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Quarterly progress report for Q1 FY06 for Complex Transient Events in Materials Studied Using Ultrafast Electron Probes and Terascale Simulation (FWP SCW0289)

Description: This quarter (Q1 FY06) marked the first time that the LLNL dynamic transmission electron microscope (DTEM) configuration had advanced to the point whereby it was possible to conduct in-situ experiments on specimens. DTEM improvements continue to progress at a rapid pace. We summarize important achievements in the following list: (1) Instrument performance and design improvements - (a) Reproducibly achieving >1 x 10{sup 7} e{sup -} per pulse. Adjustments in the cathode laser system design led… more
Date: December 27, 2005
Creator: Campbell, G.
Partner: UNT Libraries Government Documents Department
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Nitrogen Doping and Thermal Stability in HfSiOxNy Studied by Photoemission and X-ray Absorption Spectroscopy

Description: We have investigated nitrogen-doping effects into HfSiO{sub x} films on Si and their thermal stability using synchrotron-radiation photoemission and x-ray absorption spectroscopy. N 1s core-level photoemission and N K-edge absorption spectra have revealed that chemical-bonding states of N-Si{sub 3-x}O{sub x} and interstitial N{sub 2}-gas-like features are clearly observed in as-grown HfSiO{sub x}N{sub y} film and they decrease upon ultrahigh vacuum (UHV) annealing due to a thermal instability, … more
Date: December 14, 2005
Creator: Toyoda, Satoshi; Okabayashi, Jun; Takahashi, Haruhiko; Oshima, Masaharu; U., /Tokyo; Lee, Dong-Ick et al.
Partner: UNT Libraries Government Documents Department
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Study of f electron correlations in nonmagnetic Ce by means of spin resolved resonant photoemission

Description: We have studied the spin-spin coupling between two f electrons of nonmagnetic Ce by means of spin resolved resonant photoemission using circularly polarized synchrotron radiation. The two f electrons participating in the 3d{sub 5/2} {yields} 4f resonance process are coupled in a singlet while the coupling is veiled in the 3d{sub 3/2} {yields} 4f process due to an additional Coster-Kronig decay channel. The identical singlet coupling is observed in the 4d {yields} 4f resonance process. Based on … more
Date: November 28, 2005
Creator: Yu, S.; Komesu, T.; Chung, B. W.; Waddill, G. D.; Morton, S. A. & Tobin, J. G.
Partner: UNT Libraries Government Documents Department
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Evidence for the Spectroscopic Signature of Aging in (delta)-Pu(Ga)

Description: Plutonium, because of its radioactive nature, ages from the 'inside out' by means of self-irradiation damage and thus produces nanoscale internal defects. The self-irradiation induced defects come in the form of Frenkel-type defects (vacancies and self-interstitial atoms), helium in-growth, and defect clusters. At present there are neither experimental nor theoretical models describing the changes in the electronic structure caused by the aging in Pu. This fact appears to be associated primaril… more
Date: November 23, 2005
Creator: Chung, B. W.; Schwartz, A. J.; Ebbinghaus, B. B.; Fluss, M. J.; Haslam, J. J.; Blobaum, K. M. et al.
Partner: UNT Libraries Government Documents Department
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Development of Next-Generation Detectors and Instrumentation for Photoelectron Spectroscopy, Diffraction and Holography

Description: We have developed a new multichannel detector for use in photoelectron spectroscopy (as well as other types of high-count-rate spectroscopy) that will operate at rates of up to 1 GHz. Such detectors are crucial to the full utilization of the high-brightness radiation generated by third-generation synchrotron radiation sources. In addition, new software and hardware has been developed to permit rapidly and accurately scanning photoelectron spectra that will be accumulated in as little as a 200 m… more
Date: October 16, 2005
Creator: Fadley, Charles S.
Partner: UNT Libraries Government Documents Department
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Angle Resolved Photoemission Spectroscopy Studies of the Mott Insulator to Superconductor Evolution in Ca2-xNaxCuO2Cl2

Description: It is widely believed that many of the exotic physical properties of the high-T{sub c} cuprate superconductors arise from the proximity of these materials to the strongly correlated, antiferromagnetic Mott insulating state. Therefore, one of the fundamental questions in the field of high-temperature superconductivity is to understand the insulator-to-superconductor transition and precisely how the electronic structure of Mott insulator evolves as the first holes are doped into the system. This … more
Date: September 2, 2005
Creator: Shen, Kyle Michael
Partner: UNT Libraries Government Documents Department
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Quantum Efficiency and Topography of Heated and Plasma-Cleaned Copper Photocathode Surfaces

Description: We present measurements of photoemission quantum efficiency (QE) for copper photocathodes heated and cleaned by low energy argon and hydrogen ion plasma. The QE and surface roughness parameters were measured before and after processing and surface chemical composition was tracked in-situ with x-ray photoelectron spectroscopy (XPS). Thermal annealing at 230 C was sufficient to improve the QE by 3-4 orders of magnitude, depending on the initial QE. Exposure to residual gas slowly reduced the QE b… more
Date: August 4, 2005
Creator: Palmer, Dennis T.; Kirby, R. E. & King, F. K.
Partner: UNT Libraries Government Documents Department
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Advanced 3D Photocathode Modeling and Simulations Final Report

Description: High brightness electron beams required by the proposed Next Linear Collider demand strong advances in photocathode electron gun performance. Significant improvement in the production of such beams with rf photocathode electron guns is hampered by the lack high-fidelity simulations. The critical missing piece in existing gun codes is a physics-based, detailed treatment of the very complex and highly nonlinear photoemission process.
Date: June 6, 2005
Creator: Dimitrov, Dimitre A. & Bruhwiler, David L.
Partner: UNT Libraries Government Documents Department
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Spin-Resolved Electronic Structure Studies of Non-Magnetic Systems: Possible Observation of the Fano Effect in Polycrystal Ce

Description: The valence electronic structure and electron spectra of Cerium remain a subject of uncertainty and controversy. Perhaps the best and most direct method of ascertaining the valence electronic structure is the application of electron spectroscopies [1-17], e.g. photoelectron spectroscopy for the occupied states [1-10, 12-14] and x-ray absorption [2] and Bremstrahlung Isochromat Spectroscopy (inverse photoelectron spectroscopy) [3,11,13] for the unoccupied states. Much of the controversy revolves… more
Date: June 1, 2005
Creator: Tobin, J.; Morton, S.; Chung, B.; Yu, S. & Waddill, G.
Partner: UNT Libraries Government Documents Department
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Evidence of vectorial photoelectric effect on copper

Description: Quantum Efficiency (QE) measurements of single photon photoemission from a Cu(111) single crystal and a Cu polycrystal photocathodes, irradiated by 150 fs-6.28 eV laser pulses, are reported over a broad range of incidence angle, both in s and p polarizations. The maximum QE (approx. = 4x10-4) for polycrystalline Cu is obtained in p polarization at an angle of incidence theta = 65 deg. We observe a QE enhancement in p polarization which can not be explained in terms of optical absorption, a phen… more
Date: May 27, 2005
Creator: Pedersoli, E.; Banfi, F.; Ressel, B.; Pagliara, S.; Giannetti,C.; Galimberti, G. et al.
Partner: UNT Libraries Government Documents Department
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Non-free-electron momentum- and thickness-dependent evolution ofquantum well states in the Cu/Co/Cu(001) system

Description: We present systematic k{sub {parallel}}-dependent measurements of the Fermi surface and underlying band structure of quantum well states in Cu/Co/Cu(001). Compared to bands from normal emission, we find a complicated evolution of ''split'' QW states as a function of the thicknesses of both the copper overlayer and the cobalt barrier layer. Self-consistent calculations show that the penetration of the quantum well states into the cobalt barrier layer is significant and leads to the observed very… more
Date: May 21, 2005
Creator: Rotenberg, Eli; Wu, Y. Z.; An, Joonhee M.; Van Hove, Michel A.; Canning, Andrew; Wang, Lin-Wang et al.
Partner: UNT Libraries Government Documents Department
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Photoemission Studies on Bnl/Aes/Jlab All Niobium, Superconducting Rf Injector.

Description: Photoelectrons from an all niobium superconducting injector have been generated for the first time. QE of 2 x 10{sup -6} at 266 nm and 2 x 10{sup -5} at 248 nm, maximum charge of 10 nC in 10 ns and charge/cycle of 0.8 nC were measured. The lower QE observed after laser cleaning, compared to the room temperature measurements, is attributed to the long distance between the cathode and the closest ion pump and the possibility of the laser ablated material adsorbed back onto the cathode surface at … more
Date: May 16, 2005
Creator: Rao, T.; Ben-Zvi, Ilan; Burrill, A.; Hahn, H.; Kayran, D.; Zhao, Y. et al.
Partner: UNT Libraries Government Documents Department
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Surface Passivation of Germanium Nanowires

Description: The surface of single crystal, cold-wall CVD-grown germanium nanowires was studied by synchrotron radiation photoemission spectroscopy (SR-PES) and also by conventional XPS. The as-grown germanium nanowires seem to be hydrogen terminated. Exposure to laboratory atmosphere leads to germanium oxide growth with oxidation states of Ge{sup 1+}, Ge{sup 2+}, Ge{sup 3+}, while exposure to UV light leads to a predominance of the Ge{sup 4+} oxidation state. Most of the surface oxide could be removed read… more
Date: May 13, 2005
Creator: Adhikari, Hemant; Sun, Shiyu; Pianetta, Piero; Chidsey, Chirstopher E.D.; McIntyre, Paul C. & /SLAC, SSRL
Partner: UNT Libraries Government Documents Department
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A photoemission study of Pd ultrathin films on Pt(111)

Description: The origin of surface core-level shift (SCLS) of Pd thin films on Pt(111) substrate is investigated. At sub-monolayer coverage of Pd thin films, the splitting of Pd 3d core level peaks indicate the contribution of both initial and final-state of photo-ionization processes while there is almost no change on valence band (VB) spectra. When the coverage of Pd reaches to single monolayer, the final-state relaxation effect on the Pd 3d vanishes and only the initial-state effect, a negative SCLS, is … more
Date: May 11, 2005
Creator: Mun, Bongjin Simon; Lee, Choongman; Stamenkovic, Vojislav; Markovic, Nenad M. & Ross Jr., Philip N.
Partner: UNT Libraries Government Documents Department
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Chemical states and electronic structure of a HfO(-2) / Ge(001) interface

Description: We report the chemical bonding structure and valence band alignment at the HfO{sub 2}/Ge (001) interface by systematically probing various core level spectra as well as valence band spectra using soft x-rays at the Stanford Synchrotron Radiation Laboratory. We investigated the chemical bonding changes as a function of depth through the dielectric stack by taking a series of synchrotron photoemission spectra as we etched through the HfO{sub 2} film using a dilute HF-solution. We found that a ver… more
Date: May 4, 2005
Creator: Seo, Kang-ill; McIntyre, Paul C.; /Stanford U., Materials Sci. Dept.; Sun, Shiyu; Lee, Dong-Ick; Pianetta, Piero et al.
Partner: UNT Libraries Government Documents Department
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Electron-Phonon Coupling in High-Temperature CuprateSuperconductors as Revealed by Angle-resolved PhotoemissonSpectroscopy

Description: We present an application programming interface (API) used to simplify application-level access to both data and semantic range query machinery where both data and search indices are stored and accessed using the HDF5 data model. While the APIs for HDF5 data access and FastBit indexing/query are rather complex, our API simplifies use of these powerful software technologies.
Date: May 1, 2005
Creator: Zhou, X. J.; Hussain, Z. & Shen, Z. X.
Partner: UNT Libraries Government Documents Department
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Evidence against a charge density wave on Bi(111)

Description: The Bi(111) surface was studied by scanning tunneling microscopy (STM), transmission electron microscopy (TEM) and angle-resolved photoemission (ARPES) in order to verify the existence of a recently proposed surface charge density wave (CDW) [Ch. R. Ast and H. Hoechst Phys. Rev. Lett. 90, 016403 (2003)]. The STM and TEM results to not support a CDW scenario at low temperatures. Furthermore, the quasiparticle interference pattern observed in STM confirms the spin-orbit split character of the sur… more
Date: May 1, 2005
Creator: Kim, T. K.; Wells, J.; Kirkegaard, C.; Li, Z.; Hoffmann, S.V.; Gayone, J. E. et al.
Partner: UNT Libraries Government Documents Department
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Production of transverse controllable laser density distribution in Fermilab/NICADD photo injector

Description: The Fermilab/NICADD photoinjector laboratory consists of a photoemission electron source based on an L band rf-gun. The CsTe photocathode is illuminated by an ultrashort UV laser. The transport line from the laser to the photocathode was recently upgraded to allow imaging of an object plane located {approx}20 m from the photocathode. This upgrade allows the generation of transverse laser distributions with controllable non-uniformity, yielding the production of an electron beam with various tra… more
Date: May 1, 2005
Creator: Li, Jian-Liang; Tikoplav, Rodion; Piot, Philippe & Melissinos, Adrian
Partner: UNT Libraries Government Documents Department
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PHOTOEMISSION AND SECONDARY ION MASS SPECTROMETRY STUDY OF URANIUM PASSIVATION BY C+ IMPLANTATION

Description: Preventing the corrosion and oxidation of uranium is important to the continued development of advanced nuclear fuel technologies. Knowledge of the surface reactions of uranium metal with various environmental and atmospheric agents, and the subsequent degradation processes, are vitally important in 21st century nuclear technology. A review of the oxidation of actinide elements and their use in catalysis summarizes the present understanding of the kinetics and mechanisms of the reaction in dry … more
Date: April 21, 2005
Creator: Nelson, A J; Felter, T E; Wu, K J; Evans, C; Ferreira, J L; Siekhaus, W J et al.
Partner: UNT Libraries Government Documents Department
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Spectroscopic Signature of Aging in (delta)-Pu(Ga)

Description: Resonant Photoemission, a variant of Photoelectron Spectroscopy, has been demonstrated to have sensitivity to aging of Pu samples. The spectroscopic results are correlated with resistivity measurements and are shown to be the fingerprint of mesoscopic or nanoscale internal damage in the Pu physical structure. This means that a spectroscopic signature of internal damage due to aging in Pu has been established.
Date: April 15, 2005
Creator: Chung, B. W.; Schwartz, A. J.; Ebbinghaus, B. B.; Fluss, M. J.; Haslam, J. J.; Blobaum, K. M. et al.
Partner: UNT Libraries Government Documents Department
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Determination of Band Curvatures by Angle-resolved Two-photonPhotoemission in thin films of C(60) on Ag(111)

Description: The thickness-dependent interfacial band structure wasdetermined for thin films of Co(6) on Ag(111) by angle-resolvedtwo-photon photoemission spectroscopy.
Date: March 1, 2005
Creator: Shipman, Steven T.; Szymanski, Paul; Garrett-Roe, Sean; Yang,Aram; Strader, Matthew L. & Harris, Charles B.
Partner: UNT Libraries Government Documents Department
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Advanced Strained-Superlattice Photocathodes for Polarized Electron Sources

Description: Polarized electrons have been essential for high-energy parity-violating experiments and measurements of the nucleon spin structure. The availability of a polarized electron beam was crucial to the success of the Stanford Linear Collider (SLC) in achieving a precise measurement of the electroweak mixing angle, and polarized electron beams will be required for all future linear colliders. Polarized electrons are readily produced by GaAs photocathode sources. When a circularly polarized laser bea… more
Date: January 31, 2005
Creator: Moy, Dr. Aaron
Partner: UNT Libraries Government Documents Department
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4th-International Symposium on Ultrafast Surface Science - Final Report

Description: The 4-th International Symposium on Ultrafast Surface Dynamics (UDS4) was held at the Telluride Summer Research Center on June 22-27, 2003. The International Organizing Committee consisting of Hrvoje Petek (USA), Xiaoyang Zhu (USA), Pedro Echenique (Spain) and Maki Kawai (Japan) brought together a total of 51 participants 16 of whom were from Europe, 10 from Japan, and 25 from the USA. The focus of the conference was on ultrafast electron or light induced processes at well-defined surfaces. Ult… more
Date: January 26, 2005
Creator: Petek, Hrvoje
Partner: UNT Libraries Government Documents Department
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