Download or read book Assessing the Effects of Biaxial Strain and Chemical Doping on the Magnetic and Electronic Properties of Epitaxial Europium Monoxide Films written by Alexander Melville and published by . This book was released on 2014 with total page 121 pages. Available in PDF, EPUB and Kindle. Book excerpt: The ferromagnetic semiconductor EuO, which possesses several record properties relevant to devices, has been researched in an attempt to enhance and understand this novel material, i.e., raising its Curie temperature (TC) and developing it as a viable electronic material, by investigating three distinct research directions for EuO: chemical doping via trivalent rare-earth cations, biaxial strain via substrates with varying degrees of lattice mismatch, and preservation via application of a well-chosen capping layer. The use of Lu3+ as a chemical dopant for enhancing the TC of EuO up to 119 K was established. The spin-polarization for the Lu-doped EuO thin film was measured to be 96%, confirming its near-complete spin-polarization. The effect of biaxial strain on TC for EuO thin films that are commensurately strained to the substrate was explored. The use LuAlO3, which imparts an asymmetric tensile strain of +0.4% strain and +1.5% strain along the [110] and [110] EuO directions, respectively, resulted in the reduction of the TC for commensurate EuO / LuAlO3 thin films of varying thicknesses. The strain-dependence was confirmed by comparing the series to an identical series grown on the lattice-matched, i.e., unstrained, substrate yttria-stabilized zirconia (YSZ). Biaxial compressive strain was explored by growing EuO thin films on both singlecrystal diamonds and epitaxial diamond thin films grown on silicon. Diamond is 2.2% smaller than EuO, so epitaxial integration of EuO on diamond was attempted in hopes of achieving symmetric 2.2% compressive strain. Though the EuO was epitaxial and free of extraneous phases and orientations, demonstrating the first instance of a ferromagnet epitaxially integrated with diamond, the EuO was not compressively strained, and no change in TC was observed. Finally, the formation of a protective Eu2O3 capping layer by controlled oxidation of the surface of EuO in vacuum was studied. The Eu2O3 was effective at preventing the degradation of the underlying EuO, as determined by the scanning tunneling electron microscopy and electron energy loss spectroscopy analysis. The analysis, in conjunction with X-ray diffraction experiments, demonstrated that the oxygen diffusion during the capping layer formation is heavily influenced by the presence of defects in the film.

Download or read book Study of Stoichiometric and Electron Doped Europium Monoxide Thin Film written by Pan Liu and published by . This book was released on 2014 with total page 108 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this dissertation, we have successfully prepared the high quality EuO films via pulsed laser deposition (PLD) on different substrates, which opens a new simple route to prepare this interesting material. The magnetic mechanism and properties as well as the electronic band structure have been investigated for different samples. For stoichiometric EuO, firstly the superexchange coupling within the next nearest neighbors of Eu atoms were studied by growing EuO films on different substrates. We discussed the implication of such results with regard to our understanding of the magnetic coupling between neighboring Eu spins. Resonant photoemission studies give strong support for an antiferromagnetic NNN superexchange coupling hybridization mechanism. Secondly, the study of magnetoelectric coupling at the EuO/BaTiO3 interface will be presented. The magnetic properties of EuO, including the critical exponents, grown on a ferroelectric substrate will be presented. The study illustrates an importance of charge doping in magnetoelectric coupling, which can be modulated by ferroelectric polarization reversal. The properties of EuO can be tuned much by charge carrier doping. Two common methods for realizing the electron doping were also studied in this dissertation, which are rare earth elements doping and oxygen vacancy doping. We will investigate the magnetization of EuO1−−[subscript]x thin films with different oxygen vacancy concentrations as a function of temperature and applied field. A magnetic polaron model that originates from the exchange coupling between the doped electrons and Eu 4f moments is utilized to account for the ferromagnetic ordering above 69 K. We also describe the evolution of the phases of the magnetic orders as the temperature is varied in EuO1−−[subscript]x . For rare earth elements doping, Gadolinium (Gd) and cerium (Ce) were chosen to be the dopants. There are changes in the texture growth and lattice constant seen with a small amount of rare earth elements in the films. The Curie temperatures are enhanced a lot by Gd and Ce doping. Angular-resolved photoemission spectroscopy reveals electron pockets around the points in Gd-doped and Ce-doped EuO, indicating that the band gap in EuO is indirect.

Download or read book Tailoring the Electronic Properties of Epitaxial Oxide Films Via Strain for SAW and Neuromorphic Applications written by Yang Dai and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Correlation between Structural and Electronic Properties of Co Evaporated Doped Organic Thin Films written by Daniela Donhauser and published by Cuvillier Verlag. This book was released on 2014-10-23 with total page 166 pages. Available in PDF, EPUB and Kindle. Book excerpt: Devices based on organic semiconductors, like organic light emitting diodes (OLEDs) or organic solar cells, often comprise electrochemically doped charge transport layers, which improve the performance of these devices. Although very efficient devices can be realized nowadays, a comprehensive description of the physical processes taking place in electrochemically doped thin films is still missing. For instance, it was shown for a variety of different material systems that the doping efficiency, defined as the number of free charge carriers compared to the number of incorporated dopants, often amounts to only a few per cent. The organic semiconductor CBP (4,4’-Bis(N-carbazolyl)-1,1’-biphenyl), doped with the transition metal oxide molybdenum oxide (MoO3), is used here as a model system to investigate the origin for this low doping efficiency. Results from different measurement techniques, like electron tomography, EF-TEM, PES, FTIR-spectroscopy and (temperature- dependent) electrical measurements were correlated to get insight into the origin of the low doping effiencies and to obtain a model to describe charge transport in MoO3-doped CBP films as a function of the doping concentration.

Download or read book Epitaxial Strain Electric Field and Domains Controlled Functionality Modulations in Complex Oxide Heterostructures written by Binod Paudel and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The perovskite 3d- transitional metal complex oxides offer opportunities to construct artificial heterostructures and chemical doping of atoms with different atomic radii resulting in similar crystal structures but diverse functionalities. The discovery of such functionalities has been possible because of the advances in synthesis, which enables fabrication of oxide heterostructures in the form of thin films, thus providing a rich ground to study their functional response with external stimuli, such as strain, electric field, and chemical pressure. In this dissertation, I investigate how such parameters can modulate different functionalities magnetic (interfacial and bulk), transport, and optical, in the three-class of heterostructures, namely: lightly doped manganite, multiferroic heterostructures, and rare-earth chromites.In the first work, I study the magneto-electric coupling at the heterostructure interface of a ferroelectric PbZr0.2Ti0.8O3 (PZT) and ferromagnetic La0.67Sr0.33MnO3 (LSMO) layers grown on an Nb-doped SrTiO3 (001) substrate utilizing polarized neutron reflectometry (PNR) in consort with ab initio-based density functional theory (DFT) calculations. The working conditions of the functional device are mimicked by gating the heterostructure with a Pt top electrode to apply an external electric field, which alters the magnitude and switches the direction of the ferroelectric (FE) polarization, across the PZT layer. PNR results show that the gated PZT/LSMO exhibits interfacial magnetic phase modulation attributed to ferromagnetic (FM) to A-antiferromagnetic (A-AF) phase transitions resulting from the accumulation of holes. When the net FE polarization points towards the interface (positive), the interface does not undergo a magnetic phase transition and retains its global FM-ordered state. In addition to changes in the interfacial magnetic ordering, the global magnetization of LSMO increases. while switching the polarization from positive to negative and it decreases vice versa. DFT calculations indicate that this enhanced magnetization also correlates with an out-of-plane tensile strain, whereas the suppressed magnetization for positive polarization is attributed to out-of-plane compressive strain. These calculations also show the coexistence of FM and A-AF -phases at zero out of plane strain. Charge modulations throughout the LSMO layer appear to be unaffected by strain, suggesting that these charge-mediated effects do not significantly change the global magnetization. Such results verify that the interfacial magnetic modulations are due to co-action of strain- and charge-mediated effects, which dominate at different length scales. In the second work, I study the microstructural evolution induced magnetism and transport properties of ferroelastic La0.9Sr0.1MnO3 (LSMO) epitaxial thin films grown on SrTiO3 (001) substrates with different miscut angles. The substrate miscut angle plays a critical role in controlling the in-plane magnetic anisotropy. The microscopic origin of such magnetic anisotropy is attributed to the formation of anisotropic stripe domains along the step terraces at the surface. The Curie temperature is found to be decreased and magnetoresistance gradually increases with the increase in miscut angles. The magnetization in the LSMO films was found to be selectively modulated by the antiferrodistortive phase transition of the SrTiO3 substrate. This phenomenon has been qualitatively explained by a strain-modified Stoner–Wohlfarth model. We conclude that the magnetization modulation by the SrTiO3 phase transition depends on h, the ratio of the applied magnetic field to the saturation field. Such modulation is only visible with h

Download or read book Processing of Epitaxial Oxyfluoride Films and Characterization of Their Physical Properties written by Jiayi Wang and published by . This book was released on 2020 with total page 148 pages. Available in PDF, EPUB and Kindle. Book excerpt: Controlling the carrier concentration in electronic materials via doping is of fundamental importance in engineering physical properties for applications in electronic devices. In ABO3 perovskites, altering the electron count on the B-site cation is typically achieved through A-site cation substitution. In contrast, there has been less exploration of anion substitution. For example, F - substitution for O 2- provides an alternative means to tailor the nominal B-site valence, the ionicity of the B-O bond, and the lattice volume. In the study of anion substitution, while bulk oxyfluorides have received interest over the last two decades, epitaxial perovskite oxyfluorides have only been reported in recent years. The goal of this project is to develop a mechanistic understanding of topotactic fluorination reactions in epitaxial perovskite films and the resultant effects on physical properties of the incorporated F content. In this work, I demonstrate a highly controllable fluorination process using as-grown SrMnO2.5 epitaxial thin films as a model system with polytetrafluoroethylene (PTFE) as F source. The F content is systemically controlled by the fluorination time. The F is found to incorporate by substituting for the in-site O, which provides a means of electron doping the transition metal perovskites. Upon fluorination, a c-axis expansion, resistivity increase, and blue-shift of the optical absorption features are observed. In addition, the F/O site occupancy in the SrMnO 2.5- d F g epitaxial thin film is successfully engineered using substrate-induced biaxial strain. The F is found to have an apical site preference under compressive strain while it has an equatorial site preference under tensile strain. This is the first report of the strain-induced anion arrangement in oxyfluoride thin films. The B-cation alloyed SrFex Mn1-x (O,F) 3-d system with different Fe substitution level is also investigated to reveal the B-cation and anion composition influence on structural, electronic, and optical properties. Keywords: fluorination, mixed-anion, oxyfluoride, perovskite, topotactic chemistry

Download or read book Strain induced Phenomenon in Complex Oxide Thin Films written by Ryan Haislmaier and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Complex oxide materials wield an immense spectrum of functional properties such as ferroelectricity, ferromagnetism, magnetoelectricity, optoelectricity, optomechanical, magnetoresistance, superconductivity, etc. The rich coupling between charge, spin, strain, and orbital degrees of freedom makes this material class extremely desirable and relevant for next generation electronic devices and technologies which are trending towards nanoscale dimensions. Development of complex oxide thin film materials is essential for realizing their integration into nanoscale electronic devices, where theoretically predicted multifunctional capabilities of oxides could add tremendous value. Employing thin film growth strategies such as epitaxial strain and heterostructure interface engineering can greatly enhance and even unlock novel material properties in complex oxides, which will be the main focus of this work. However, physically incorporating oxide materials into devices remains a challenge. While advancements in molecular beam epitaxy (MBE) of thin film oxide materials has led to the ability to grow oxide materials with atomic layer precision, there are still major limitations such as controlling stoichiometric compositions during growth as well as creating abrupt interfaces in multi-component layered oxide structures. The work done in this thesis addresses ways to overcome these limitations in order to harness intrinsic material phenomena.The development of adsorption-controlled stoichiometric growth windows of CaTiO3 and SrTiO3 thin film materials grown by hybrid MBE where Ti is supplied using metal-organic titatnium tetraisopropoxide material is thoroughly outlined. These growth windows enable superior epitaxial strain-induced ferroelectric and dielectric properties to be accessed as demonstrated by chemical, structural, electrical, and optical characterization techniques. For tensile strained CaTiO3 and compressive strained SrTiO3 films, the critical effects of nonstoichiometry on ferroelectric properties are investigated, where enhanced ferroelectric responses are only found for stoichiometric films grown inside of the growth windows, whereas outside of the optimal growth window conditions, ferroelectric properties are greatly deteriorated and eventually disappear for highly nonstoichiometric film compositions. Utilizing these stoichiometric growth windows, high temperature polar phase transitions are discovered for compressively strained CaTiO3 films with transition temperatures in excess of 700 K, rendering this material as a strong candidate for high temperature electronic applications. Beyond the synthesis of single phase materials using hybrid MBE, a methodology is presented for constructing layered (SrTiO3)n/(CaTiO3)n superlattice structures, where precise control over the unit cell layering thickness (n) is demonstrated using in-situ reflection high energy electron diffraction. The effects of interface roughness and layering periodicity (n) on the strain-induced ferroelectric properties for a series of n=1-10 (SrTiO3)n/(CaTiO3)n superlattice films are investigated. It is found that the stabilization of a ferroelectric phase is independent of n, but is however strongly dominated by the degree of interface roughness which is quantified by measuring the highest nth order X-ray diffraction peak splitting of each superlattice film. A counter-intuitive realization is made whereby a critical amount of interface roughness is required in order to enable the formation of the predicted strain-stabilized ferroelectric phase, whereas sharp interfaces actually suppress this ferroelectric phase from manifesting. It is shown how high-quality complex oxide superlattices can be constructed using hybrid MBE technique, allowing the ability to control layered materials at the atomic scale. Furthermore, a detailed growth methodology is provided for constructing a layered n=4 SrO(SrTiO3)n Ruddlesden-Popper (RP) phase by hybrid MBE, where the ability to deposit single monolayers of SrO and TiO2 is utilized to build the RP film structure over a time period of 5 hours. This is the first time that a thin film RP phase has been grown using hybrid MBE, where an a stable control over the fluxes is demonstrated during relatively long time periods of growth, which advantageously facilitates the synthesis of high-quality RP materials with excellent structural and chemical homogeneity.Additionally, this work demonstrates some major advancements in optical second harmonic generation (SHG) characterization techniques of ferroelectric thin film materials. The SHG characterization techniques developed here proved to be the bread-and-butter for most of the work performed in this thesis, providing a powerful tool for identifying the existence of strain-induced ferroelectric phases, including their temperature dependence and polar symmetry. The work presented in this dissertation will hopefully provide a preliminary road map for future hybrid MBE growers, scientists and researchers, to develop and investigate epitaxial strain and heterostructure layering induced phenomena in other complex oxide systems.

Download or read book Manipulating the Structural and Electronic Properties of Epitaxial NaNbO3 Films Via Strain and Stoichiometry written by Biya Cai and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Oxygen Incorporation During Low temperature Chemical Vapor Deposition and Its Effects on the Electronic Properties of Epitaxial Si and Si 1 x Ge x Films written by Peter V. Schwartz and published by . This book was released on 1992 with total page 270 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Chemical Abstracts written by and published by . This book was released on 2002 with total page 2566 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Magnetic Oxides written by Gerald F. Dionne and published by Springer Science & Business Media. This book was released on 2010-03-26 with total page 474 pages. Available in PDF, EPUB and Kindle. Book excerpt: Magnetic Oxides offers a cohesive up-to-date introduction to magnetism in oxides. Emphasizing the physics and chemistry of local molecular interactions essential to the magnetic design of small structures and thin films, this volume provides a detailed view of the building blocks for new magnetic oxide materials already advancing research and development of nano-scale technologies. Clearly written in a well-organized structure, readers will find a detailed description of the properties of magnetic oxides through the prism of local interactions as an alternative to collective electron concepts that are more applicable to metals and semiconductors. Researchers will find Magnetic Oxides a valuable reference.

Download or read book Ceramic Abstracts written by and published by . This book was released on 1998 with total page 250 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Fundamentals of Semiconductors written by Peter YU and published by Springer Science & Business Media. This book was released on 2007-05-08 with total page 651 pages. Available in PDF, EPUB and Kindle. Book excerpt: Excellent bridge between general solid-state physics textbook and research articles packed with providing detailed explanations of the electronic, vibrational, transport, and optical properties of semiconductors "The most striking feature of the book is its modern outlook ... provides a wonderful foundation. The most wonderful feature is its efficient style of exposition ... an excellent book." Physics Today "Presents the theoretical derivations carefully and in detail and gives thorough discussions of the experimental results it presents. This makes it an excellent textbook both for learners and for more experienced researchers wishing to check facts. I have enjoyed reading it and strongly recommend it as a text for anyone working with semiconductors ... I know of no better text ... I am sure most semiconductor physicists will find this book useful and I recommend it to them." Contemporary Physics Offers much new material: an extensive appendix about the important and by now well-established, deep center known as the DX center, additional problems and the solutions to over fifty of the problems at the end of the various chapters.

Download or read book Oxide Electronics written by Asim K. Ray and published by John Wiley & Sons. This book was released on 2021-04-12 with total page 628 pages. Available in PDF, EPUB and Kindle. Book excerpt: Oxide Electronics Multiple disciplines converge in this insightful exploration of complex metal oxides and their functions and properties Oxide Electronics delivers a broad and comprehensive exploration of complex metal oxides designed to meet the multidisciplinary needs of electrical and electronic engineers, physicists, and material scientists. The distinguished author eschews complex mathematics whenever possible and focuses on the physical and functional properties of metal oxides in each chapter. Each of the sixteen chapters featured within the book begins with an abstract and an introduction to the topic, clear explanations are presented with graphical illustrations and relevant equations throughout the book. Numerous supporting references are included, and each chapter is self-contained, making them perfect for use both as a reference and as study material. Readers will learn how and why the field of oxide electronics is a key area of research and exploitation in materials science, electrical engineering, and semiconductor physics. The book encompasses every application area where the functional and electronic properties of various genres of oxides are exploited. Readers will also learn from topics like: Thorough discussions of High-k gate oxide for silicon heterostructure MOSFET devices and semiconductor-dielectric interfaces An exploration of printable high-mobility transparent amorphous oxide semiconductors Treatments of graphene oxide electronics, magnetic oxides, ferroelectric oxides, and materials for spin electronics Examinations of the calcium aluminate binary compound, perovoksites for photovoltaics, and oxide 2Degs Analyses of various applications for oxide electronics, including data storage, microprocessors, biomedical devices, LCDs, photovoltaic cells, TFTs, and sensors Suitable for researchers in semiconductor technology or working in materials science, electrical engineering, and physics, Oxide Electronics will also earn a place in the libraries of private industry researchers like device engineers working on electronic applications of oxide electronics. Engineers working on photovoltaics, sensors, or consumer electronics will also benefit from this book.

Download or read book Thin Film Metal Oxides written by Shriram Ramanathan and published by Springer Science & Business Media. This book was released on 2009-12-03 with total page 344 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Materials Chemistry written by Bradley D. Fahlman and published by Springer. This book was released on 2018-08-28 with total page 817 pages. Available in PDF, EPUB and Kindle. Book excerpt: The 3rd edition of this successful textbook continues to build on the strengths that were recognized by a 2008 Textbook Excellence Award from the Text and Academic Authors Association (TAA). Materials Chemistry addresses inorganic-, organic-, and nano-based materials from a structure vs. property treatment, providing a suitable breadth and depth coverage of the rapidly evolving materials field — in a concise format. The 3rd edition offers significant updates throughout, with expanded sections on sustainability, energy storage, metal-organic frameworks, solid electrolytes, solvothermal/microwave syntheses, integrated circuits, and nanotoxicity. Most appropriate for Junior/Senior undergraduate students, as well as first-year graduate students in chemistry, physics, or engineering fields, Materials Chemistry may also serve as a valuable reference to industrial researchers. Each chapter concludes with a section that describes important materials applications, and an updated list of thought-provoking questions.

Download or read book Integration of Functional Oxides with Semiconductors written by Alexander A. Demkov and published by Springer Science & Business Media. This book was released on 2014-02-20 with total page 284 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book describes the basic physical principles of the oxide/semiconductor epitaxy and offers a view of the current state of the field. It shows how this technology enables large-scale integration of oxide electronic and photonic devices and describes possible hybrid semiconductor/oxide systems. The book incorporates both theoretical and experimental advances to explore the heteroepitaxy of tuned functional oxides and semiconductors to identify material, device and characterization challenges and to present the incredible potential in the realization of multifunctional devices and monolithic integration of materials and devices. Intended for a multidisciplined audience, Integration of Functional Oxides with Semiconductors describes processing techniques that enable atomic-level control of stoichiometry and structure and reviews characterization techniques for films, interfaces and device performance parameters. Fundamental challenges involved in joining covalent and ionic systems, chemical interactions at interfaces, multi-element materials that are sensitive to atomic-level compositional and structural changes are discussed in the context of the latest literature. Magnetic, ferroelectric and piezoelectric materials and the coupling between them will also be discussed. GaN, SiC, Si, GaAs and Ge semiconductors are covered within the context of optimizing next-generation device performance for monolithic device processing.