Prof. David D. Allred Profile

Prof. David D. Allred

Professor at Brigham Young Univ

SPIE Involvement:

Author

Publications (28)

Proceedings Article | 26 August 2024 Presentation + Paper

Stability of XeF2 passivated Al plus LiF as possible coating for HWO

Devin Lewis, Tanner Rydalch, David Allred, Luis Rodriguez de Marcos, Manuel Quijada, Javier del Hoyo, Mateo Batkis

Proceedings Volume 13100, 131000K (2024) https://doi.org/10.1117/12.3018471

KEYWORDS: Aluminum, Reflectivity, Laser induced fluorescence, Humidity, X-ray photoelectron spectroscopy, Atomic force microscopy, Relative humidity, Coating, Semiconducting wafers, Mirrors

Read Abstract +

Proceedings Article | 21 August 2024 Paper

Enhanced far ultra-violet optical properties of physical vapor deposited aluminum mirrors through fluorination

Manuel Quijada, Javier Del Hoyo, Luis Rodriguez de Marcos, Edward Wollack, Mateo Batkis, Devin Lewis, Tanner Rydalch, David Allred

Proceedings Volume 13093, 1309340 (2024) https://doi.org/10.1117/12.3021592

KEYWORDS: Aluminum, Reflectivity, Silicon, Mirrors, Laser induced fluorescence, Far ultraviolet, Semiconducting wafers, Zerodur, Vacuum chambers, Relative humidity

Read Abstract +

Astronomical instrumentation for measurements in the Far Ultraviolet (FUV, 90−200 nm) have historically considered aluminum (Al) thin film mirrors due to this material high reflectance over this wavelength range. However, the native aluminum oxide layer that forms on Al upon exposure to the atmosphere is strongly absorbing in this wavelength range, requiring that the films be protected with a dielectric that inhibits oxidation. Typically, magnesium fluoride (MgF₂) or lithium fluoride (LiF) coatings are used as protective layers, but each has shortcomings. For example, MgF₂ has an absorption cutoff at 115 nm that reduces performance below this wavelength, which is a critical part of the FUV spectrum for observational astrophysics. The use of LiF as a protection for Al provides a lower absorption cutoff at 100 nm, but it is hygroscopic and thus susceptible to degradation in humid conditions. Our team at GSFC has developed a new reactive Physical Vapor Deposition (rPVD) process that consists of a fluorination process with XeF₂ gas combined with our traditional PVD process. We have found that this new rPVD process produces Al+XeF₂+LiF (XeLiF) and Al+XeF₂+MgF₂ (XeMgF₂) mirror coatings with unprecedented reflectance. In addition, the rPVD process seems to produce much more environmentally stable coatings (when compared to the conventional process without the XeF₂ fluorination). We report on IR/Vis/UV reflectance of XeLiF and XeMgF₂ mirrors. The surface roughness as well as the FUV reflectance measured over a period of 8 months for a XeLiF sample with a relatively thin (≃ 30 nm) Al layer are also reported. We have also been investigating the compatibility of this rPVD coating process for potential efficiency enhancements of Si-based gratings. Since it is known that the XeF₂ vapor is a strong Si etchant, we are investigating if the native SiO₂ layer on Si is sufficient to protect the groove profile of E-beam-ruled Si gratings from degradation. Preliminary results indicate that the native SiO₂ layer is an effective barrier against etching of Si by XeF₂.

Proceedings Article | 3 October 2023 Presentation + Paper

Addressing calibration of high-harmonic generation sources used for studying magnetism

Taylor Buckway, Aaron Redd, Devin Lewis, Eric Gullikson, Joshua Vawdrey, Karine Chesnel, David Allred, Richard Sandberg

Proceedings Volume 12694, 1269404 (2023) https://doi.org/10.1117/12.2692397

KEYWORDS: Iron, Magnetism, Extreme ultraviolet, Calibration, Spectral calibration, Gold, High harmonic generation, X-rays

Read Abstract +

Proceedings Article | 2 October 2023 Presentation + Paper

Variable-angle, spectroscopic ellipsometry study on the repeated application of first contact polymer on silicon-based surfaces

Joshua Vawdrey, James Hamilton, David Allred

Proceedings Volume 12666, 1266609 (2023) https://doi.org/10.1117/12.2692390

KEYWORDS: Silicon, Oxides, Contamination, Silicon nitride, Optical surfaces, Silica, Statistical analysis, Linear regression, Spectroscopic ellipsometry, Ellipsometry

Read Abstract +

Proceedings Article | 3 October 2022 Presentation + Paper

Carbon nanotube microfabricated window with extreme ultraviolet transmission and differential pumping

Scott Olsen, Richard Vanfleet, David Allred, Robert Davis

Proceedings Volume 12201, 1220102 (2022) https://doi.org/10.1117/12.2631989

KEYWORDS: Plasmas, Extreme ultraviolet, Carbon nanotubes, Helium, Microfabrication, Carbon, Systems modeling, MATLAB, Light emitting diodes, Diffraction

Read Abstract +

Proceedings Article | 31 August 2022 Poster + Presentation + Paper

Evidence that evaporated Al/AlF3 bilayer thin films stored in a 327 K oven for over 2500 hours have not degraded

Kenan Fronk, David Allred

Proceedings Volume 12181, 121813A (2022) https://doi.org/10.1117/12.2630711

KEYWORDS: Aluminum, Data modeling, Thin films, Reflectivity, Statistical modeling, Mirrors, Silicon, Oscillators, Oxidation, Spectroscopic ellipsometry, Far ultraviolet, Space observatories, Magnesium fluoride

Read Abstract +

Proceedings Article | 29 August 2022 Poster + Presentation + Paper

Stability of lithium fluoride thin films as a function of humidity and temperature

Tanner D. Rydalch, Devin M. Lewis, David D. Allred

Proceedings Volume 12188, 121884M (2022) https://doi.org/10.1117/12.2630514

KEYWORDS: Atomic force microscopy, Humidity, Aluminum, Thin films, Lithium, Silicon, Surface roughness, Mirrors

Read Abstract +

Proceedings Article | 15 December 2020 Poster + Paper

Illuminating the degradation of lithium fluoride mirror coatings in humid environments

Devin Lewis, Caleb Michael Plewe, Alexandra Gallion Stapley, Joshua Vawdrey, R. Steven Turley, David Allred

Proceedings Volume 11451, 1145141 (2020) https://doi.org/10.1117/12.2576258

KEYWORDS: Laser induced fluorescence, Mirrors, Lithium, Scanning electron microscopy, Humidity, Thin films, Aluminum, Temperature metrology, Spectroscopy, Spectroscopic ellipsometry

Read Abstract +

Proceedings Article | 13 December 2020 Poster + Paper

Retardation of the oxidation of aluminum thin films in low-oxygen and cryogenic environments

S. Merlin Hart, Donovan Smith, David Allred

Proceedings Volume 11451, 1145149 (2020) https://doi.org/10.1117/12.2576339

KEYWORDS: Mirrors, Aluminum, Ultraviolet radiation, Reflection, Thin films, Scanning electron microscopy, Oxidation, Nitrogen, Liquids, Spectroscopic ellipsometry

Read Abstract +

Proceedings Article | 21 August 2020 Presentation + Paper

A carbon nanotube structure for an EUV window with differential pumping

Scott Olsen, Richard Vanfleet, David Allred, Steve Turley, Robert Davis

Proceedings Volume 11491, 1149104 (2020) https://doi.org/10.1117/12.2569049

KEYWORDS: Optical collimators, Extreme ultraviolet, Carbon nanotubes, Plasma, Lamps, Photodiodes, Plasma etching, Helium, Semiconducting wafers, Scanning electron microscopy

Read Abstract +

Proceedings Article | 9 September 2019 Presentation + Paper

Using ellipsometry and x-ray photoelectron spectroscopy for real-time monitoring of the oxidation of aluminum mirrors protected by ultrathin MgF2 layers

Brian Johnson, Tahereh Avval, Grant Hodges, Victoria Carver, Karen Membreno, David Allred, Matthew Linford

Proceedings Volume 11116, 111160O (2019) https://doi.org/10.1117/12.2529893

KEYWORDS: Aluminum, Oxidation, Data modeling, Silicon, Oxides, Magnesium fluoride, Statistical modeling, Mirrors, Metals, Statistical analysis

Read Abstract +

Proceedings Article | 10 July 2018 Presentation

A study of ultrathin fluoride and removable barrier films on aluminum for space-observatories with far UV observations. (Conference Presentation)

David Allred, Yhoshua Wug-Jerez, R. Steven Turley, J. Gabriel Richardson, James Hamilton

Proceedings Volume 10699, 1069903 (2018) https://doi.org/10.1117/12.2314382

KEYWORDS: Aluminum, Ultraviolet radiation, Mirrors, Amorphous silicon, Earth's atmosphere, Reflectivity, Space mirrors, Magnesium fluoride, Lithium, Mirror pointing

Read Abstract +

Proceedings Article | 5 September 2017 Presentation + Paper

Adding EUV reflectance to aluminum-coated mirrors for space-based observation

David Allred, R. Steven Turley, Stephanie Thomas, Spencer Willett, Michael Greenburg, Spencer Perry

Proceedings Volume 10398, 103980Y (2017) https://doi.org/10.1117/12.2274694

KEYWORDS: Mirrors, Aluminum, Reflectivity, Space telescopes, Extreme ultraviolet, Observatories, Hydrogen, Plasma, Space mirrors, Dry etching

Read Abstract +

Protective layers on aluminum mirror surfaces which can be removed via the use of atomic hydrogen or hydrogen plasmas at the point of use in space may allow an expansion of broad-band mirrors into the EUV. LUVOIR (large, UV-optical-IR telescope) is a potential NASA flagship space-based observatory of the 2020’s or 30’s. It would utilize the largest mirrors ever flown1 . Their reflective coating will almost certainly be aluminum, since such telescopes would profit from truly broad-band mirrors. To achieve reflectance over the broadest band, the top surface of such aluminum mirrors, however, needs to be bare, without the oxide layers that naturally form in air. This will open the 11 to 15 eV band. Since thin aluminum films are largely transparent between 15 and 70 eV an EUV mirror under the aluminum could make EUV bands such as 30.4 nm available for space-based astrophysics without sacrificing mirror IR, visible and UV reflectance. The local space environment for the observatory is sufficiently oxygen-free that the surface should remain bare for decades. We discuss protecting as-deposited aluminum mirrors with robust, oxygenimpenetrable, barrier layers applied in vacuo to the aluminum immediately after deposition and before air contact. The goal is that the barrier could also be cleanly, and relatively easily, removed once the mirror is in space. We propose hydrogen atoms as the means for removing the overcoat, since they can be expected to meet the criteria that the means is gentle enough to not roughen the mirror surface, and does not redeposit material on the mirror or other spacecraft components. We have investigated both organic and inorganic (such as, a-Si) hydrogen-removable films that can be applied to the aluminum immediately after its deposition have been investigated. We also examined the REVAP technique, using Cd and Zn. Agglomeration limited their effectiveness as barrier layers. That and dealing with the reevaporated atoms may limit their utility as barrier materials.

Proceedings Article | 29 August 2006 Paper

Thorium dioxide thin films in the extreme ultraviolet

Nicole Brimhall, Amy Grigg, R. Steven Turley, David Allred

Proceedings Volume 6317, 631710 (2006) https://doi.org/10.1117/12.687201

KEYWORDS: Reflectivity, Thorium, Transmittance, Extreme ultraviolet, Reflection, Thin films, Silicon, Uranium, Diodes, Oxidation

Read Abstract +

Proceedings Article | 29 August 2006 Paper

Understanding DC-bias sputtered thorium oxide thin films useful in EUV optics

William Evans, Sarah Barton, Michael Clemens, David Allred

Proceedings Volume 6317, 631711 (2006) https://doi.org/10.1117/12.687499

KEYWORDS: Absorption, Thin films, Thorium, Silicon, Oxides, Data modeling, Sputter deposition, Reflectivity, Crystals, Statistical modeling

Read Abstract +

Proceedings Article | 14 October 2004 Paper

Optical properties and application of uranium-based thin films for the extreme ultraviolet and soft x-ray region

Richard Sandberg, David Allred, Shannon Lunt, Marie Urry, R. Steven Turley

Proceedings Volume 5538, (2004) https://doi.org/10.1117/12.560717

KEYWORDS: Uranium, Reflectivity, Oxides, Nickel, Thin films, Gold, X-rays, Extreme ultraviolet, Absorption, Zone plates

Read Abstract +

Proceedings Article | 14 October 2004 Paper

Determining ruthenium's optical constants in the spectral range 11-14 nm

Luke Bissell, David Allred, R. Steven Turley, William Evans, Jed Johnson

Proceedings Volume 5538, (2004) https://doi.org/10.1117/12.560900

KEYWORDS: Ruthenium, Reflectivity, Extreme ultraviolet, Refraction, Data modeling, Mirrors, Thin films, Silicon, Extreme ultraviolet lithography, Oxidation

Read Abstract +

Proceedings Article | 13 January 2004 Paper

A comparison of uranium oxide and nickle as single-layer reflectors from 2.7 to 11.6 nm

Richard Sandberg, David Allred, J. Johnson, R. Turley

Proceedings Volume 5193, (2004) https://doi.org/10.1117/12.523478

KEYWORDS: Nickel, Reflectivity, Uranium, Oxides, Quartz, X-rays, Carbon, Absorption, Reflectors, Thin films

Read Abstract +

Proceedings Article | 24 December 2002 Paper

Highly reflective uranium mirrors for astrophysics applications

David Allred, Matthew Squires, R. Steven Turley, Webster Cash, Ann Shipley

Proceedings Volume 4782, (2002) https://doi.org/10.1117/12.451359

KEYWORDS: Uranium, Reflectivity, Carbon, Mirrors, Nickel, X-rays, Oxides, Thin films, Chemical elements, Oxidation

Read Abstract +

Proceedings Article | 23 November 1999 Paper

Optical constants of sputtered U and a-Si at 30.4 and 58.4 nm

Matthew Squires, David Allred, R. Steven Turley

Proceedings Volume 3767, (1999) https://doi.org/10.1117/12.371141

KEYWORDS: Uranium, Reflectivity, Amorphous silicon, Multilayers, Mirrors, Oxides, Sensors, Extreme ultraviolet, Silicon, Plasma

Read Abstract +

Proceedings Article | 23 November 1999 Paper

Dual-function EUV multilayer mirrors for the IMAGE mission

David Allred, R. Steven Turley, Matthew Squires

Proceedings Volume 3767, (1999) https://doi.org/10.1117/12.371140

KEYWORDS: Mirrors, Multilayers, Reflectivity, Extreme ultraviolet, Uranium, Sensors, Silicon, Aluminum, Imaging systems, Monochromators

Read Abstract +

We have developed a new family of EUV multilayer mirror coatings using uranium. Using this approach we have coated a set of six mirrors for the EUV Imager, a component of the IMAGE mission. This mission is a Medium Explorer (MIDEX) program, which is scheduled for launch early in 2000. The EUV Imager will study the distribution of He⁺ in the Earth's plasmasphere by detecting its resonantly scattered emission at 30.4 nm (41 eV) and will produce images of the structure and dynamics of the cold plasma on a global scale. There is, however, a bright emission at 58.4 nm (21 eV), which comes from neutral helium in the earth's ionosphere which also must be blocked. These photons are at too high an energy to filter with aluminum but at too low an energy to have negligible reflectance from most materials commonly used in EUV mirrors. Thus, a multilayer system which satisfied two optical functions, high reflectance (greater than 20%) at 41 eV and low reflectance (less than 2%) at 21 eV, were designed and successfully fabricated. Such mirrors with dual optical functions in the soft x-ray/EUV had not previously been designed or built. These specifications were particularly challenging because many materials have higher single layer reflectances at 58.4 nm than at 30.4 nm. Essentially, the mirror must have low reflectance at 21 eV without loss of reflection at 30.4 nm. This was accomplished. The top part of the multilayer, which reflects well at 30.4 nm, also acts as antireflection layers at 58.4 nm. In the past, multilayers usually have consisted of periodic bilayers. We have explored the use of a periodic mirrors in place of the standard periodic designs. Along the way we have created the computational tools, which include genetic algorithms, to optimize selection of materials and thicknesses. We are currently in the process of building up an EUV characterization system and developing a general way of measuring the optical constants of air-sensitive thin films. We discuss the other material and fabrication challenges faced, which include: (1) The high absorption of almost everything in the EUV. This means that only a few interfaces in a multilayer will contribute to its reflectance. (2) Surface contamination and corrosion. (3) The deposition on flight mirrors that are highly curved (f equals 0.8).

Proceedings Article | 11 November 1994 Paper

Plane multilayer amplitude gratings fabrication and measurement: recent results

Douglas Hansen, Hans Pew, David Allred, John Colton, Gary Stradling, John Gunther, Serban Porumbescu

Proceedings Volume 2279, (1994) https://doi.org/10.1117/12.193174

KEYWORDS: Reflectivity, X-rays, Diffraction gratings, Sensors, Spectral resolution, Monochromators, Polarization, X-ray detectors, X-ray telescopes, Ultraviolet radiation

Read Abstract +

Proceedings Article | 24 June 1993 Paper

Use of Raman spectroscopy in characterizing soft x-ray multilayers: tools in understanding structure and interfaces

Ming Cai, Qi Wang, David Allred, Larry Knight, Dorian Hatch, Arturo Reyes-Mena, Guizhong Zhang

Proceedings Volume 1848, (1993) https://doi.org/10.1117/12.147396

KEYWORDS: Raman spectroscopy, Multilayers, Annealing, Silicon, Interfaces, Crystals, X-rays, Molybdenum, X-ray diffraction, Amorphous silicon

Read Abstract +

Proceedings Article | 21 January 1993 Paper

Multilayer phase-diffraction gratings modeled as a structure in three dimensions

Douglas Hansen, Arturo Reyes-Mena, John Colton, Larry Knight, David Allred

Proceedings Volume 1742, (1993) https://doi.org/10.1117/12.140581

KEYWORDS: Diffraction gratings, Interfaces, Diffraction, 3D modeling, Optical design, Multilayers, Reflection, X-ray diffraction, Wavefronts, Lithography

Read Abstract +

Proceedings Article | 13 January 1993 Paper

X-ray diode using a silicon field-emission photocathode

Wael Karain, Larry Knight, David Allred, Arturo Reyes-Mena

Proceedings Volume 1741, (1993) https://doi.org/10.1117/12.138731

KEYWORDS: Silicon, X-rays, Etching, Oxides, Diodes, X-ray sources, Modulation, X-ray microscopy, Aluminum, Semiconducting wafers

Read Abstract +

Proceedings Article | 1 October 1991 Paper

Transmittances of thin polymer films and their suitability as a supportive substrate for a soft x-ray solar filter

Memorie Williams, Evan Hansen, Arturo Reyes-Mena, David Allred

Proceedings Volume 1549, (1991) https://doi.org/10.1117/12.48335

KEYWORDS: Polymers, X-rays, X-ray astronomy, Image filtering, Extreme ultraviolet, Polymer thin films, Telescopes, Optical filters, Sensors, Gamma radiation

Read Abstract +

Proceedings Article | 1 January 1991 Paper

Advanced infrared optically black baffle materials

Roland Seals, Charles Egert, David Allred

Proceedings Volume 1330, (1991) https://doi.org/10.1117/12.22638

KEYWORDS: Beryllium, Reflectivity, Optics manufacturing, Infrared radiation, Bidirectional reflectance transmission function, Boron, Scanning electron microscopy, Sensors, Photomicroscopy, Manufacturing

Read Abstract +

Proceedings Article | 1 December 1990 Paper

Diffuse absorbing beryllium coatings produced by magnetron sputtering

Charles Egert, David Allred

Proceedings Volume 1331, (1990) https://doi.org/10.1117/12.22676

KEYWORDS: Beryllium, Optical coatings, Etching, Reflectivity, Sputter deposition, Bidirectional reflectance transmission function, Absorption, Photomicroscopy, Light scattering, Optical design

Read Abstract +

Showing 5 of 28 publications

Conference Committee Involvement (1)

Optical Constants of Materials for UV to X-Ray Wavelengths

4 August 2004 | Denver, Colorado, United States

View contact details

UPDATE YOUR PROFILE

Is this your profile? Update it now.

Sign into your SPIE.org account

Don’t have a profile and want one?

Create an account on SPIE.org

Keywords/Phrases

Search In:

Publication Years