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Lamassa S.M.,Yale University | Yaqoob T.,NASA | Ptak A.F.,NASA | Jia J.,Johns Hopkins University | And 4 more authors.
Astrophysical Journal | Year: 2014

Using self-consistent, physically motivated models, we investigate the X-ray obscuration in 19 Type 2 [O III] 5007 Å selected active galactic nuclei (AGNs), 9 of which are local Seyfert 2 galaxies and 10 of which are Type 2 quasar candidates. We derive reliable line-of-sight and global column densities for these objects, which is the first time this has been reported for an AGN sample; four AGNs have significantly different global and line-of-sight column densities. Five sources are heavily obscured to Compton-thick. We comment on interesting sources revealed by our spectral modeling, including a candidate "naked" Sy2. After correcting for absorption, we find that the ratio of the rest-frame, 2-10 keV luminosity (L 2-10 keV, in) to L [O III] is 1.54 ± 0.49 dex which is essentially identical to the mean Type 1 AGN value. The Fe Kα luminosity is significantly correlated with L [O III] but with substantial scatter. Finally, we do not find a trend between L 2-10 keV, in and global or line-of-sight column density, between column density and redshift, between column density and scattering fraction, or between scattering fraction and redshift. © 2014. The American Astronomical Society. All rights reserved.. Source

Haxton T.K.,Lawrence Berkeley National Laboratory | Zhou H.,Columbia University | Zhou H.,Brion Technologies | Tamblyn I.,Lawrence Berkeley National Laboratory | And 7 more authors.
Physical Review Letters | Year: 2013

Controlling the self-assembly of surface-adsorbed molecules into nanostructures requires understanding physical mechanisms that act across multiple length and time scales. By combining scanning tunneling microscopy with hierarchical ab initio and statistical mechanical modeling of 1,4-substituted benzenediamine (BDA) molecules adsorbed on a gold (111) surface, we demonstrate that apparently simple nanostructures are selected by a subtle competition of thermodynamics and dynamics. Of the collection of possible BDA nanostructures mechanically stabilized by hydrogen bonding, the interplay of intermolecular forces, surface modulation, and assembly dynamics select at low temperature a particular subset: low free energy oriented linear chains of monomers and high free energy branched chains. © 2013 American Physical Society. Source

Liu P.,Brion Technologies
ECS Transactions | Year: 2013

Full-chip computational lithography is an important technology that enables low-k1 patterning. Examples of its applications include optical proximity correction (OPC), source-mask optimization (SMO) and verifications. In these applications, lithography models are required to predict the printed patterns on the wafer. Therefore the model accuracy has a direct impact to the quality of the final result. Rigorous physical models are accurate but computationally expensive. Therefore simple approximate models are generally used in full-chip applications. As the k1-factor continues to shrink, the errors produced by these simple models become unacceptable. Advanced models with improved accuracy and reasonable speed are required for low-k1 applications. In this work we will discuss the issues with the existing full-chip models and the development of advanced models. Copyright © 2013 by ECS - The Electrochemical Society. Source

Cohen J.G.,California Institute of Technology | Huang W.,Brion Technologies | Kirby E.N.,California Institute of Technology
Astrophysical Journal | Year: 2011

NGC2419 is a massive outer halo Galactic globular cluster (GC) whose stars have previously been shown to have somewhat peculiar abundance patterns. We have observed seven luminous giants that are members of NGC2419 with Keck/HIRES at reasonable signal-to-noise ratio. One of these giants is very peculiar, with an extremely low [Mg/Fe] and high [K/Fe] but normal abundances of most other elements. The abundance pattern does not match the nucleosynthetic yields of any supernova model. The other six stars show abundance ratios typical of inner halo Galactic GCs, represented here by a sample of giants in the nearby GC M30. Although our measurements show that NGC2419 is unusual in some respects, its bulk properties do not provide compelling evidence for a difference between inner and outer halo GCs. © 2011. The American Astronomical Society. All rights reserved. Source

Lorusso G.F.,IMEC | Hendrickx E.,IMEC | Davydova N.,ASML Netherlands BV | Peng Y.,ASML Netherlands BV | And 3 more authors.
Journal of Vacuum Science and Technology B:Nanotechnology and Microelectronics | Year: 2011

Extreme ultraviolet lithography (EUVL) is the leading candidate for lithography beyond the 22 nm half-pitch device manufacturing node. These geometries impose tighter requirements for standard critical dimension metrology and call for new strategies able to quantify and monitor extreme ultraviolet (EUV) specific parameters. In this paper, the approaches to measure two key EUV imaging parameters, namely flare and out-of-band (OoB) radiation, are discussed. EUV sources are known to emit a broad spectrum of wavelengths ranging from EUV to deep ultraviolet (DUV) and beyond. As the DUV can contribute to the photoresist exposure and degrade imaging performance, it is critical to accurately determine the amount of DUV OoB in EUVL exposure tools at the wafer level. In this paper, a methodology using an aluminum-coated reticle to measure the DUVEUV ratio in resist is discussed. Such a mask is able to provide quantitative in situ information on the scanner DUV content thanks to its ability to transmit DUV and absorb EUV. The experimental OoB results for two EUVL tools are reported and compared with modeling predictions. Flare in EUVL is caused by light scattered by the surface roughness of the optical elements and has a larger impact as compared to optical lithography. As a consequence, a precise and accurate flare metrology is essential to guarantee a proper qualification of the effect, as well as to implement an effective compensation strategy. However, the flare level estimate has been historically based on operator and tool-dependent procedures that are unable to meet the requirements for accuracy and precision dictated by EUVL. A robust in-line approach to flare metrology is developed and qualified. As in the case of OoB, experimental flare results for two EUVL tools are reported. The experimental data are compared to full-chip simulations using the point spread function of the tool's optical system. © 2011 American Vacuum Society. Source

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