 |
|
Discovery by UC Riverside physicists could enable development of faster computers
June 24, 2008RIVERSIDE, Calif. - Physicists at UC Riverside have made an accidental discovery in the lab that has potential to change how information in computers can be transported or stored. Dependent on the "spin" of electrons, a property electrons possess that makes them behave like tiny magnets, the discovery could help in the development of spin-based semiconductor technology such as ultrahigh-speed computers.
The researchers were experimenting with ferromagnet/semiconductor (FM/SC) structures, which are key building blocks for semiconductor spintronic devices (microelectronic devices that perform logic operations using the spin of electrons). The FM/SC structure is sandwich-like in appearance, with the ferromagnet and semiconductor serving as microscopically thin slices between which lies a thinner still insulator made of a few atomic layers of magnesium oxide (MgO).
The researchers found that by simply altering the thickness of the MgO interface they were able to control which kinds of electrons, identified by spin, traveled from the semiconductor, through the interface, to the ferromagnet.
Study results appear in the June 13 issue of Physical Review Letters.
Experimental results:
The spin of an electron is represented by a vector, pointing up for an Earth-like west-to-east spin; and down for an east-to-west spin.
In the researchers' experiment with the FM/SC structures, both spin up and spin down electrons were allowed to travel from the semiconductor to the ferromagnet.
The researchers found that when the structure's MgO interface is very thin (less than two atomic layers), spin down electrons pass through to the ferromagnet, while spin up electrons are reflected back, leaving only spin up electrons in the semiconductor.
They also found that when the interface is thicker than six atomic layers, both spin up and spin down electrons are reflected back, leaving electrons with zero net spin in the semiconductor.
But the surprising result for the researchers was that at an intermediate thickness, ranging from two to six atomic layers, the selectivity of the interface completely changes.
"We see a dramatic and complete reversal in the spin of electrons that pass through the interface," said Roland Kawakami, an assistant professor of physics who led the research team. "This time, spin up electrons pass through while spin down electrons are reflected back to the semiconductor. In other words, the thickness of the MgO interface determines whether spin up or spin down electrons are allowed to pass through it."
According to his research team, such a "spin reversal" can be used to control current flow.
Significance of the discovery:
"Electron spins are oriented at random in an ordinary electric circuit, and, therefore, do not affect current flow," explained Yan Li, the first author of the research paper, who made the discovery. "But if spin is polarized, that is, aligned in one direction, you can manipulate the flow of current and the transport of information - a feature that would be of great interest to the semiconductor industry. What is amazing is that only a couple of atomic layers of MgO can completely reverse the spin selection of the interface. This is unexpected because MgO is not a magnetic material."
Li, a graduate student in the Department of Physics and Astronomy working toward her doctorate in physics, said the research team will work next on making electronic devices based on the spin reversal. "This will not only test its feasibility for applications, but also help determine the cause of the spin reversal, which is still unclear," she said.
Kawakami's lab is one of very few labs in the world that perform both the advanced material synthesis and pulsed laser measurements needed for experiments with FM/SC structures.
"Without the strong interplay between the materials development and optical measurements, the type of discovery we made probably would not have been possible," Kawakami said.
A new area of research, spintronics already has helped develop disk-drive read heads and non-volatile memory chips. Researchers believe spintronics also will make "instant-on" computers one day, as well as chips that can store and process data.
University of California - Riverside
Study results appear in the June 13 issue of Physical Review Letters.
Experimental results:
The spin of an electron is represented by a vector, pointing up for an Earth-like west-to-east spin; and down for an east-to-west spin.
In the researchers' experiment with the FM/SC structures, both spin up and spin down electrons were allowed to travel from the semiconductor to the ferromagnet.
The researchers found that when the structure's MgO interface is very thin (less than two atomic layers), spin down electrons pass through to the ferromagnet, while spin up electrons are reflected back, leaving only spin up electrons in the semiconductor.
They also found that when the interface is thicker than six atomic layers, both spin up and spin down electrons are reflected back, leaving electrons with zero net spin in the semiconductor.
But the surprising result for the researchers was that at an intermediate thickness, ranging from two to six atomic layers, the selectivity of the interface completely changes.
"We see a dramatic and complete reversal in the spin of electrons that pass through the interface," said Roland Kawakami, an assistant professor of physics who led the research team. "This time, spin up electrons pass through while spin down electrons are reflected back to the semiconductor. In other words, the thickness of the MgO interface determines whether spin up or spin down electrons are allowed to pass through it."
According to his research team, such a "spin reversal" can be used to control current flow.
Significance of the discovery:
"Electron spins are oriented at random in an ordinary electric circuit, and, therefore, do not affect current flow," explained Yan Li, the first author of the research paper, who made the discovery. "But if spin is polarized, that is, aligned in one direction, you can manipulate the flow of current and the transport of information - a feature that would be of great interest to the semiconductor industry. What is amazing is that only a couple of atomic layers of MgO can completely reverse the spin selection of the interface. This is unexpected because MgO is not a magnetic material."
Li, a graduate student in the Department of Physics and Astronomy working toward her doctorate in physics, said the research team will work next on making electronic devices based on the spin reversal. "This will not only test its feasibility for applications, but also help determine the cause of the spin reversal, which is still unclear," she said.
Kawakami's lab is one of very few labs in the world that perform both the advanced material synthesis and pulsed laser measurements needed for experiments with FM/SC structures.
"Without the strong interplay between the materials development and optical measurements, the type of discovery we made probably would not have been possible," Kawakami said.
A new area of research, spintronics already has helped develop disk-drive read heads and non-volatile memory chips. Researchers believe spintronics also will make "instant-on" computers one day, as well as chips that can store and process data.
University of California - Riverside
UBC researchers put a new spin on electrons
In the first demonstration of its kind, researchers at the University of British Columbia have controlled the spin of electrons using a ballistic technique--bouncing electrons through a microscopic channel of precisely constructed, two-dimensional layer of semiconductor.
Device controls electron spin at room temperature
In a breakthrough for applied physics, North Carolina State University researchers have developed a magnetic semiconductor memory device, using GaMnN thin films, which utilizes both the charge and spin of electrons at room temperature.
Quantum dance: Discovery led by Princeton researchers could revolutionize computing
An international team of scientists, led by a Princeton University group, has observed an exciting and strange behavior in electrons' spin within a new material that could be harnessed to transform computing and electronics.
More Spin Electrons Current Events and Spin Electrons News Articles
 |
Handbook of Electron Spin Resonance by Charles P. Jr. Poole (Editor), Horacio A. Farach (Editor) Market: Physicists, chemists, biochemists, and biologists. Here's the first book to gather the vast range of experimental data in electron spin resonance (ESR) into a single volume. Concise yet comprehensive, it offers an easy-to-use collection of up-to-date experimental data, methods, and theory. The Handbook includes key contributions from leading scientists and provides over 200 tables and figures. Although specific ESR subfields are covered in numerous books and journals, the Handbook of Electron Spin Resonance is the only comprehensive reference to present extensive tabulation of data and experimental results. The Handbook also provides introductions to theoretical backgrounds, methods, and instrumentation. |
 |
Spin 2004: 16th International Spin Physics Symposium; Workshop On Polerized Electron Sources and Polarimeters by Kurt Aulenbacher (Author), Italy) Spin 200 (2004 Trieste (Author), Workshop on Polarized Electron Sources A (Author), Franco Bradamante (Editor), Andrea Bressan (Editor), Anna Martin (Editor) This comprehensive volume covers the most recent advances in the field of spin physics, including the latest research in high energy and nuclear physics and the study of nuclear spin structure. The comprehensive coverage also includes polarized proton and electron acceleration and storage, as well as polarized ion sources and targets. Many significant new results and achievements on the different topics considered at the symposium are presented in this book for the first time. |
 |
Single Electron Spin Measurements in Submicron Si MOS-FETs: Random Telegraph Signal, Single Electron Spin Resonance by Ming Xiao (Author) Presented is our measurements of a single electronic spin in the gate oxide of submicron-size silicon field effect transistors. Defects near the silicon and silicon dioxide interface have profound effects on the transistor conduction properties. For a submicron transistor, there might be only one isolated trap state that is within a proper tunneling distance regarding to both the coordinate and energy. We have studied the statistics and dynamics of individual defects extensively by random telegraph signal (RTS), the stochastic switching of the channel conductivity due to the trapping of single channel electrons by the defect. We also have, for the first time, studied the spin properties of these individual defects. By investigating the dependence of RTS statistics on a ... |
 |
Electron Spin Resonance Spectroscopy for Organic Radicals by Fabian Gerson (Author), Walter Huber (Author) Electron spin resonance spectroscopy is the method used to determine the structure and life expectancy of a number of radicals. Written by Fabian Gerson and Walter Huber, top experts in the field of electron spin resonance spectroscopy, this book offers a compact yet readily comprehensible introduction to the modern world of ESR. Thanks to its comprehensive coverage, ranging from fundamental theory right up to the treatment of all important classes of organic radicals and triplet-state molecules that can be analyzed using ESR spectroscopy, this unique book is suitable for users in both research and industry. Instead of using complex mathematical derivations, the authors present a readily understandable approach to the field by interpreting sample spectra and classifying experimental... |
|
|
Handbook of Electron Spin Resonance: Vol. 2 by Charles P. Jr. Poole (Editor), Horacio A. Farach (Editor) The continuously expanding field of electron spin resonance (ESR) has broadened our understanding of physics, chemistry, biology, medicine and related sciences over the last fifty years. In the first volume Professors Poole and Farach provided one of the first definitive reference tools for this field. These handbooks bring together wide-ranging data from diverse disciplines within ESR and integrate the data into a comprehesive and definitive resource. In this second volume of the Handbook of Electron Spin Resonance, the authors present a comprehensive source subfields of ESR not covered in the first volume. Topics covered in this volume include: * Sensitivity * Field Swept versus Frequency Swept Spectra * Resonators * Line Shapes * Electron Spin Echo Envelope Modulation *... |
 |
Electron Spin Resonance: Webster's Timeline History, 1958 - 2007 by Icon Group International (Author) Webster's bibliographic and event-based timelines are comprehensive in scope, covering virtually all topics, geographic locations and people. They do so from a linguistic point of view, and in the case of this book, the focus is on "Electron Spin Resonance," including when used in literature (e.g. all authors that might have Electron Spin Resonance in their name). As such, this book represents the largest compilation of timeline events associated with Electron Spin Resonance when it is used in proper noun form. Webster's timelines cover bibliographic citations, patented inventions, as well as non-conventional and alternative meanings which capture ambiguities in usage. These furthermore cover all parts of speech (possessive, institutional usage, geographic usage) and contexts, including... |
 |
New Applications of Electron Spin Resonance: Esr Dating, Dosimetry& Microscopy by M. Ikeya (Author) This book covers an interdisciplinary field between microwave spectroscopy of electron spin resonance (ESR) and chronology science or radiation dosimetry. The main object is to determine the elapsed time with ESR from forensic medicine to the age and radiation dose in earth and space science. This book is written primarily for earth scientists as well as for archaeologists and for physicists and chemists interested in new application of the method. This book can serve as an undergraduate and graduate school textbook on applications of ESR or electron paramagnetic resonance (EPR) to geological and archaelogical dating, radiation dosimetry and microscopic magnetic resonance imaging (MRI). Introduction to ESR (EPR) and chronology science and principle of ESR dating and dosimetry are... |
 |
Electron Spin Resonance: Analysis and Interpretation by P. Rieger (Author) Electron Spin Resonance covers the obtaining, analysing and interpreting of cw X-band ESR spectra of molecules with unpaired electron (s). The purpose of the book is to describe in mathematical terms the extraction of useful information from ESR spectra about the interaction of unpaired electrons with atoms in the molecules being studied. A reader familiar with quantum mechanics should gain a thorough understanding of the origins of the phenomena which make ESR spectra possible. The information that can be obtained from the spectra are explained in detail and in a logical step-by-step fashion. Examples of spectra of organic, inorganic and organometallic molecules, both in solution and in frozen solution are shown, analysed and interpreted and the mathematical basis of this... |
|
Electron Spin Resonance: A Review of Recent Literature to Mid-1986, Part B (Electron Spin Resonance; a Review of the Literature) by M. C. R. Symons (Author), Et Al (Author) Specialist Periodical Reports provide systematic and detailed review coverage of progress in the major areas of chemical research. Written by experts in their specialist fields the series creates a unique service for the active research chemist, supplying regular critical in-depth accounts of progress in particular areas of chemistry. For over 80 years the Royal Society of Chemistry and its predecessor, the Chemical Society, have been publishing reports charting developments in chemistry, which originally took the form of Annual Reports. However, by 1967 the whole spectrum of chemistry could no longer be contained within one volume and the series Specialist Periodical Reports was born. The Annual Reports themselves still existed but were divided into two, and subsequently three, volumes... | |
|
Electron Spin Resonance: A Comprehensive Treatise on Experimental Techniques by Charles P., Jr. Poole (Author) Second edition of classic reference offers overall summary and bibliography of experimental techniques and a balanced treatment of both theoretical and practical aspects of ESR instrumentation. Includes coverage of enhancement techniques, helices and acoustic spin resonance; how to build and use ESR spectrometer. References. 411 text figures. 1982 edition. |
| © 2009 BrightSurf.com |