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Author: Wei Guo (Ph. D.) Publisher: ISBN: Category : Languages : en Pages : 286
Book Description
Transition metals (TMs) have an immense range of intriguing physical properties and phenomena. Transition metals and transition metal oxides (TMOs) play a very important role in modern day scientific research and industry. TMs and TMOs exhibit an even broader range of structural, electrical, magnetic, and optical properties when fabricated as thin films on other materials compared to their the bulk forms. SrTiO3 (STO) is a widely used cubic perovskite oxide material known for its excellent electronic properties. When TMs and TMOs are integrated on STO, effects based on their interaction with STO have lead researchers to explore the physics behind such effects and their possible industrial device applications. In this thesis, we will mainly focus on the integration of TMs and TMOs with STO and with epitaxial STO grown on Si. The interactions of the transition metal Pt and rare earth metal Eu when deposited on STO by molecular beam epitaxy (MBE) were investigated. For Pt growth on STO, I investigated the properties of ultrathin Pt as a function of coverage on TiO2-terminated SrTiO3 substrate at different temperatures. I used in situ x-ray photoelectron spectroscopy (XPS), ex situ scanning electron microscopy (SEM) and atomic force microscopy (AFM) to observe the evolution of the electronic structure and surface morphology of Pt. I compared the electronic structure of Pt and the different growth patterns at low and high temperatures. I also performed high temperature annealing of low temperature-grown samples and found a “bubble-up” behavior of the continuous film. We also performed ultra-high vacuum deposition of Eu metal on STO (001) and achieved EuO epitaxy on STO via oxygen scavenging. I explored the oxygen scavenging behavior of Eu using STO films on Si by varying the STO thickness and Eu deposition temperature. In situ XPS was used to investigate the electronic structure of the nominal Eu/STO/Si stack. Our XPS results on the Eu/EuO stack revealed an unusual downward band bending at the interface. This is supported by density functional theory calculations by Gao. This work has been published in J. Appl. Phys. 121, 105302 (2017) and J. Appl. Phys. 124, 235301 (2018). Theoretical calculations performed in our group predicted the existence of a 2-dimensional electron gas (2DEG) at the EuO/STO interface and demonstrated that the 2DEG location can be controlled if an additional layer of BaTiO3 is included. To explore this effect on the 2DEG, I performed soft x-ray angle-resolved photoemission spectroscopy (SX-ARPES) with our collaborators at the Swiss Light Source. The results are currently being summarized for publication. For possible applications in Si photonics, I performed a detailed study of dry oxidation of a Si substrate below a thin epitaxial SrTiO3. Annealing time and temperature are the key factors to optimize the SiO2 thickness. I developed a theoretical model based on a modification of the Deal-Grove-Massoud formalism that predicted the thickness of SiO2 formed underneath STO as a function of time and temperature. The model fits the experimental data well. This work has been published in J. Appl. Phys. 127, 055302 (2020). In addition, I performed preliminary studies on free-standing STO membranes. I developed a fabrication process and performed Raman measurements. We also proposed a quantum well structure design of BaSnO3/SrTiO3/Al2O3 to make use of the conduction offset as large as ~3.5eV between BaSnO3 (BSO) and Al2O3. The whole deposition process is done by MBE and characterized by reflection high energy electron diffraction (RHEED) and XPS to confirm the BSO film quality. We are still working on improving the quantum well quality to be able to make multiple quantum well structures
Author: Wei Guo (Ph. D.) Publisher: ISBN: Category : Languages : en Pages : 286
Book Description
Transition metals (TMs) have an immense range of intriguing physical properties and phenomena. Transition metals and transition metal oxides (TMOs) play a very important role in modern day scientific research and industry. TMs and TMOs exhibit an even broader range of structural, electrical, magnetic, and optical properties when fabricated as thin films on other materials compared to their the bulk forms. SrTiO3 (STO) is a widely used cubic perovskite oxide material known for its excellent electronic properties. When TMs and TMOs are integrated on STO, effects based on their interaction with STO have lead researchers to explore the physics behind such effects and their possible industrial device applications. In this thesis, we will mainly focus on the integration of TMs and TMOs with STO and with epitaxial STO grown on Si. The interactions of the transition metal Pt and rare earth metal Eu when deposited on STO by molecular beam epitaxy (MBE) were investigated. For Pt growth on STO, I investigated the properties of ultrathin Pt as a function of coverage on TiO2-terminated SrTiO3 substrate at different temperatures. I used in situ x-ray photoelectron spectroscopy (XPS), ex situ scanning electron microscopy (SEM) and atomic force microscopy (AFM) to observe the evolution of the electronic structure and surface morphology of Pt. I compared the electronic structure of Pt and the different growth patterns at low and high temperatures. I also performed high temperature annealing of low temperature-grown samples and found a “bubble-up” behavior of the continuous film. We also performed ultra-high vacuum deposition of Eu metal on STO (001) and achieved EuO epitaxy on STO via oxygen scavenging. I explored the oxygen scavenging behavior of Eu using STO films on Si by varying the STO thickness and Eu deposition temperature. In situ XPS was used to investigate the electronic structure of the nominal Eu/STO/Si stack. Our XPS results on the Eu/EuO stack revealed an unusual downward band bending at the interface. This is supported by density functional theory calculations by Gao. This work has been published in J. Appl. Phys. 121, 105302 (2017) and J. Appl. Phys. 124, 235301 (2018). Theoretical calculations performed in our group predicted the existence of a 2-dimensional electron gas (2DEG) at the EuO/STO interface and demonstrated that the 2DEG location can be controlled if an additional layer of BaTiO3 is included. To explore this effect on the 2DEG, I performed soft x-ray angle-resolved photoemission spectroscopy (SX-ARPES) with our collaborators at the Swiss Light Source. The results are currently being summarized for publication. For possible applications in Si photonics, I performed a detailed study of dry oxidation of a Si substrate below a thin epitaxial SrTiO3. Annealing time and temperature are the key factors to optimize the SiO2 thickness. I developed a theoretical model based on a modification of the Deal-Grove-Massoud formalism that predicted the thickness of SiO2 formed underneath STO as a function of time and temperature. The model fits the experimental data well. This work has been published in J. Appl. Phys. 127, 055302 (2020). In addition, I performed preliminary studies on free-standing STO membranes. I developed a fabrication process and performed Raman measurements. We also proposed a quantum well structure design of BaSnO3/SrTiO3/Al2O3 to make use of the conduction offset as large as ~3.5eV between BaSnO3 (BSO) and Al2O3. The whole deposition process is done by MBE and characterized by reflection high energy electron diffraction (RHEED) and XPS to confirm the BSO film quality. We are still working on improving the quantum well quality to be able to make multiple quantum well structures
Author: Shriram Ramanathan Publisher: Springer Science & Business Media ISBN: 1441906649 Category : Technology & Engineering Languages : en Pages : 344
Book Description
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: Jason Lapano Publisher: ISBN: Category : Languages : en Pages :
Book Description
The three core tenants of materials science are theory, synthesis, and characterization. A solid theoretical framework is required for understanding of the problem at hand and using that knowledge to advance new areas of research. Synthesis of pristine materials is required to study the theory in a physical system and prevent misinterpretation of results. Complex structures and compositions are often the most interesting, and when defects and impurities are of interest, perfectly-imperfect samples are required which are often the most challenging to synthesize. Characterization of these materials is equally as important and complex, requiring careful sample preparation and experimental setups. Further, it is not always clear how to observe the property of scientific interest, and new characterization techniques must be developed. This dissertation focuses on using these three tenants to understand and advance the field of transition metal perovskite complex oxides using thin films of the incipient ferroelectrics CaTiO3 and SrTiO3 and antiferromagnetic Mott-Insulators LaVO3 and YVO3. The knowledge gained in this thesis can be applied to other complex oxide materials in better understanding magnetic and electronic transitions, high Tc superconductivity and quantum hall effect. Coupled with the relatively simple structure and ease of integration of multiple different chemical compounds into a single heterostructure leads to near numerous avenues to design functionality into materials.The first sections of this thesis begin with (1) an introduction to the basic science and past work in perovskite oxides, followed by (2) exploring the most common and promising synthesis routes, and finally (3) the various characterization methods used. The 4th chapter addresses the specific challenges of growth of ternary complex oxide thin films in an industrially profitable fashion. The three primary criterion that these deposition methods must adhere to is that they must (a) control film stoichiometry to less than 1% deviations, (b) deposit conformal coatings over standard 8 silicon wafers, (c) and exhibit deposition rates in excess of 1 m/hr. We show that these can be achieved using a hybrid molecular beam (hMBE) epitaxy approach and outline a route for commercially viable growth of complex oxides on silicon. This method is applied directly to the deposition of SrTiO3 on silicon for virtual single crystal perovskite substrates. The 5th chapter of this thesis discusses the effect of epitaxial strain, stoichiometry and interfacial coupling in heterostructures of complex oxides. In the (SrTiO3)n(CaTiO3)n series of superlattices grown by hMBE, it is found that interfacial energies play a large role in dictating the macroscopic properties, particularly ferroelectricity. In coherently strained thin films, both CaTiO3 and SrTiO3 exhibit relaxor-like ferroelectric behavior below room temperature. However, certain superlattices of these materials show nonpolar behavior when probed using second harmonic generation (SHG). High resolution scanning transmission electron microscopy (STEM) reveals that the symmetry in the superlattice is different from the individual parent compounds at the same strain state. It is found these are directly related to the high density of interfacial layers present in the films. Further, interfacial mixing of the constituent layers on certain superlattices leads to the development of a Ca1-xSrxTiO3 alloy which develops a ferroelectric moment at low temperatures, leading to spurious SHG signals. The findings of this experiment highlight the sensitivity of these complex layered structures to strain, stoichiometry, distortion coupling effects, and interfacial mixing.
Author: Alexander A. Demkov Publisher: Springer Science & Business Media ISBN: 146149320X Category : Technology & Engineering Languages : en Pages : 284
Book Description
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.
Author: Nini Pryds Publisher: Elsevier ISBN: 0081017529 Category : Technology & Engineering Languages : en Pages : 562
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: 9780387258027 Category : Technology & Engineering Languages : en Pages : 440
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: Marilyn Hawley Publisher: ISBN: Category : Science Languages : en Pages : 408
Book Description
The exceptional properties of multicomponent oxides, combined with the inability of simpler materials to meet the increasing demands of the electronics industry, have motivated tremendous interest and activity in utilizing multicomponent oxides for electronic applications. For these applications, it is often desirable to integrate complex oxides in thin-film form with other materials. This book focuses on common materials issues involved in the processing and characterization of multicomponent oxides and how these issues relate to device applications. Papers range from theoretical explanations of the magnetic and electronic properties of transition metal oxides, to integration with silicon technology. Noteworthy is the progress being made in the deposition and characterization of these complex materials, as well as their applicability in ferroelectric memories, MOSFETs, optical devices, infrared imaging arrays, etc. Topics include: epitaxial multicomponent oxide film growth; properties, characterization and modeling; properties of multicomponent oxides; and multicomponent oxide devices.
Author: Wei Guo (Ph. D.)
Author: Wei Guo (Ph. D.)
Author: Shriram Ramanathan
Author: Jason Lapano
Author: Alexander A. Demkov
Author: Nini Pryds
Author: Pandurang Ashrit
Author: Satishchandra B. Ogale
Author: L. Cook
Author: Marilyn Hawley
Author: C. Claeys