Electron Microscopy Studies Of Magnetic Tunnel Junctions
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Electron Microscopy Studies Of Magnetic Tunnel Junctions
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Author : Chak Chung Andrew Yu
language : en
Publisher:
Release Date : 1999
Electron Microscopy Studies Of Magnetic Tunnel Junctions written by Chak Chung Andrew Yu and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1999 with Ferromagnetism categories.
Ballistic Electron Magnetic Microscopy
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Author : William Horrocks Rippard
language : en
Publisher:
Release Date : 2001
Ballistic Electron Magnetic Microscopy written by William Horrocks Rippard and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2001 with categories.
Switching Studies Of Perpendicular Magnetic Anisotropy Materials And Magnetic Tunnel Junctions
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Author : Joseph Bukari Abugri
language : en
Publisher:
Release Date : 2019
Switching Studies Of Perpendicular Magnetic Anisotropy Materials And Magnetic Tunnel Junctions written by Joseph Bukari Abugri and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2019 with Electronic dissertations categories.
The development of new materials for spintronic applications, such as STT-MRAM, continues to expand at a rapid rate, attracting a great deal of research interest. Our group has tried to simplify the design of the perpendicular magnetic tunnel junction (pMTJ) stack by replacing the complex Co/Pd multilayer synthetic antiferromagnet pinning layer with a CoPd alloy. In my PhD work, I have studied systems in which these CoPd layers are used to pin the reference layers of pMTJs. We have examined the influence of composition, thickness, and seed layers on the coercivity, remanence and perpendicular anisotropy of CoPd alloys, and related them to their structural properties and switching behavior utilizing various characterization methods. Results utilizing First Order Reversal Curve (FORC) analysis, atomic force microscopy (AFM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), magnetic force microscropy (MFM), X-ray diffraction (XRD) and transmission electron microscopy (TEM) will be detailed in this dissertation. It will be clearly shown that improved magnetic properties depend upon improved crystal structure of the CoPd alloy, which in turn, depends upon the seed layer upon which it is grown.
Advanced Electron Microscopy Of Novel Ferromagnetic Materials And Ferromagnet Oxide Interfaces In Magnetic Tunnel Junctions
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Author :
language : en
Publisher:
Release Date : 2013
Advanced Electron Microscopy Of Novel Ferromagnetic Materials And Ferromagnet Oxide Interfaces In Magnetic Tunnel Junctions written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013 with categories.
We have studied novel ferromagnetic (FM) materials and FM electrode/tunnel barrier interfaces in magnetic tunnel junctions (MTJs) by advanced electron microscopy including scanning transmission electron microscopy (HRSTEM) and electron energy loss spectroscopy (EELS). MTJs are one of the prototypical spintronic devices, with applications in magnetic random access memory, sensors and read heads. The performance of MTJs depends on several factors, including the FM electrodes and the FM/tunnel barrier interfaces. Therefore, to realize the high performance of MTJs, we first need high quality ferromagnetic electrodes with high spin polarization. High-quality Fe3O4 and Fe4N electrodes with theoretically predicted -100% spin polarization were fabricated by various methods and investigated by HRSTEM and STEM EELS. The Fe3O4 and Fe4N thin films have low defect density and good crystallinity, but when integrated as electrodes in a MTJ, problems emerged. In a Fe4N/AlOx/Fe MTJ, the magnetoresistance was negative, but relatively small, due to a defective Fe3O4 reaction layer formed at the Fe4N/tunnel barrier interface revealed by HRSTEM and EELS. The interfacial reaction layer was thin and discontinuous which made direct imaging difficult. Therefore, STEM EELS was used to map out the reaction layer. A Fe3O4 reaction layer was also found in a nominally symmetric CoFe/AlOx/CoFe MTJs after annealing, which also exhibited inverse TMR and a non-symmetric bias dependence. We also investigated the MTJs with the Heusler alloy Co2MnSi as one or both electrode and crystalline MgO as the tunnel barrier, which exhibit quite high TMR due to coherent tunneling. We showed that the Co2MnSi/MgO interface in these junctions is dominated by a configuration of a pure Mn plane bonded across the interface to O. This was the first observation of that interface termination. HRSTEM images also show that the fraction of MnMn/O interface termination increases with increasing Mn concentration in the CMS electrode. With the help of electron microscopy, we have found methods to increase the TMR of MTJs with half metallic materials as electrodes including Fe3O4 and Co2MnSi. We believe that the potential of half metallic materials will be realized with the development of new materials and new design of FM/tunnel barrier interfaces.
Ballistic Electron Magnetic Microscopy
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Author : William Horrocks Rippard
language : en
Publisher:
Release Date : 2001
Ballistic Electron Magnetic Microscopy written by William Horrocks Rippard and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2001 with categories.
Electron transport through thin AlOx based magnetic tunnel junctions has also been studied at the nanometer length scale. The effective barrier height of these insulating barriers has been determined to be 1.25 +/- 0.5 eV. The transmission probability of hot electrons through these barriers has also been measured. Tunnel junctions prepared by thermal evaporation and sputter deposition are compared. While the effective barrier height of junctions formed by the two techniques are very similar, the electron transmission probabilities through the two types of barriers are different.
Transmission Electron Microscopy Characterisation For Development Of Cofeb Mgo Based Magnetic Tunnel Junctions
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Author : Viyada Harnchana
language : en
Publisher:
Release Date : 2011
Transmission Electron Microscopy Characterisation For Development Of Cofeb Mgo Based Magnetic Tunnel Junctions written by Viyada Harnchana and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2011 with categories.
Electron Microscopy And Analysis 2003
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Author : S McVitie
language : en
Publisher: CRC Press
Release Date : 2004-02-19
Electron Microscopy And Analysis 2003 written by S McVitie and has been published by CRC Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 2004-02-19 with Science categories.
Electron microscopy is now a mainstay characterization tool for solid state physicists and chemists as well as materials scientists. Containing the proceedings from the Electron Microscopy and Analysis Group (EMAG) conference in September 2003, this volume covers current developments in the field, primarily in the UK. These conferences are biennial events organized by the EMAG of the Institute of Physics to provide a forum for discussion of the latest developments in instrumentation, techniques, and applications of electron and scanning probe microscopies.
Scanning Tunneling Microscopy
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Author : H. Neddermeyer
language : en
Publisher: Springer Science & Business Media
Release Date : 2012-12-06
Scanning Tunneling Microscopy written by H. Neddermeyer and has been published by Springer Science & Business Media this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012-12-06 with Science categories.
The publication entitled "Surface Studies by Scanning Tunneling Mi Rl croscopy" by Binnig, Rohrer, Gerber and Weibel of the IBM Research Lab oratory in Riischlikon in 1982 immediately raised considerable interest in the sur face science community. It was demonstrated in Reference R1 that images from atomic structures of surfaces like individual steps could be obtained simply by scanning the surface with a sharp metal tip, which was kept in a constant distance of approximately 10 A from the sample surface. The distance control in scanning tunneling microscopy (STM) was realized by a feedback circuit, where the electri cal tunneling current through the potential barrier between tip and sample is used for regulating the tip position with a piezoelectric xyz-system. A similar experi mental approach has already been described by Young et al. for the determination l of the macroscopic roughness of a surface. A number of experimental difficulties had to be solved by the IBM group until this conceptual simple microscopic method could be applied successfully with atomic resolution. Firstly, distance and scanning control of the tip have to be operated with sufficient precision to be sensitive to atomic structures. Secondly, sample holder and tunneling unit have to be designed in such a way that external vibrations do not influence the sample-tip distance and that thermal or other drift effects become small enough during measurement of one image.
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.
Handbook Of Magnetic Materials
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Author : K.H.J. Buschow
language : en
Publisher: Elsevier
Release Date : 2007-12-15
Handbook Of Magnetic Materials written by K.H.J. Buschow and has been published by Elsevier this book supported file pdf, txt, epub, kindle and other format this book has been release on 2007-12-15 with Science categories.
Volume 17 of the Handbook on the Properties of Magnetic Materials, as the preceding volumes, has a dual purpose. As a textbook it is intended to be of assistance to those who wish to be introduced to a given topic in the field of magnetism without the need to read the vast amount of literature published. As a work of reference it is intended for scientists active in magnetism research. To this dual purpose, Volume 17 of the Handbook is composed of topical review articles written by leading authorities. In each of these articles an extensive description is given in graphical as well as in tabular form, much emphasis being placed on the discussion of the experimental material in the framework of physics, chemistry and material science. It provides the readership with novel trends and achievements in magnetism. *composed of topical review articles written by leading authorities *intended to be of assistance to those who wish to be introduced to a given topic in the field of magnetism *as a work of reference it is intended for scientists active in magnetism research *provide the readership with novel trends and achievements in magnetism