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University of Nebraska - Lincoln
Department of Electrical and Computer Engineering: Faculty Publications
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Articles 1 - 9 of 9
Full-Text Articles in Engineering
Giant Photoresistivity And Optically Controlled Switching In Self-Assembled Nanowires, N. Kouklin, L. Menon, A. Z. Wong, Daniel W. Thompson, John A. Woollam, P. F. Williams, Supriyo Bandyopadhyay
Giant Photoresistivity And Optically Controlled Switching In Self-Assembled Nanowires, N. Kouklin, L. Menon, A. Z. Wong, Daniel W. Thompson, John A. Woollam, P. F. Williams, Supriyo Bandyopadhyay
Department of Electrical and Computer Engineering: Faculty Publications
We report the observation of giant photoresistivity in electrochemically self-assembled CdS and ZnSe nanowires electrodeposited in a porous alumina film. The resistance of these nanowires increases by one to two orders of magnitude when exposed to infrared radiation, possibly because of real-space transfer of electrons from the nanowires into the surrounding alumina by photon absorption. This phenomenon has potential applications in ‘‘normally on’’ infrared photodetectors and optically controlled switches.
Mechanical, Geometrical, And Electrical Characterization Of Silicon Membranes For Open Stencil Masks, E. Sossna, A. Degen, I. W. Rangelow, M. Drzik, P. Hudek, T. E. Tiwald, John A. Woollam
Mechanical, Geometrical, And Electrical Characterization Of Silicon Membranes For Open Stencil Masks, E. Sossna, A. Degen, I. W. Rangelow, M. Drzik, P. Hudek, T. E. Tiwald, John A. Woollam
Department of Electrical and Computer Engineering: Faculty Publications
Silicon membranes are used for stencil masks which are key to charged particle projection lithography, particularly for ion projection lithography, electron beam projection. Quantitative and qualitative determination of the mechanical properties of the true thickness, thickness variations (morphology), electrical conductivity and stress is critical to the development of next generation lithography. The metrology setup includes high accuracy thickness, refractive index and electrical conductivity measurement based on infrared variable angle spectroscopic ellipsometry, thickness variation characterization based on the Fizeau interferometric scheme and mechanical stress evaluation based on a novel double bulging technique.
Statistical Evaluation Of Image Quality Measures, Ismail Avcibas, Bulent Sankur, Khalid Sayood
Statistical Evaluation Of Image Quality Measures, Ismail Avcibas, Bulent Sankur, Khalid Sayood
Department of Electrical and Computer Engineering: Faculty Publications
In this work we comprehensively categorize image quality measures, extend measures defined for gray scale images to their multispectral case, and propose novel image quality measures. They are categorized into pixel difference-based, correlation-based, edge-based, spectral-based, context-based and human visual system (HVS)-based measures. Furthermore we compare these measures statistically for still image compression applications. The statistical behavior of the measures and their sensitivity to coding artifacts are investigated via analysis of variance techniques. Their similarities or differences are illustrated by plotting their Kohonen maps. Measures that give consistent scores across an image class and that are sensitive to coding artifacts are …
Inverse Synthetic Aperture Radar Imaging Using A Coherent Ultrawideband Random Noise Radar System, Daryl C. Bell, Ram M. Narayanan
Inverse Synthetic Aperture Radar Imaging Using A Coherent Ultrawideband Random Noise Radar System, Daryl C. Bell, Ram M. Narayanan
Department of Electrical and Computer Engineering: Faculty Publications
The University of Nebraska-Lincoln has developed an ultrawideband random noise radar operating over the 1- to 2-GHz frequency range. The system uses the technique of heterodyne correlation, and is thus phase coherent. It has therefore been used in applications such as interferometry, polarimetry, and Doppler estimation. This assesses the performance of this radar as a range-Doppler imaging system, in particular, inverse synthetic aperture radar (ISAR). By performing turntable experiments, we examine a number of issues that arise both from the wideband nature of the radar system and from the randomness of the transmit signal. Although the ultrawideband nature of the …
Infrared Optical Properties Of Aged Porous Gaas, S. Zangooie, Mathias Schubert, T. E. Tiwald, John A. Woollam
Infrared Optical Properties Of Aged Porous Gaas, S. Zangooie, Mathias Schubert, T. E. Tiwald, John A. Woollam
Department of Electrical and Computer Engineering: Faculty Publications
Aging properties of porous GaAs were investigated nondestructively using variable angle of incidence infrared spectroscopic ellipsometry. In addition to the thickness and volume porosity, properties of the solid part of the porous material are investigated in terms of the long-wavelength dielectric function and chemical composition. The high sensitivity is employed to detect and identify infrared resonant absorptions related to different vibration modes of cubic and amorphous As2O3. Resonances centered at 333.3, 480, 785.8, 838, and 1045.5 cm-1 are from cubic As2O3, whereas resonances centered at 350, 490, and 808.5 cm-1 …
Aspect Sensitivity Measurements Of Polar Mesosphere Summer Echoes Using Coherent Radar Imaging, P. B. Chilson, T.-Y. Yu, R. D. Palmer, S. Kirkwood
Aspect Sensitivity Measurements Of Polar Mesosphere Summer Echoes Using Coherent Radar Imaging, P. B. Chilson, T.-Y. Yu, R. D. Palmer, S. Kirkwood
Department of Electrical and Computer Engineering: Faculty Publications
The Esrange VHF radar (ESRAD), located in northern Sweden (67.88) N, 21.10- E), has been used to investigate polar mesosphere summer echoes (PMSE). During July and August of 1998, coherent radar imaging (CRI) was used to study the dynamic evolution of PMSE with high temporal and spatial resolution. A CRI analysis provides an estimate of the angular brightness distribution within the radar’s probing volume. The brightness distribution is directly related to the radar reflectivity. Consequently, these data are used to investigate the aspect sensitivity of PMSE. In addition to the CRI analysis, the full correlation analysis (FCA) is used to …
Study Of Surface Chemical Changes And Erosion Rates For Cv-1144-O Silicone Under Electron Cyclotron Resonance Oxygen Plasma Exposure, Li Yan, Xiang Gao, Corey Bungay, John A. Woollam
Study Of Surface Chemical Changes And Erosion Rates For Cv-1144-O Silicone Under Electron Cyclotron Resonance Oxygen Plasma Exposure, Li Yan, Xiang Gao, Corey Bungay, John A. Woollam
Department of Electrical and Computer Engineering: Faculty Publications
CV-1144-O silicone thin films were irradiated in an electron cyclotron resonance oxygen plasma, which is a simulation of the low earth orbital environment. A crude equivalence between this plasma system and the low earth orbital environment was determined by measuring Kapton weight loss in the plasma and comparing to Kapton weight loss in space experiments. Changes in optical properties and erosion rates under ultraviolet light and atomic oxygen radiation were studied using in situ spectroscopic ellipsometry (SE). The erosion rate at the beginning of the plasma exposure was significantly faster than that at later stages. Approximately one third of the …
Infrared Response Of Multiple-Component Free-Carrier Plasma In Heavily Doped P-Type Gaas, S. Zangooie, Mathias Schubert, Daniel W. Thompson, John A. Woollam
Infrared Response Of Multiple-Component Free-Carrier Plasma In Heavily Doped P-Type Gaas, S. Zangooie, Mathias Schubert, Daniel W. Thompson, John A. Woollam
Department of Electrical and Computer Engineering: Faculty Publications
Spectroscopic ellipsometry is used to measure the dielectric function of heavily doped p-type GaAs for wave numbers from 100 to 2000 cm-1. Due to partial filling of the heavy- and light-hole valence bands, heavy holes as well as light holes form a multiple-component plasma coupled with longitudinal optical phonons. Line-shape analysis of the infrared response allows differentiating between light- and heavy-hole contributions to the carrier plasma, and the results observed suggest nonparabolicity effects of the heavy- and light-hole valence bands in GaAs.
Polarimetric Processing Of Coherent Random Noise Radar Data For Buried Object Detection, Yi Xu, Ram M. Narayanan, Xiojian Xu, John O. Curtis
Polarimetric Processing Of Coherent Random Noise Radar Data For Buried Object Detection, Yi Xu, Ram M. Narayanan, Xiojian Xu, John O. Curtis
Department of Electrical and Computer Engineering: Faculty Publications
Random noise polarimetry is a new radar technique for high-resolution probing of subsurface objects and interfaces. The University of Nebraska has developed a polarimetric random noise radar system based on the heterodyne correlation technique. Simulation studies and performance tests on the system confirm its ability to respond to phase differences in the received signals. In addition to polarimetric processing capability and the simplified system design, random noise radar also possesses other desirable features, such as immunity from radio frequency interference (RFI). The paper discusses the theoretical foundations of random noise polarimetry, and presents examples out of the entire data set …