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Full-Text Articles in Engineering
In Situ Infrared And Visible-Light Ellipsometric Investigations Of Boron Nitride Thin Films At Elevated Temperatures, E. Franke, Mathias Schubert, J.-D. Hecht, H. Neumann, T. E. Tiwald, Daniel W. Thompson, H. Yao, John A. Woollam
In Situ Infrared And Visible-Light Ellipsometric Investigations Of Boron Nitride Thin Films At Elevated Temperatures, E. Franke, Mathias Schubert, J.-D. Hecht, H. Neumann, T. E. Tiwald, Daniel W. Thompson, H. Yao, John A. Woollam
Department of Electrical and Computer Engineering: Faculty Publications
In situ infrared (IR) spectroscopy and visible-light (VIS) spectroscopic ellipsometry over the spectral range from 700 to 2000 cm-1 and 1.5–3.5 eV, respectively, were used to investigate the optical behavior of boron nitride (BN) thin films at temperatures from room temperature (RT) to 600 °C. The polycrystalline hexagonal (h) and mixed-phase h- and cubic (c)-BN thin films were deposited by magnetron sputtering on [001] silicon. We observe a reversible moisture incorporation process in as-grown h-BN samples. When stored in normal ambient, the h-BN thin films absorb water into thin-film micropores. When annealed in ultrahigh vacuum or a …
System And Method For Performing Optical Code Division Multiple Access Communication Using Bpolar Codes, James F. Young, Benhaam Aazhnag, Lim Nguyen
System And Method For Performing Optical Code Division Multiple Access Communication Using Bpolar Codes, James F. Young, Benhaam Aazhnag, Lim Nguyen
Department of Electrical and Computer Engineering: Faculty Publications
An optical encoding and decoding system which performs code-division multiple access (CDMA) communication in the incoherent, or direct detection, optical domain using bipolar +1/-1 codes. The present invention uses code modu lation and detection principles that permit all-optical imple mentation of the bipolar. +1/-1. code and correlation detec tion that have been developed for the radio frequency (RF) systems. This is possible in spite of the non-negative, or unipolar, +1/0, nature of the incoherent optical system that only detects and processes the signal intensity. The unipolar optical system of the present invention is equivalent to the bipolar RF system in …
Thickness Dependence Of Interfacial Magneto-Optic Effects, Xiang Gao, Michael J. Devries, Daniel W. Thompson, John A. Woollam
Thickness Dependence Of Interfacial Magneto-Optic Effects, Xiang Gao, Michael J. Devries, Daniel W. Thompson, John A. Woollam
Department of Electrical and Computer Engineering: Faculty Publications
Spectroscopic ellipsometry and magneto-optic Kerr effects are measured on Pt/Co multilayers with a series of Co layer thicknesses from 0.08 to 1 nm. An electromagnetic theory of multilayered structures allows regression analysis fits between acquired data and parameter dependent model analysis. Recently, we determined the single layer Co magneto-optic Voigt parameter and found that it depends on Co layer thickness. In the present work, we report an in-depth study of interfacial magneto-optic effects for a large number of Pt/Co multilayer samples. Kerr rotation and ellipticity were measured over the spectral range from 200 to 1700 nm. Voigt parameters of the …
System And Method For Improving Data Acquisition Capability In Spectroscopic Ellipsometers, Steven E. Green, Craig M. Herzinger, Blaine D. Johs, John A. Woollam
System And Method For Improving Data Acquisition Capability In Spectroscopic Ellipsometers, Steven E. Green, Craig M. Herzinger, Blaine D. Johs, John A. Woollam
Department of Electrical and Computer Engineering: Faculty Publications
The present invention is applicable generally to Spectroscopic Rotatable and Rotating Element Ellipsometers which utilize a relatively large range of wavelengths. Disclosed is a system and method for controlling the polarization state of a polarized beam of light so that it is in a range where the sensitivity of a Polarization State Detector used to measure changes in said polarized beam of light resulting from interaction with a Sample System. to noise and measurement errors etc.. is reduced. Exemplified is a system. and method of use, for simultaneously setting both measured ellipsometric ALPHA, and ellipsometric BETA parameter values, (or equivalents), …
Ellipsometric Determination Of Optical Constants For Silicon And Thermally Grown Silicon Dioxide Via A Multi-Sample, Multi-Wavelength, Multi-Angle Investigation, C. M. Herzinger, B. Johs, W. A. Mcgahan, John A. Woollam, W. Paulson
Ellipsometric Determination Of Optical Constants For Silicon And Thermally Grown Silicon Dioxide Via A Multi-Sample, Multi-Wavelength, Multi-Angle Investigation, C. M. Herzinger, B. Johs, W. A. Mcgahan, John A. Woollam, W. Paulson
Department of Electrical and Computer Engineering: Faculty Publications
Optical constant spectra for silicon and thermally grown silicon dioxide have been simultaneously determined using variable angle of incidence spectroscopic ellipsometry from 0.75 to 6.5 eV. Spectroscopic ellipsometric data sets acquired at multiple angles of incidence from seven samples with oxide thicknesses from 2 to 350 nm were analyzed using a self-contained multi-sample technique to obtain Kramers–Kronig consistent optical constant spectra. The investigation used a systematic approach utilizing optical models of increasing complexity in order to investigate the need for fitting the thermal SiO2 optical constants and including an interface layer between the silicon and SiO2 in modeling …
Studies Of Metallic Multilayer Structures, Optical Properties, And Oxidation Using In Situ Spectroscopic Ellipsometry, Xiang Gao, Jeff Hale, Scott Heckens, John A. Woollam
Studies Of Metallic Multilayer Structures, Optical Properties, And Oxidation Using In Situ Spectroscopic Ellipsometry, Xiang Gao, Jeff Hale, Scott Heckens, John A. Woollam
Department of Electrical and Computer Engineering: Faculty Publications
In situ spectroscopic ellipsometry (SE) has been successfully used to accurately measure sputter deposition rates and optical constants of un-oxidized metal layers and to control the growth of magnetic multilayers. The structures include [Co/Cu] n , [Co/Au] n , [Co/Ni] n , [Co/Pd] n and [Co/Pd/ Au] n . Layer thickness precision is better than ±0.05 nm for layer thicknesses in the range of 0.2 nm to 10 nm. Closed-loop feedback control of layer thickness is also demonstrated. Good consistency was obtained by comparing the in situ SE results to x-ray diffraction measurements. Dynamic oxidation studies of [Co/Au] n and …
Design, Performance, And Applications Of A Coherent Ultra-Wideband Random Noise Radar, Ram M. Narayanan, Yi Xu, Paul D. Hoffmeyer, John O. Curtis
Design, Performance, And Applications Of A Coherent Ultra-Wideband Random Noise Radar, Ram M. Narayanan, Yi Xu, Paul D. Hoffmeyer, John O. Curtis
Department of Electrical and Computer Engineering: Faculty Publications
A novel coherent ultra-wideband radar system operating in the 1- to 2-GHz frequency range has been developed recently at the University of Nebraska. The radar system transmits white Gaussian noise. Detection and localization of buried objects is accomplished by correlating the reflected waveform with a time-delayed replica of the transmitted waveform. Broadband dual-polarized log-periodic antennas are used for transmission and reception. A unique signal-processing scheme is used to inject coherence into the system by frequency translation of the ultrawideband signal by a coherent 160-MHz phase-locked source prior to performing heterodyne correlation. The system coherence allows the extraction of a target’s …
Electromagneticbeamdirecting Means-Sampleanalyss System Stage, And Method Of Use, Daniel W. Thompson, Darin W. Glenn, John A. Woollam
Electromagneticbeamdirecting Means-Sampleanalyss System Stage, And Method Of Use, Daniel W. Thompson, Darin W. Glenn, John A. Woollam
Department of Electrical and Computer Engineering: Faculty Publications
Disclosed is an electromagnetic beam directing means for use with sample analysis systems, such as reflectometers, ellipsometers and polarimeters and the like, use of which facilitates investigation of sample systems which are not mounted to a sample analysis system sample system supporting stage. The present invention eliminates the requirement of extensive sample analysis system component realignment when alternatingly performing analysis of sample systems mounted upon, and mounted other than upon, a sample analysis system sample system supporting stage.
Apparatus And Method For Detection And Concentration Measurement Of Trace Metals Using Laser Induced Breakdown Spectroscopy, Dennis R. Alexander
Apparatus And Method For Detection And Concentration Measurement Of Trace Metals Using Laser Induced Breakdown Spectroscopy, Dennis R. Alexander
Department of Electrical and Computer Engineering: Faculty Publications
A method and apparatus for in situ detection and concentration measurement of trace elements in an analysis Sample is disclosed. The invention uses laser induced breakdown spectroscopy (LIBS) wherein femtosecond pulsed laser energy is employed to produce the plasma. The femtosecond pulsed laser energy is focused on the analysis Sample to produce the plasma and the resulting emission is delivered for spectral analysis. Because the method and apparatus of the present invention allow breakdown of the analysis Sample without propagation of energy to the Sample-air interface, a plasma is produced that consists essentially of Sample materials without being contaminated by …
Infrared Ellpsometer/ Polarmeter System, Method Of Calibration, And Use Thereof, Daniel W. Thompson, Blaine D. Johs
Infrared Ellpsometer/ Polarmeter System, Method Of Calibration, And Use Thereof, Daniel W. Thompson, Blaine D. Johs
Department of Electrical and Computer Engineering: Faculty Publications
A sample system investigation system, such as an ellipsometer or polarimeter system, for use in investigating sample systems with electromagnetic wavelengths in the infrared range, and a calibration method for compensating nonidealities in multi-dimensional system rotated and non-rotated component representing matricies, are disclosed. An essentially achromatic compensator of dual-rhomb construction, which introduces a (3*LAMBDA/4) phase shift, but essentially no deviation in the direction of propagation of a polarized beam of electromagnetic wavelengths caused to pass there through, even when said compensator is caused to continuously rotate, is also disclosed.
A New Radiosonde System For Profiling The Lower Troposphere, Brian R Corner, Robert D. Palmer
A New Radiosonde System For Profiling The Lower Troposphere, Brian R Corner, Robert D. Palmer
Department of Electrical and Computer Engineering: Faculty Publications
A new, inexpensive radiosonde transmitter and receiver system has been developed for measuring wind field inhomogeneities in the planetary boundary layer using multiple simultaneously launched balloons. The radio- sondes use a narrowband-frequency-modulated carrier signal to transmit atmospheric pressure and temperature information to a surface receiver. The pressure and temperature data transmitted by the radiosondes allow their height above the surface to be ascertained. In addition, the radiosondes can be tracked with a photographic camera system to provide the azimuth and elevation angles of the radiosondes during their ascent, so that their three-dimensional horizontal position can be determined. By tracking the …
Electromagnetic Beam Directing Means-Sample Analysis System Stage, And Method Of Use, Daniel W. Thomspon, Darin W. Glenn, John A. Woollam
Electromagnetic Beam Directing Means-Sample Analysis System Stage, And Method Of Use, Daniel W. Thomspon, Darin W. Glenn, John A. Woollam
Department of Electrical and Computer Engineering: Faculty Publications
Disclosed is an electromagnetic beam directing means for use with sample analysis systems, such as relfectometers, ellipsometers and polarimeters and the like, use of which facilitates investigation of sample systems which are not mounted to a sample analysis system sample system supporting stage. The present invention eliminates the requirement os extensice sample analysis system component realignment when alternatingly performing analysis of sample systems mounted upon, and mounted other than upon, a sample analysis system sample system supporting stage.
Optical Determination Of Shallow Carrier Profiles Using Fourier Transform Infrared Ellipsometry, Thomas E. Tiwald, John A. Woollam, John A. Woollam
Optical Determination Of Shallow Carrier Profiles Using Fourier Transform Infrared Ellipsometry, Thomas E. Tiwald, John A. Woollam, John A. Woollam
Department of Electrical and Computer Engineering: Faculty Publications
Dopant profiles were determined by ex situ Fourier transform infrared variable-angle spectroscopic ellipsometry. The technique exploits carrier absorption in the mid-infrared spectral range and combines the sensitivity of ellipsometry with a simple Drude free carrier absorption model to determine the carrier profile. The noncontact, nondestructive nature of the measurement suggests both ex situ and in situ monitoring and control applications. In this study, the carrier profiles were modeled as graded multilayers that can be constrained to a given functional form (Gaussian, erfc, etc.) when desired. Boron and arsenic implanted silicon wafers that were rapid thermal anneal and furnace annealed were …