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Erbium Emission from Silicon Based Photonic Bandgap Materials

MRS Online Proceedings Library (OPL) 2011年第1期638卷 F17.2.1-F17.2.1页

作者： Herman A. Lopez J. Eduardo Lugo Selena Chan Sharon M. Weiss Christopher C. Striemer Philippe M. Fauchet Materials Science Program Electrical and Computer Engineering University of Rochester Rochester NY 14627 U.S.A Centro de Investigacion en Energia UNAM A.P. 34 C.P. 62580 Morelos Mexico Center for Future Health Electrical and Computer Engineering University of Rochester Rochester NY 14627 U.S.A Institute of Optics and Electrical and Computer Engineering University of Rochester Rochester NY 14627 U.S.A Department of Electrical and Computer Engineering University of Rochester Rochester NY 14627 U.S.A

Control over the 1.5 µm emission from erbium is desirable for communication and computational technologies because the erbium emission falls in the window of maximum transmission for silica based fiber optics. Tunable, narrow, directional, and enhanced erbium emission from silicon based 1-D photonic bandgap structures will be demonstrated. The structures are prepared by anodic etching of crystalline silicon and consist of two highly reflecting Bragg reflectors sandwiching an active layer. The cavities are doped by electro-migrating the erbium ions into the porous silicon matrix, followed by high temperature oxidation. By controlling the oxidation temperature, porosity, and thickness of the structure, the position of the erbium emission is tuned to emit in regions where the normal erbium emission is very weak. The erbium emission from the cavity is narrowed to a full width at half maximum (FWHM) of 12 nm with a cavity quality factor Q of 130, highly directional with a 20 degree emission cone around the normal axis, and enhanced by more than one order of magnitude when compared to its lateral emission. Erbium photoluminescence (PL) from porous silicon 2-D photonic bandgap structures is also demonstrated.

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SOI TFET $I_{\rm ON}/I_{\rm OFF}$ Enhancement via Back Biasing

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IEEE Transactions on Electron Devices 2011年第10期58卷 3283-3285页

作者： Alex Guo Peter Matheu Tsu-Jae King Liu University of California Berkeley CA USA Applied Science & Technology Graduate Program University of California Berkeley CA USA Department of Electrical Engineering and Computer Sciences University of California Berkeley CA USA

The effect of back biasing on the performance of a planar tunnel field-effect transistor (TFET) implemented on a silicon-on-insulator substrate is investigated. It is found that reverse back biasing reduces the subthreshold swing SS and increases the range of drain current over which SS is less than ( k B T / q ) ln (10); hence, it is effective for improving the TFET on/off current ratio for low operating voltages (≤ 0.5 V).

关键词： Logic gates Tunneling Doping Transistors Silicon Photonic band gap Junctions

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Characteristics of step-graded InxGa1-xAs and InGaPySb1-y metamorphic buffer layers on GaAs substrates

Characteristics of step-graded InxGa1-xAs and InGaPySb1-y me...

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作者： Kirch, J. Dudley, P. Kim, T. Radavich, K. Ruder, S. Mawst, L.J. Kuech, T.F. Lalumondiere, S.D. Sin, Y. Lotshaw, W.T. Moss, S.C. Department of Electrical and Computer Engineering University of Wisconsin - Madison 1415 Engineering Dr. Madison WI 53706 United States Materials Science Program University of Wisconsin - Madison 1415 Engineering Dr. Madison WI 53706 United States Department of Chemical and Biological Engineering University of Wisconsin - Madison 1415 Engineering Dr. Madison WI 53706 United States Aerospace Corporation Electronics and Photonics Lab El Segundo CA 90245 United States

ISBN: (纸本)9781457717536

Step-graded InGaPySb1-y and InxGa 1-xAs metamorphic buffer layer (MBL) structures are grown on GaAs substrates by metal-organic chemical vapor deposition (MOCVD). AFM analysis indicates that graded group V InGaPySb1-y MBLs exhibit significantly lower surface roughness (∼4.7nm) compared with more conventional graded group III InxGa1-xAs MBLs, which typically have rms surface roughness in the range of 7- 14nm. To reduce the surface roughness of the InxGa1-xAs MBL, a post growth Chemical-Mechanical Polishing (CMP) procedure is implemented. AFM image analysis indicates the CMP process is effective in reducing the step-graded In xGa1-xAs MBL surface roughness from ∼7.3 nm (as-grown) to 2.3 nm post CMP. Preliminary studies indicate that bulk InGaAs layers regrown on top of the MBL subjected to CMP exhibit improved static and transient PL characteristics compared with those deposited on as-grown MBLs. © VDE VERLAG GMBH.

关键词： III-V semiconductors

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Structure and magnetic properties characterization of electrodeposited Co37Fe63 alloys containing oxygen for magnetic recording applications

Structure and magnetic properties characterization of electr...

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作者： Elhalawaty, S. Carpenter, R.W. George, J. Brankovic, S.R. Materials Science and Engineering Graduate Program School for Engineering of Matter Transport and Energy Arizona State University 85287-6106 United States LeRoy Eyring Center for Solid State Science Arizona State University AZ 85287-9506 United States Center for Nanomagnetic Systems University of Houston TX 77204-4005 United States Electrical and Computer Engineering Department University of Houston TX 77204-4005 United States

ISBN: (纸本)9781118029473

Soft and high magnetic moment Co37Fe63 films were electro-deposited with variable additives on Cu/Ti/Si substrates. The correlation between structure and magnetic properties has been investigated. TEM showed the crystal structure of the films to be BCC with a 〈111〉 texture, and a grain size in the range of 10-20 nm. Oxygen in the deposited films has been identified by EDS and EELS using HAADF STEM. SIMS analysis revealed the presence of hydrogen and oxygen in the deposited CoFe films. Electron microscopy results showed that the oxygen was mainly distributed along the grain boundaries in the CoFe film. In regions where oxygen was present in the films, the Fe content was enhanced relative to Co. The magnetic properties of the deposits have been measured by Vibrating Sample Magnetometer (VSM), quantifying the impact of incorporated oxygen in the film on the saturation magnetization and the coercivity.

关键词： Magnetic properties

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Redundant information encoding in primary motor cortex during motor tasks

Redundant information encoding in primary motor cortex durin...

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International IEEE/EMBS Conference on Neural engineering, CNE

作者： Kelvin So Karunesh Ganguly Michael Gastpar Jose M. Carmena Department of Electrical Engineering and Computer Sciences University of California Berkeley CA USA Neurology and Rehabilitation Services San Francisco Veterans Affairs Medical Center San Francisco CA USA Department of Electrical Engineering and Computer Sciences and the Helen Wills Neuroscience Institute University of California Berkeley CA USA Department of Electrical Engineering and Computer Sciences the Program in Cognitive Science and the Helen WillsNeuroscience Institute University of California Berkeley CA USA

Information encoded in neuron ensembles has previously been hypothesized to be highly redundant, despite the apparent inefficiency of a redundant encoding system. The recent availability of intracortical, multi-electrode recordings has enabled the possibility of exploring how neuronal ensembles encode information as a whole. Applying concepts from information theory, we examined the redundancy of the target information encoded in both contralateral and ipsilateral hemispheres of the primary motor cortex (M1) in macaque monkeys performing a center-out reaching task. During movement, we reliably found neurons in contralateral M1 to contain higher target information and to be more redundant than ipsilateral M1 neurons, which is consistent with the conventional understanding that motor control is mainly governed by contralateral M1. Secondly, neuron ensembles in both hemispheres showed largely redundant information encoding. These results suggest that redundancy in information encoding is highly prevalent in the motor cortex and may contribute to proficient motor control.

关键词： Neurons Redundancy Encoding Neuroscience Muscles Firing Mutual information

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Combining wireless neural recording and video capture for the analysis of natural gait

Combining wireless neural recording and video capture for th...

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International IEEE/EMBS Conference on Neural engineering, CNE

作者： Justin D. Foster Oren Freifeld Paul Nuyujukian Stephen I. Ryu Michael J. Black Krishna V. Shenoy Department of Electrical Engineering University of Stanford Stanford CA USA Division of Applied Mathematics Brown University Providence RI USA Bioengineering and Stanford Medical School University of Stanford Stanford CA USA Department of Neurosurgery Palo Alto Medical Foundation Palo Alto CA USA Department of Computer Science Brown University Providence RI USA Max-Planck Institute Tubingen Germany Departments of Electrical Engineering Bioengineering and Neurobiology and the Neurosciences Program University of Stanford Stanford CA USA

Neural control of movement is typically studied in constrained environments where there is a reduced set of possible behaviors. This constraint may unintentionally limit the applicability of findings to the generalized case of unconstrained behavior. We hypothesize that examining the unconstrained state across multiple behavioral contexts will lead to new insights into the neural control of movement and help advance the design of neural prosthetic decode algorithms. However, to pursue electrophysiological studies in such a manner requires a more flexible framework for experimentation. We propose that head-mounted neural recording systems with wireless data transmission, combined with markerless computer-vision based motion tracking, will enable new, less constrained experiments. As a proof-of-concept, we recorded and wirelessly transmitted broadband neural data from 32 electrodes in premotor cortex while acquiring single-camera video of a rhesus macaque walking on a treadmill. We demonstrate the ability to extract behavioral kinematics using an automated computer vision algorithm without use of markers and to predict kinematics from the neural data. Together these advances suggest that a new class of “freely moving monkey” experiments should be possible and should help broaden our understanding of the neural control of movement.

关键词： Animals Kinematics Decoding Neuroscience Synchronization Image segmentation Wireless communication

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Complex-valued functional link network design by orthogonal least squares method for function approximation problems

Complex-valued functional link network design by orthogonal ...

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International Joint Conference on Neural Networks (IJCNN)

作者： Md. Faijul Amin Ramasamy Savitha Muhammad Ilias Amin Kazuyuki Murase Department of Systems Design Engineering Graduate School of Engineering University of Fukui Fukui Japan School of Electrical and Electronics Engineering Nanyang Technological University Singapore Department of Computer Science and Engineering United International University Dhaka Bangladesh Research and Education Program for Life Science University of Fukui Fukui Japan

This paper presents a fully complex-valued functional link network (CFLN). The CFLN is a single-layered neural network, which introduces nonlinearity in the input layer using nonlinear functions of the original input variables. In this study, we consider multivariate polynomials as the nonlinear functions. Unlike multilayer neural networks, the CFLN is free from local minima problem, and it offers very fast learning in parameters because of its linear structure. In the complex domain, polynomial based CFLN has an additional advantage of not requiring activation functions, which is a major concern in the complex-valued neural networks. However, it is important to select a smaller subset of polynomial terms (monomials) for faster and better performance, since the number of all possible monomials may be quite large. In this paper, we use the orthogonal least squares method in a constructive fashion (starting from lower degree to higher) for the selection of a parsimonious subset of monomials. Simulation results demonstrate that computing CFLN in purely complex domain is advantageous than in double-dimensional real domain, in terms of number of connection parameters, faster design, and possibly generalization performance. Moreover, our proposed CFLN compares favorably with several other multilayer networks in the complex domain.

关键词： Polynomials Nonhomogeneous media Educational institutions Algorithm design and analysis Function approximation Neural networks Input variables

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Noninvasive Analysis of Motor Unit Behavior in Pathological Tremor

Noninvasive Analysis of Motor Unit Behavior in Pathological ...

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Annual International Conference of the IEEE engineering in Medicine and Biology Society

作者： A. Holobar V. Glaser J. A. Gallego J. L. Dideriksen D. Farina Faculty of Electrical Engineering and Computer Science University of Maribor Bioengineering Group Consejo Superior de Investigaciones Cientificas Center for Sensor-Motor Interaction Department of Health Science and Technology Aalborg University Department of Neurorehabilitation Engineering Bernstein Center for Computational Neuroscience University Medical Center Gottingen Georg-August University

ISBN: (纸本)9781424441211

A robust surface EMG decomposition tool, referred to as tremor-optimized Convolution Kernel Compensation (CKC) technique, is described. This technique modifies and extends the previously published CKC method in order to circumvent the typical assumption on regularity and asynchrony of motor unit firings in normal condition and adapt to the discharge patterns in pathological tremor. The results on synthetic and experimental surface EMG signals demonstrate high performance of decomposition. In the case of simulated surface EMG with 20 dB SNR, excitation level of 20% maximum voluntary contraction (MVC) and simulated tremor frequency of 8 Hz, the newly proposed method identified 8 ± 2 motor units with sensitivity of motor unit discharge identification ≥ 95% and false alarm and miss rates ≤ 5%. The performance worsened with increasing noise power, with 5 ± 2 motor units identified at 10 dB SNR and 3 ± 1 at 0 dB SNR. In 24 recordings of high-density surface EMG signals from four tremor-affected patients, the modified CKC technique identified 134 motor units (6 ± 4 motor units per contraction).

关键词： Motor units Surface Electromyography Tremor noise power normal condition False alarms Supernova remnants signal to noise ratios dubnium decibel

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A Modelling Study on Transmission of the Central Oscillator in Tremor by a Motor Neuron Pool

A Modelling Study on Transmission of the Central Oscillator ...

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Annual International Conference of the IEEE engineering in Medicine and Biology Society

作者： J. A. Gallego J. L. Dideriksen D. Farina E. Rocon A. Holobar J. L. Pons Bioengineering Group Consejo Superior de Investigaciones Cientificas Center for Sensor-Motor Interaction Department of Health Science and Technology Aalborg University Department of Neurorehabilitation Engineering Bernstein Center for Computational Neuroscience University Medical Center Gottingen Georg-August University Faculty of Electrical Engineering and Computer Science University of Maribor

ISBN: (纸本)9781424441211

In spite of decades of intense research, pathological tremors still constitute unknown disorders. This study addresses, based on a multi-scale model, the behavior of an entire pool of motor neurons in tremor, under the hypothesis that tremor is an oscillation of central origin commonly projected to all motor neurons that innervate a muscle. Our results show that under such conditions both paired discharges and enhanced motor neuron synchronization, two of the characteristic landmarks of tremor, emerge. Moreover, coherence and correlation analyses suggest that the central tremor oscillator is transmitted linearly by the motor neuron pool given that a small set (7 or 8) of motor neurons are sampled.

关键词： Motor Neurons, Alpha Tremor Oscillators Oscillations

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Low-frequency 1/f noise in bismuth selenide Topological Insulators

Low-frequency 1/f noise in bismuth selenide Topological Insu...

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International Conference on Noise and Fluctuations (ICNF)

作者： M. Z. Hossain K. M. F. Shahil D. Teweldebrhan A. A. Balandin S. L. Rumyantsev M. Shur Nano-Device Laboratory Department of Electrical Engineering and Materials Science and Engineering Program University of California Riverside CA USA Department of Electrical Computer and Systems Engineering and Center for Integrated Electronics Rensselaer Polytechnic Institute New York USA Ioffe Institute The Russian Academy of Sciences St. Petersburg Russia

ISBN: (纸本)9781457701894

Topological insulators is a newly discovered class of materials with the Dirac cone type dispersion at the surface and conventional band in the volume of the material. We present results of the study of the low-frequency excess noise in thin films made of Bi 2 Se 3 topological insulator material. The films were prepared through mechanically cleavage from the bulk crystal via the “graphene-like” exfoliation procedure. We verified the quality and crystallinity of Bi 2 Se 3 samples with the micro-Raman spectroscopy. Our fabricated devices have linear current voltage characteristics in the low bias region with the current fluctuation noise spectral density SI proportional to 1/f for frequency f less than 10 kHz. The noise spectral density SI showed the square law dependence on the source-drain current and changed from about ~10 -22 to 10 -18 A 2 /Hz as current changes form ~10 -7 to 10 -5 A. Our results can be used for understanding electron transport and trap dynamics, and for reducing low-frequency noise in topological insulator devices.

关键词： Noise Insulators Films Crystals Temperature measurement Resistance

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