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Interfacial Widths of Conjugated Polymer Bilayers

Description: The interfaces of conjugated polyelectrolyte (CPE)/poly[2-methoxy-5-(2{prime}-ethylhexyloxy)-p-phenylene vinylene] (MEH-PPV) bilayers cast from differential solvents are shown by resonant soft X-ray reflectivity (RSoXR) to be very smooth and sharp. The chemical interdiffusion due to casting is limited to less than 0.6 nm, and the interface created is thus nearly 'molecularly' sharp. These results demonstrate for the first time and with high precision that the nonpolar MEH-PPV layer is not much disturbed by casting the CPE layer from a polar solvent. A baseline is established for understanding the role of interfacial structure in determining the performance of CPE-based polymer light-emitting diodes. More broadly, we anticipate further applications of RSoXR as an important tool in achieving a deeper understanding of other multilayer organic optoelectronic devices, including multilayer photovoltaic devices.
Date: August 13, 2009
Creator: NCSU; Berkeley, UC; UCSB; Source, Advanced Light; Garcia, Andres; Yan, Hongping et al.
Partner: UNT Libraries Government Documents Department

Millimeter Wave Cloud Radar (MMCR) Handbook

Description: The millimeter cloud radar (MMCR) systems probe the extent and composition of clouds at millimeter wavelengths. The MMCR is a zenith-pointing radar that operates at a frequency of 35 GHz. The main purpose of this radar is to determine cloud boundaries (e.g., cloud bottoms and tops). This radar will also report radar reflectivity (dBZ) of the atmosphere up to 20 km. The radar possesses a doppler capability that will allow the measurement of cloud constituent vertical velocities.
Date: January 30, 2005
Creator: Widener, KB & Johnson, K
Partner: UNT Libraries Government Documents Department

EUV mask reflectivity measurements with micro-scale spatial resolution

Description: The effort to produce defect-free mask blanks for EUV lithography relies on increasing the detection sensitivity of advanced mask inspection tools, operating at several wavelengths. They describe the unique measurement capabilities of a prototype actinic (EUV) wavelength microscope that is capable of detecting small defects and reflectivity changes that occur on the scale of microns to nanometers. The defects present in EUV masks can appear in many well-known forms: as particles that cause amplitude or phase variations in the reflected field; as surface contamination that reduces reflectivity and contrast; and as damage from inspection and use that reduces the reflectivity of the multilayer coating. This paper presents an overview of several topics where scanning actinic inspection makes a unique contribution to EUVL research. They describe the role of actinic scanning inspection in defect repair studies, observations of laser damage, actinic inspection following scanning electron microscopy, and the detection of both native and programmed defects.
Date: February 1, 2008
Creator: Goldberg, Kenneth A.; Rekawa, Senajith B.; Kemp, Charles D.; Barty, Anton; Anderson, Erik; Kearney, Patrick et al.
Partner: UNT Libraries Government Documents Department

Reflectivity of plasmas created by high-intensity, ultra-short laser pulses

Description: Experiments were performed to characterize the creation and evolution of high-temperature (T{sub e}{approximately}100eV), high-density (n{sub e}>10{sup 22}cm{sup {minus}3}) plasmas created with intense ({approximately}10{sup 12}-10{sup 16}W/cm{sup 2}), ultra-short (130fs) laser pulses. The principle diagnostic was plasma reflectivity at optical wavelengths (614nm). An array of target materials (Al, Au, Si, SiO{sub 2}) with widely differing electronic properties tested plasma behavior over a large set of initial states. Time-integrated plasma reflectivity was measured as a function of laser intensity. Space- and time-resolved reflectivity, transmission and scatter were measured with a spatial resolution of {approximately}3{mu}m and a temporal resolution of 130fs. An amplified, mode-locked dye laser system was designed to produce {approximately}3.5mJ, {approximately}130fs laser pulses to create and nonintrusively probe the plasmas. Laser prepulse was carefully controlled to suppress preionization and give unambiguous, high-density plasma results. In metals (Al and Au), it is shown analytically that linear and nonlinear inverse Bremsstrahlung absorption, resonance absorption, and vacuum heating explain time-integrated reflectivity at intensities near 10{sup 16}W/cm{sup 2}. In the insulator, SiO{sub 2}, a non-equilibrium plasma reflectivity model using tunneling ionization, Helmholtz equations, and Drude conductivity agrees with time-integrated reflectivity measurements. Moreover, a comparison of ionization and Saha equilibration rates shows that plasma formed by intense, ultra-short pulses can exist with a transient, non-equilibrium distribution of ionization states. All targets are shown to approach a common reflectivity at intensities {approximately}10{sup 16}W/cm{sup 2}, indicating a material-independent state insensitive to atomic or solid-state details.
Date: June 1, 1994
Creator: Gold, D.M.
Partner: UNT Libraries Government Documents Department

Stereoscopic Height Estimation from Multiple Aspect Synthetic Aperture Radar Images

Description: A Synthetic Aperture Radar (SAR) image is a two-dimensional projection of the radar reflectivity from a 3-dimensional object or scene. Stereoscopic SAR employs two SAR images from distinct flight paths that can be processed together to extract information of the third collapsed dimension (typically height) with some degree of accuracy. However, more than two SAR images of the same scene can similarly be processed to further improve height accuracy, and hence 3-dimensional position accuracy. This report shows how.
Date: August 1, 2001
Partner: UNT Libraries Government Documents Department

Structure of water adsorbed on a mica surface

Description: Monte Carlo simulations of hydration water on the mica (001) surface under ambient conditions revealed water molecules bound closely to the ditrigonal cavities in the surface, with a lateral distribution of approximately one per cavity, and water molecules interposed between K{sup +} counter ions in a layer situated about 2.5 {angstrom} from a surface O along a direction normal to the (001) plane. The calculated water O density profile was in quantitative agreement with recent X-ray reflectivity measurements indicating strong lateral ordering of the hydration water but liquid-like disorder otherwise.
Date: January 29, 2002
Creator: Park, Sung-Ho & Sposito, Garrison
Partner: UNT Libraries Government Documents Department

Measurement of the Shock-Heated Melt Curve of Lead Using Pyrometry and Reflectometry

Description: Data on the high-pressure melting temperatures of metals is of great interest in several fields of physics including geophysics. Measuring melt curves is difficult but can be performed in static experiments (with laser-heated diamond-anvil cells for instance) or dynamically (i.e., using shock experiments). However, at the present time, both experimental and theoretical results for the melt curve of lead are at too much variance to be considered definitive. As a result, we decided to perform a series of shock experiments designed to provide a measurement of the melt curve of lead up to about 50 GPa in pressure. At the same time, we developed and fielded a new reflectivity diagnostic, using it to make measurements on tin. The results show that the melt curve of lead is somewhat higher than the one previously obtained with static compression and heating techniques.
Date: January 1, 2004
Creator: Partouche-Sebban, D.; Pelissier, J. L.; Abeyta F. G.; Anderson, W. W.; Byers, M. E.; Dennis-Koller, D. et al.
Partner: UNT Libraries Government Documents Department

Carbon contamination topography analysis of EUV masks

Description: The impact of carbon contamination on extreme ultraviolet (EUV) masks is significant due to throughput loss and potential effects on imaging performance. Current carbon contamination research primarily focuses on the lifetime of the multilayer surfaces, determined by reflectivity loss and reduced throughput in EUV exposure tools. However, contamination on patterned EUV masks can cause additional effects on absorbing features and the printed images, as well as impacting the efficiency of cleaning process. In this work, several different techniques were used to determine possible contamination topography. Lithographic simulations were also performed and the results compared with the experimental data.
Date: March 12, 2010
Creator: Fan, Y.-J.; Yankulin, L.; Thomas, P.; Mbanaso, C.; Antohe, A.; Garg, R. et al.
Partner: UNT Libraries Government Documents Department

Tri-material multilayer coatings with high reflectivity and wide bandwidth for 25 to 50 nm extreme ultraviolet light

Description: Magnesium/silicon carbide (Mg/SiC) multilayers have been fabricated with normal incidence reflectivity in the vicinity of 40% to 50% for wavelengths in the 25 to 50 nm wavelength range. However many applications, for example solar telescopes and ultrafast studies using high harmonic generation sources, desire larger bandwidths than provided by high reflectivity Mg/SiC multilayers. We investigate introducing a third material, Scandium, to create a tri-material Mg/Sc/SiC multilayer allowing an increase the bandwidth while maintaining high reflectivity.
Date: September 9, 2009
Creator: Aquila, Andrew; Salmassi, Farhad; Liu, Yanwei & Gullikson, Eric M.
Partner: UNT Libraries Government Documents Department

Thorough characterization of a EUV mask

Description: We reported that we were successful in our 45nm technology node device demonstration in February 2008 and 22nm node technology node device patterning in February 2009 using ASML's Alpha Demo Tool (ADT). In order to insert extreme ultraviolet (EUV) lithography at the 15nm technology node and beyond, we have thoroughly characterized one EUV mask, a so-called NOVACD mask. In this paper, we report on three topics, The first topic is an analysis of line edge roughness (LER) using a mask Scanning Electron Microscope (SEM), an Atomic Force Microscope (AFM) and the Actinic Inspection Tool (AIT) to compare resist images printed with the ASML ADT. The results of the analysis show a good correlation between the mask AFM and the mask SEM measurements, However, the resist printing results for the isolated space patterns are slightly different. The cause ofthis discrepancy may be resist blur, image log slope and SEM image quality and so on. The second topic is an analysis of mask topography using an AFM and relative reflectivity of mirror and absorber surface using the AIT, The AFM data show 6 and 7 angstrom rms roughness for mirror and absorber, respectively. The reflectivity measurements show that the mirror reflects EUV light about 20 times higher than absorber. The last topic is an analysis of a 32nm technology node SRAM cell which includes a comparison of mask SEM image, AIT image, resist image and simulation results. The ADT images of the SRAM pattern were of high quality even though the mask patters were not corrected for OPC or any EUV-specific effects. Image simulation results were in good agreement with the printing results.
Date: June 25, 2009
Creator: Mizuno, H.; McIntyre, G.; Koay, C.-W.; Burkhardt, M.; He, L.; Hartley, J. et al.
Partner: UNT Libraries Government Documents Department

Arrayed resonant subwavelength gratings : LDRD 38618 final report.

Description: This report describes a passive, optical component called resonant subwavelength gratings (RSGs), which can be employed as one element in an RSG array. An RSG functions as an extremely narrow wavelength and angular band reflector, or mode selector. Theoretical studies predict that the infinite, laterally-extended RSG can reflect 100% of the resonant light while transmitting the balance of the other wavelengths. Experimental realization of these remarkable predictions has been impacted primarily by fabrication challenges. Even so, we will present large area (1.0mm) RSG reflectivity as high as 100.2%, normalized to deposited gold. Broad use of the RSG will only truly occur in an accessible micro-optical system. This program at Sandia is a normal incidence array configuration of RSGs where each array element resonates with a distinct wavelength to act as a dense array of wavelength- and mode-selective reflectors. Because of the array configuration, RSGs can be matched to an array of pixels, detectors, or chemical/biological cells for integrated optical sensing. Micro-optical system considerations impact the ideal, large area RSG performance by requiring finite extent devices and robust materials for the appropriate wavelength. Theoretical predictions and experimental measurements are presented that demonstrate the component response as a function of decreasing RSG aperture dimension and off-normal input angular incidence.
Date: November 1, 2003
Creator: Grotbeck, Carter L.; Kemme, Shanalyn A.; Wendt, Joel Robert; Warren, Mial E.; Samora, Sally; Carter, Tony Ray et al.
Partner: UNT Libraries Government Documents Department

Using Data Fusion to Characterize Breast Tissue

Description: New ultrasound data, obtained with a circular experimental scanner, are compared with data obtained with standard X-ray CT. Ultrasound data obtained by scanning fixed breast tissue were used to generate images of sound speed and reflectivity. The ultrasound images exhibit approximately 1 mm resolution and about 20 dB of dynamic range. All data were obtained in a circular geometry. X-ray CT scans were used to generate X-ray images corresponding to the same 'slices' obtained with the ultrasound scanner. The good match of sensitivity, resolution and angular coverage between the ultrasound and X-ray data makes possible a direct comparison of the three types of images. We present the results of such a comparison for an excised breast fixed in formalin. The results are presented visually using various types of data fusion. A general correspondence between the sound speed, reflectivity and X-ray morphologies is found. The degree to which data fusion can help characterize tissue is assessed by examining the quantitative correlations between the ultrasound and X-ray images.
Date: January 23, 2002
Creator: Littrup, P; Duric, N; Leach, R R; Azevedo, S G; Candy, J V; Moore, T et al.
Partner: UNT Libraries Government Documents Department

Integrated X-Ray Reflectivity Measurements for Elliptically Curved PET Crystals

Description: Spectroscopy provides valuable information about the temperature and density of a compressed pellet in a plasma. Elliptically curved pentaerythritol (PET) crystals are used as components for spectrometers. Their elliptical geometry gives several advantages related to spectral energy range, source focus, and spectral image compression.[1] The crystal curvature increases the spectrometer throughput but at the cost of a loss in resolution. Four different crystals are used in a spectrometer at the National Ignition Facility (NIF) target chamber at Lawrence Livermore National Laboratory (LLNL). Figure 1 shows the arrangement of the elliptical PET crystals in the snout of a NIF target diagnostic shown in Figure 2. The spectrum from the crystals is captured by four image plates located behind the crystals. A typical mandrel, the darkened section, upon which the PET crystal is glued, is shown in Figure 3, which also shows the complete ellipse. There are four elliptical segment types, each having the same major axis but a different minor axis. The crystals are 150 mm long in the diffraction direction and 25.4 mm high. Two crystals of each type were calibrated. The throughput for each spectrometer is determined by the integrated reflectivity of the PET crystal.[1] The goal of this effort was to measure the reflectivity curve of the PET curved crystal at several energies and determine the integrated reflectivity and the curve width as a function of the X-ray spectral energy and location on the ellipse where the beam strikes.
Date: April 26, 2012
Creator: Haugh, M J; Ross, P W; Regan, P W; Magoon, J; Shoup, M J; Barrios, M A et al.
Partner: UNT Libraries Government Documents Department

Photoinduced changes of reflectivity in single crystals of YBa2Cu3O6.5 (Ortho II)

Description: We report measurements of the photoinduced change in reflectivity of an untwinned single crystal of YBa2Cu3O6.5 in the ortho II structure. The decay rate of the transient change in reflectivity is found to decrease rapidly with decreasing temperature and, below Tc, with decreasing laser intensity. We interpret the decay as a process of thermalization of antinodal quasiparticles, with a rate determined by inelastic scattering of quasiparticle pairs.
Date: March 14, 2002
Creator: Segre, Gino P.; Gedik, Nuh; Orenstein, Joseph; Bonn, Doug A.; Liang, Ruixing & Hardy, Walter N.
Partner: UNT Libraries Government Documents Department

Molecular orientation in soft matter thin films studied by resonant soft X-ray reflectivity

Description: We present a technique to study depth profiles of molecular orientation in soft matter thin films with nanometer resolution. The method is based on dichroism in resonant soft X-ray reflectivity using linear s- and p-polarization. It combines the chemical sensitivity of Near-Edge X-ray Absorption Fine Structure spectroscopy to specific molecular bonds and their orientation relative to the polarization of the incident beam with the precise depth profiling capability of X-ray reflectivity. We demonstrate these capabilities on side chain liquid crystalline polymer thin films with soft X-ray reflectivity data at the carbon K edge. Optical constants of the anisotropic refractive index ellipsoid were obtained from a quantitative analysis using the Berreman formalism. For films up to 50 nm thickness we find that the degree of orientation of the long axis exhibits no depth variation and isindependent of the film thickness.
Date: January 12, 2011
Creator: Mezger, Markus; Jerome, Blandine; Kortright, Jeffrey B.; Valvidares, Manuel; Gullikson, Eric; Giglia, Angelo et al.
Partner: UNT Libraries Government Documents Department

Native SrTiO3 (001) surface layer from resonant Ti L2,3 reflectance spectroscopy

Description: We quantitatively model resonant Ti L2,3 reflectivity Rs,p(q, hn) from several SrTiO3 (001) single crystals having different initial surface preparations and stored in ambient conditions before and between measurements. All samples exhibit unexpected 300 K Rs(hn) - Rp(hn) anisotropy corresponding to weak linear dichroism and tetragonal distortion of the TiO6 octahedra indicating a surface layer with properties different from cubic SrTiO3. Oscillations in Rs(q) confirm a ubiquitous surface layer 2-3 nm thick that evolves over a range of time scales. Resonant optical constant spectra derived from Rs,p(hn) assuming a uniform sample are refined using a single surface layer to fit measured Rs(q). Differences in surface layer and bulk optical properties indicate that the surface is significantly depleted in Sr and enriched in Ti and O. While consistent with the tendency of SrTiO3 surfaces toward non-stoichiometry, this layer does not conform simply to existing models for the near surface region and apparently forms via room temperature surface reactions with the ambient. This new quantitative spectral modeling approach is generally applicable and has potential to study near-surface properties of a variety of systems with unique chemical and electronic sensitivities.
Date: November 3, 2010
Creator: Valvidares, Manuel; Huijben, Mark; Yu, Pu; Ramesh, Ramamoorthy & Kortright, Jeffrey
Partner: UNT Libraries Government Documents Department

Multilayer reflective coatings for extreme-ultraviolet lithography

Description: Multilayer mirror coatings which reflect extreme ultraviolet (EUV) radiation are a key enabling technology for EUV lithography. Mo/Si multilayers with reflectances of 67.5% at 13.4 nm are now routinely achieved and reflectances of 70 2% at 11.4 nm were obtained with MO/Be multilayers. High reflectance is achieved with careful control of substrate quality, layer thicknesses, multilayer materials, interface quality, and surface termination. Reflectance and film stress were found to be stable relative to the requirements for application to EUV lithography. The run-to-run reproducibility of the reflectance peak position was characterized to be better than 0.2%, providing the required wavelength matching among the seven multilayer-coated mirrors used in the present lithography system design. Uniformity of coating was improved to better than 0.5% across 150 mm diameter substrates. These improvements in EUV multilayer mirror technology will enable us to meet the stringent specifications for coating the large optical substrates for our next-generation EUV lithography system.
Date: March 10, 1998
Creator: Montcalm, C., LLNL
Partner: UNT Libraries Government Documents Department

Advanced Model for SBS of a Randomized Laser Beam and Application to Polarization Smoothing Experiments with Preformed Underdense Plasmas

Description: An advanced statistical model is presented, which describes the SBS of a randomized laser beam interacting with an underdense, expanding plasma. The model accounts for the self-focusing of speckles and for its influence on the speckles SBS reflectivity in the regime where the effect of plasma heating is important. Plasma heating has an important effect on speckle self-focusing and it decreases the SBS threshold and also decreases the SBS reflectivity. The model exhibit a good agreement with the measured SBS levels at the LULI multi-beam facility for a broad range of the laser and plasma parameters and both types of beam smoothing--RPP and PS. Both the model and the experiments confirm that the PS technique allows to control the SBS level more efficiently than RPP.
Date: June 30, 2000
Creator: Labaune, C.; Depierreux, S.; Baldis, H. A.; Huller, S; Myatt, J. & Pesme, D.
Partner: UNT Libraries Government Documents Department

Laser Surface Profiler

Description: By accurately measuring the angle of reflection of a laser beam incident on a reflective surface with a position sensitive detector, changes in the surface normal direction (slope of the surface) can be determined directly. An instrument has been built that makes repeated measurements over the surface, and uses this data to produce a grayscale image of the slope. The resolution of this system to changes in the surface normal direction is found to be better than 0.01 degrees. By focusing the Iaser beam to achieve a lateral resolution of 5 pm, the resolvable surface height change due to a variation in slope is estimated to be <1 nm.
Date: November 24, 1998
Creator: Butler, M.A. & Chu, A.
Partner: UNT Libraries Government Documents Department

Plasma mirrors for short pulse lasers

Description: We show experimentally and theoretically that plasmas created by a sufficiently (1014 1015 2 short (<500 fs) intense W/cm ) laser pulse on the surface of dielectric material act as nearly perfect mirrors: reflecting p to 90% of the incident radiation with a wavefront quality equal to that of the initial solid surface.
Date: June 11, 1997
Creator: Yanovksy, V.P.; Perry, M.D.; Brown, C.G.; Feit, M.D. & Rubenchik, A.
Partner: UNT Libraries Government Documents Department

ASTM standards for measuring solar reflectance and infrared emittance of construction materials and comparing their steady-state surface temperatures

Description: Numerous experiments on individual buildings in California and Florida show that painting roofs white reduces air conditioning load up to 50%, depending on the thermal resistance or amount of insulation under the roof. The savings, of course, are strong functions of the thermal integrity of a building and climate. In earlier work, the authors have estimated the national energy savings potential from reflective roofs and paved surfaces. Achieving this potential, however, is conditional on receiving the necessary Federal, states, and electric utilities support to develop materials with high solar reflectance and design effective implementation programs. An important step in initiating an effective program in this area is to work with the american Society for Testing and Materials (ASTM) and the industry to create test procedures, rating, and labeling for building and paving materials. A subcommittee of ASTM E06, E06.42, on Cool Construction Materials, was formed as the vehicle to develop standard practices for measuring, rating, and labeling cool construction materials. The subcommittee has also undertaken the development of a standard practice for calculating a solar reflectance index (SRI) of horizontal and low-sloped surfaces. SRI is a measure of the relative steady-state temperature of a surface with respect to a standard white surface (SRI = 100) and a standard black surface (SRI = 0) under standard solar and ambient conditions. This paper discusses the technical issues relating to development of these two ASTM standards.
Date: August 1, 1996
Creator: Akbari, H.; Levinson, R. & Berdahl, P.
Partner: UNT Libraries Government Documents Department

Recent highlights of X-ray magnetic scattering studies from surfaces

Description: In this work, recent studies of surface magnetism, as observed by x-ray scattering techniques, are described. The experiments were concerned with uranium dioxide crystals for which x-ray resonance effects enhance the small magnetic signal from the surface. The main result is that, in contrast to the bulk which exhibits a discontinuous magnetic ordering transition, both the (001) and (111) surface layers order continuously. This is reminiscent of the general phenomenon of surface wetting, but had not been previously observed for magnetic materials. Magnetic reflectivity studies show further that the near-surface magnetic layers are more disordered than layers deep in the bulk, even at low temperatures.
Date: December 31, 1998
Creator: Watson, G.M.; Gibbs, D. & Lander, G.H.
Partner: UNT Libraries Government Documents Department

Near-ground cooling efficacies of trees and high-albedo surfaces

Description: Daytime summer urban heat islands arise when the prevalence of dark-colored surfaces and lack of vegetation make a city warmer than neighboring countryside. Two frequently-proposed summer heat island mitigation measures are to plant trees and to increase the albedo (solar reflectivity) of ground surfaces. This dissertation examines the effects of these measures on the surface temperature of an object near the ground, and on solar heating of air near the ground. Near-ground objects include people, vehicles, and buildings. The variation of the surface temperature of a near-ground object with ground albedo indicates that a rise in ground albedo will cool a near-ground object only if the object`s albedo exceeds a critical value. This critical value of object albedo depends on wind speed, object geometry, and the height of the atmospheric thermal boundary layer. It ranges from 0.15 to 0.37 for a person. If an object has typical albedo of 0.3, increasing the ground albedo by.
Date: May 1, 1997
Creator: Levinson, R.M.
Partner: UNT Libraries Government Documents Department