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Full-Text Articles in Engineering
Near-Band-Gap Cupt-Order-Induced Birefringence In Al0.48Ga0.52Inp2, Mathias Schubert, Tino Hofmann, Bernd Rheinlander, Ines Pietzonka, Torsten Sass, Volker Gottschalch, John A. Woollam
Near-Band-Gap Cupt-Order-Induced Birefringence In Al0.48Ga0.52Inp2, Mathias Schubert, Tino Hofmann, Bernd Rheinlander, Ines Pietzonka, Torsten Sass, Volker Gottschalch, John A. Woollam
Department of Electrical and Computer Engineering: Faculty Publications
The order-induced birefringence in the near-band-gap spectral range (0.75 to 2.5 eV), and its dependence on the degree of ordering η is reported for Al0.48Ga0.52InP2. Transmission and reflection generalized variable angle spectroscopic ellipsometry, dark-field spectroscopy, and cross-polarized reflectance difference spectroscopy (CRDS) are used to determine precisely the room-temperature dielectric functions for polarization parallel and perpendicular to the ordering direction of a series of spontaneously CuPt-ordered samples grown by metalorganic vapor-phase epitaxy. The CRDS technique is introduced as an approach to sense extremely weak anisotropy at oblique angles of incidence. The observed order birefringence is …
Coulomb Crystals And Glasses For Self-Assembly Of Nanoparticles, P. F. Williams, A. Belolipetski, A. Goussev, M. E. Markes
Coulomb Crystals And Glasses For Self-Assembly Of Nanoparticles, P. F. Williams, A. Belolipetski, A. Goussev, M. E. Markes
P. F. (Paul Frazer) Williams Publications
Under proper conditions, small particles may be suspended in a regularly-spaced array called a Coulomb crystal. In this paper we discuss the application of this phenomenon to the self-assembly of nanoparticles in a lattice-lie array on a substrate. Issues associated with depositing the particles, and the size and lattice spacing of the particles are discussed.
Carrier Concentration And Lattice Absorption In Bulk And Epitaxial Silicon Carbide Determined Using Infrared Ellipsometry, Thomas E. Tiwald, John A. Woollam, Stefan Zollner, Jim Christiansen, R. B. Gregory, T. Wetteroth, S. R. Wilson, Adrian R. Powell
Carrier Concentration And Lattice Absorption In Bulk And Epitaxial Silicon Carbide Determined Using Infrared Ellipsometry, Thomas E. Tiwald, John A. Woollam, Stefan Zollner, Jim Christiansen, R. B. Gregory, T. Wetteroth, S. R. Wilson, Adrian R. Powell
Department of Electrical and Computer Engineering: Faculty Publications
We have measured the dielectric function of bulk nitrogen-doped 4H and 6H SiC substrates from 700 to 4000 cm-1 using Fourier-transform infrared spectroscopic ellipsometry. Photon absorption by transverse optical phonons produces a strong reststrahlen band between 797 and 1000 cm-1 with the effects of phonon anisotropy being observed in the region of the longitudinal phonon energy (960 to 100 cm-1). The shape of this band is influenced by plasma oscillations of free electrons, which we describe with a classical Drude equation. For the 6H-SiC samples, we modify the Drude equation to account for the strong effective …
System And Method For Improving Data Acquisistion Capability In Spectroscopic Rotatable Element, Rotating Element, Modulation Element, And Other Ellipsometer And Polarimeter And The Like Systems, Steven E. Green, Craig M. Heringer, Blaine D. Johs, John A. Woollam, Stephen P. Ducharme
System And Method For Improving Data Acquisistion Capability In Spectroscopic Rotatable Element, Rotating Element, Modulation Element, And Other Ellipsometer And Polarimeter And The Like Systems, Steven E. Green, Craig M. Heringer, Blaine D. Johs, John A. Woollam, Stephen P. Ducharme
Department of Electrical and Computer Engineering: Faculty Publications
Disclosed is a System and method for controlling polarization State determining parameters of a polarized beam of light in an ellipSometer or polarimeter and the like System, (e.g. a modulation element ellipsometer System), So that they are in ranges wherein the Sensitivity, (of a Sample system characterizing PSI and DELTA value monitoring detector used to measure changes in Said polarization State resulting from interaction with a “composite Sample System,” comprised of a Sample System per Se.. and a beam polarization State determining variable retarder, to noise and measurement errors etc. therein), is reduced. The present invention allows determining Sample System …
Optical Constants Of Crystalline Wo3 Deposited By Magnetron Sputtering, Michael J. Devries, Chris Trimble, Thomas E. Tiwald, Daniel W. Thompson, John A. Woollam, Jeffrey S. Hale
Optical Constants Of Crystalline Wo3 Deposited By Magnetron Sputtering, Michael J. Devries, Chris Trimble, Thomas E. Tiwald, Daniel W. Thompson, John A. Woollam, Jeffrey S. Hale
Department of Electrical and Computer Engineering: Faculty Publications
Crystalline WO3-x is an infrared (IR) electrochromic material having possible applications in satellite thermal control and IR switches. Optical constants of electrochromic materials change upon ion intercalation, usually with H+ or Li+. Of primary concern for device design are the optical constants in both the intercalated and deintercalated states. In situ and ex situ ellipsometric data are used to characterize both the deposition process and the optical constants of the films. Ex situ data from a UV-Vis-NIR ellipsometer are combined with data from a mid-infrared Fourier-transform-infrared-based ellipsometer to provide optical constants over a spectral range …
Isotropic Dielectric Functions Of Highly Disordered AlXGa1-XInp (0≤X≤1) Lattice Matched To Gaas, Mathias Schubert, John A. Woollam, G. Leibiger, B. Rheinlander, I. Pietzonka, T. Sab, V. Gottschalch
Isotropic Dielectric Functions Of Highly Disordered AlXGa1-XInp (0≤X≤1) Lattice Matched To Gaas, Mathias Schubert, John A. Woollam, G. Leibiger, B. Rheinlander, I. Pietzonka, T. Sab, V. Gottschalch
Department of Electrical and Computer Engineering: Faculty Publications
Determination of the complex dielectric function and the critical-point energies of (AlxGa1-x)0.51In0.49P, over the full range of composition x and for photon energies E from 0.75 to 5 eV is reported from variable angle of incidence spectroscopic ellipsometry. Native-oxide effects on the (AlxGa1-x)0.51In0.49P optical functions are removed numerically. The highly disordered state of the metalorganic vapor-phase epitaxy grown samples is analyzed by transmission electron microscopy. Optical anisotropy investigations revealed that the order-induced optical birefringence is negligible throughout. The augmentation of A. D. …
Variable Angle Of Incidence Analysis Of Magneto-Optic Multilayers, William A. Mcgahan, Liang-Yao Chen, John A. Woollam
Variable Angle Of Incidence Analysis Of Magneto-Optic Multilayers, William A. Mcgahan, Liang-Yao Chen, John A. Woollam
Department of Electrical and Computer Engineering: Faculty Publications
We have applied the technique of variable angle of incidence spectroscopic ellipsometry (VASE) to the analysis of multilayered magneto-optic structures. With this instrument we measure the complete pseudodielectric tensor (diagonal and off-diagonal elements) for the sample of interest at variable angles of incidence. We have also developed computer software to perform a best-fit analysis of the measured data, providing optical constants, Voigt parameters, and layer thicknesses for the individual layers in the sample. Additionally, given an estimate of the material parameters, this software will provide an estimate of the optimum spectral range and angles of incidence for accurate characterization of …
Complete Maps Of The Aspect Sensitivity Of Vhf Atmospheric Radar Echoes, R. M. Worthington, R. D. Palmer, S. Fukao
Complete Maps Of The Aspect Sensitivity Of Vhf Atmospheric Radar Echoes, R. M. Worthington, R. D. Palmer, S. Fukao
Department of Electrical and Computer Engineering: Faculty Publications
Using the MU radar at Shigaraki, Japan (34.85°N, 136.10°E), we measure the power distribution pattern of VHF radar echoes from the mid-troposphere. The large number of radar beam-pointing directions (320) allows the mapping of echo power from 0° to 40° from zenith, and also the dependence on azimuth, which has not been achieved before at VHF wavelengths. The results show how vertical shear of the horizontal wind is associated with a definite skewing of the VHF echo power distribution, for beam angles as far as 30° or more from zenith, so that aspect sensitivity cannot be assumed negligible at any …
Doppler Measurements Using A Coherent Ultrawideband Random Noise Radar, Muhammad Dawood, Ram M. Narayanan
Doppler Measurements Using A Coherent Ultrawideband Random Noise Radar, Muhammad Dawood, Ram M. Narayanan
Department of Electrical and Computer Engineering: Faculty Publications
The University of Nebraska has developed a random noise radar system which transmits an ultrawideband random noise waveform with a uniform power spectral density (PSD) in the 1-2 GHz frequency range. Simulation studies and controlled laboratory tests confirm the system's ability to preserve the instantaneous phase of the received signal [l, 2]. The potential of the system to characterize the Doppler shift of moving targets exhibiting varying linear and rotational velocities was clearly demonstrated [2]. This paper provides with the results of recent field experiments at a range of about 200 m which confirm the ability of the system to …