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Articles 1 - 7 of 7
Full-Text Articles in Physics
Effective Medium Theory, Rough Surfaces, And Moth’S Eyes, David D. Allred, Zephne Larsen, Joseph Muhlestein, R. Steven Turley, Anthony Willey
Effective Medium Theory, Rough Surfaces, And Moth’S Eyes, David D. Allred, Zephne Larsen, Joseph Muhlestein, R. Steven Turley, Anthony Willey
Faculty Publications
Optics in the extreme ultraviolet (XUV) have important applications in microelectronics, microscopy, space physics, and in imaging plasmas. Because of the short wavelengths involved in these applications, it is critical to account for interfacial roughness to accurately predict the reflection and absorption of XUV optics. This paper examines two possible effects of roughness on optical absorption, non-specular reflection and enhanced transmission and compares these to measured experimental data on a rough Y2O3 thin film.
Implementation Of Optical Spectra Calculations In Fireball: A Local-Orbital Density Functional Theory Approach, Ivan Grigoryevich Okhrimenko
Implementation Of Optical Spectra Calculations In Fireball: A Local-Orbital Density Functional Theory Approach, Ivan Grigoryevich Okhrimenko
Theses and Dissertations
We have expanded the capabilities of the ab initio tight-binding molecular dynamics package FIREBALL to include calculations of optical properties. Basic zero order approximation is based on transitions between Kohn-Sham states. Corrections for electron-electron interactions are based on time dependant density functional theory (TDDFT). Consistent with the FIREBALL approach, we use precalculated integrals and approximations to make the program faster.
Thorium-Based Thin Films As Highly Reflective Mirrors In The Euv, David D. Allred, William R. Evans, Jed E. Johnson, Richard L. Sandberg, R. Steven Turley
Thorium-Based Thin Films As Highly Reflective Mirrors In The Euv, David D. Allred, William R. Evans, Jed E. Johnson, Richard L. Sandberg, R. Steven Turley
Faculty Publications
As applications for extreme ultraviolet (EUV) radiation have been identified, the demand for better optics has also increased. Thorium and thorium oxide thin films (19 to 61 nm thick) were RF-sputtered and characterized using atomic force microscopy (AFM), spectroscopic ellipsometry, low-angle x-ray diffraction (LAXRD), x-ray photoelectron spectroscopy (XPS), and x-ray absorption near edge structure (XANES) in order to assess their capability as EUV reflectors. Their reflectance and absorption at different energies were also measured and analyzed at the Advanced Light Source in Berkeley. The reflectance of oxidized thorium is reported between 2 and 32 nm at 5, 10, and 15 …
Xenon 147-Nm Resonance Ƒ Value And Trapped Decay Rates, H. M. Anderson, Scott D. Bergeson, D. A. Doughty, J. E. Lawler
Xenon 147-Nm Resonance Ƒ Value And Trapped Decay Rates, H. M. Anderson, Scott D. Bergeson, D. A. Doughty, J. E. Lawler
Faculty Publications
The absorption oscillator strength of the xenon 147-nm resonance transition is measured to be 0.264±0.016. This value is from direct absorption measurements with equivalent widths from ≈ 1 to ≈ 10 cm-1. This ƒ-value measurement is compared to others in the literature and is used in Monte Carlo simulations of trapped decay rates. The simulations include an angle-dependent partial frequency redistribution. The simulation results are compared to trapped decay rates in the literature.
Photoluminescence And Absorption Studies Of Defects In Cdte And Znxcd1-Xte Crystals, Cheryl Barnett Davis, David D. Allred, A. Reyes-Mena, Jesus González-Hernández, Ovidio González, Bret C. Hess, Worth P. Allred
Photoluminescence And Absorption Studies Of Defects In Cdte And Znxcd1-Xte Crystals, Cheryl Barnett Davis, David D. Allred, A. Reyes-Mena, Jesus González-Hernández, Ovidio González, Bret C. Hess, Worth P. Allred
Faculty Publications
We have studied at cryogenic temperatures photoluminescence features which lie more than 0.15 eV below the band edge in ZnxCd1-xTe (0≤x≤0.09) crystals. The same features, namely a defect band which lies at about 0.13-0.20 eV below the band-gap energy and a peak at 1.1 eV, that are observed in pure CdTe samples are observed in these alloy materials. In annealed samples we observe that the 1.1 eV feature, which has been attributed to tellurium vacancies, increases with fast cooling. Increased concentrations of tellurium vacancies can be understood in terms of the phase diagram of CdTe which indicates that higher concentrations …
Design Of High Performance Soft X-Ray Windows, Raymond T. Perkins, David D. Allred, Larry V. Knight, James M. Thorne
Design Of High Performance Soft X-Ray Windows, Raymond T. Perkins, David D. Allred, Larry V. Knight, James M. Thorne
Faculty Publications
X-ray windows are used in sources and detectors to separate the neighborhood of the x-ray generation or detection from the use environment. While each use has its own requirements, there are some principles that should be used in designing an optimal x-ray window. Because x-rays are absorbed to some extent by all materials, minimizing absorption is one criterion in preparing windows. Also, for most uses there is a pressure difference across the window so that ensuring pinhole-free structure and sufficient mechanical strength to support the differential is another criterion for window design. Traditionally, absorption is minimized by fabricating the window …
Chemical Vapor Deposited Amorphous Silicon For Use In Photothermal Conversion, David D. Allred, D. C. Booth, M. Janai, G. Weiser, B. O. Seraphin
Chemical Vapor Deposited Amorphous Silicon For Use In Photothermal Conversion, David D. Allred, D. C. Booth, M. Janai, G. Weiser, B. O. Seraphin
Faculty Publications
Efficient photothermal conversion requires surfaces of high solar absorptance and low thermal emittance. This can be accomplished by the tandem action of a good infrared reflector overlaid by a film of sufficient solar absorptance that is transparent in the infrared. Crystalline silicon is a suitable candidate for the absorber layer. Its indirect band gap, however, results in a shallow absorption edge that extends to far into the visible. In contrast, the absorption edge of amorphous silicon is steeper and located farther into the infrared, resulting in a larger solar absorptance. We report on the fabrication of amorphous silicon absorbers by …