Matching Items (12)
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Description
Much of Mars' surface is mantled by bright dust, which masks the spectral features used to interpret the mineralogy of the underlying bedrock. Despite the wealth of near-infrared (NIR) and thermal infrared data returned from orbiting spacecraft in recent decades, the detailed bedrock composition of approximately half of the martian

Much of Mars' surface is mantled by bright dust, which masks the spectral features used to interpret the mineralogy of the underlying bedrock. Despite the wealth of near-infrared (NIR) and thermal infrared data returned from orbiting spacecraft in recent decades, the detailed bedrock composition of approximately half of the martian surface remains relatively unknown due to dust cover. To address this issue, and to help gain a better understanding of the bedrock mineralogy in dusty regions, data from the Thermal Emission Spectrometer (TES) Dust Cover Index (DCI) and Mars Reconnaissance Orbiter (MRO) Mars Color Imager (MARCI) were used to identify 63 small localized areas within the classical bright dusty regions of Arabia Terra, Elysium Planitia, and Tharsis as potential "windows" through the dust; that is, areas where the dust cover is thin enough to permit infrared remote sensing of the underlying bedrock. The bedrock mineralogy of each candidate "window" was inferred using processed spectra from the Mars Express (MEx) Observatoire pour la Mineralogie, l'Eau, les Glaces et l'Activité (OMEGA) NIR spectrometer and, where possible, TES. 12 areas of interest returned spectra that are consistent with mineral species expected to be present at the regional scale, such as high- and low-calcium pyroxene, olivine, and iron-bearing glass. Distribution maps were created using previously defined index parameters for each species present within an area. High-quality TES spectra, if present within an area of interest, were deconvolved to estimate modal mineralogy and support NIR results. OMEGA data from Arabia Terra and Elysium Planitia are largely similar and indicate the presence of high-calcium pyroxene with significant contributions of glass and olivine, while TES data suggest an intermediate between the established southern highlands and Syrtis Major compositions. Limited data from Tharsis indicate low-calcium pyroxene mixed with lesser amounts of high-calcium pyroxene and perhaps glass. TES data from southern Tharsis correlate well with the previously inferred compositions of the Aonium and Mare Sirenum highlands immediately to the south.
ContributorsLai, Jason Chi-Shun (Author) / Bell, James (Thesis advisor) / Christensen, Philip R. (Philip Russel) (Committee member) / Hervig, Richard (Committee member) / Arizona State University (Publisher)
Created2014
Description
As the demand for power increases in populated areas, so will the demand for water. Current power plant technology relies heavily on the Rankine cycle in coal, nuclear and solar thermal power systems which ultimately use condensers to cool the steam in the system. In dry climates, the amount of

As the demand for power increases in populated areas, so will the demand for water. Current power plant technology relies heavily on the Rankine cycle in coal, nuclear and solar thermal power systems which ultimately use condensers to cool the steam in the system. In dry climates, the amount of water to cool off the condenser can be extremely large. Current wet cooling technologies such as cooling towers lose water from evaporation. One alternative to prevent this would be to implement a radiative cooling system. More specifically, a system that utilizes the volumetric radiation emission from water to the night sky could be implemented. This thesis analyzes the validity of a radiative cooling system that uses direct radiant emission to cool water. A brief study on potential infrared transparent cover materials such as polyethylene (PE) and polyvinyl carbonate (PVC) was performed. Also, two different experiments to determine the cooling power from radiation were developed and run. The results showed a minimum cooling power of 33.7 W/m2 for a vacuum insulated glass system and 37.57 W/m2 for a tray system with a maximum of 98.61 Wm-2 at a point when conduction and convection heat fluxes were considered to be zero. The results also showed that PE proved to be the best cover material. The minimum numerical results compared well with other studies performed in the field using similar techniques and materials. The results show that a radiative cooling system for a power plant could be feasible given that the cover material selection is narrowed down, an ample amount of land is available and an economic analysis is performed proving it to be cost competitive with conventional systems.
ContributorsOvermann, William (Author) / Phelan, Patrick (Thesis advisor) / Trimble, Steve (Committee member) / Taylor, Robert (Committee member) / Arizona State University (Publisher)
Created2011
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Description
HgCdTe is the dominant material currently in use for infrared (IR) focal-plane-array (FPA) technology. In this dissertation, transmission electron microscopy (TEM) was used for the characterization of epitaxial HgCdTe epilayers and HgCdTe-based devices. The microstructure of CdTe surface passivation layers deposited either by hot-wall epitaxy (HWE) or molecular beam epitaxy

HgCdTe is the dominant material currently in use for infrared (IR) focal-plane-array (FPA) technology. In this dissertation, transmission electron microscopy (TEM) was used for the characterization of epitaxial HgCdTe epilayers and HgCdTe-based devices. The microstructure of CdTe surface passivation layers deposited either by hot-wall epitaxy (HWE) or molecular beam epitaxy (MBE) on HgCdTe heterostructures was evaluated. The as-deposited CdTe passivation layers were polycrystalline and columnar. The CdTe grains were larger and more irregular when deposited by HWE, whereas those deposited by MBE were generally well-textured with mostly vertical grain boundaries. Observations and measurements using several TEM techniques showed that the CdTe/HgCdTe interface became considerably more abrupt after annealing, and the crystallinity of the CdTe layer was also improved. The microstructure and compositional profiles of CdTe(211)B/ZnTe/Si(211) heterostructures grown by MBE was investigated. Many inclined {111}-type stacking faults were present throughout the thin ZnTe layer, terminating near the point of initiation of CdTe growth. A rotation angle of about 3.5° was observed between lattice planes of the Si substrate and the final CdTe epilayer. Lattice parameter measurement and elemental profiles indicated that some local intermixing of Zn and Cd had taken place. The average widths of the ZnTe layer and the (Cd, Zn)Te transition region were found to be roughly 6.5 nm and 3.5 nm, respectively. Initial observations of CdTe(211)B/GaAs(211) heterostructures indicated much reduced defect densities near the vicinity of the substrate and within the CdTe epilayers. HgCdTe epilayers grown on CdTe(211)B/GaAs(211) composite substrate were generally of high quality, despite the presence of precipitates at the HgCdTe/CdTe interface. The microstructure of HgCdSe thin films grown by MBE on ZnTe/Si(112) and GaSb(112) substrates were investigated. The quality of the HgCdSe growth was dependent on the growth temperature and materials flux, independent of the substrate. The materials grown at 100°C were generally of high quality, while those grown at 140°C had {111}-type stacking defects and high dislocation densities. For epitaxial growth of HgCdSe on GaSb substrates, better preparation of the GaSb buffer layer will be essential in order to ensure that high-quality HgCdSe can be grown.
ContributorsZhao, Wenfeng (Author) / Smith, David J. (Thesis advisor) / McCartney, Martha (Committee member) / Carpenter, Ray (Committee member) / Bennett, Peter (Committee member) / Treacy, Michael J. (Committee member) / Arizona State University (Publisher)
Created2011
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Description
Semiconductor nanowires (NWs) are one dimensional materials and have size quantization effect when the diameter is sufficiently small. They can serve as optical wave guides along the length direction and contain optically active gain at the same time. Due to these unique properties, NWs are now very promising and extensively

Semiconductor nanowires (NWs) are one dimensional materials and have size quantization effect when the diameter is sufficiently small. They can serve as optical wave guides along the length direction and contain optically active gain at the same time. Due to these unique properties, NWs are now very promising and extensively studied for nanoscale optoelectronic applications. A systematic and comprehensive optical and microstructural study of several important infrared semiconductor NWs is presented in this thesis, which includes InAs, PbS, InGaAs, erbium chloride silicate and erbium silicate. Micro-photoluminescence (PL) and transmission electron microscope (TEM) were utilized in conjunction to characterize the optical and microstructure of these wires. The focus of this thesis is on optical study of semiconductor NWs in the mid-infrared wavelengths. First, differently structured InAs NWs grown using various methods were characterized and compared. Three main PL peaks which are below, near and above InAs bandgap, respectively, were observed. The octadecylthiol self-assembled monolayer was employed to passivate the surface of InAs NWs to eliminate or reduce the effects of the surface states. The band-edge emission from wurtzite-structured NWs was completely recovered after passivatoin. The passivated NWs showed very good stability in air and under heat. In the second part, mid-infrared optical study was conducted on PbS wires of subwavelength diameter and lasing was demonstrated under optical pumping. The PbS wires were grown on Si substrate using chemical vapor deposition and have a rock-salt cubic structure. Single-mode lasing at the wavelength of ~3000-4000 nm was obtained from single as-grown PbS wire up to the temperature of 115 K. PL characterization was also utilized to demonstrate the highest crystallinity of the vertical arrays of InP and InGaAs/InP composition-graded heterostructure NWs made by a top-down fabrication method. TEM-related measurements were performed to study the crystal structures and elemental compositions of the Er-compound core-shell NWs. The core-shell NWs consist of an orthorhombic-structured erbium chloride silicate shell and a cubic-structured silicon core. These NWs provide unique Si-compatible materials with emission at 1530 nm for optical communications and solid state lasers.
ContributorsSun, Minghua (Author) / Ning, Cun-Zheng (Thesis advisor) / Yu, Hongbin (Committee member) / Carpenter, Ray W. (Committee member) / Johnson, Shane (Committee member) / Arizona State University (Publisher)
Created2011
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Description
Infrared photodetectors, used in applications for sensing and imaging, such as military target recognition, chemical/gas detection, and night vision enhancement, are predominantly comprised of an expensive II-VI material, HgCdTe. III-V type-II superlattices (SLs) have been studied as viable alternatives for HgCdTe due to the SL advantages over HgCdTe: greater control

Infrared photodetectors, used in applications for sensing and imaging, such as military target recognition, chemical/gas detection, and night vision enhancement, are predominantly comprised of an expensive II-VI material, HgCdTe. III-V type-II superlattices (SLs) have been studied as viable alternatives for HgCdTe due to the SL advantages over HgCdTe: greater control of the alloy composition, resulting in more uniform materials and cutoff wavelengths across the wafer; stronger bonds and structural stability; less expensive substrates, i.e., GaSb; mature III-V growth and processing technologies; lower band-to-band tunneling due to larger electron effective masses; and reduced Auger recombination enabling operation at higher temperatures and longer wavelengths. However, the dark current of InAs/Ga1-xInxSb SL detectors is higher than that of HgCdTe detectors and limited by Shockley-Read-Hall (SRH) recombination rather than Auger recombination. This dissertation work focuses on InAs/InAs1-xSbx SLs, another promising alternative for infrared laser and detector applications due to possible lower SRH recombination and the absence of gallium, which simplifies the SL interfaces and growth processes. InAs/InAs1-xSbx SLs strain-balanced to GaSb substrates were designed for the mid- and long-wavelength infrared (MWIR and LWIR) spectral ranges and were grown using MOCVD and MBE by various groups. Detailed characterization using high-resolution x-ray diffraction, atomic force microscopy, photoluminescence (PL), and photoconductance revealed the excellent structural and optical properties of the MBE materials. Two key material parameters were studied in detail: the valence band offset (VBO) and minority carrier lifetime. The VBO between InAs and InAs1-xSbx strained on GaSb with x = 0.28 - 0.41 was best described by Qv = ÄEv/ÄEg = 1.75 ± 0.03. Time-resolved PL experiments on a LWIR SL revealed a lifetime of 412 ns at 77 K, one order of magnitude greater than that of InAs/Ga1-xInxSb LWIR SLs due to less SRH recombination. MWIR SLs also had 100's of ns lifetimes that were dominated by radiative recombination due to shorter periods and larger wave function overlaps. These results allow InAs/InAs1-xSbx SLs to be designed for LWIR photodetectors with minority carrier lifetimes approaching those of HgCdTe, lower dark currents, and higher operating temperatures.
ContributorsSteenbergen, Elizabeth H (Author) / Zhang, Yong-Hang (Thesis advisor) / Brown, Gail J. (Committee member) / Vasileska, Dragica (Committee member) / Johnson, Shane R. (Committee member) / Arizona State University (Publisher)
Created2012
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Description
Many planetary science missions study thermophysical properties of surfaces using infrared spectrometers and infrared cameras. Thermal inertia is a frequently derived thermophysical property that quantifies the ability for heat to exchange through planetary surfaces.

To conceptualize thermal inertia, the diffusion equation analogies are extended using a general effusivity term: the square

Many planetary science missions study thermophysical properties of surfaces using infrared spectrometers and infrared cameras. Thermal inertia is a frequently derived thermophysical property that quantifies the ability for heat to exchange through planetary surfaces.

To conceptualize thermal inertia, the diffusion equation analogies are extended using a general effusivity term: the square root of a product of conductivity and capacity terms. A hypothetical thermal inductance was investigated for diurnal planetary heating. The hyperbolic heat diffusion equation was solved to derive an augmented thermal inertia. The hypothetical thermal inductance was modeled with negligible effect on Mars.

Extending spectral performance of infrared cameras was desired for colder bodies in the outer solar system where peak infrared emission is at longer wavelengths. The far-infrared response of an infrared microbolometer array with a retrofitted diamond window was determined using an OSIRIS-REx—OTES interferometer. An instrument response function of the diamond interferometer-microbolometer system shows extended peak performance from 15 µm out to 20 µm and 40% performance to at least 30 µm. The results are folded into E-THEMIS for the NASA flagship mission: Europa Clipper.

Infrared camera systems are desired for the expanding smallsat community that can inherit risk and relax performance requirements. The Thermal-camera for Exploration, Science, and Imaging Spacecraft (THESIS) was developed for the Prox-1 microsat mission. THESIS, incorporating 2001 Mars Odyssey—THEMIS experience, consists of an infrared camera, a visible camera, and an instrument computer. THESIS was planned to provide images for demonstrating autonomous proximity operations between two spacecraft, verifying deployment of the Planetary Society’s LightSail-B, and conducting remote sensing of Earth. Prox-1—THESIS was selected as the finalist for the competed University Nanosatellite Program-7 and was awarded a launch on the maiden commercial SpaceX Falcon Heavy. THESIS captures 8-12 µm IR images with 100 mm optics and RGB color images with 25 mm optics. The instrument computer was capable of instrument commanding, automatic data processing, image storage, and telemetry recording. The completed THESIS has a mass of 2.04 kg, a combined volume of 3U, and uses 7W of power. THESIS was designed, fabricated, integrated, and tested in ASU’s 100K clean lab.
ContributorsVeto, Michael (Author) / Christensen, Philip C (Thesis advisor) / Bell III, Jim (Committee member) / Clarke, Amanda B (Committee member) / Asphaug, Erik (Committee member) / Sariapli, Srikanth (Committee member) / Ruff, Steven (Committee member) / Arizona State University (Publisher)
Created2018
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Description
The goal of this project was to explore biomimetics by creating a jellyfish flying device that uses propulsion of air to levitate while utilizing electromyography signals and infrared signals as mechanisms to control the device. Completing this project would require knowledge of biological signals, electrical circuits, computer programming, and physics

The goal of this project was to explore biomimetics by creating a jellyfish flying device that uses propulsion of air to levitate while utilizing electromyography signals and infrared signals as mechanisms to control the device. Completing this project would require knowledge of biological signals, electrical circuits, computer programming, and physics to accomplish. An EMG sensor was used to obtain processed electrical signals produced from the muscles in the forearm and was then utilized to control the actuation speed of the tentacles. An Arduino microprocessor was used to translate the EMG signals to infrared blinking sequences which would propagate commands through a constructed circuit shield to the infrared receiver on jellyfish. The receiver will then translate the received IR sequence into actions. Then the flying device must produce enough thrust to propel the body upwards. The application of biomimetics would best test my skills as an engineer as well as provide a method of applying what I have learned over the duration of my undergraduate career.
ContributorsTsui, Jessica W (Author) / Muthuswamy, Jitteran (Thesis director) / Blain Christen, Jennifer (Committee member) / Barrett, The Honors College (Contributor) / Harrington Bioengineering Program (Contributor)
Created2014-05
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Description
Optoelectronic and microelectronic applications of germanium-based materials have received considerable research interest in recent years. A novel method for Ge on Si heteroepitaxy required for such applications was developed via molecular epitaxy of Ge5H12. Next, As(GeH3)3, As(SiH3)3, SbD3, S(GeH3)2 and S(SiH3)2 molecular sources were utilized in degenerate n-type doping of

Optoelectronic and microelectronic applications of germanium-based materials have received considerable research interest in recent years. A novel method for Ge on Si heteroepitaxy required for such applications was developed via molecular epitaxy of Ge5H12. Next, As(GeH3)3, As(SiH3)3, SbD3, S(GeH3)2 and S(SiH3)2 molecular sources were utilized in degenerate n-type doping of Ge. The epitaxial Ge films produced in this work incorporate donor atoms at concentrations above the thermodynamic equilibrium limits. The donors are nearly fully activated, and led to films with lowest resistivity values thus far reported.

Band engineering of Ge was achieved by alloying with Sn. Epitaxy of the alloy layers was conducted on virtual Ge substrates, and made use of the germanium hydrides Ge2H6 and Ge3H8, and the Sn source SnD4. These films exhibit stronger emission than equivalent material deposited directly on Si, and the contributions from the direct and indirect edges can be separated. The indirect-direct crossover composition for Ge1-ySny alloys was determined by photoluminescence (PL). By n-type doping of the Ge1-ySny alloys via P(GeH3)3, P(SiH3)3 and As(SiH3)3, it was possible to enhance photoexcited emission by more than an order-of-magnitude.

The above techniques for deposition of direct gap Ge1-ySny alloys and doping of Ge were combined with p-type doping methods for Ge1-ySny using B2H6 to fabricate pin heterostructure diodes with active layer compositions up to y=0.137. These represent the first direct gap light emitting diodes made from group IV materials. The effect of the single defected n-i¬ interface in a n-Ge/i-Ge1-ySny/p-Ge1-zSnz architecture on electroluminescence (EL) was studied. This led to lattice engineering of the n-type contact layer to produce diodes of n-Ge1-xSnx/i-Ge1-ySny/p-Ge1-zSnz architecture which are devoid of interface defects and therefore exhibit more efficient EL than the previous design. Finally, n-Ge1-ySny/p-Ge1-zSnz pn junction devices were synthesized with varying composition and doping parameters to investigate the effect of these properties on EL.
ContributorsSenaratne, Charutha Lasitha (Author) / Kouvetakis, John (Thesis advisor) / Chizmeshya, Andrew (Committee member) / Menéndez, Jose (Committee member) / Arizona State University (Publisher)
Created2016
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Description
In the upcoming decade, powerful new astronomical facilities such as the James Webb Space Telescope (JWST), the Square Kilometer Array (SKA), and ground-based 30-meter telescopes will open up the epoch of reionization to direct astronomical observation. One of the primary tools used to understand the bulk astrophysical properties of the

In the upcoming decade, powerful new astronomical facilities such as the James Webb Space Telescope (JWST), the Square Kilometer Array (SKA), and ground-based 30-meter telescopes will open up the epoch of reionization to direct astronomical observation. One of the primary tools used to understand the bulk astrophysical properties of the high-redshift universe are empirically-derived star-forming laws, which relate observed luminosity to fundamental astrophysical quantities such as star formation rate. The radio/infrared relation is one of the more mysterious of these relations: despite its somewhat uncertain astrophysical origins, this relation is extremely tight and linear, with 0.3 dex of scatter over five orders of magnitude in galaxy luminosity. The effects of primordial metallicities on canonical star-forming laws is an open question: a growing body of evidence suggests that the current empirical star forming laws may not be valid in the unenriched, metal-poor environment of the very early universe.

In the modern universe, nearby dwarf galaxies with less than 1/10th the Solar metal abundance provide an opportunity to recalibrate our star formation laws and study the astrophysics of extremely metal-deficient (XMD) environments in detail. I assemble a sample of nearby dwarf galaxies, all within 100 megaparsecs, with nebular oxygen abundances between 1/5th and 1/50th Solar. I identify the subsample of these galaxies with space-based mid- and far-infrared data, and investigate the effects of extreme metallicities on the infrared-radio relationship. For ten of these galaxies, I have acquired 40 hours of observations with the Jansky Very Large Array (JVLA). C-band (4-8 GHz) radio continuum emission is detected from all 10 of these galaxies. These represent the first radio continuum detections from seven galaxies in this sample: Leo A, UGC 4704, HS 0822+3542, SBS 0940+544, and SBS 1129+476. The radio continuum in these galaxies is strongly associated with the presence of optical H-alpha emission, with spectral slopes suggesting a mix of thermal and non-thermal sources. I use the ratio of the radio and far-infrared emission to investigate behavior of the C-band (4-8 GHz) radio/infrared relation at metallicities below 1/10th Solar.

I compare the low metallicity sample with the 4.8 GHz radio/infrared relationship from the KINGFISHER nearby galaxy sample Tabatabaei et al. 2017 and to the 1.4 GHz radio/infrared relationship from the blue compact dwarf galaxy sample of Wu et al. 2008. The infrared/radio ratio q of the low metallicity galaxies is below the average q of star forming galaxies in the modern universe. I compare these galaxies' infrared and radio luminosities to their corresponding Halpha luminosities, and find that both the infrared/Halpha and the radio/H-alpha ratios are reduced by nearly 1 dex in the low metallicity sample vs. higher metallicity galaxies; however the deficit is not straightforwardly interpreted as a metallicity effect.
ContributorsMonkiewicz, Jacqueline Ann (Author) / Bowman, Judd (Thesis advisor) / Scowen, Paul (Thesis advisor) / Mauskopf, Philip (Committee member) / Scannapieco, Evan (Committee member) / Jansen, Rolf (Committee member) / Arizona State University (Publisher)
Created2018
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Description
Several key, open questions in astrophysics can be tackled by searching for and

mining large datasets for transient phenomena. The evolution of massive stars and

compact objects can be studied over cosmic time by identifying supernovae (SNe) and

gamma-ray bursts (GRBs) in other galaxies and determining their redshifts. Modeling

GRBs and their afterglows to

Several key, open questions in astrophysics can be tackled by searching for and

mining large datasets for transient phenomena. The evolution of massive stars and

compact objects can be studied over cosmic time by identifying supernovae (SNe) and

gamma-ray bursts (GRBs) in other galaxies and determining their redshifts. Modeling

GRBs and their afterglows to probe the jets of GRBs can shed light on the emission

mechanism, rate, and energetics of these events.

In Chapter 1, I discuss the current state of astronomical transient study, including

sources of interest, instrumentation, and data reduction techniques, with a focus

on work in the infrared. In Chapter 2, I present original work published in the

Proceedings of the Astronomical Society of the Pacific, testing InGaAs infrared

detectors for astronomical use (Strausbaugh, Jackson, and Butler 2018); highlights of

this work include observing the exoplanet transit of HD189773B, and detecting the

nearby supernova SN2016adj with an InGaAs detector mounted on a small telescope

at ASU. In Chapter 3, I discuss my work on GRB jets published in the Astrophysical

Journal Letters, highlighting the interesting case of GRB 160625B (Strausbaugh et al.

2019), where I interpret a late-time bump in the GRB afterglow lightcurve as evidence

for a bright-edged jet. In Chapter 4, I present a look back at previous years of

RATIR (Re-ionization And Transient Infra-Red Camera) data, with an emphasis on

the efficiency of following up GRBs detected by the Fermi Space Telescope, before

some final remarks and brief discussion of future work in Chapter 5.
ContributorsStrausbaugh, Robert (Author) / Butler, Nathaniel (Thesis advisor) / Jansen, Rolf (Committee member) / Mauskopf, Phil (Committee member) / Windhorst, Rogier (Committee member) / Arizona State University (Publisher)
Created2019