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Department of Electrical and Computer Engineering: Faculty Publications

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Articles 721 - 733 of 733

Full-Text Articles in Electrical and Computer Engineering

Variable Angle Spectroscopic Magneto-Optics And Ellipsometry: Application To Dyco Multilayers, Thomas E. Tiwald, William A. Mcgahan, Z. S. Shan, Alan M. Massengale, John A. Woollam Nov 1988

Variable Angle Spectroscopic Magneto-Optics And Ellipsometry: Application To Dyco Multilayers, Thomas E. Tiwald, William A. Mcgahan, Z. S. Shan, Alan M. Massengale, John A. Woollam

Department of Electrical and Computer Engineering: Faculty Publications

The purpose of this paper is twofold. First, we describe the adaptation of a variable angle spectroscopic ellipsometer (VASE) to magneto-optic measurements covering 3000–8000 Å, and 0 to ±8 kOe. Second, we describe application of VASE to determine Kerr rotation and ellipticity for a series of Dy/Co multilayers prepared by sputter deposition. We report spectroscopic ellipsometric and Kerr effect results for samples exhibiting perpendicular magnetic anisotropy, since these are relevant as magneto-optic recording media.

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Thin-Film Hermeticity: A Quantitative Analysis Of Diamond-Like Carbon Using Variable Angle Spectroscopic Ellipsometry, S. Orzeszko, Bhola N. De, John A. Woollam, John J. Pouch, Samuel A. Alterovitz, David C. Ingram Oct 1988

Thin-Film Hermeticity: A Quantitative Analysis Of Diamond-Like Carbon Using Variable Angle Spectroscopic Ellipsometry, S. Orzeszko, Bhola N. De, John A. Woollam, John J. Pouch, Samuel A. Alterovitz, David C. Ingram

Department of Electrical and Computer Engineering: Faculty Publications

The purpose of this paper is twofold. First, we report on the successful application of variable angle spectroscopic ellipsometry to quantitative thin-film hermeticity evaluation. Secondly, it is shown that under a variety of film preparations and moisture introduction conditions water penetrates only a very thin diamondlike carbon (DLC) top surface-roughness region. Thus DLC is an excellent candidate for use as protective coatings in adverse chemical and aqueous environments.

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Variable Angle Of Incidence Spectroscopic Ellipsometric Characterization Of Tio2/Ag/Tio2 Optical Coatings, Kazem Memarzadeh, John A. Woollam, Abe Belkind Oct 1988

Variable Angle Of Incidence Spectroscopic Ellipsometric Characterization Of Tio2/Ag/Tio2 Optical Coatings, Kazem Memarzadeh, John A. Woollam, Abe Belkind

Department of Electrical and Computer Engineering: Faculty Publications

Optical constants (3000–8000 Å) and layer thicknesses of TiO2/Ag/TiO2 optical coatings are determined using variable angle of incidence spectroscopic ellipsometry. Ellipsometrically determined silver layer thicknesses agree well with those obtained by cross-sectional transmission electron microscopy. Also, spectral characteristics, absent in bulk silver data, are observed in n and k spectra for the thin silver layers. It is suggested that these structures may be caused by plasmon effects from the silver layers.

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Study Of Mo, Au, And Ni Implanted Molybdenum Laser Mirrors By Spectroscopic Ellipsometry, Paul G. Snyder, George H. Bu-Abbud, Jae Oh, John A. Woollam, David Poker, D. E. Aspnes, David Ingram, Peter Pronko Jan 1985

Study Of Mo, Au, And Ni Implanted Molybdenum Laser Mirrors By Spectroscopic Ellipsometry, Paul G. Snyder, George H. Bu-Abbud, Jae Oh, John A. Woollam, David Poker, D. E. Aspnes, David Ingram, Peter Pronko

Department of Electrical and Computer Engineering: Faculty Publications

The implantation of 150 kev molybdenum ions into polished molybdenum laser mirrors is found to increase the complex dielectric constant in the visible spectrum. Analysis using the Bruggeman effective medium approximation demonstrates that the increase is due to surface smoothing and that the surface is made nearly atomically smooth by a fluence of 5 x 1015 /cm2. Implantation of Au at 1Mev caused considerable microscopic roughening, as well as a change in the bulk optical properties. 3 MeV Ni ion implantation caused only a slight surface roughening. A thin dielectric film (probably a hydrocarbon) is found to …

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Interfacial Electrical Properties Of Ion-Beam Sputter Deposited Amorphous Carbon On Silicon, A. Azim Khan, John A. Woollam, Y. Chung, B. Banks May 1983

Interfacial Electrical Properties Of Ion-Beam Sputter Deposited Amorphous Carbon On Silicon, A. Azim Khan, John A. Woollam, Y. Chung, B. Banks

Department of Electrical and Computer Engineering: Faculty Publications

Amorphous, “diamond-like” Carbon films have been deposited on Si substrates, using ion-beam sputtering. The interfacial properties are studied using capacitance and conductance measurements. Data are analyzed using existing theories for interfacial electrical properties. The density of electronic states at the interface, along with corresponding time constants are determined, and the density of interface states is unusually low for an as yet unoptimized

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Atomic Hydrogen Storage, John A. Woollam Mar 1980

Atomic Hydrogen Storage, John A. Woollam

Department of Electrical and Computer Engineering: Faculty Publications

Atomic hydrogen, for use as a fuel or as an explosive, is stored in the presence of a strong magnetic field in exfoliated layered compounds such as molybdenum disulfide or an elemental layer material such as graphite. The compound is maintained at liquid temperatures and the atomic hydrogen is collected on the surfaces of the layered compound which are exposed during delamination (exfoliation). The strong magnetic field and the low temperature combine to prevent the atoms of hydrogen from recombining to form molecules.

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Electronic Properties Of Metal Chloride Intercalants Of Graphite*, **, John A. Woollam, M. B. Dowell, A. Yavrouian, A. G. Lozier, G. Matulka Jan 1980

Electronic Properties Of Metal Chloride Intercalants Of Graphite*, **, John A. Woollam, M. B. Dowell, A. Yavrouian, A. G. Lozier, G. Matulka

Department of Electrical and Computer Engineering: Faculty Publications

The Shubnikov-deHaas (SdH) effect has been used to study the electronic properties of graphite intercalated with PdC12 (stage 3), FeC13 (stages 2, 4, 6, and 11), CuC12 (stage 1), and WC16 (stage 5). For the palladium chloride, ferric chloride, and copper chloride intercalants the SdH spectra are similar: these show frequencies of approximately, 27, 80, 380, and 550 Tesla for fields parallel to the c-axis. The effective masses have been measured for each of these carriers, and are of the order of 0.1 m0, where m0 is the free electron mass. These carriers …

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Atomic Hydrogen Storage Method And Apparatus, John A. Woollam Mar 1978

Atomic Hydrogen Storage Method And Apparatus, John A. Woollam

Department of Electrical and Computer Engineering: Faculty Publications

Atomic hydrogen, for use as a fuel or as an explosive, is stored in the presence of a strong magnetic field in exfoliated layered compounds such as molybdenum disulfide or an elemental layer material such as graphite. The compound is maintained at liquid helium temperatures and the atomic hydrogen is collected on the surfaces of the layered compound which are exposed during delamination (exfoliation). The strong magnetic field and the low temperature combine to prevent the atoms of hydrogen from recombining to form molecules.

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Sio2-Si Film-Substrate Single-Reflection Retarders For Different Mercury Spectral Lines, A.R.M. Zaghloul, R.M.A Azzam Feb 1977

Sio2-Si Film-Substrate Single-Reflection Retarders For Different Mercury Spectral Lines, A.R.M. Zaghloul, R.M.A Azzam

Department of Electrical and Computer Engineering: Faculty Publications

Design parameters for SiO2- Si film-substrate single reflection retarders for several mercury spectral lines are presented. An example of an angle-of-incidence tunable retarder (AITR) capable of multiple wavelength operation (MWO) is reported Simple, approximate formulae for calculating film-substrate retarder design parameters (least film thickness d' and incidence angle) are presented.

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Optimal And Suboptimal Estimation In Differential Pcm And Adaptive Predictive Coding Systems, Jerry Gibson Dec 1975

Optimal And Suboptimal Estimation In Differential Pcm And Adaptive Predictive Coding Systems, Jerry Gibson

Department of Electrical and Computer Engineering: Faculty Publications

Both differential pulse code modulation (DPCM) and adaptive predictive coding (APC) systems have been used somewhat successfully for low date rate digital voice transmission. A DPCM system has as its goal the removal of signal redundancy prior to transmission by a linear prediction of the incoming signal with a weighted combination of past signal estimates. The error in the prediction process is then quantized and transmitted to the receiver. An identical prediction loop is used at the receiver to reinsert the redundancy, and hence, to reconstruct the speech signal. Both the quantizer and predictor may or may not be adaptive.

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Hall Effect Magnetometer, John A. Woollam, Harry A. Beale, Ian L. Spain Jan 1974

Hall Effect Magnetometer, John A. Woollam, Harry A. Beale, Ian L. Spain

Department of Electrical and Computer Engineering: Faculty Publications

A magnetometer utilizing a single crystal of Bi2Se3 having a rhombohedral crystal structure is described along with a method for making such a device. The Bi2Se3 has a positive or negative Hall coefficient and a carrier concentration of about 1018to1020 per cubic centimeter.

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A Noise Figure Lower Bound And A Frequency Converter, Grant Myers Jul 1969

A Noise Figure Lower Bound And A Frequency Converter, Grant Myers

Department of Electrical and Computer Engineering: Faculty Publications

This article establishes a lower bound for the noise figure of two networks in cascade. This is illustrated by means of a passive low-level frequency converter which utilizes a back diode as a nonlinear conductance. Other investigators have analyzed the properties of low-level frequency converters. However, the greatest lower bound of a combination of the converter and intermediate frequency amplifier system was not considered previously and is the subject of this paper. Knowledge of this lower bound has practical significance because if a measured value of noise figure is less than this lower bound, it follows that the measurement is …

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The Magnetocardiogram A New Approach To The Fields Surrounding The Heart, R. A. Stratbucker, C. M. Hyde, S. E. Wixon Oct 1963

The Magnetocardiogram A New Approach To The Fields Surrounding The Heart, R. A. Stratbucker, C. M. Hyde, S. E. Wixon

Department of Electrical and Computer Engineering: Faculty Publications

Experiments have been conducted which reveal the existence of a detectable magnetic field associated with cardiac electrical activity. The relationship between the magnetic record and the electrocardiogram has been explored and it is shown that under certain conditions of axis orientation the voltage induced into a toroidal sensing element around the heart has the form of the first time derivative of the electrocardiogram. A formula based on Maxwell's equations has been developed to relate these two phenomona.

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