Author: Ajay Kumar Yadav
Publisher:
ISBN:
Category :
Languages : en
Pages : 294
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Book Description
It is historically proven that artificial heterostructures are of paramount importance for both fundamental research and technological application. One distinguishable example is superlattices and quantum-well heterostructures of conventional semiconductors (III-V). Several fundamental observations such as two-dimensional electron gas, quantum confinement effect, quantum Hall effect and fractional quantum Hall effect, were first realized in artificial heterostructures of conventional semiconductors. On the technological front, artificial heterostructures of conventional semiconductors were found to revolutionize optoelectronic and high-speed electronic industry. Given the capability of artificial heterostructures to enable new physical phenomena, with an appropriate choice of material system, these heterostructures hold the potential to uncover hidden physical phenomena and exotic phases, which are otherwise not observed in bulk systems. One choice of such a system could be a strongly correlated material where the presence of strong electronic correlations has been known to enable unique electronic and magnetic properties. Complex oxides, in particular, are known to exhibit a strong interaction between various degrees of freedom available such as spin, charge, orbital and lattice degree, and thus offer a suitable choice of material system. In literature, one can find plenty of examples from different areas of research such as superconductivity, magnetism, ferroelectricity and thermoelectricity, where artificial superlattices led to the observation of fundamentally different behavior, compared to bulk superlattice constituents. These artificial superlattices and heterostructures continue to be the most promising candidate for exploring new phenomena and enhancing physical properties in complex oxide material systems. In this dissertation, artificial superlattices of complex oxides were synthesized in a thin-film geometry to enable the observation of fundamentally new physical phenomena, compared to their bulk counterparts, in few selected areas of investigation. First, I will present the experimental results on heat transport across superlattice structures composed of insulating perovskite oxides. The measured thermal conductivity of these artificial superlattices exhibited a unique phonon transport, i.e. coherent phonon transport, phenomenon that is extremely rare to observe in bulk form. The key element for enabling the coherent transport of phonon in these superlattice systems is the range of phonon wavelengths, which carry most of the heat in the material. The critical range being between 1-3 nanometers, the size of the system needs to reduce to this length scale in order to observe the effect of the wave nature of phonons on heat transport. Thus, superlattice structures offer an ideal candidate to search for this novel phenomenon. Several theoretical studies predicted the existence of these phenomena, but the experimental evidence of their existence remained largely absent or inconclusive. By synthesizing the superlattice of perovskite oxides, I’ve observed unambiguous evidence of the coherent transport of phonons at short-period superlattices of SrTiO3-CaTiO3 and BaTiO3-SrTiO3. In contrast to conventional heat conduction mechanisms, where phonon transport can be described by energy-carrying particles, the uniqueness of this phenomenon is highlighted by the fact that the wave aspect of phonons needs to be invoked to understand their transport behavior. After observing the wave nature of phonons in dictating heat conduction across periodic superlattices, other artificial heterostructures were studied to understand the nature of coherent phonon transport at the superlattice interfaces. Designed superlattice-like sequences, where the structural order can be controlled from a periodic sequence to a completely random sequence, were synthesized to further understand the role of the coherent scattering of phonons in thermal transport across superlattice structures. Next, I will discuss the experimental observation of another unique phenomenon, which was enabled by artificial superlattices of complex oxides in a different subject of research, i.e. ferroelectricity. Several theoretical studies on nanostructured ferroelectric systems such as nanodisc, nanocomposites, superlattices etc., predicted the stabilization of novel ferroelectric ground states. A number of different topologies of electrical polarization such as vortices and skyrmions, were predicted in ferroelectric nanostructures, which showed a strong resemblance to spin topologies such as skyrmion, merons etc. found in magnetic systems. Experimental confirmation for the existence of these exotic polarization states, however, remained absent. By leveraging the competition among charge, orbital and lattice degrees of freedom in superlattices of a paraelectric (SrTiO3) and ferroelectric (PbTiO3) material, vortex-antivortex structures of electrical polarization were stabilized in ferroelectric (PbTiO3) layers of PbTiO3-SrTiO3 superlattice. Only for a narrow range of superlattice periods, the polarization vortices are stabilized with a balance between one gradient energy associated with the non-uniform polarization profile of the vortex structure and the other’s electrostatic and elastic energies associated with depolarization fields and epitaxial constraints from the substrate, respectively. In the last section, I will describe unique and unusual phenomena associated with the existence of polarization vortices in paraelectric/ferroelectric superlattices. Superlattices of PbTiO3-SrTiO3 with varying periodicity showed a rich spectrum of characteristically different ferroelectric domains. Specifically, in the short-period regime, domain size was observed to evolve with a negative scaling coefficient, which is unusual for typical ferroelectrics. When the superlattice periodicity was increased, the average domain size decreased, suggesting an opposite behavior to the universal Kittel’s Law, where in the latter, an increase in ferroelectric thickness leads to an increase in the average domain size. Second, I will present intriguing results on the fundamental characteristics of polarization vortices as revealed from X-ray circular dichroism studies. The finite difference in absorption spectra of left-circular vs. right-circular polarized light from vortex structures, suggested that vortex-antivortex arrays are chiral in nature. The presence of chirality in polarization vortex structures is a characteristically different behavior compared to bulk ferroelectric systems where uniformly polarized regions are expected to exhibit a linear X-ray dichroism (i.e. a difference in the absorption spectra of linearly polarized light in a direction parallel and perpendicular to ferroelectric order). Lastly, a possibility of manipulating phonon dispersion using vortex ordering or vortex “lattice” is discussed, along with a hypothesis of inducing localization in propagative phonons.
Author: Evgeny Y. Tsymbal
Publisher: OUP Oxford
ISBN: 0191642223
Category : Science
Languages : en
Pages : 416
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Book Description
This book is devoted to the rapidly developing field of oxide thin-films and heterostructures. Oxide materials combined with atomic-scale precision in a heterostructure exhibit an abundance of macroscopic physical properties involving the strong coupling between the electronic, spin, and structural degrees of freedom, and the interplay between magnetism, ferroelectricity, and conductivity. Recent advances in thin-film deposition and characterization techniques made possible the experimental realization of such oxide heterostructures, promising novel functionalities and device concepts. The book consists of chapters on some of the key innovations in the field over recent years, including strongly correlated oxide heterostructures, magnetoelectric coupling and multiferroic materials, thermoelectric phenomena, and two-dimensional electron gases at oxide interfaces. The book covers the core principles, describes experimental approaches to fabricate and characterize oxide heterostructures, demonstrates new functional properties of these materials, and provides an overview of novel applications.
Author: Alex Frano
Publisher: Springer
ISBN: 3319070703
Category : Technology & Engineering
Languages : en
Pages : 162
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Book Description
This thesis presents the results of resonant and non-resonant x-ray scattering experiments demonstrating the control of collective ordering phenomena in epitaxial nickel-oxide and copper-oxide based superlattices. Three outstanding results are reported: (1) LaNiO3-LaAlO3 superlattices with fewer than three consecutive NiO2 layers exhibit a novel spiral spin density wave, whereas superlattices with thicker nickel-oxide layer stacks remain paramagnetic. The magnetic transition is thus determined by the dimensionality of the electron system. The polarization plane of the spin density wave can be tuned by epitaxial strain and spatial confinement of the conduction electrons. (2) Further experiments on the same system revealed an unusual structural phase transition controlled by the overall thickness of the superlattices. The transition between uniform and twin-domain states is confined to the nickelate layers and leaves the aluminate layers unaffected. (3) Superlattices based on the high-temperature superconductor YBa2Cu3O7 exhibit an incommensurate charge density wave order that is stabilized by heterointerfaces. These results suggest that interfaces can serve as a powerful tool to manipulate the interplay between spin order, charge order, and superconductivity in cuprates and other transition metal oxides.
Author: Nikolay Nikitenkov
Publisher: BoD – Books on Demand
ISBN: 953513003X
Category : Science
Languages : en
Pages : 446
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Book Description
Development of the thin film and coating technologies (TFCT) made possible the technological revolution in electronics and through it the revolution in IT and communications in the end of the twentieth century. Now, TFCT penetrated in many sectors of human life and industry: biology and medicine; nuclear, fusion, and hydrogen energy; protection against corrosion and hydrogen embrittlement; jet engine; space materials science; and many others. Currently, TFCT along with nanotechnologies is the most promising for the development of almost all industries. The 20 chapters of this book present the achievements of thin-film technology in many areas mentioned above but more than any other in medicine and biology and energy saving and energy efficiency.
Author: Tamalika Banerjee
Publisher: CRC Press
ISBN: 0429886896
Category : Science
Languages : en
Pages : 207
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Book Description
Oxide materials have been used in mainstream semiconductor technology for several decades and have served as important components, such as gate insulators or capacitors, in integrated circuits. However, in recent decades, this material class has emerged in its own right as a potential contender for alternative technologies, generally designated as ‘beyond Moore’. The 2004 discovery by Ohtomo and Hwang was a global trendsetter in this context. It involved observing a two-dimensional, high-mobility electron gas at the heterointerface between two insulating oxides, LaAlO3 and SrTiO3, supported by the rise of nascent deposition and growth-monitoring techniques, which was an important direction in materials science research. The quest to understand the origin of this unparalleled physical property and to find other emergent properties has been an active field of research in condensed matter that has united researchers with expertise in diverse fields such as thin-film growth, defect control, advanced microscopy, semiconductor technology, computation, magnetism and electricity, spintronics, nanoscience, and nanotechnology.
Author: Ōsaka Daigaku. Sangyō Kagaku Kenkyūjo
Publisher:
ISBN:
Category :
Languages : en
Pages : 780
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Book Description
Author: Nini Pryds
Publisher: Elsevier
ISBN: 0081017529
Category : Technology & Engineering
Languages : en
Pages : 562
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Book Description
Metal Oxide-Based Thin Film Structures: Formation, Characterization and Application of Interface-Based Phenomena bridges the gap between thin film deposition and device development by exploring the synthesis, properties and applications of thin film interfaces. Part I deals with theoretical and experimental aspects of epitaxial growth, the structure and morphology of oxide-metal interfaces deposited with different deposition techniques and new developments in growth methods. Part II concerns analysis techniques for the electrical, optical, magnetic and structural properties of thin film interfaces. In Part III, the emphasis is on ionic and electronic transport at the interfaces of Metal-oxide thin films. Part IV discusses methods for tailoring metal oxide thin film interfaces for specific applications, including microelectronics, communication, optical electronics, catalysis, and energy generation and conservation. This book is an essential resource for anyone seeking to further their knowledge of metal oxide thin films and interfaces, including scientists and engineers working on electronic devices and energy systems and those engaged in research into electronic materials. - Introduces the theoretical and experimental aspects of epitaxial growth for the benefit of readers new to the field - Explores state-of-the-art analysis techniques and their application to interface properties in order to give a fuller understanding of the relationship between macroscopic properties and atomic-scale manipulation - Discusses techniques for tailoring thin film interfaces for specific applications, including information, electronics and energy technologies, making this book essential reading for materials scientists and engineers alike
Author: Satishchandra B. Ogale
Publisher: Springer Science & Business Media
ISBN: 0387260897
Category : Technology & Engineering
Languages : en
Pages : 416
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Book Description
Oxides form a broad subject area of research and technology development which encompasses different disciplines such as materials science, solid state chemistry, physics etc. The aim of this book is to demonstrate the interplay of these fields and to provide an introduction to the techniques and methodologies involving film growth, characterization and device processing. The literature in this field is thus fairly scattered in different research journals covering one or the other aspect of the specific activity. This situation calls for a book that will consolidate this information and thus enable a beginner as well as an expert to get an overall perspective of the field, its foundations, and its projected progress.
Author:
Publisher: Academic Press
ISBN: 012812296X
Category : Technology & Engineering
Languages : en
Pages : 1881
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Book Description
Comprehensive Nanoscience and Technology, Second Edition, Five Volume Set allows researchers to navigate a very diverse, interdisciplinary and rapidly-changing field with up-to-date, comprehensive and authoritative coverage of every aspect of modern nanoscience and nanotechnology. Presents new chapters on the latest developments in the field Covers topics not discussed to this degree of detail in other works, such as biological devices and applications of nanotechnology Compiled and written by top international authorities in the field
Author: Satishchandra Balkrishna Ogale
Publisher: John Wiley & Sons
ISBN: 3527654887
Category : Technology & Engineering
Languages : en
Pages : 478
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Book Description
Functional oxides are used both as insulators and metallic conductors in key applications across all industrial sectors. This makes them attractive candidates in modern technology ? they make solar cells cheaper, computers more efficient and medical instrumentation more sensitive. Based on recent research, experts in the field describe novel materials, their properties and applications for energy systems, semiconductors, electronics, catalysts and thin films. This monograph is divided into 6 parts which allows the reader to find their topic of interest quickly and efficiently. * Magnetic Oxides * Dopants, Defects and Ferromagnetism in Metal Oxides * Ferroelectrics * Multiferroics * Interfaces and Magnetism * Devices and Applications This book is a valuable asset to materials scientists, solid state chemists, solid state physicists, as well as engineers in the electric and automotive industries.
