vanadium Dioxide Thin Films for Flat Panel Display Appliciations written by Scott H. Beasor and published by . This book was released on 2000 with total page 190 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Solid solid Phase Transition in Vanadium Dioxide Thin Films written by Joyeeta Nag and published by . This book was released on 2011 with total page 192 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Vanadium Dioxide written by Jaime Monzon Reyes and published by . This book was released on 1974 with total page 456 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Master s Theses Directories written by and published by . This book was released on 2001 with total page 396 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Education, arts and social sciences, natural and technical sciences in the United States and Canada".

Download or read book Near field Optical Investigation of Vanadium Dioxide Thin Films written by Raul Torrico and published by . This book was released on 2014 with total page 491 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Thin Film Phase Transition Materials Development Program written by W. E. Case and published by . This book was released on 1985 with total page 355 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Phase Transitions in Surface Films written by J.G. Dash and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 369 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Shining Light on the Phase Transitions of Vanadium Dioxide written by Tyler J. Huffman and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Solid Phase Crystallization of Vanadium Dioxide Thin Films and Characterization Through Scanning Electron Microscopy written by Felipe Rivera and published by . This book was released on 2007 with total page 95 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Vanadium Oxide Phase Transitions written by Ilya Valmianski and published by . This book was released on 2017 with total page 92 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Semiconductor metal Transition in Epitaxial VO 2 Thin Films on TiO 2 100 Considering a Phase Equilibrium written by Xing Zhong and published by . This book was released on 2013 with total page 133 pages. Available in PDF, EPUB and Kindle. Book excerpt: Vanadium dioxide (VO_2), standing out from the thermochromic vanadium oxide family (VO, V_2 O_3,V_2 O_5,VO_2), is intensively studied for its abrupt and reversible semiconductormetal transition (SMT) that happens slightly above room temperature (T_c 340 K). Interestingly, the transition can be triggered not only by temperature change, but also by many other forms of excitations, e.g. infrared irradiation, external strain, and applied voltage. The underlying mechanism of the transition is still in debate, and a model to describe the transport properties near T_c is needed for utilizing this material. Recent studies have revealed that near the transition, there is a phase coexistence between the semiconducting monoclinic phase and the metallic rutile phase in this material. In this presentation, the growth of epitaxial VO_2 thin films on TiO_2 substrates by chemical vapor deposition and the characterizations of their structural and electrical properties will be discussed. Detailed studies on DC resistivity, current-voltage characteristics and impedance spectroscopy of deposited films at various ambient temperatures have been performed. By considering the ensemble average of the transport properties of VO_2 films near T_c as a superposition of the transport properties of the two phases, and assuming a distribution of transition temperatures across the whole film, we have derived parameterized models to fit the temperature dependence of both resistivity and impedance of VO_2 thin films in the vicinity of SMT. Voltage triggered breakdown in micron-scale two-terminal planar VO_2 devices has been tested and modeled. An avalanching-like breakdown mechanism is elicited by considering a competition between Joule heating and heat dissipation, that could explain the faster-than-expected transition observed in this kind of devices. To further study the physics of SMT, the design and implementation of a cross-spectrum analyzer for measuring VO_2 transport noise near T_c will be demonstrated. Our preliminary results reveal a significant increase in the noise power spectral density near the transition, possibly induced by the metastability of current percolation.

Download or read book Phase Transition in Bulk Single Crystals and Thin Films of math mrow mi Mathvariant written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We have systematically studied a variety of vanadium dioxide (VO2) crystalline forms, including bulk single crystals and oriented thin films, using infrared (IR) near-field spectroscopic imaging techniques. By measuring the IR spectroscopic responses of electrons and phonons in VO2 with sub-grain-size spatial resolution (~20nm), we show that epitaxial strain in VO2 thin films not only triggers spontaneous local phase separations, but leads to intermediate electronic and lattice states that are intrinsically different from those found in bulk. Generalized rules of strain- and symmetry-dependent mesoscopic phase inhomogeneity are also discussed. Furthermore, these results set the stage for a comprehensive understanding of complex energy landscapes that may not be readily determined by macroscopic approaches.

Download or read book Insulator to Metal Transition Dynamics of Vanadium Dioxide Thin Films written by Scott Eric Madaras and published by . This book was released on 2020 with total page 146 pages. Available in PDF, EPUB and Kindle. Book excerpt: Vanadium Dioxide (VO2) is a strongly correlated material which has been studied for many decades. VO2 has been proposed for uses in technologies such as optical modulators, IR modulators, optical switches and Mott memory devices. These technologies are taking advantage of VO2’s insulator to metal transition (IMT) and the corresponding changes to the optical and material properties. The insulator to metal transition in VO2 can be accessed by thermal heating, applied electric field, or ultra-fast photo induced processes. Recently, thin films of VO2 grown on Titanium Dioxide doped with Niobium (TiO2:Nb), have shown promise as a possible UV photo detector with high quantum efficiency which utilizes a heterostructure between these two materials. In this work, the dynamics of the IMT on thin films of VO2 is explored. We show that surface plasmons generated in an Au thin film can induce the insulator to metal transition in a thin film of VO2 due to the enhanced electric field as well as help detect the IMT via changes in its resonance condition. Time resolved pump probe studies were also done on thin films of VO2 grown on TiO2 and TiO2:Nb, using UV photon energy of 3.1 eV (400nm wavelength). The fluence threshold of the IMT at 3.1 eV was significantly lower than published values for the 1.55 eV pump fluence. The time response of the IMT shows uncommon reflectivity dynamics in these samples. The response was partially attributed to internal interference of the reflected probe beam from the inhomogeneous layers formed inside the film by different phases of VO2, and can be elucidated by a diffusion model with respect to its optical properties. Finally, the photocurrent generation time constants for the sample with highest quantum efficiency are given and compared to its ultrafast photo induced IMT time constants.

Download or read book Excited State Dynamics and Semiconductor to Metallic Phase Transition of VO2 Thin Film written by and published by . This book was released on 2004 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: VO2 thin films deposited on fused-quartz substrates were prepared by a pulsed laser deposition technique. Vanadium dioxide shows an ultrafast, passive phase transition (PT) from a monoclinic semiconductor phase to a metallic tetragonal rutile structure when the sample temperature is above 68 degrees C. The fast PT also can be optically induced by laser excitation. In this paper, the authors report on the optical properties of prepared thin films by absorption and photoluminescence (PL) measurements. In addition, a degenerate-four-wave-mixing (DFWM) measurement also was conducted using a 30 ps YAG pulsed laser operated at 532 nm. It is the first time, to their knowledge, that large polarizability and relatively slow nanosecond excited state dynamical processes have been identified in VO2. The polarizability is found to be 300 times greater than the chi(exp 3) value of a CS2 reference. The mechanism for slow process is believed to be associated with the structural change. (3 figures, 15 refs.).

Download or read book Phase Transformation Kinetics in Thin Films Volume 230 written by M. Chen and published by . This book was released on 1992-02-28 with total page 390 pages. Available in PDF, EPUB and Kindle. Book excerpt: The MRS Symposium Proceeding series is an internationally recognised reference suitable for researchers and practitioners.

Download or read book Thin Films and Phase Transition on Surfaces written by M. Michailov and published by . This book was released on 1994 with total page 390 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Structure property Relationships of Oxide Surfaces and Interfaces written by and published by . This book was released on 2000 with total page 356 pages. Available in PDF, EPUB and Kindle. Book excerpt: