Film Deposition And Microfabrication Of Magnetic Tunnel Junctions With An Mgo Barrier
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Film Deposition And Microfabrication Of Magnetic Tunnel Junctions With An Mgo Barrier
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Author : Yuqing Du
language : en
Publisher:
Release Date : 2012
Film Deposition And Microfabrication Of Magnetic Tunnel Junctions With An Mgo Barrier written by Yuqing Du and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012 with categories.
Magnetic tunnel junctions (MTJs), which consist of a thin insulation layer sandwiched by two ferromagnetic (FM) layers, are among the key devices of spintronics that have promising technological applications for computer hard disk drives, magnetic random access memory (MRAM) and other future spintronic devices. The work presented here is related to the development of relevant techniques for the preparation and characterization of magnetic films, exchanged biased systems and MTJs. The fabrication and characterization of PtMn/CoFe exchange biased systems and MTJs with Al-O barriers were undertaken when the new Aviza StratIon fxP ion beam deposition tool was developed by the project consortium funded by DTI MNT. After the Nordiko 9550 spintronic deposition tool was installed at Plymouth, the work focused on the development of MTJ multilayer stacks with layer structures of CoFeB/MgO/CoFe/IrMn and IrMn/CoFeB/MgO/CoFeB to achieve coherent tunneling with a crystalline MgO barrier. The film deposition, microfabrication, magnetic field annealing, microstructural and nano-scale characterization, magnetic and magneto-transport measurement for these devices have been systematically studied to achieve smooth interfaces and desired crystallographic textures and magnetic properties of layer stacks. Magnetoresistance (MR) of up to 200% was obtained from MTJs with a layer structure of Ta/CuN/Ta/CoFeB/MgO/CoFe/IrMn/Ta and a CuN bottom electrode. Enhanced exchange anisotropy from the bottom pinned IrMn/CoFeB stacks has been obtained, which demonstrated the possibility of fabricating MTJs with CoFeB as both the top and bottom FM electrodes with strong exchange bias. The origin of the enhanced exchange bias field was studied by employing high resolution transmission electron microscopy (HRTEM) and x-ray magnetic circular dichroism (XMCD) to examine the mmicrostructure properties and element specific magnetic properties of the stacks. Results demonstrate that the enhanced exchange anisotropy in the IrMn/CoFeB system is closely associated with the increased uncompensated interfacial spins. MTJs with layered structures of IrMn/CoFeB/MgO/CoFeB were prepared based on this exchange bias system. However, further work is required for the optimisation of the (001) crystallographic textures of the CoFeB/MgO/CoFeB stack to achieve coherent tunneling.
Magnesium Boron Oxide Tunnel Barriers
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Author : John Creighton Read
language : en
Publisher:
Release Date : 2009
Magnesium Boron Oxide Tunnel Barriers written by John Creighton Read and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2009 with categories.
In this dissertation I investigate the materials physics of thin film growth processes for magnetic tunnel junctions (MTJs) and Josephson junctions (JJs). The studies I present focus primarily on the chemical, electronic, and structural properties of the tunnel barriers and their interfaces with the adjacent electrodes. I developed a growth process for making MgO (MgBO)-based MTJs, studied this film stack in detail, and also examined the materials properties of MgB2 oxidation processes and AlN tunnel barrier formation for JJ development. I conducted x-ray photoelectron spectroscopy (XPS) studies on CoFeB / MgO bilayers to explore the MgO growth process. MgO that is rf sputtered directly on CoFeB or on a thin Mg protective layer forms MgBO with promising physical and chemical properties. Post-growth annealing reduces Fe and Co oxides formed in the deposition process through a reaction of B from the electrode with O in the transition metal oxides. Annealing also causes an atomic rearrangement of the Mg, B, and O species in these barriers. In sputtered MTJs with thin barriers, reaction between B from the electrode and sputter deposited MgO is an inherent part of the formation of MgO-based MTJs. I studied the correlated results of scanning tunneling electron microscopy (STEM) utilizing electron energy-loss spectroscopy (EELS), scanning tunneling spectroscopy (STS), current-in-plane tunneling (CIPT), and magnetometry studies. These investigations show that MgBO barriers have fewer low energy defect states than MgO barriers and comparison of MTJs with MgBO barriers with MTJs with Mg/MgO bilayer barriers shows that MgBO barriers yield higher TMR values and lower RA values than MgO barriers of comparable thickness. MgBO MTJs are also compatible with permalloy-B (PyB) free electrodes that show desirable magnetic characteristics. The electrode B content is important for the formation of low defect MgBO barriers and for the use of superior Py-based electrode materials for spin torque magnetic random access memory (MRAM) and magnetic sensor applications. I also studied MgBO barriers in an exploration of the oxidation of MgB2 thin films. The oxidation of the MgB2 film surface forms MgBO that is chemically similar to the MgBO materials formed in MTJ structures. Exposure to N2 or O2 promotes formation of MgO on the MgB2 film surface which becomes completely composed of MgO if the oxidation process is carried out at elevated temperatures for an extended time. Lower temperatures form oxides similar to the native surface oxide, and promote formation of elemental B, and B sub-oxide near the film surface. These B species are likely to effect JJs made with these barrier formation processes. These chemical studies provide insights into optimal MgBO barrier formation techniques for future MgB2 -based JJ devices. Finally, I started developing growth processes for AlN tunnel barriers formed both by N beam exposure of Al films and by reactive rf sputtering of AlN in either Ar or N2 for use in Nb / AlN / Nb JJs. Both AlN growth processes introduce O into the AlN film, which could possibly be controlled with the use of a getter material during barrier deposition. These XPS studies show that when a pure N2 atmosphere is used for reactive rf sputtering of AlN, the film growth nitridizes the underlying Nb film, similar to the way MgO oxidizes CoFeB. These studies provide some insights as to optimal AlN barrier formation for JJ structures that can now be further developed.
Realization Of Cofeb Mgo Cofeb Magnetic Tunnel Junction Devices Through Materials Analysis Process Integration And Circuit Simulation
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Author : Sankha S. Mukherjee
language : en
Publisher:
Release Date : 2009
Realization Of Cofeb Mgo Cofeb Magnetic Tunnel Junction Devices Through Materials Analysis Process Integration And Circuit Simulation written by Sankha S. Mukherjee and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2009 with Integrated circuits categories.
"Spin based magnetic tunnel junctions (MTJs) consist of two ferromagnetic thin films separated by a nonmagnetic insulating barrier. The MTJ exhibits two switchable resistive states, making them ideal candidates for non-volatile memory. The discovery of high Tunneling Magnetoresistance (TMR) in MgO-based MTJs has brought spintronics into the forefronts of modern technology. A device structure CoFeB/MgO/CoFeB achieved by physical vapor deposition (PVD) has revolutionized the hard-drive industry to go beyond densities of gigabyte per square inch. There is increasing interest in the application of these devices toward other technical areas, such as sensors, logic and reconfigurable computing. In these structures, the thicknesses of the layers are in the order of a few nanometers. For integration of these devices in other platforms, particularly on silicon, to augment the well-developed CMOS technology, it is imperative to (1) investigate processing constraints, (2) develop appropriate physical models, and (3) build circuit models for effective circuit implementation. The work presented in this dissertation focuses on these three important aspects for the realization of CoFeB/MgO/CoFeB MTJs on silicon. A systematic annealing study has been carried out to investigate the role of boron in the device structure. It has been shown using electron energy loss spectroscopy (EELS), and 2D x-ray diffraction (2D XRD) that boron diffuses into MgO with an activation energy of 1.3±0.4 eV and facilitates the crystallization of CoFe with (200) out-of-plane oriented crystals, with MgO as a template. The grain size of CoFe has been definitively shown to be smaller than the grain size of MgO, which were otherwise believed to be the same. A process temperature of 385°C has been determined to be the optimum limit of processing. A low temperature (
Engineering And Characterization Of Alox Based Magnetic Tunnel Junctions
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Author : Chengxiang Ji
language : en
Publisher:
Release Date : 2008
Engineering And Characterization Of Alox Based Magnetic Tunnel Junctions written by Chengxiang Ji and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2008 with categories.
Spin Current
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Author : Sadamichi Maekawa
language : en
Publisher: Oxford University Press
Release Date : 2017
Spin Current written by Sadamichi Maekawa and has been published by Oxford University Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 2017 with Science categories.
In a new branch of physics and technology, called spin-electronics or spintronics, the flow of electrical charge (usual current) as well as the flow of electron spin, the so-called "spin current", are manipulated and controlled together. This book is intended to provide an introduction and guide to the new physics and applications of spin current.
Structural Modifications Of Epitaxial Mgo Based Tunnel Barriers For Engineering Magneto Transport Properties Of Magnetic Tunnel Junction Devices
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Author : Eran Amsellem
language : en
Publisher:
Release Date : 2015
Structural Modifications Of Epitaxial Mgo Based Tunnel Barriers For Engineering Magneto Transport Properties Of Magnetic Tunnel Junction Devices written by Eran Amsellem and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015 with categories.
Nanomagnetism And Spintronics
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Author : Yoshishige Suzuki
language : en
Publisher: Elsevier Inc. Chapters
Release Date : 2013-10-07
Nanomagnetism And Spintronics written by Yoshishige Suzuki and has been published by Elsevier Inc. Chapters this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013-10-07 with Science categories.
Current and voltage applied to the magnetic nanopillars induce a spin injection and an accumulation of nonequilibrium charges in a nanosize magnetic cell and result a spin torque exerted on the magnetic moment. Using such torques, we may amplify a precession of magnetization and induct a magnetization switching. These phenomena provide new techniques to write information into tiny magnetic cells and to construct oscillators and rectifiers that are several tens of nanometers in size. In this chapter, spin injections, and current and voltage-induced spin torques in magnetic multilayers, which show giant magnetoresistance effect in current-perpendicular-to-plane (CPP-GMR) geometry, and magnetic tunneling junctions are described. Further, mechanisms of spin injection and voltage-induced magnetization switching and its high-speed observations are explained. Then, phenomena related to spin injection, namely, spin-transfer oscillation and the spin-torque diode effect, are described. Finally, applications related to the spin-injection technology are reviewed.
Nanomagnetism And Spintronics
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Author : Teruya Shinjo
language : en
Publisher: Elsevier
Release Date : 2013-10-07
Nanomagnetism And Spintronics written by Teruya Shinjo and has been published by Elsevier this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013-10-07 with Science categories.
The concise and accessible chapters of Nanomagnetism and Spintronics, Second Edition, cover the most recent research in areas of spin-current generation, spin-calorimetric effect, voltage effects on magnetic properties, spin-injection phenomena, giant magnetoresistance (GMR), and tunnel magnetoresistance (TMR). Spintronics is a cutting-edge area in the field of magnetism that studies the interplay of magnetism and transport phenomena, demonstrating how electrons not only have charge but also spin. This second edition provides the background to understand this novel physical phenomenon and focuses on the most recent developments and research relating to spintronics. This exciting new edition is an essential resource for graduate students, researchers, and professionals in industry who want to understand the concepts of spintronics, and keep up with recent research, all in one volume. Provides a concise, thorough evaluation of current research Surveys the important findings up to 2012 Examines the future of devices and the importance of spin current
Growth And Characterization Of Epitaxial Feco Mgo Eus Magnetic Tunnel Junctions On Mgo Buffered 100 Si
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Author : Zhiwei Gao
language : en
Publisher:
Release Date : 2016
Growth And Characterization Of Epitaxial Feco Mgo Eus Magnetic Tunnel Junctions On Mgo Buffered 100 Si written by Zhiwei Gao and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016 with categories.
In the last few decades, due to the dramatic improvement of the TMR (tunneling magnetoresistance) effect in MTJs (Magnetic Tunnel Junctions), the data storage industry has been revolutionized. There are so many applications based on this technology, e.g.: read head in hard disk drives; magnetic sensors, etc., while its most advanced application nowadays is on the Magnetoresistive Random Access Memory (MRAM), a type of nonvolatile, high speed, high density, yet low power consumption memory - often termed the "universal memory" [1]. For most applications, magnetic tunnel junctions are fabricated with thin film technologies. In industry, they are mostly deposited by magnetron sputtering for mass production purposes. While in research laboratories, MBE (Molecular Beam Epitaxy), PLD (Pulsed Laser Deposition), and E-beam (Electron beam physical vapor deposition) are often used to deposit well-controlled, high quality layers. The very core component of an MRAM cell is an MTJ, which possesses the desired TMR effect. An MTJ basically consists two ferromagnetic materials separated by a thin insulator. Typically, the connection across the insulating layer is what we call a junction, and the layer is usually a few nanometers thick, which ensures that the junction is thin enough to let the electrons tunnel from one side of the insulator to the other. This is a purely quantum mechanical phenomenon and will be forbidden in classical physics because classically an insulator cannot conduct. In this thesis, we demonstrated the epitaxial growth of the tunnel junctions FeCo/MgO/EuS/Ti on MgO-buffered Si (100) wafers, and showed that TMR in these junction reaches up to 64% at 4.2K. We also discovered how different thicknesses of MgO and measurement temperatures affect the TMR of these junctions. We then optimized the growth conditions of the junctions, and used XPS (X-Ray Photoelectron Spectroscopy) to analyze their chemical characteristic features. The best TMR occurring at 1nm MgO thickness is a result of the competition between symmetry enhancement through MgO, and thickness induced multistep hopping.
Fabrication And Characterizations Of Fe Nacl Fe Magnetic Tunnel Junctions
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Author : Yuantao Ji
language : en
Publisher:
Release Date : 2015
Fabrication And Characterizations Of Fe Nacl Fe Magnetic Tunnel Junctions written by Yuantao Ji and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015 with categories.
The tunneling magnetoresistance (TMR) of magnetic tunnel junctions (MTJ) was discovered in the middle of the last century, and it has attracted many researchers' attention and led to a revolution in the field of data storage and magnetic sensing technologies over the past two decades. There are different methods of fabricating the magnetic tunnel junctions. The industry tends to use the sputtering method at room temperature, which is more time and cost effective. While in laboratories researchers tend to use high vacuum electron-beam deposition system or Molecular Beam Epitaxy system (MBE) to grow the layers at elevated temperatures to make them epitaxial. The basic structure of the magnetic tunnel junctions has two ferromagnetic electrode layers separated by a thin insulation barrier layer. Currently most industry is using cobalt-iron alloys as the ferromagnetic electrodes and magnesium oxide as the insulation layer. The most famous and profitable industrial products with this technology are non-volatile data storage and readout devices used in magnetic random access memory (MRAM) and hard disc drives. In this thesis, high vacuum electron-beam deposition system is used to grow Fe/NaCl/Fe magnetic tunnel junctions on Si (100). We found that epitaxial tunnel junctions were prone to pinholes and electrode oxidation which severely reduced tunneling magnetoresistance. The highest tunneling magnetoresistance achieved in this system was on polycrystalline tunnel barriers with a 0.7nm thin Mg layer insertion, the tunneling magnetoresistance of which was 22.3% at room temperature and 37.8% at 77K in liquid nitrogen.