30 results on '"Dale Batchelor"'
Search Results
2. Author Correction: A Tunguska sized airburst destroyed Tall el-Hammam a Middle Bronze Age city in the Jordan Valley near the Dead Sea
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Ted E. Bunch, Malcolm A. LeCompte, A. Victor Adedeji, James H. Wittke, T. David Burleigh, Robert E. Hermes, Charles Mooney, Dale Batchelor, Wendy S. Wolbach, Joel Kathan, Gunther Kletetschka, Mark C. L. Patterson, Edward C. Swindel, Timothy Witwer, George A. Howard, Siddhartha Mitra, Christopher R. Moore, Kurt Langworthy, James P. Kennett, Allen West, and Phillip J. Silvia
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Medicine ,Science - Published
- 2022
- Full Text
- View/download PDF
3. A Tunguska sized airburst destroyed Tall el-Hammam a Middle Bronze Age city in the Jordan Valley near the Dead Sea
- Author
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Ted E. Bunch, Malcolm A. LeCompte, A. Victor Adedeji, James H. Wittke, T. David Burleigh, Robert E. Hermes, Charles Mooney, Dale Batchelor, Wendy S. Wolbach, Joel Kathan, Gunther Kletetschka, Mark C. L. Patterson, Edward C. Swindel, Timothy Witwer, George A. Howard, Siddhartha Mitra, Christopher R. Moore, Kurt Langworthy, James P. Kennett, Allen West, and Phillip J. Silvia
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Medicine ,Science - Abstract
Abstract We present evidence that in ~ 1650 BCE (~ 3600 years ago), a cosmic airburst destroyed Tall el-Hammam, a Middle-Bronze-Age city in the southern Jordan Valley northeast of the Dead Sea. The proposed airburst was larger than the 1908 explosion over Tunguska, Russia, where a ~ 50-m-wide bolide detonated with ~ 1000× more energy than the Hiroshima atomic bomb. A city-wide ~ 1.5-m-thick carbon-and-ash-rich destruction layer contains peak concentrations of shocked quartz (~ 5–10 GPa); melted pottery and mudbricks; diamond-like carbon; soot; Fe- and Si-rich spherules; CaCO3 spherules from melted plaster; and melted platinum, iridium, nickel, gold, silver, zircon, chromite, and quartz. Heating experiments indicate temperatures exceeded 2000 °C. Amid city-side devastation, the airburst demolished 12+ m of the 4-to-5-story palace complex and the massive 4-m-thick mudbrick rampart, while causing extreme disarticulation and skeletal fragmentation in nearby humans. An airburst-related influx of salt (~ 4 wt.%) produced hypersalinity, inhibited agriculture, and caused a ~ 300–600-year-long abandonment of ~ 120 regional settlements within a > 25-km radius. Tall el-Hammam may be the second oldest city/town destroyed by a cosmic airburst/impact, after Abu Hureyra, Syria, and possibly the earliest site with an oral tradition that was written down (Genesis). Tunguska-scale airbursts can devastate entire cities/regions and thus, pose a severe modern-day hazard.
- Published
- 2021
- Full Text
- View/download PDF
4. Voltage-tunable surface-enhanced Raman scattering substrates based on electroactive polymeric membranes containing plasmonic nanoparticles
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Yashna Sharma, Enes Cakmak, Hsiang-kuo Yuan, Roberto Garcia, Dale Batchelor, Tuan Vo-Dinh, Tushar Ghosh, and Anuj Dhawan
- Abstract
We describe voltage-controlled surface-enhanced Raman scattering (SERS) substrates in which the SERS-signals can be actively modulated by applying voltage. These SERS-substrates employ a dielectric electroactive polymer (D-EAP) membrane with a pair of electrically-actuated active regions. When these regions are simultaneously activated, they produce an in-plane contractile strain in the regions of the D-EAP where SERS dye-coated nanoparticles are placed. We demonstrate that SERS-signals from dye-coated silver nanoparticles, deposited on the D-EAP membrane, increases by ∼100% upon application of an actuating voltage. Upon removal of the voltage, actuated active-areas move towards their original positions, leading to a decrease in the SERS-signals.
- Published
- 2022
5. A Tunguska sized airburst destroyed Tall el-Hammam a Middle Bronze Age city in the Jordan Valley near the Dead Sea
- Author
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Timothy Witwer, James P. Kennett, Kurt Langworthy, Edward C. Swindel, Ted E. Bunch, George Howard, Malcolm A. LeCompte, Dale Batchelor, Phillip J. Silvia, Mark C. L. Patterson, Allen West, Joel Kathan, Siddhartha Mitra, C. B. Mooney, Christopher R. Moore, Wendy S. Wolbach, T. David Burleigh, James H. Wittke, Gunther Kletetschka, A. Victor Adedeji, and Robert E. Hermes
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Population dynamics ,Science ,Fragmentation (weaponry) ,Article ,biomass-burning episode ,Bolide ,Bronze Age ,origin ,shock metamorphism ,Shocked quartz ,cosmic-impact ,Sedimentology ,Quartz ,Multidisciplinary ,platinum-group minerals ,diamonds ,Geology ,Geomagnetism ,planar deformation features ,quartz ,Archaeology ,placer deposits ,Geochemistry ,Meteoritics ,refractory-metal nuggets ,Medicine ,Pottery ,Zircon - Abstract
We present evidence that in ~ 1650 BCE (~ 3600 years ago), a cosmic airburst destroyed Tall el-Hammam, a Middle-Bronze-Age city in the southern Jordan Valley northeast of the Dead Sea. The proposed airburst was larger than the 1908 explosion over Tunguska, Russia, where a ~ 50-m-wide bolide detonated with ~ 1000× more energy than the Hiroshima atomic bomb. A city-wide ~ 1.5-m-thick carbon-and-ash-rich destruction layer contains peak concentrations of shocked quartz (~ 5–10 GPa); melted pottery and mudbricks; diamond-like carbon; soot; Fe- and Si-rich spherules; CaCO3 spherules from melted plaster; and melted platinum, iridium, nickel, gold, silver, zircon, chromite, and quartz. Heating experiments indicate temperatures exceeded 2000 °C. Amid city-side devastation, the airburst demolished 12+ m of the 4-to-5-story palace complex and the massive 4-m-thick mudbrick rampart, while causing extreme disarticulation and skeletal fragmentation in nearby humans. An airburst-related influx of salt (~ 4 wt.%) produced hypersalinity, inhibited agriculture, and caused a ~ 300–600-year-long abandonment of ~ 120 regional settlements within a > 25-km radius. Tall el-Hammam may be the second oldest city/town destroyed by a cosmic airburst/impact, after Abu Hureyra, Syria, and possibly the earliest site with an oral tradition that was written down (Genesis). Tunguska-scale airbursts can devastate entire cities/regions and thus, pose a severe modern-day hazard.
- Published
- 2021
6. A multi-proxy study of changing environmental conditions in a Younger Dryas sequence in southwestern Manitoba, Canada, and evidence for an extraterrestrial event
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Malcolm A. LeCompte, Matthew Boyd, Alice M. Telka, James T. Teller, Roberto Garcia, Victor Adedeji, C. B. Mooney, James Kennett, Allen West, Aura Diaz, and Dale Batchelor
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geography ,geography.geographical_feature_category ,Peat ,Bedrock ,Fluvial ,Arts and Humanities (miscellaneous) ,General Earth and Planetary Sciences ,Younger Dryas ,Physical geography ,Ice sheet ,Glacial lake ,Meltwater ,Holocene ,Geology ,Earth-Surface Processes - Abstract
Multi-proxy analyses of a sequence spanning the Younger Dryas (YD) in the Glacial Lake Hind basin of Manitoba provides insight into regional paleohydrology and paleovegetation of meltwater rivers and lakes spanning >4000 yr; the sequence is controlled by 25 new accelerator mass spectrometry ages. This lake, dammed by the Laurentide Ice Sheet, overflowed into Lake Agassiz. The pre-YD interval records rapid sedimentation from meltwaters that headed in proglacial lakes in the Canadian Prairies that are known to have been catastrophically released when ice or sediment barriers were breached. Pollen in this phase is dominated by pre-Quaternary forms eroded from Paleocene bedrock. At the onset of the YD at ~12.8 cal ka, the sudden appearance of concentrations of nanodiamonds, high-temperature magnetic spherules, platinum, and iridium provide evidence of an extraterrestrial (ET) event that others have identified at more than 40 sites in North America. Major changes in oceans and climate, and the catastrophic outflow of nearby Lake Agassiz at the onset of the YD, may be related. Lower water levels and a reduction of Souris River inflow to Lake Hind followed, which are reflected by more clayey and organic-rich sediments and a decrease in pre-Quaternary palynomorphs. This may have resulted from the deepening of river valleys caused by the release of meltwater triggered by the ET event. Wetlands then began to develop, leading to peat deposition from 12.3 to 11 cal ka. This was followed by a fluvial episode depositing sand and then by increased Holocene aridity that resulted in accumulation of a thick sequence of dune sands. A dry woodland environment with a mix of conifers (especially Picea and Larix) and deciduous trees (especially Populus and Quercus) covered the uplands from ~13 to 10 cal ka.
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- 2019
7. Hybrid Top-Down and Bottom-Up Fabrication Approach for Wafer-Scale Plasmonic Nanoplatforms
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Donovon Leonard, Michael Gerhold, Veena Misra, Tuan Vo-Dinh, Dale Batchelor, Mehmet C. Öztürk, Yan Du, Anuj Dhawan, and Hsin-Neng Wang
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Fabrication ,Materials science ,Scale (ratio) ,Nanowires ,Nanowire ,Nanotechnology ,General Chemistry ,Article ,Biomaterials ,General Materials Science ,Wafer ,Plasmon ,Biotechnology - Published
- 2011
8. pn Junction Location Using an EBIC Technique in a Scanning Transmission Electron Microscope
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Kristin Lee Bunker, Terry J. Stark, Dale Batchelor, Juan Carlos Gonzalez, and Phillip E. Russell
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Electrical and Electronic Engineering ,Safety, Risk, Reliability and Quality - Abstract
STEM-EBIC imaging, a nano-characterization technique, has been used in the study of electrically active defects, minority carrier diffusion length, surface recombination velocity, and inhomogeneities in Si pn junctions. In this article, the authors explain how they developed and built a STEM-EBIC system, which they then used to determine the junction location of an InGaN quantum well LED. They also developed a novel FIB-based sample preparation method and a custom sample holder, facilitating the simultaneous collection of Z-contrast, EBIC, and energy dispersive spectroscopy images. The relative position of the pn junction with respect to the quantum well was found to be 19 ± 3 nm from the center of well.
- Published
- 2002
9. Effects of Arsenic Doping on Chemical Vapor Deposition of Titanium Silicide
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Hua Fang, Dale Batchelor, Mehmet C. Öztürk, and Edmund G. Seebauer
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Passivation ,Silicon ,Renewable Energy, Sustainability and the Environment ,Chemistry ,Nucleation ,Mineralogy ,chemistry.chemical_element ,Substrate (electronics) ,Chemical vapor deposition ,Condensed Matter Physics ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Adsorption ,Chemical engineering ,Desorption ,Materials Chemistry ,Electrochemistry ,Layer (electronics) - Abstract
This work examines the effects of implanted arsenic on nucleation and growth of TiSi 2 formed by rapid thermal chemical vapor deposition using SiH 4 and TiCl 4 as the precursors. In this study depositions were carried out in a temperature range of 750 to 850°C on Si substrates implanted with As atoms. The As implant doses ranged from 3 × 10 14 to 5 × 10 15 cm -2 . It is shown that heavy dose As can result in a barrier to TiSi 2 nucleation and enhance silicon substrate consumption. A surface passivation model is proposed to explain the effects. On Si, As provides a stable surface structure which inhibits adsorption of SiH 4 and TiCl 4 . Higher temperatures aid As desorption from the Si surface providing nucleation sites. With moderate implant doses, As results in an incubation time whereas very high doses (≥5 × 10 15 cm -2 ) almost completely suppress nucleation. During deposition, As diffuses through the TiSi 2 layer and plays a similar role on the TiSi 2 surface. Because TiCl 4 adsorption on TiSi 2 is favored, the substrate supplies the Si atoms for TiSi 2 formation resulting in enhanced consumption. Because this process relies on Si diffusion through TiSi 2 , beyond a threshold thickness the efficiency of the Si diffusion process drops resulting in suppression of the deposition process. The results indicate that the As dose also plays a role in grain size and surface morphology of the deposited layers. Higher As doses result in smaller grained TiSi 2 films which can be attributed to the role of As in nucleation.
- Published
- 1999
10. Structure and properties of rapid thermal chemical vapor deposited polycrystalline silicon–germanium films on SiO2 using Si2H6, GeH4, and B2H6 gases
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M. Xu, M. R. Mirabedini, R. T. Kuehn, Dennis M. Maher, Dale Batchelor, V. Z-Q Li, Jimmie J. Wortman, H.H. Heinisch, and B.E. Hornung
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Materials science ,Inorganic chemistry ,Nucleation ,Oxide ,General Physics and Astronomy ,chemistry.chemical_element ,Germanium ,Chemical vapor deposition ,engineering.material ,chemistry.chemical_compound ,Polycrystalline silicon ,chemistry ,Chemical engineering ,engineering ,Deposition (phase transition) ,Crystallite ,Layer (electronics) - Abstract
Deposition of undoped and in situ boron-doped polycrystalline silicon-germanium (poly-Si1−xGex) films on oxide has been investigated at temperatures below 625 °C and a pressure of 4 Torr in a rapid thermal chemical vapor deposition system. The influences of reactant gases such as Si2H6, SiH4, GeH4, and B2H6 on the nucleation behavior, and structural properties of poly-Si1−xGex films formed on oxide were studied. The experimental results showed that in situ boron-doped or undoped poly-Si1−xGex films can be directly deposited on oxide without an initial Si predeposition layer to provide the necessary nucleation sites on the surface when using Si2H6 as the Si source gas. However, when SiH4 was used as the Si source gas, only in situ boron-doped films can be deposited nonselectively on the oxide without the initial Si predeposition layer, and to deposit undoped poly-Si1−xGex films, Si predeposition is needed, otherwise Si1−xGex islands are formed on the oxide. X-ray diffraction analysis showed that poly-Si1−x...
- Published
- 1998
11. Optimization of Process Conditions for Selective Silicon Epitaxy Using Disilane, Hydrogen, and Chlorine
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Katherine E. Violette, Mehmet C. Öztürk, Dale Batchelor, Patricia A. O'Neil, K. Christensen, and Dennis M. Maher
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Silicon ,Hydrogen ,Renewable Energy, Sustainability and the Environment ,Mineralogy ,chemistry.chemical_element ,Partial pressure ,Condensed Matter Physics ,Epitaxy ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Volumetric flow rate ,chemistry.chemical_compound ,chemistry ,Chemical engineering ,Materials Chemistry ,Electrochemistry ,Chlorine ,Disilane ,Selectivity - Abstract
We have previously reported a process for low temperature selective silicon epitaxy using Si 2 H 6 , H 2 , and Cl 2 in an ultrahigh vacuum rapid thermal chemical vapor deposition reactor. Selective deposition implies that growth occurs on the Si surface but not on any of the surrounding insulator surfaces. Using this method and process chemistry, the level of Cl species required to maintain adequate selectivity has been greatly reduced in comparison to SiH 2 Cl 3 -based, conventional CVD approaches. In this report, we have extended upon the previous work and provide information regarding the selectivity of the silicon deposition process to variations in the growth conditions. We have investigated the selectivity of the process to variations in disilane flow/partial pressure, growth temperature, and system contamination. We demonstrate that increases in either the Si 2 H 6 partial pressure or flow rate, the process temperature, or the source contamination levels can lead to selectivity degradation. In regard to the structural quality of the selective epitaxial layers, we have observed epitaxial defects that have appeared to be a strong function of two basic conditions: the contamination level of the process and the chlorine flow rate or chlorine partial pressure. Overall, the results in this study indicate several process conditions that can inhibit the quality of a selective silicon deposition process developed for single-wafer manufacturing.
- Published
- 1997
12. Reply to Boslough: Prior studies validating research are ignored
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Edward K. Vogel, Malcolm A. LeCompte, C. B. Mooney, Alfred W. Seidel, Barrett N. Rock, Dale Batchelor, and Mark Demitroff
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Multidisciplinary ,business.industry ,MEDLINE ,Library science ,Medicine ,business ,Data science - Abstract
In PNAS, M. Boslough (1) raises issues about carbon spherules and nanodiamonds unrelated to our magnetic spherule focused research (2). Boslough should instead address the questions he raises to the appropriate investigators.
- Published
- 2013
13. Molecular sentinel-on-chip for SERS-based biosensing
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Veena Misra, Dale Batchelor, Hsin-Neng Wang, Yan Du, Anuj Dhawan, Donovan N. Leonard, and Tuan Vo-Dinh
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Silicon ,Materials science ,Nanowire ,General Physics and Astronomy ,Nanotechnology ,Breast Neoplasms ,Biosensing Techniques ,Spectrum Analysis, Raman ,Article ,law.invention ,Atomic layer deposition ,law ,Humans ,Wafer ,Physical and Theoretical Chemistry ,Oligonucleotide Array Sequence Analysis ,Nanowires ,DNA ,Dna detection ,Metal deposition ,Nanolithography ,Ki-67 Antigen ,Female ,Photolithography ,Oligonucleotide Probes ,Biosensor ,Biomarkers - Abstract
The development of DNA detection techniques on large-area plasmonics-active platforms is critical for many medical applications such as high-throughput screening, medical diagnosis and systems biology research. Here, we report for the first time a unique “molecular sentinel-on-chip” (MSC) technology for surface-enhanced Raman scattering (SERS)-based DNA detection. This unique approach allows label-free detection of DNA molecules on chips developed on a wafer scale using large area nanofabrication methodologies. To develop plasmonics-active biosensing platforms in a repeatable and reproducible manner, we employed a combination of deep UV lithography, atomic layer deposition, and metal deposition to fabricate triangular-shaped nanowire (TSNW) arrays having controlled sub-10 nm gaps nanostructures over an entire 6-inch wafer. The detection of a DNA sequence of the Ki-67 gene, a critical breast cancer biomarker, on the TSNW substrate illustrates the usefulness and potential of the MSC technology as a novel SERS-based DNA detection method.
- Published
- 2013
14. Insects groom their antennae to enhance olfactory acuity
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M. I. Zhukovskaya, Coby Schal, Katalin Böröczky, Dale Batchelor, and Ayako Wada-Katsumata
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Arthropod Antennae ,Male ,animal structures ,Insecta ,media_common.quotation_subject ,Zoology ,Olfaction ,Insect ,Botany ,Animals ,Housefly ,Sensilla ,media_common ,German cockroach ,Multidisciplinary ,biology ,fungi ,Biological Sciences ,biology.organism_classification ,Grooming ,Hydrocarbons ,Smell ,Sex pheromone ,behavior and behavior mechanisms ,Environmental Pollutants ,sense organs ,American cockroach ,Integumentary System ,human activities ,Periplaneta ,Carpenter ant - Abstract
Grooming, a common behavior in animals, serves the important function of removing foreign materials from body surfaces. When antennal grooming was prevented in the American cockroach, Periplaneta americana , field emission gun scanning electron microscopy images revealed that an unstructured substance accumulated on nongroomed antennae, covering sensillar pores, but not on groomed antennae of the same individuals. Gas chromatography analysis of antennal extracts showed that over a 24-h period nongroomed antennae accumulated three to four times more cuticular hydrocarbons than groomed antennae. Moreover, nongroomed antennae accumulated significantly more environmental contaminants from surfaces (stearic acid) and from air (geranyl acetate) than groomed antennae. We hypothesized that the accumulation of excess native cuticular hydrocarbons on the antennae would impair olfactory reception. Electroantennogram experiments and single-sensillum recordings supported this hypothesis: antennae that were prevented from being groomed were significantly less responsive than groomed antennae to the sex pheromone component periplanone-B, as well as to the general odorants geranyl acetate and hexanol. We therefore conclude that antennal grooming removes excess native cuticular lipids and foreign chemicals that physically and/or chemically interfere with olfaction, and thus maintains the olfactory acuity of the antennae. Similar experimental manipulations of the German cockroach ( Blattella germanica ), carpenter ant ( Camponotus pennsylvanicus ), and the housefly ( Musca domestica ), which use different modes of antennal grooming, support the hypothesis that antennal grooming serves a similar function in a wide range of insect taxa.
- Published
- 2013
15. Independent evaluation of conflicting microspherule results from different investigations of the Younger Dryas impact hypothesis
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Dale Batchelor, Edward K. Vogel, Mark Demitroff, Barrett N. Rock, Alfred W. Seidel, C. B. Mooney, Albert C. Goodyear, and Malcolm A. LeCompte
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education.field_of_study ,Multidisciplinary ,Population ,Authigenic ,Archaeology ,Paleontology ,Geography ,Younger Dryas impact hypothesis ,PNAS Plus ,Megafauna ,Sedimentary rock ,Letters ,Younger Dryas ,education ,Ejecta - Abstract
Firestone et al. sampled sedimentary sequences at many sites across North America, Europe, and Asia [Firestone RB, et al. (2007) Proc Natl Acad Sci USA 106:16016–16021]. In sediments dated to the Younger Dryas onset or Boundary (YDB) approximately 12,900 calendar years ago, Firestone et al. reported discovery of markers, including nanodiamonds, aciniform soot, high-temperature melt-glass, and magnetic microspherules attributed to cosmic impacts/airbursts. The microspherules were explained as either cosmic material ablation or terrestrial ejecta from a hypothesized North American impact that initiated the abrupt Younger Dryas cooling, contributed to megafaunal extinctions, and triggered human cultural shifts and population declines. A number of independent groups have confirmed the presence of YDB spherules, but two have not. One of them [Surovell TA, et al. (2009) Proc Natl Acad Sci USA 104:18155–18158] collected and analyzed samples from seven YDB sites, purportedly using the same protocol as Firestone et al., but did not find a single spherule in YDB sediments at two previously reported sites. To examine this discrepancy, we conducted an independent blind investigation of two sites common to both studies, and a third site investigated only by Surovell et al. We found abundant YDB microspherules at all three widely separated sites consistent with the results of Firestone et al. and conclude that the analytical protocol employed by Surovell et al. deviated significantly from that of Firestone et al. Morphological and geochemical analyses of YDB spherules suggest they are not cosmic, volcanic, authigenic, or anthropogenic in origin. Instead, they appear to have formed from abrupt melting and quenching of terrestrial materials.
- Published
- 2012
16. Contaminant interferences with SIMS analyses of microparticle impactor residues on LDEF surfaces
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D. A. Ricks, Dieter P. Griffis, J. L. Hunter, Dale Batchelor, Veena Misra, C. G. Simon, and Jimmie J. Wortman
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Atmospheric Science ,Materials science ,Micrometeoroid ,Aerospace Engineering ,Astronomy and Astrophysics ,Contamination ,Particulates ,Debris ,Secondary ion mass spectrometry ,Geophysics ,Space and Planetary Science ,Environmental chemistry ,Hypervelocity ,General Earth and Planetary Sciences ,Microparticle ,Layer (electronics) - Abstract
Elemental analyses of impactor residues on high purity surfaces exposed to the LEO environment for 5.8 years on LDEF has revealed several probable sources for microparticles at this altitude, including natural micrometeorites and manmade debris ranging from paint pigments to bits of stainless steel. A myriad of contamination interferences were identified and their effects on impactor debris identification mitigated during the course of this study. These interferences included pre-, post- and in-flight deposited particulate surface contaminants, as well as indigenous heterogeneous material contaminants. Non-flight contaminants traced to human origins, including spittle and skin oils, contributed significant levels of alkali-rich carbonaceous interferences. A ubiquitous layer of in-flight deposited silicaceous contamination varied in thickness with LDEF location and proximity to active electrical fields. In-flight deposited (low velocity) contaminants included urine droplets and bits of metal film from eroded thermal blankets.
- Published
- 1993
17. Pendeoepitaxy of gallium nitride thin films
- Author
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Kevin J. Linthicum, Dale Batchelor, Timothy M. Smith, Pradeep Rajagopal, Robert F. Davis, Darren B. Thomson, Eric Carlson, and Thomas Gehrke
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Materials science ,Photoluminescence ,Physics and Astronomy (miscellaneous) ,business.industry ,Wide-bandgap semiconductor ,Gallium nitride ,Chemical vapor deposition ,Epitaxy ,chemistry.chemical_compound ,Crystallography ,Silicon nitride ,chemistry ,Optoelectronics ,Metalorganic vapour phase epitaxy ,Thin film ,business - Abstract
Pendeoepitaxy, a form of selective lateral growth of GaN thin films has been developed using GaN/AlN/6H–SiC(0001) substrates and produced by organometallic vapor phase epitaxy. Selective lateral growth is forced to initiate from the (1120) GaN sidewalls of etched GaN seed forms by incorporating a silicon nitride seed mask and employing the SiC substrate as a pseudomask. Coalescence over and between the seed forms was achieved. Transmission electron microscopy revealed that all vertically threading defects stemming from the GaN/AlN and AlN/SiC interfaces are contained within the seed forms and a substantial reduction in the dislocation density of the laterally grown GaN. Atomic force microscopy analysis of the (1120) face of discrete pendeoepitaxial structures revealed a root mean square roughness of 0.98 A. The pendeoepitaxial layer photoluminescence band edge emission peak was observed to be 3.454 eV and is blueshifted by 12 meV as compared to the GaN seed layer.
- Published
- 1999
18. Rapid thermal chemical vapor deposition ofin situboron-doped polycrystalline silicon-germanium films on silicon dioxide for complimentary-metal-oxide-semiconductor applications
- Author
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Mehmet C. Öztürk, Dennis M. Maher, V. Z-Q Li, R. T. Kuehn, Jimmie J. Wortman, K. Christensen, M. R. Mirabedini, and Dale Batchelor
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Materials science ,Physics and Astronomy (miscellaneous) ,Silicon ,Doping ,chemistry.chemical_element ,Germanium ,Chemical vapor deposition ,Combustion chemical vapor deposition ,engineering.material ,Carbon film ,Polycrystalline silicon ,chemistry ,Chemical engineering ,engineering ,Boron - Abstract
In situ boron-doped polycrystalline Si1−xGex (x>0.4) films have been formed on the thermally grown oxides in a rapid thermal chemical vapor deposition processor using SiH4-GeH4-B2H6-H2 gas system. Our results showed that in situ boron-doped Si1−xGex films can be directly deposited on the oxide surface, in contrast to the rapid thermal deposition of undoped silicon-germanium (Si1−xGex) films on oxides which is a partially selective process and requires a thin silicon film pre-deposition to form a continuous film. For the in situ boron-doped Si1−xGex films, we observed that with the increase of the germane percentage in the gas source, the Ge content and the deposition rate of the film are increased, while its resistivity is decreased down to 0.66 mΩ cm for a Ge content of 73%. Capacitance-voltage characteristics of p-type metal-oxide-semiconductor capacitors with p+-Si1−xGex gates showed negligible polydepletion effect for a 75 A gate oxide, indicating that a high doping level of boron at the poly-Si1−xGex...
- Published
- 1997
19. Low Temperature Selective Si Epitaxy Using Si2H6 and Cl2: Investigations into Selectivity Robustness and Epitaxial Film Quality
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Katherine E. Violette, Mehmet C. Öztürk, Dennis M. Maher, Dale Batchelor, and Patricia A. O'Neil
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Materials science ,Silicon ,chemistry ,Desorption ,Analytical chemistry ,chemistry.chemical_element ,Degradation (geology) ,Insulator (electricity) ,Partial pressure ,Epitaxy ,Selectivity ,Volumetric flow rate - Abstract
In this paper, we explore selective Si epitaxy by UltraHigh Vacuum Rapid Thermal Chemical Vapor Deposition (UHV-RTCVD) using Si2H6, H2, and C12 with particular emphasis on selectivity robustness. Two key parameters considered in this study were partial pressures of Si2H6 and H2. It was found that excessive increases in either partial pressure could lead to selectivity degradation. The two mechanisms by which the observed selectivity degradation can be explained are as follows: A higher Si2H6 partial pressure provides a larger flux of Si atoms which directly influences the probability of reaching the critical nuclei size for stable nuclei formation while an increase in H2 partial pressure reduces the desorption rate of Si adatoms from the insulator surface by reducing the available Cl in the gas phase for SiC12 formation. The impact of process parameters on epitaxial defect density was also evaluated using darkfield imaging. The results clearly indicate increasing defect density upon increases in both the chlorine flow rate and the level of contamination introduced through the silicon source gas.
- Published
- 1996
20. Rapid Thermal Chemical Vapor Deposition of Polycrystalline Silicon-Germanium Films on SiO2 and Their Properties
- Author
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R. T. Kuehn, V. Z-Q Li, K. Christenson, Jim J. Wortman, Dale Batchelor, Dennis M. Maher, M. R. Mirabedini, D. B. Gladden, and Mehmet C. Öztürk
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Materials science ,business.industry ,Ion plating ,chemistry.chemical_element ,Germanium ,Chemical vapor deposition ,Combustion chemical vapor deposition ,engineering.material ,Electron beam physical vapor deposition ,Polycrystalline silicon ,Carbon film ,chemistry ,Plasma-enhanced chemical vapor deposition ,engineering ,Optoelectronics ,business - Abstract
In this work, polycrystalline SiGe has been viewed as an alternative gate material to polysilicon in single wafer processing for the deep submicrometer VLSI applications. We studied deposition of the silicon-germanium (SiGe) films with different germanium concentrations (up to 85%) on SiO2 in a rapid thermal chemical vapor deposition reactor using GeH4 and SiH4/H2 gas mixture with the temperature ranging from 550°C to 625°C. Since the SiGe RTCVD process is selective toward oxide and does not form nucleation sites on the oxide easily, an in-situ polysilicon flash technique is used to provide the necessary nucleation sites for the deposition of SiGe films with high germanium content. It was observed that with the in-situ polysilicon flash as a pre-nucleation seed, the SiGe deposited on SiO2 forms a continuous polycrystalline layer. Polycrystalline SiGe films of about 2000Å in thickness have a columnar grain structure with a grain size of approximately 1000Å. Compositional analyses from Auger Electron Spectroscopy (AES) and Rutherford backscattering (RBS) show that the high germanium incorporation in the SiGe films has a weak dependence on the deposition temperature. It is also noted that the germanium content across the film thickness is fairly constant which is a critical factor for the application of SiGe films as the gate material. Lastly, we found that the surface morphology of SiGe films become smoother at lower deposition temperature.
- Published
- 1995
21. Silicon Etching in Rapid Thermal Chemical Vapor Deposition of Tisi2
- Author
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Mehmet C. Öztürk, Dannellia B. Gladden, Xiaowei Ren, and A. Dale Batchelor
- Subjects
Materials science ,Silicon ,chemistry ,Chemical engineering ,Hybrid physical-chemical vapor deposition ,Etching (microfabrication) ,Plasma-enhanced chemical vapor deposition ,chemistry.chemical_element ,Deposition (phase transition) ,Reactive-ion etching ,Electron beam physical vapor deposition ,Plasma processing - Abstract
Downscaling of microelectronics devices into the deep submicron regime requires ultrashallow junctions with reliable, low-resistivity contacts. The conventional self-aligned TiSi2 technology exhibits a serious limitation in forming contacts to ultra-shallow junctions due to silicon substrate consumption. Selective chemical vapor deposition of TiSi2 is being investigated because of its potential for overcoming this difficulty. In this process Si and Ti are supplied from the gas phase. The standard source gas for Ti has been TiCl4 while several gases including SiH4, Si2H6 and SiH2Cl2 are available for Si. The reports on this process indicate that optimized process conditions can deliver TiSi2 films without substrate consumption. Although this promise is significant, the deposition has a complicated chemistry involving processes such as silicon etching, silicon consumption or silicon pedestal deposition taking place along with TiSi2 deposition. Although, suppression of Si-substrate etching by excess H2 has been reported previously, a broad quantitative analysis has been lacking up until this reporting. In this work, we have examined silicon etching trends as a function of temperature for different H2:TiCl4 flow ratios using thermodynamic equilibrium calculations. We have also performed experiments in a lamp heated rapid thermal chemical vapor deposition reactor to study substrate etching over the temperature range of 600°C to 800°C and for H2 flows from 0 to 1000 sccm. A silicon conversion efficiency is defined as a measure of the amount of Si converted to TiSi2 relative to total Si used from the substrate and it is evaluated via both thermodynamic calculations and experiments with good agreement between the two. Our calculations suggest that at high temperatures, etching occurs mainly via formation of SiCl2. Addition of H2 into the reaction chemistry encourages formation of HCl reducing the amount of Cl available for SiCl2 formation responsible for substrate etching. Our results show that by optimizing the H2 flow rate and the process temperature silicon substrate etching can be effectively suppressed.
- Published
- 1995
22. Oxide Removal on Silicon by Rapid Thermal Processing Using SiH2CI2 and H2
- Author
-
G. Harris, Xiaowei Ren, Dale Batchelor, Dennis M. Maher, and Mehmet C. Öztürk
- Subjects
chemistry.chemical_compound ,Materials science ,chemistry ,Rapid thermal processing ,Desorption ,Torr ,Oxide ,Analytical chemistry ,chemistry.chemical_element ,Limiting oxygen concentration ,Partial pressure ,Atmospheric temperature range ,Oxygen - Abstract
In this paper, we report in-situ oxygen removal on Si using SiH2Cl2 and H2 in a high vacuum rapid thermal chemical vapor deposition reactor. The system consists of a main process chamber and a load-lock with base pressures of ∼ 1×10−7 Torr and 1×10−5 Torr respectively. The experiments were conducted in the temperature range of 750°C to 865 °C, and SiH2Cl2/H2 flow ratios of 1% to 7%. For comparison, samples were also prepared with only H2 prebaking in the same temperature and pressure range as well as with no in-situ cleaning. With no in-situ cleaning, the oxygen content was found to decrease at higher temperatures suggesting partial oxygen removal during early stages of growth. The results indicate a strong temperature dependence for the H2 clean with an increased effectiveness at higher temperatures which is believed to be due to temperature dependence of oxygen desorption from Si. In the temperature range studied, the SiH2Cl2 clean was found to be effective at 750°C. An additional oxygen removal mechanism appears to be introduced by the addition of SiH2Cl2. Using this approach, at 750°C, the peak oxygen concentration can be reduced to 4×1018 cm−3 whereas the H2 anneal at the same temperature results in a concentration of 6×1018 cm−3. At higher temperatures, the oxide can be removed in pure H2 just as efficiently or desorbed during initial stages of growth. The results show that the efficiency of the process increases as more SiH2 Cl2 is added to the system up to a critical pressure. However, if the SiH2Cl2 partial pressure is above this critical value, Si deposition can occur on the Si surface yielding an optimum partial pressure which is a function of temperature. The results indicate that the use of a small amount of SiH2Cl2 as a cleaning agent may provide a low temperature pre-epi clean.
- Published
- 1994
23. Electrical and Structural Characterization of Polysilicon Deposited in a Rapid Thermal Processor
- Author
-
E. Niccolian, Xiaowei Ren, Dennis M. Maher, C. Blat, Dale Batchelor, M.C. Öztüirk, and Jim J. Wortman
- Subjects
Auger electron spectroscopy ,Materials science ,Dopant ,business.industry ,Doping ,Chemical vapor deposition ,law.invention ,Capacitor ,law ,Transmission electron microscopy ,Optoelectronics ,Scanning tunneling microscope ,business ,Deposition (law) - Abstract
Low pressure chemical vapor deposition of polysilicon in a lamp heated rapid thermal processor (RTCVD) has been studied. Polysilicon films were deposited using SiH4 diluted in Ar. Structural characterization of the films was accomplished by transmissionelectron microscopy (TEM), scanning tunneling microscopy (STM), secondary ion mass spectroscopy (SIMS), auger electron spectroscopy (AES) and ultraviolet surface reflectance measurements. Smooth polysilicon films were obtained at deposition temperatures above 700ºC with rms roughness values better than 100 Å. Both p- and n- polysilicon gated MOS capacitors were fabricated using 80 - 200 Å thick gate oxides grown by dry oxidation in a conventional furnace. Polysilicon doping was achieved by ion-implantation and rapid thermal annealing (RTA). Our results show that the electrical properties ofthe capacitors fabricated using RTCVD polysilicon are comparable to those of conventional polysilicon. Dopant diffusion through the gate is a problem for both types of polysilicon and can lead to a degradation of the electrical properties.
- Published
- 1990
24. Effects of Si Source Gases (SiH[sub 4] and Si[sub 2]H[sub 6]) on Polycrystalline-Si[sub 1−x]Ge[sub x] Deposited on Oxide by RTCVD
- Author
-
M. R. Mirabedini, V. Z-Q Li, R. T. Kuehna, Eric M. Vogel, Dale Batchelor, K. Henson, and Jim J. Wortman
- Subjects
chemistry.chemical_compound ,Materials science ,chemistry ,General Chemical Engineering ,Electrochemistry ,Analytical chemistry ,Oxide ,General Materials Science ,Crystallite ,Electrical and Electronic Engineering ,Physical and Theoretical Chemistry - Published
- 1999
25. Deposition and characterization of polysilicon films deposited by rapid thermal processing
- Author
-
Mehmet C. Öztürk, Xiaowei Ren, Dale Batchelor, Dennis M. Maher, Bojun Zhang, and Jimmie J. Wortman
- Subjects
Amorphous silicon ,Auger electron spectroscopy ,Materials science ,Silicon ,General Engineering ,Analytical chemistry ,chemistry.chemical_element ,Mineralogy ,Chemical vapor deposition ,engineering.material ,chemistry.chemical_compound ,Polycrystalline silicon ,chemistry ,Rapid thermal processing ,Surface roughness ,engineering ,Thin film - Abstract
Low‐pressure chemical vapor deposition (LPCVD) of polycrystalline silicon in a cold‐wall, lamp‐heated, rapid‐thermal processor was investigated. Blanket polysilicon films were obtained by the pyrolysis of a 10% silane–argon gas mixture onto (100) Si wafers which were capped with a thermal SiO2 layer. The depositions were performed at a total pressure ranging from 1 to 5 Torr and in a temperature range from 575 to 850 °C. It was found that the deposition of films was controlled by a surface limited reaction at temperatures below ∼780 °C, and an activation energy of 39±2 kcal/mol was measured for this reaction. Above 780 °C, a decrease in activation energy was observed. To meet the throughput requirement of single wafer processing, deposition temperatures higher than 700 °C are needed. In this temperature range, deposition rates exceed 1000 A/min as compared to 20–300 A/min in conventional LPCVD furnaces. The structural characteristics of the films were assessed by ultraviolet surface reflectance, Raman spectroscopy, and transmission electron microscopy. The transition temperature from amorphous silicon to polycrystalline silicon occurs at ∼600 °C. Processing windows, which result in smooth films with a root‐mean‐square roughness of less than 100 A, are defined. Polysilicon films (∼2500 A in thickness) have a columnarlike grain structure, and the grains span distances as little as ∼100 A near the SiO2 interface to ≥1000 A as they approarch the upper surface. A correlation between average projected grain size and surface roughness is demonstrated. Oxygen levels were derived from secondary ion mass and Auger electron spectroscopic data. The oxygen content of the polysilicon films is estimated to be in the range of 3%–4%. We speculate that relatively high oxygen levels in the films may be responsible for smooth films at high temperatures. If this is true, it may be possible to obtain smooth polysilicon films at high deposition temperatures by adding measured amounts of oxygen to the gas stream.
- Published
- 1992
26. Interaction of Topical and Oral Timolol in Glaucoma
- Author
-
E. Dale Batchelor, Alastair J. J. Wood, Denis M. O'Day, and David G. Shand
- Subjects
Adult ,medicine.medical_specialty ,Intraocular pressure ,genetic structures ,Administration, Topical ,Administration, Oral ,Timolol ,Glaucoma ,Blood Pressure ,Drug Administration Schedule ,Propanolamines ,Double-Blind Method ,Ophthalmology ,medicine ,Humans ,In patient ,Pulse ,Intraocular Pressure ,Aged ,Timolol maleate ,Clinical Trials as Topic ,integumentary system ,business.industry ,Middle Aged ,medicine.disease ,eye diseases ,sense organs ,business ,medicine.drug - Abstract
The interaction of oral and topical timolol maleate was studied in patients with open-angle glaucoma. The oral and topical preparations given separately produced a significant and comparable reduction of the intraocular pressure, but no additive effect was observed when both preparations were given together. Pulse- and blood pressure-lowering effects of oral timolol were not enhanced by the application of topical timolol. These systemic effects were not found in those patients using topical timolol alone.
- Published
- 1979
27. Trainee involvement in the training process
- Author
-
Dale Batchelor and John H. Austin
- Subjects
Medical education ,Process (engineering) ,General Chemistry ,Business ,Training (civil) ,Water Science and Technology - Published
- 1981
28. Staff training for water supply projects in the West Indies
- Author
-
Fred E. Harem, Merlevyn A. Sankeralli, and Dale Batchelor
- Subjects
Engineering ,Trainer ,business.industry ,Water supply ,General Chemistry ,Training (civil) ,System engineer ,Computerized maintenance management system ,Operations management ,Training program ,business ,Water Science and Technology ,West indies ,Staff training - Abstract
An ongoing staff training program and a comprehensive maintenance management system are evolving as a result of recently constructed water treatment plants on the island of Trinidad. With approximately 130 trained technical staff needed to operate the treatment systems, an accelerated four-phase training program was initiated. Local water system engineer and superintendent trainees were sent to the United States for specialized classes and plant tours; a full-time operator trainer was employed; and, with guidance from outside consultants, operators and maintenance technicians are being trained in specializations by equipment manufacturers and suppliers.
- Published
- 1981
29. TIMOLOL MALEATE—A PROMISING NEW BETA ADRENERGIC BLOCKER FOR GLAUCOMA
- Author
-
David G. Shand, Alastair J. J. Wood, Denis M. O'Day, and E. Dale Batchelor
- Subjects
Timolol maleate ,Intraocular pressure ,Beta-adrenergic blocking agent ,genetic structures ,business.industry ,Adrenergic ,Systemic blood pressure ,Glaucoma ,Pharmacology ,medicine.disease ,eye diseases ,Ophthalmology ,medicine ,sense organs ,business - Abstract
Summary The pharmacology and clinical effects of timolol maleate, an adrenergic beta-blocking agent, are discussed. Timolol maleate appears to exert its action by reducing aqueous production. It produces a significant drop in intraocular pressure of prolonged duration and is remarkably free from side effects. The systemic preparation reduces both intraocular pressure and systemic blood pressure.
- Published
- 1979
30. Selective Rapid Thermal Cvd of Germanium
- Author
-
D. T. Grider, Michael A. Littlejohn, M.C. Özttürk, Y. Zhong, Dale Batchelor, Phillip E. Russell, and Jim J. Wortman
- Subjects
Materials science ,Silicon ,business.industry ,Contact resistance ,chemistry.chemical_element ,Germanium ,Germanide ,chemistry.chemical_compound ,chemistry ,Germane ,Electrical resistivity and conductivity ,Optoelectronics ,Wafer ,Thin film ,business - Abstract
Selective depositions of germanium thin films have been investigated in a cold-wall, lamp heated rapid thermal processor. Films were deposited at low pressures (1 Torr-8 Torr) using the thermal decomposition of germane. Selectivity was maintained throughout the temperature range investigated, 350°C-600°C. Growth rates as high as 800 Å/min were obtained at 425°C where deposition is controlled by the surface reactions, making germanium compatible with the throughput requirements of single wafer manufacturing. Three dimensional growth was seen at temperatures above 450°C resulting in a rough surface morphology. Smooth films were deposited below 450°C with the films characterized by two dimensional growth. In this work, germanium is considered as a potential material to fabricate MOS transistors with raised source and drain junctions (UPMOS). Kelvin structures were fabricated to study the effect of the intermediate germanium layer between aluminum and silicon on contact resistance. It is shown that contact resistivity is improved by approximately 17% using an Al/p-Ge/p+-Si structure. In this work, it is also shown that titanium germanide formation can be used as a means of reducing the resistivity of the Ge buffer layer.
- Published
- 1989
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