Surface Control of Epitaxial Manganite Films Via Oxygen Pressure
Surface Control of Epitaxial Manganite Films Via Oxygen Pressure

Author:

Publisher:

Published: 2015

Total Pages: 12

ISBN-13:

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The trend to reduce device dimensions demands increasing attention to atomic-scale details of structure of thin films as well as to pathways to control it. We found that this is of special importance in the systems with multiple competing interactions. We have used in situ scanning tunneling microscopy to image surfaces of La5/8Ca3/8MnO3 films grown by pulsed laser deposition. The atomically resolved imaging was combined with in situ angle-resolved X-ray photoelectron spectroscopy. We find a strong effect of the background oxygen pressure during deposition on structural and chemical features of the film surface. Deposition at 50 mTorr of O2 leads to mixed-terminated film surfaces, with B-site (MnO2) termination being structurally imperfect at the atomic scale. Moreover, a relatively small reduction of the oxygen pressure to 20 mTorr results in a dramatic change of the surface structure leading to a nearly perfectly ordered B-site terminated surface with only a small fraction of A-site (La, Ca)O termination. This is accompanied, however, by surface roughening at a mesoscopic length scale. The results suggest that oxygen has a strong link to the adatom mobility during growth. The effect of the oxygen pressure on dopant surface segregation is also pronounced: Ca surface segregation is decreased with oxygen pressure reduction.

Carbon Dioxide Reduction through Advanced Conversion and Utilization Technologies
Carbon Dioxide Reduction through Advanced Conversion and Utilization Technologies

Author: Yun Zheng

Publisher: CRC Press

Published: 2019-05-03

Total Pages: 274

ISBN-13: 1351597302

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Carbon Dioxide Reduction through Advanced Conversion and Utilization Technologies covers fundamentals, advanced conversion technologies, economic feasibility analysis, and future research directions in the field of CO2 conversion and utilization. This book emphasizes principles of various conversion technologies for CO2 reduction such as enzymatic conversion, mineralization, thermochemical, photochemical, and electrochemical processes. It addresses materials, components, assembly and manufacturing, degradation mechanisms, challenges, and development strategies. Applications of conversion technologies for CO2 reduction to produce useful fuels and chemicals in energy and industrial systems are discussed as solutions to reduce greenhouse effects and energy shortages. Particularly, the advanced materials and technology of high temperature co-electrolysis of H2O and CO2 to produce sustainable fuels using solid oxide cells (SOCs) are reviewed and the introduction, fundamentals, and some significant topics regarding this CO2 conversion process are discussed. This book provides a comprehensive and clear picture of advanced technologies in CO2 conversion and utilization. Written in a clear and detailed manner, it is suitable for students as well as industry professionals, researchers, and academics.

Development and Surface Science Investigations of Epitaxial Thin Films Suitable for Elucidating Mechanisms of Water Formation and Migration on the Moon
Development and Surface Science Investigations of Epitaxial Thin Films Suitable for Elucidating Mechanisms of Water Formation and Migration on the Moon

Author: Bijoya Dhar

Publisher:

Published: 2021

Total Pages: 136

ISBN-13:

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The growth and characterization of epitaxial thin films see ubiquitous use in both research and applications spanning a number of scientific and industrial fields with overlapping interests in materials science. The central theme of this work centers on leveraging the structural control afforded through the ultrahigh vacuum (UHV) approaches to thin-film epitaxy to derive atomically specific structure-chemistry relationships of key importance to various interface-mediated reactions. The first project was aimed at developing gold (Au) and ceria (CeO2) thin films using advanced surface-science techniques. In that project, a thoroughly wetted Au film on Ta metal substrate has been identified. This model system is necessary due to its potential candidacy as a promising electro-catalyst for oxygen reduction reaction (ORR) in proton exchange membrane fuel cell cathodes. The second film is CeO2(100), grown on a silver (Ag) single crystal substrate. Cerium oxide is a fascinating material with unique properties and has applications in many fields. The (100) plane of ceria is particularly interesting because it is the most active plane among the low index planes. Here in-situ growth of ceria islands on Ag has been reported.

Phase Control of Manganese Dioxide Thin Films by Plasma Assisted Laser Ablation
Phase Control of Manganese Dioxide Thin Films by Plasma Assisted Laser Ablation

Author: Maya Nadim Abi Akl

Publisher:

Published: 2009

Total Pages: 192

ISBN-13:

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The aim of this work is to investigate the growth of manganese dioxide thin film s by conventional Pulsed Laser Deposition (PLD) and Remote Plasma Assisted-PLD (RPA-PLD) in order to assess the role of plasma activation on promoting high oxid ation state of manganese and to improve the structural and morphological properties of the grown layers. For this purpose, films were grown on Si (100) substrate by K rF excimer laser ablation of a MnO target. The effects of substrate temperature, oxygen pressure and plasma activation on composition, crystallinity, structure, surface morphology, and growth rate were studied using Grazing Incidence X-Ray Diffraction (GIXRD), Fourier Transform Infra-Red Spectroscopy (FTIR), Raman Spec troscopy, Atomic Force Microscopy (AFM) and Surface Profilometry. The optimal temperature to grow manganese dioxide films in terms of crystalline quality was found to be 500 degreesC. Crystallinity appears to deteriorate at lo wer deposition temperature, while at higher temperature, the Dimanganese trioxid e phase is stabilized. Deposition at high oxygen pressures (250 and 500 mTorr) r esulted in the formation of stoichiometric manganese dioxide films, but the unde rlying structure of the layers was identified as gamma-manganese dioxide, consis ting of an irregular intergrowth of R- and beta-manganese dioxide which caused b roadening of XRD peaks and IR bands. Plasma activation of the process leads to l ittle improvement of film quality in this range of pressure. Alternatively, oper ation at low pressure values (1 to 50 mTorr) with plasma assistance was examined . While deposition in oxygen ambient in this pressure range led to the formation of di-manganese trioxide and Hausmanite, plasma activation induced a shift in t he Mn-O phase diagram allowing the synthesis of manganese dioxide, even at such low pressures. The corresponding films consisted of pure and highly crystalline beta-manganese dioxide with extremely smooth sur faces of roughness values as low as 0.5 nm. Such results highlight the necessity of using RPAPLD when aiming to grow high quality oxide films such as manganese dioxide.

Frontiers in Magnetic Materials
Frontiers in Magnetic Materials

Author: Anant V. Narlikar

Publisher: Springer Science & Business Media

Published: 2005-10-17

Total Pages: 813

ISBN-13: 3540272844

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Frontiers in Magnetic Materials focuses on the current achievements and state-of-the-art advancements in magnetic materials. Several lines of development- High-Tc Superconductivity, Nanotechnology and refined experimental techniques among them – raised knowledge and interest in magnetic materials remarkably. The book comprises 24 chapters on the most relevant topics written by renowned international experts in the field. It is of central interest to researchers and specialists in Physics and Materials Science, both in academic and industrial research, as well as advanced students.

Thin Film Analysis by X-Ray Scattering
Thin Film Analysis by X-Ray Scattering

Author: Mario Birkholz

Publisher: John Wiley & Sons

Published: 2006-05-12

Total Pages: 378

ISBN-13: 3527607048

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With contributions by Paul F. Fewster and Christoph Genzel While X-ray diffraction investigation of powders and polycrystalline matter was at the forefront of materials science in the 1960s and 70s, high-tech applications at the beginning of the 21st century are driven by the materials science of thin films. Very much an interdisciplinary field, chemists, biochemists, materials scientists, physicists and engineers all have a common interest in thin films and their manifold uses and applications. Grain size, porosity, density, preferred orientation and other properties are important to know: whether thin films fulfill their intended function depends crucially on their structure and morphology once a chemical composition has been chosen. Although their backgrounds differ greatly, all the involved specialists a profound understanding of how structural properties may be determined in order to perform their respective tasks in search of new and modern materials, coatings and functions. The author undertakes this in-depth introduction to the field of thin film X-ray characterization in a clear and precise manner.