Molecular Beam Epitaxial Growth And Characterization Of The Manganese Based Heusler Alloy Films For Application In Spintronics

This multi-contributor handbook discusses Molecular Beam Epitaxy (MBE), an epitaxial deposition technique which involves laying down layers of materials with atomic thicknesses on to substrates. It summarizes MBE research and application in epitaxial growth with close discussion and a ‘how to’ on processing molecular or atomic beams that occur on a surface of a heated crystalline substrate in a vacuum. MBE has expanded in importance over the past thirty years (in terms of unique authors, papers and conferences) from a pure research domain into commercial applications (prototype device structures and more at the advanced research stage). MBE is important because it enables new device phenomena and facilitates the production of multiple layered structures with extremely fine dimensional and compositional control. The techniques can be deployed wherever precise thin-film devices with enhanced and unique properties for computing, optics or photonics are required. This book covers the advances made by MBE both in research and mass production of electronic and optoelectronic devices. It includes new semiconductor materials, new device structures which are commercially available, and many more which are at the advanced research stage. Condenses fundamental science of MBE into a modern reference, speeding up literature review Discusses new materials, novel applications and new device structures, grounding current commercial applications with modern understanding in industry and research Coverage of MBE as mass production epitaxial technology enhances processing efficiency and throughput for semiconductor industry and nanostructured semiconductor materials research community

This book gives an overview of the physics of Heusler compounds ranging from fundamental properties of these alloys to their applications. Especially Heusler compounds as half-metallic ferromagnetic and topological insulators are important in condensed matter science due to their potential in magnetism and as materials for energy conversion. The book is written by world-leaders in this field. It offers an ideal reference to researchers at any level.

Over two volumes and 1500 pages, the Handbook of Spintronics will cover all aspects of spintronics science and technology, including fundamental physics, materials properties and processing, established and emerging device technology and applications. Comprising 60 chapters from a large international team of leading researchers across academia and industry, the Handbook provides readers with an up-to-date and comprehensive review of this dynamic field of research. The opening chapters focus on the fundamental physical principles of spintronics in metals and semiconductors, including an introduction to spin quantum computing. Materials systems are then considered, with sections on metallic thin films and multilayers, magnetic tunnelling structures, hybrids, magnetic semiconductors and molecular spintronic materials. A separate section reviews the various characterisation methods appropriate to spintronics materials, including STM, spin-polarised photoemission, x-ray diffraction techniques and spin-polarised SEM. The third part of the Handbook contains chapters on the state of the art in device technology and applications, including spin valves, GMR and MTJ devices, MRAM technology, spin transistors and spin logic devices, spin torque devices, spin pumping and spin dynamics and other topics such as spin caloritronics. Each chapter considers the challenges faced by researchers in that area and contains some indications of the direction that future work in the field is likely to take. This reference work will be an essential and long-standing resource for the spintronics community.

Faculties, publications and doctoral theses in departments or divisions of chemistry, chemical engineering, biochemistry and pharmaceutical and/or medicinal chemistry at universities in the United States and Canada.

The Bi1-xSbx alloy has garnered significant attention in the fields of semimetals and narrow bandgap semiconductors due to its unique properties in temperature and magnetic fields. The presence of topological surface states in bulk single crystals of the Bi1-xSbx alloy has sparked interest in exploring its potential for spin-orbit-torque (SOT) devices. Thin films of Bi1-xSbx exhibit high electrical conductivity, making them promising candidates for energy-efficient SOT devices. Previous studies have reported remarkable spin Hall angles and magnetization switching at ultralow current densities in Bi1-xSbx films interfaced with metallic ferromagnets, as well as giant unidirectional spin Hall magnetoresistance when interfaced with ferromagnetic semiconductors. These exciting findings have motivated further investigation into the growth of high-quality, single-crystal Bi1-xSbx films using molecular beam epitaxy (MBE) on various substrates. In this dissertation, we present a systematic study of epitaxial Bi1-xSbx thin films grown on (0001) sapphire substrates using MBE, incorporating a thin (Bi0.95,Sb0.05)2Te3 buffer layer. Various characterization techniques, including transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), atomic force microscopy (AFM), electrical transport, and Raman spectroscopy, were employed to investigate the microscopic structure, quality, and composition of the films. Raman spectroscopy provided valuable insights into the influence of strain on the phonon modes within the thin films. Our results demonstrate the successful growth of epitaxial Bi1-xSbx films with a well-defined growth direction, a crucial aspect for achieving high spin Hall angles in SOT devices. Furthermore, this dissertation emphasizes the effectiveness of characterization techniques for thin films, with a particular focus on XRD pole figure scans. Addressing the lack of standardized documentation in pole figure measurements, we present a clear and consistent approach, contributing to the development of a more standardized methodology in this area. To illustrate the capabilities of pole figure scans, analysis results from our own samples are presented. By comparing peak locations between the sample and substrate, we could assess the quality of epitaxial growth. Moreover, we suggest the potential for qualitative analysis of sample quality through pole figure measurements by examining the full width at half maximum (FWHM) values obtained from azimuthal scans at the maximum intensity, which may provide further insights into sample characteristics. Additionally, this dissertation provides an in-depth overview of two other characterization methods: XPS and Raman spectroscopy. XPS enables accurate analysis of elemental composition, oxidation states, and element migration in thin films. Precise determination of the composition ratio of Bi-Sb thin films using XPS measurements allows for adjustments in the growth process to enhance film quality. Raman spectroscopy, on the other hand, offers insights into bonding, crystal structure, contamination, strain, and material composition. By utilizing these complementary characterization techniques, a comprehensive understanding of Bi1-xSbx thin films can be achieved. Further investigations, such as detailed comparisons with Raman spectroscopy or the utilization of pole figure measurements, have the potential to enable the quantified reporting of strains and other challenging-to-measure information in thin film samples.

Proceedings of the NATO Advanced Study Institute on Molecular Beam Epitaxy (MBE) and Heterostructures, Erice, Italy, March 7-19, 1983