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Sample records for angle-resolved photoemission spectroscopy

  1. Angle-resolved photoemission spectroscopy (ARPES) studies of cuprate superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Palczewski, Ari Deibert [Iowa State Univ., Ames, IA (United States)

    2010-01-01

    This dissertation is comprised of three different angle-resolved photoemission spectroscopy (ARPES) studies on cuprate superconductors. The first study compares the band structure from two different single layer cuprates Tl2Ba2CuO6+δ (Tl2201) Tc, max ≈ 95 K and (Bi 1.35Pb0.85)(Sr1.47La0.38)CuO6+δ (Bi2201) Tc, max ≈ 35 K. The aim of the study was to provide some insight into the reasons why single layer cuprate's maximum transition temperatures are so different. The study found two major differences in the band structure. First, the Fermi surface segments close to (π,0) are more parallel in Tl2201 than in Bi2201. Second, the shadow band usually related to crystal structure is only present in Bi2201, but absent in higher Tc Tl2201. The second study looks at the different ways of doping Bi2Sr2CaCu2O8+δ (Bi2212) in-situ by only changing the post bake-out vacuum conditions and temperature. The aim of the study is to systematically look into the generally overlooked experimental conditions that change the doping of a cleaved sample in ultra high vacuum (UHV) experiments. The study found two major experimental facts. First, in inadequate UHV conditions the carrier concentration of Bi2212 increases with time, due to the absorption of oxygen from CO2/CO molecules, prime contaminants present in UHV systems. Second, in a very clean UHV system at elevated temperatures (above about 200 K), the carrier concentration decreases due to the loss of oxygen atoms from the Bi-O layer. The final study probed the particle-hole symmetry of the pseudogap phase in high temperature superconducting cuprates by looking at the thermally excited bands above the Fermi level. The data showed a particle-hole symmetric pseudogap which symmetrically closes away from the nested FS before the node. The data is

  2. High-harmonic XUV source for time- and angle-resolved photoemission spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Dakovski, Georgi L [Los Alamos National Laboratory; Li, Yinwan [Los Alamos National Laboratory; Durakiewicz, Tomasz [Los Alamos National Laboratory; Rodriguez, George [Los Alamos National Laboratory

    2009-01-01

    We present a laser-based apparatus for visible pump/XUV probe time- and angle-resolved photoemission spectroscopy (TRARPES) utilizing high-harmonic generation from a noble gas. Femtosecond temporal resolution for each selected harmonic is achieved by using a time-delay-compensated monochromator (TCM). The source has been used to obtain photoemission spectra from insulators (UO{sub 2}) and ultrafast pump/probe processes in semiconductors (GaAs).

  3. Time and angle resolved photoemission spectroscopy using femtosecond visible and high-harmonic light

    Energy Technology Data Exchange (ETDEWEB)

    Mathias, S; Deicke, F; Ruffing, A; Aeschlimann, M [Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, 67663 Kaiserslautern (Germany); Wiesenmayer, M; Bauer, M [Institut fuer experimentelle und angewandte Physik, Christian-Albrechts Universitaet zu Kiel, 24118 Kiel (Germany); Miaja-Avila, L; Murnane, M M; Kapteyn, H C, E-mail: SMathias@gmx.d [JILA, University of Colorado and National Institute of Standards and Technology, and Department of Physics, University of Colorado, Boulder, Colorado 80309-0440 (United States)

    2009-02-01

    The angle resolved photoelectron spectroscopy (ARPES) has emerged as a leading technique in identifying static key properties of complex systems such as the electronic band structure of adsorbed molecules, ultrathin quantum-well films or high temperature superconductors. We efficiently combined ARPES by using a two-dimensional analyzer for parallel energy (E) and momentum (k{sub ||}) detection with femtosecond time-resolved spectroscopies. Using time and angle resolved two photon photoemission (2PPE) with visible light pulses, the hot electron dynamics in complex electronic structures are directly accessible by means of angle resolved hot electron lifetime mapping. Furthermore, femtosecond ARPES spectra recorded with high harmonic generation (HHG) light pulses are presented, showing the potential of this technique for future investigations of surface dynamics and photo-induced phase transition processes.

  4. Metal-insulator transition of naxwo3 studied by angle-resolved photoemission spectroscopy

    OpenAIRE

    Raj, Satyabrata; Sato, Takafumi; Souma, Seigo; Takahashi, Takashi; Sarma, DD; Mahadevan, Priya

    2009-01-01

    The electronic structure of sodium tungsten bronzes NaxWO3 is investigated by high-resolution angle-resolved photoemission spectroscopy (ARPES). The ARPES spectra measured in both insulating and metallic phases of NaxWO3 reveals the origin of metal-insulator transition (MIT) in sodium tungsten bronze system. It is found that in insulating NaxWO3 the states near the Fermi level (E-F) are localized due to the strong disorder caused by the random distribution of Na+ ions in WO3 lattice. Due t...

  5. Angle resolved photoemission spectroscopy of Sr_2CuO_2Cl_2 - a revisit

    OpenAIRE

    Duerr, C; Legner, S.; Hayn, R.; Borisenko, S. V.; Z. Hu; Theresiak, A.; Knupfer, M.; Golden, M. S.; Fink, J.; Ronning, F.; Shen, Z.-X.; Eisaki, H.; Uchida, S.; Janowitz, C.; Mueller, R.

    2000-01-01

    We have investigated the lowest binding-energy electronic structure of the model cuprate Sr_2CuO_2Cl_2 using angle resolved photoemission spectroscopy (ARPES). Our data from about 80 cleavages of Sr_2CuO_2Cl_2 single crystals give a comprehensive, self-consistent picture of the nature of the first electron-removal state in this model undoped CuO_2-plane cuprate. Firstly, we show a strong dependence on the polarization of the excitation light which is understandable in the context of the matri...

  6. Dynamics of Molecular Orientation Observed Using Angle Resolved Photoemission Spectroscopy during Deposition of Pentacene on Graphite.

    Science.gov (United States)

    Park, Sang Han; Kwon, Soonnam

    2016-04-19

    A real-time method to observe both the structural and the electronic configuration of an organic molecule during deposition is reported for the model system of pentacene on graphite. Structural phase transition of the thin films as a function of coverage is monitored by using in situ angle resolved photoemission spectroscopy (ARPES) results to observe the change of the electronic configuration at the same time. A photoemission theory that uses independent atomic center approximations is introduced to identify the molecular orientation from the ARPES technique. This study provides a practical insight into interpreting ARPES data regarding dynamic changes of molecular orientation during initial growth of molecules on a well-defined surface. PMID:26999332

  7. Accessing Phonon Polaritons in Hyperbolic Crystals by Angle-Resolved Photoemission Spectroscopy

    Science.gov (United States)

    Tomadin, Andrea; Principi, Alessandro; Song, Justin C. W.; Levitov, Leonid S.; Polini, Marco

    2015-08-01

    Recently studied hyperbolic materials host unique phonon-polariton (PP) modes. The ultrashort wavelengths of these modes, as well as their low damping, hold promise for extreme subdiffraction nanophotonics schemes. Polar hyperbolic materials such as hexagonal boron nitride can be used to realize long-range coupling between PP modes and extraneous charge degrees of freedom. The latter, in turn, can be used to control and probe PP modes. Here we analyze coupling between PP modes and plasmons in an adjacent graphene sheet, which opens the door to accessing PP modes by angle-resolved photoemission spectroscopy (ARPES). A rich structure in the graphene ARPES spectrum due to PP modes is predicted, providing a new probe of PP modes and their coupling to graphene plasmons.

  8. Direct angle resolved photoemission spectroscopy and superconductivity of strained high-c films

    Indian Academy of Sciences (India)

    Davor Pavuna; Daniel Ariosa; Dominique Cloetta; Claudia Cancellieri; Mike Abrecht

    2008-02-01

    Since 1997 we systematically perform direct angle resolved photoemission spectroscopy (ARPES) on in-situ grown thin (< 30 nm) cuprate films. Specifically, we probe low-energy electronic structure and properties of high-c superconductors (HTSC) under different degrees of epitaxial (compressive vs. tensile) strain. In overdoped and underdoped in-plane compressed (the strain is induced by the choice of substrate) ≃ 15 nm thin La2-SrCuO4 (LSCO) films we almost double c to 40 K, from 20 K and 24 K, respectively. Yet the Fermi surface (FS) remains essentially two-dimensional. In contrast, ARPES data under tensile strain exhibit the dispersion that is three-dimensional, yet c drastically decreases. It seems that the in-plane compressive strain tends to push the apical oxygen far away from the CuO2 plane, enhances the two-dimensional character of the dispersion and increases c, while the tensile strain acts in the opposite direction and the resulting dispersion is three-dimensional. We have established the shape of the FS for both cases, and all our data are consistent with other ongoing studies, like EXAFS. As the actual lattice of cuprates is like a `Napoleon-cake', i.e. rigid CuO2 planes alternating with softer `reservoir', that distort differently under strain, our data rule out all oversimplified two-dimensional (rigid lattice) mean field models. The work is still in progress on optimized La-doped Bi-2201 films with enhanced c.

  9. Angle resolved photoemission spectroscopy study on the non-saturate magnetoresistance material WTe2

    Science.gov (United States)

    Jiang, Juan; Niu, Xiaohai; Xie, Binping; Zhang, Tong; Feng, Donglai

    2015-03-01

    By performing high resolution angle-resolved photoemission spectroscopy, we obtain the detailed electronic structure of WTe2, which has an extremely large non-saturated magnetoresistance. Unlike the simple one electron and one hole pocket as expected, we resolved a rather complicated Fermi surface in WTe2. There is a hole pocket around the Brillouin zone center Γ, two hole pockets and two electron pockets along the tungsten chain direction. Thus the large magnetoresistance cannot be simply attributed to the electron-hole compensation, since this is based on a two carrier assumption model, the real case in WTe2 should be more complicated. Surprisingly, the circular dichroism ARPES result shows a strong intensity inversion between the data under the right-circular polarized light and the left-circular polarized light. This, indicates a proper different orbital angular momentum along the tungsten chain direction, which might also related to the different spin angular momentum since there're coupled with each other. Therefore, we propose that to fully understand the large magnetoresistance in WTe2, spin channel should also be involved where backscattering are forbidden under zero field.

  10. Direct angle resolved photoemission spectroscopy and superconductivity of strained high-Tc films

    International Nuclear Information System (INIS)

    Since 1997 we systematically perform direct angle resolved photoemission spectroscopy (ARPES) on in-situ grown thin (c superconductors (HTSC) under different degrees of epitaxial (compressive vs. tensile) strain. In overdoped and underdoped in-plane compressed (the strain is induced by the choice of substrate) ≅ 15 nm thin La2-xSrxCuO4 (LSCO) films we almost double Tc to 40 K, from 20 K and 24 K, respectively. Yet the Fermi surface (FS) remains essentially two-dimensional. In contrast, ARPES data under tensile strain exhibit the dispersion that is three-dimensional, yet Tc drastically decreases. It seems that the in-plane compressive strain tends to push the apical oxygen far away from CuO2 plane, enhances the two-dimensional character of the dispersion and increases Tc, while the tensile strain acts in the opposite direction and the resulting dispersion is three-dimensional. We have established the shape of the FS for both cases, and all our data are consistent with other ongoing studies, like EXAFS. As the actual lattice of cuprates is like a Napoleon-cake, i.e. rigid CuO2 planes alternating with softer reservoir, that distort differently under strain, our data rule out all oversimplified two-dimensional (rigid lattice) mean field models. The work is still in progress on optimized La-doped Bi-2201 films with enhanced Tc. (author)

  11. Direct angle resolved photoemission spectroscopy and superconductivity of strained high-Tc films

    Science.gov (United States)

    Pavuna, Davor; Ariosa, Daniel; Cloetta, Dominique; Cancellieri, Claudia; Abrecht, Mike

    2008-02-01

    Since 1997 we systematically perform direct angle resolved photoemission spectroscopy (ARPES) on in-situ grown thin (<30 nm) cuprate films. Specifically, we probe low-energy electronic structure and properties of high-T_{c} superconductors (HTSC) under different degrees of epitaxial ({compressive vs. tensile}) strain. In overdoped and underdoped in-plane compressed (the strain is induced by the choice of substrate) ≈15 nm thin La_{2-x}Sr_{x}CuO_{4} (LSCO) films we almost double T_{c} to 40 K, from 20 K and 24 K, respectively. Yet the Fermi surface (FS) remains essentially two-dimensional. In contrast, ARPES data under {tensile} strain exhibit the dispersion that is three-dimensional, yet T_{c} drastically decreases. It seems that the in-plane compressive strain tends to push the apical oxygen far away from the CuO_{2} plane, enhances the two-dimensional character of the dispersion and increases T_{c}, while the tensile strain acts in the opposite direction and the resulting dispersion is three-dimensional. We have established the shape of the FS for both cases, and all our data are consistent with other ongoing studies, like EXAFS. As the actual lattice of cuprates is like a `Napoleon-cake', i.e. rigid CuO_{2 } planes alternating with softer `reservoir', that distort differently under strain, our data rule out all oversimplified two-dimensional (rigid lattice) mean field models. The work is still in progress on optimized La-doped Bi-2201 films with enhanced T_{c}.

  12. Angle-resolved photoemission spectroscopy of the insulating NaxWO3: Anderson localization, polaron formation, and remnant Fermi surface.

    Science.gov (United States)

    Raj, S; Hashimoto, D; Matsui, H; Souma, S; Sato, T; Takahashi, T; Sarma, D D; Mahadevan, Priya; Oishi, S

    2006-04-14

    The electronic structure of the insulating sodium tungsten bronze, Na(0.025)WO(3), is investigated by high-resolution angle-resolved photoemission spectroscopy. We find that near-E(F) states are localized due to the strong disorder arising from random distribution of Na+ ions in the WO(3) lattice, which makes the system insulating. The temperature dependence of photoemission spectra provides direct evidence for polaron formation. The remnant Fermi surface of the insulator is found to be the replica of the real Fermi surface in the metallic system. PMID:16712121

  13. Tunable VUV laser based spectrometer for Angle Resolved Photoemission Spectroscopy (ARPES)

    CERN Document Server

    Jiang, Rui; Wu, Yun; Huang, Lunan; McMillen, Colin D; Kolis, Joseph; Giesber, Henry G; Egan, John J; Kaminski, Adam

    2014-01-01

    We have developed an angle-resolved photoemission spectrometer with tunable VUV laser as a photon source. The photon source is based on the fourth harmonic generation of a near IR beam from a Ti:sapphire laser pumped by a CW green laser and tunable between 5.3eV and 7eV. The most important part of the set-up is a compact, vacuum enclosed fourth harmonic generator based on KBBF crystals, grown hydrothermally in the US. This source can deliver a photon flux of over 10^14 photons/s. We demonstrate that this energy range is sufficient to measure the kz dispersion in an iron arsenic high temperature superconductor, which was previously only possible at synchrotron facilities.

  14. Tunable vacuum ultraviolet laser based spectrometer for angle resolved photoemission spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Rui; Mou, Daixiang; Wu, Yun; Huang, Lunan; Kaminski, Adam [Division of Materials Science and Engineering, Ames Laboratory, Ames, Iowa 50011 (United States); Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011 (United States); McMillen, Colin D.; Kolis, Joseph [Department of Chemistry, Clemson University, Clemson, South Carolina 29634 (United States); Giesber, Henry G.; Egan, John J. [Advanced Photonic Crystals LLC, Fort Mill, South Carolina 29708 (United States)

    2014-03-15

    We have developed an angle-resolved photoemission spectrometer with tunable vacuum ultraviolet laser as a photon source. The photon source is based on the fourth harmonic generation of a near IR beam from a Ti:sapphire laser pumped by a CW green laser and tunable between 5.3 eV and 7 eV. The most important part of the set-up is a compact, vacuum enclosed fourth harmonic generator based on potassium beryllium fluoroborate crystals, grown hydrothermally in the US. This source can deliver a photon flux of over 10{sup 14} photon/s. We demonstrate that this energy range is sufficient to measure the k{sub z} dispersion in an iron arsenic high temperature superconductor, which was previously only possible at synchrotron facilities.

  15. Orbital Rashba effect and its detection by circular dichroism angle-resolved photoemission spectroscopy

    Science.gov (United States)

    Park, Jin-Hong; Kim, Choong H.; Rhim, Jun-Won; Han, Jung Hoon

    2012-05-01

    We show, by way of tight-binding and first-principles calculations, that a one-to-one correspondence between an electron's crystal momentum k and nonzero orbital angular momentum (OAM) is a generic feature of surface bands. The OAM forms a chiral structure in momentum space much as its spin counterpart in Rashba model does, as a consequence of the inherent inversion symmetry breaking at the surface but not of spin-orbit interaction. This is the orbital counterpart of conventional Rashba effect and may be called the “orbital Rashba effect.” The circular dichroism (CD) angle-resolved photoemission (ARPES) method is an efficient way to detect this new order, and we derive formulas explicitly relating the CD-ARPES signal to the existence of OAM in the band structure. The cases of degenerate p- and d-orbital bands are considered.

  16. Metal-insulator transition in sodium tungsten bronzes, NaxWO3, studied by angle-resolved photoemission spectroscopy

    International Nuclear Information System (INIS)

    We report high-resolution angle-resolved photoemission spectroscopy on sodium tungsten bronzes, NaxWO3, which exhibit a metal-insulator transition as a function of x. We found that the near-EF states are localized in NaxWO3 (x=+ ions in the WO3 lattice, which makes the system insulating. In the metallic regime we found that the rigid shift of band structure can explain the metallic NaxWO3 band structure with respect to Na doping

  17. Soft X-ray angle-resolved photoemission spectroscopy of heavily boron-doped superconducting diamond films

    Directory of Open Access Journals (Sweden)

    T. Yokoya, T. Nakamura, T. Matushita, T. Muro, H. Okazaki, M. Arita, K. Shimada, H. Namatame, M. Taniguchi, Y. Takano, M. Nagao, T. Takenouchi, H. Kawarada and T. Oguchi

    2006-01-01

    Full Text Available We have performed soft X-ray angle-resolved photoemission spectroscopy (SXARPES of microwave plasma-assisted chemical vapor deposition diamond films with different B concentrations in order to study the origin of the metallic behavior of superconducting diamond. SXARPES results clearly show valence band dispersions with a bandwidth of ~23 eV and with a top of the valence band at gamma point in the Brillouin zone, which are consistent with the calculated valence band dispersions of pure diamond. Boron concentration-dependent band dispersions near the Fermi level (EF exhibit a systematic shift of EF, indicating depopulation of electrons due to hole doping. These SXARPES results indicate that diamond bands retain for heavy boron doping and holes in the diamond band are responsible for the metallic states leading to superconductivity at low temperature. A high-resolution photoemission spectroscopy spectrum near EF of a heavily boron-doped diamond superconductor is also presented.

  18. Angle-Resolved Photoemission Spectroscopy on Electronic Structure and Electron-Phonon Coupling in Cuprate Superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, X.J.

    2010-04-30

    In addition to the record high superconducting transition temperature (T{sub c}), high temperature cuprate superconductors are characterized by their unusual superconducting properties below T{sub c}, and anomalous normal state properties above T{sub c}. In the superconducting state, although it has long been realized that superconductivity still involves Cooper pairs, as in the traditional BCS theory, the experimentally determined d-wave pairing is different from the usual s-wave pairing found in conventional superconductors. The identification of the pairing mechanism in cuprate superconductors remains an outstanding issue. The normal state properties, particularly in the underdoped region, have been found to be at odd with conventional metals which is usually described by Fermi liquid theory; instead, the normal state at optimal doping fits better with the marginal Fermi liquid phenomenology. Most notable is the observation of the pseudogap state in the underdoped region above T{sub c}. As in other strongly correlated electrons systems, these unusual properties stem from the interplay between electronic, magnetic, lattice and orbital degrees of freedom. Understanding the microscopic process involved in these materials and the interaction of electrons with other entities is essential to understand the mechanism of high temperature superconductivity. Since the discovery of high-T{sub c} superconductivity in cuprates, angle-resolved photoemission spectroscopy (ARPES) has provided key experimental insights in revealing the electronic structure of high temperature superconductors. These include, among others, the earliest identification of dispersion and a large Fermi surface, an anisotropic superconducting gap suggestive of a d-wave order parameter, and an observation of the pseudogap in underdoped samples. In the mean time, this technique itself has experienced a dramatic improvement in its energy and momentum resolutions, leading to a series of new discoveries not

  19. Electronic structure study of Cu-doped 1T-TiSe{sub 2} by angle-resolved photoemission spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Jeong, Jinwon; Jeong, Jinhwan [Department of Physics, Chonnam National University, Gwangju 500-757 (Korea, Republic of); Noh, Han-Jin, E-mail: ffnhj@chonnam.ac.k [Department of Physics, Chonnam National University, Gwangju 500-757 (Korea, Republic of); Kim, Sung Baek [Laboratory of Pohang Emergent Materials and Department of Physics, POSTECH, Pohang 790-784 (Korea, Republic of); Kim, H.-D. [Pohang Accelerator Laboratory, POSTECH, Pohang 790-784 (Korea, Republic of)

    2010-12-15

    We synthesized single crystals of TiSe{sub 2} with various Cu concentrations, and have performed an angle-resolved photoemission spectroscopy (ARPES) study in order to understand the CDW mechanism and to reveal the role of the Cu atoms in Cu-doped 1T-TiSe{sub 2}. The measurements reveal that during the well-known charge density wave (CDW) transition the pristine TiSe{sub 2} sample undergoes a transition from a very small indirect gap semiconductor to a larger one. No nesting sign was observed in the Fermi surface in the CDW phase. The transition is suppressed in the Cu-doped samples, and an electron pocket appears near the L point, which may help appearance of the superconductivity of Cu{sub x}TiSe{sub 2} through the BCS-Eliashberg relation.

  20. Angle-resolved photoemission spectroscopy study on the Fermi surface topology of NaxCoO2

    International Nuclear Information System (INIS)

    We report a systematic study on NaxCoO2 (0.3≤x≤0.72) using angle-resolved photoemission spectroscopy (ARPES), with a focus on the Fermi surface topology of the metallic samples. Within this doping range, we observed only one large hexagonal Fermi surface around the Γ-point, which comes from the a1g band. Contrary to most band calculations, our results show that the eg' bands never cross the Fermi level to form small Fermi surface pockets near the K-point. The enclosed area of the a1g Fermi surface is found to be consistent with the Luttinger theorem within the doping range in this study. We also found that, at x = 1/3, the Fermi surface coincides with the zone boundary of the √3x√3 commensurate ordering, indicating the importance of charge fluctuations in this material

  1. Angle-resolved photoemission spectroscopy of band tails in lightly doped cuprates

    OpenAIRE

    Alexandrov, A. S.; Reynolds, K.

    2007-01-01

    We amend ab initio strongly-correlated band structures by taking into account the band-tailing phenomenon in doped charge-transfer Mott-Hubbard insulators. We show that the photoemission from band tails accounts for sharp "quasi-particle" peaks, rapid loss of their intensities in some directions of the Brillouin zone ("Fermi-arcs") and high-energy "waterfall" anomalies as a consequence of matrix-element effects of disorder-localised states in the charge-transfer gap of doped cuprates.

  2. Angle-resolved photoemission spectroscopy for VO2 thin films grown on TiO2 (0 0 1) substrates

    International Nuclear Information System (INIS)

    We present the results of angle-resolved photoemission spectroscopy (ARPES) measurements of metallic VO2 thin films. The VO2 thin films have been grown on TiO2 (0 0 1) single crystal substrates using pulsed laser deposition. The films exhibit a first-order metal-insulator transition (MIT) at 305 K. In the ARPES spectra of the metallic phase for the films, the O 2p band shows highly dispersive feature in the binding energy range of 3-8 eV along the Γ-Z direction. The periodicity of the dispersive band is found to be 2.2 A-1 which is almost identical with the periodicity expected from the c-axis length of the VO2 thin films. The overall feature of the experimental band structure is similar to the band structure calculations, supporting that we have succeeded in observing the dispersive band of the O 2p state in the metallic VO2 thin film. The present work indicates that the ARPES measurements using epitaxial thin films are promising for determining the band structure of VO2.

  3. Angle-resolved photoemission extended fine structure

    International Nuclear Information System (INIS)

    Measurements of the Angle-Resolved Photoemission Extended Fine Structure (ARPEFS) from the S(1s) core level of a c(2 x 2)S/Ni(001) are analyzed to determine the spacing between the S overlayer and the first and second Ni layers. ARPEFS is a type of photoelectron diffraction measurement in which the photoelectron kinetic energy is swept typically from 100 to 600 eV. By using this wide range of intermediate energies we add high precision and theoretical simplification to the advantages of the photoelectron diffraction technique for determining surface structures. We report developments in the theory of photoelectron scattering in the intermediate energy range, measurement of the experimental photoemission spectra, their reduction to ARPEFS, and the surface structure determination from the ARPEFS by combined Fourier and multiple-scattering analyses. 202 refs., 67 figs., 2 tabs

  4. Doping dependence of the (π, π) shadow band in La-based cuprates studied by angle-resolved photoemission spectroscopy

    International Nuclear Information System (INIS)

    The (π, π) shadow band (SB) in the La-based cuprate family (La214) was studied by angle-resolved photoemission spectroscopy over a wide doping range from x=0.01 to x=0.25. Unlike the well-studied case of the Bi-based cuprate family, an overall strong, monotonic doping dependence of the SB intensity at the Fermi level (EF) was observed. In contrast to a previous report for the presence of the SB only close to x=1/8, we found that it exists in a wide doping range, associated with a doping-independent (π, π) wave vector but a strongly doping-dependent intensity: it is strongest at x∼0.03 and systematically diminishes as the doping increases until it becomes negligible in the overdoped regime. This SB with the observed doping dependence of intensity can in principle be caused by the antiferromagnetic fluctuations or a particular form of low-temperature orthorhombic lattice distortion known to persist up to x∼0.21 in the system, with both being weakened with increasing doping. However, a detailed binding-energy-dependent analysis of the SB at x=0.07 does not appear to support the former interpretation, leaving the latter as a more plausible candidate, despite a challenge in quantitatively linking the doping dependences of the SB intensity and the magnitude of the lattice distortion. Our finding highlights the necessity for a careful and global consideration of the inherent structural complications for correctly understanding the cuprate Fermiology and its microscopic implication.

  5. In situ positioning of a few hundred micrometer-sized cleaved surfaces for soft-x-ray angle-resolved photoemission spectroscopy by use of an optical microscope

    International Nuclear Information System (INIS)

    A method to position samples with small cleaved regions has been developed to be applied to the angle-resolved photoemission spectroscopy (ARPES) which uses soft-x-ray synchrotron radiation focused down to 160x180 μm2. A long-working-distance optical microscope is used for the sample observation. A selected region on a sample can be optimally set at the position of measurements, which is realized by the spatial resolution of the photoelectron analyzer. Using this method, electronic band dispersions of bulk silicon have been measured by ARPES for a partially cleaved region with a size of ∼200x500 μm2.

  6. Metal-insulator transition in sodium tungsten bronzes, Na{sub x}WO{sub 3}, studied by angle-resolved photoemission spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Raj, S. [Department of Physics, Tohoku University, Sendai 980-8578 (Japan)]. E-mail: raj@arpes.phys.tohoku.ac.jp; Hashimoto, D. [Department of Physics, Tohoku University, Sendai 980-8578 (Japan); Matsui, H. [Department of Physics, Tohoku University, Sendai 980-8578 (Japan); Souma, S. [Department of Physics, Tohoku University, Sendai 980-8578 (Japan); CREST, Japan Science and Technology Agency (JST), Kawaguchi 332-0012 (Japan); Sato, T. [Department of Physics, Tohoku University, Sendai 980-8578 (Japan); CREST, Japan Science and Technology Agency (JST), Kawaguchi 332-0012 (Japan); Takahashi, T. [Department of Physics, Tohoku University, Sendai 980-8578 (Japan); CREST, Japan Science and Technology Agency (JST), Kawaguchi 332-0012 (Japan); Ray, S. [Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560012 (India); Chakraborty, A. [Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560012 (India); Sarma, D.D. [Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560012 (India); Mahadevan, P. [S.N. Bose National Centre for Basic Sciences, JD Block, Sector 3, Salt Lake, Kolkata 700098 (India); Oishi, S. [Faculty of Engineering, Shinshu University, Nagano 380-8553 (Japan); McCarroll, W.H. [Department of Chemistry and Biochemistry, Rider University, NJ 08648 (United States); Greenblatt, M. [Department of Chemistry and Chemical Biology, The State University of New Jersey, NJ 08854 (United States)

    2007-03-15

    We report high-resolution angle-resolved photoemission spectroscopy on sodium tungsten bronzes, Na{sub x}WO{sub 3}, which exhibit a metal-insulator transition as a function of x. We found that the near-E{sub F} states are localized in Na{sub x}WO{sub 3} (x=<0.25) due to the strong disorder caused by the random distribution of Na{sup +} ions in the WO{sub 3} lattice, which makes the system insulating. In the metallic regime we found that the rigid shift of band structure can explain the metallic Na{sub x}WO{sub 3} band structure with respect to Na doping.

  7. Angle-resolved photoemission spectroscopy with 9-eV photon-energy pulses generated in a gas-filled hollow-core photonic crystal fiber

    Energy Technology Data Exchange (ETDEWEB)

    Bromberger, H., E-mail: Hubertus.Bromberger@mpsd.mpg.de; Liu, H.; Chávez-Cervantes, M.; Gierz, I. [Max Planck Institute for the Structure and Dynamics of Matter, Luruper Chaussee 149, 22761 Hamburg (Germany); Ermolov, A.; Belli, F.; Abdolvand, A.; Russell, P. St. J.; Travers, J. C. [Max Planck Institute for the Science of Light, Günther-Scharowsky-Str. 1, 91058 Erlangen (Germany); Calegari, F. [Max Planck Institute for the Structure and Dynamics of Matter, Luruper Chaussee 149, 22761 Hamburg (Germany); Institute for Photonics and Nanotechnologies, IFN-CNR, Piazza Leonardo da Vinci 32, I-20133 Milano (Italy); Li, M. T.; Lin, C. T. [Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart (Germany); Cavalleri, A. [Max Planck Institute for the Structure and Dynamics of Matter, Luruper Chaussee 149, 22761 Hamburg (Germany); Clarendon Laboratory, Department of Physics, University of Oxford, Parks Rd. Oxford OX1 3PU (United Kingdom)

    2015-08-31

    A recently developed source of ultraviolet radiation, based on optical soliton propagation in a gas-filled hollow-core photonic crystal fiber, is applied here to angle-resolved photoemission spectroscopy (ARPES). Near-infrared femtosecond pulses of only few μJ energy generate vacuum ultraviolet radiation between 5.5 and 9 eV inside the gas-filled fiber. These pulses are used to measure the band structure of the topological insulator Bi{sub 2}Se{sub 3} with a signal to noise ratio comparable to that obtained with high order harmonics from a gas jet. The two-order-of-magnitude gain in efficiency promises time-resolved ARPES measurements at repetition rates of hundreds of kHz or even MHz, with photon energies that cover the first Brillouin zone of most materials.

  8. Angle-resolved photoemission spectroscopy with 9-eV photon-energy pulses generated in a gas-filled hollow-core photonic crystal fiber

    CERN Document Server

    Bromberger, H; Belli, F; Liu, H; Calegari, F; Chavez-Cervantes, M; Li, M T; Lin, C T; Abdolvand, A; Russell, P St J; Cavalleri, A; Travers, J C; Gierz, I

    2015-01-01

    A recently developed source of ultraviolet radiation, based on optical soliton propagation in a gas-filled hollow-core photonic crystal fiber, is applied here to angle-resolved photoemission spectroscopy (ARPES). Near-infrared femtosecond pulses of only few {\\mu}J energy generate vacuum ultraviolet (VUV) radiation between 5.5 and 9 eV inside the gas-filled fiber. These pulses are used to measure the band structure of the topological insulator Bi2Se3 with a signal to noise ratio comparable to that obtained with high order harmonics from a gas jet. The two-order-of-magnitude gain in efficiency promises time-resolved ARPES measurements at repetition rates of hundreds of kHz or even MHz, with photon energies that cover the first Brillouin zone of most materials.

  9. Angle-resolved photoemission spectroscopy with 9-eV photon-energy pulses generated in a gas-filled hollow-core photonic crystal fiber

    International Nuclear Information System (INIS)

    A recently developed source of ultraviolet radiation, based on optical soliton propagation in a gas-filled hollow-core photonic crystal fiber, is applied here to angle-resolved photoemission spectroscopy (ARPES). Near-infrared femtosecond pulses of only few μJ energy generate vacuum ultraviolet radiation between 5.5 and 9 eV inside the gas-filled fiber. These pulses are used to measure the band structure of the topological insulator Bi2Se3 with a signal to noise ratio comparable to that obtained with high order harmonics from a gas jet. The two-order-of-magnitude gain in efficiency promises time-resolved ARPES measurements at repetition rates of hundreds of kHz or even MHz, with photon energies that cover the first Brillouin zone of most materials

  10. Electronic structure of charge-density-wave state in quasi-2D KMo6O17 purple bronze characterized by angle resolved photoemission spectroscopy

    Science.gov (United States)

    Valbuena, M. A.; Avila, J.; Drouard, S.; Guyot, H.; Asensio, M. C.

    2006-01-01

    We report on an angle-resolved-photoemission spectroscopy (ARPES) investigation of layered quasi-two dimensional (2D) Molybdenum purple bronze KMo6O17 in order to study and characterizes the transition to a charge-density-wave (CDW) state. We have performed photoemission temperature dependent measurements cooling down from room temperature (RT) to 32 K, well below the Peierls transition for this material, with CDW transition temperature Tc =110 K. The spectra have been taken at a selected kF point of the Fermi surface (FS) that satisfies the nesting condition of the FS, looking for the characteristic pseudo-gap opening in this kind of materials. The pseudogap has been estimated and it result to be in agreement with our previous works. The shift to lower binding energy of crossing Fermi level ARPES feature have been also confirmed and studied as a function of temperature, showing a rough like BCS behaviour. Finally we have also focused on ARPES measurements along ΓM¯ high symmetry direction for both room and low temperature states finding some insight for ‘shadow’ or back folded bands indicating the new periodicity of real lattice after the CDW lattice distortion.

  11. Fermi surface of MoO2 studied by angle-resolved photoemission spectroscopy, de Haas-van Alphen measurements, and electronic structure calculations

    Science.gov (United States)

    Moosburger-Will, Judith; Kündel, Jörg; Klemm, Matthias; Horn, Siegfried; Hofmann, Philip; Schwingenschlögl, Udo; Eyert, Volker

    2009-03-01

    A comprehensive study of the electronic properties of monoclinic MoO2 from both an experimental and a theoretical point of view is presented. We focus on the investigation of the Fermi body and the band structure using angle-resolved photoemission spectroscopy, de Haas-van Alphen measurements, and electronic structure calculations. For the latter, the full-potential augmented spherical wave method has been applied. Very good agreement between the experimental and theoretical results is found. In particular, all Fermi surface sheets are correctly identified by all three approaches. Previous controversies concerning additional holelike surfaces centered around the Z and B points could be resolved; these surfaces were artifacts of the atomic-sphere approximation used in the old calculations. Our results underline the importance of electronic structure calculations for the understanding of MoO2 and the neighboring rutile-type early transition-metal dioxides. This includes the low-temperature insulating phases of VO2 and NbO2 , which have crystal structures very similar to that of molybdenum dioxide and display the well-known prominent metal-insulator transitions.

  12. Orbital character and electron correlation effects on two- and three-dimensional Fermi surfaces in KFe2As2 revealed by angle-resolved photoemission spectroscopy

    Directory of Open Access Journals (Sweden)

    Teppei eYoshida

    2014-04-01

    Full Text Available We have investigated orbital character and electron correlation effects on Fermi surfaces in the hole-overdoped iron pnictide superconductor KFe2As2, which shows a low Tc of ~4 K, by angle-resolved photoemission spectroscopy. From the polarization-dependence of the ARPES spectra, we have determined the orbital character of each Fermi surface. Electron mass renormalization of each band is quantitatively consistent with de Haas-van Alphen results. The outer beta and middle zeta Fermi surfaces show large renormalization factor of m*/mb ~6-7, while the inner Fermi surface has a smaller factor m*/mb ~2. Middle hole Fermi surface zeta has strong three-dimensionality compared to other Fermi surfaces, indicating the d3z2-r2 orbital character, which may be related to the octet-line nodes recently observed by laser ARPES. The observed orbital-dependent mass renormalization would give constraints on the pairing mechanism with line nodes of this system.

  13. Angle-resolved photoemission spectroscopy observation of anomalous electronic states in EuFe2As2−xPx

    International Nuclear Information System (INIS)

    We used angle-resolved photoemission spectroscopy to investigate the electronic structure and the Fermi surface of EuFe2As2, EuFe2As1.4P0.6 and EuFe2P2. We observed doubled core level peaks associated with the pnictide atoms. Using K atoms evaporated at the surface to affect the surface quality, we show that one component of these doubled peaks is related to a surface state. Nevertheless, strong electronic dispersion along the c-axis, especially pronounced in EuFe2P2, is observed for at least one band, thus indicating that the Fe states, albeit probably affected at the surface, do not form pure two-dimensional surface states. We determine the evolution of the Fermi surface as a function of the P content and reveal that the hole Fermi surface pockets enlarge with increasing P content. We also show that the spectral weight near the Fermi level of EuFe2P2 is reduced as compared to that of EuFe2As2 and EuFe2As1.4P0.6. Finally, we identify the electronic states associated with the Eu2+ f states and show an anomalous jump in EuFe2P2. (paper)

  14. Valence band structure of the ZnO(1-bar 0-bar 1-bar -bar 0) surface studied by angle-resolved photoemission spectroscopy

    International Nuclear Information System (INIS)

    The electronic band structure of the ZnO(1-bar 0-bar 1-bar -bar 0) surface has been studied by angle-resolved photoemission spectroscopy utilizing synchrotron radiation. Photon-energy-dependent measurements and K- and O2-adsorption studies revealed that the O 2p dangling-bond state exists at 3.7eV below the Fermi level at the Γ-bar point. Polarization-dependent measurements show that the state has dominant contribution of the O 2px orbital (x is parallel to the (1-bar 2-bar -bar 1-bar 0) direction) at the Γ-bar point. It is found that the O 2p dangling-bond band lies within the projected bulk bands along the ΓX-bar -bar and-bar ΓX'-bar axes in the surface Brillouin zone. This result settles a controversial issue on the energetic position of the O 2p dangling-bond band, which has been in dispute among theoretical studies. The dispersion widths are found to be 0.8 and 0.5eV along the ΓX-bar -bar and-bar ΓX'-bar directions, respectively

  15. Spin-polarized surface bands of a three-dimensional topological insulator studied by high-resolution spin- and angle-resolved photoemission spectroscopy

    International Nuclear Information System (INIS)

    The spin-polarized surface band structure of the three-dimensional (3D) quantum spin Hall phase of Bi1-xSbx (x=0.12-0.13) was studied by spin- and angle-resolved photoemission spectroscopy (SARPES) using a high-yield spin polarimeter equipped with a high-resolution electron spectrometer. The spin-integrated spectra were also measured and compared to those of Bi1-xSbx with x=0.04. Band dispersions of the edge states were fully elucidated between the two time-reversal-invariant points, Γ-bar and M-bar, of the (111) surface Brillouin zone. The observed spin-polarized band dispersions at x=0.12-0.13 indicate an odd number of the band crossing at the Fermi energy, giving unambiguous evidence that this system is a 3D strong topological insulator, and determine the 'mirror chirality' to be -1, which excludes the existence of a Dirac point in the middle of the Γ-bar-M-bar line. The present research demonstrates that the SARPES measurement with energy resolution ≤50 meV is one of the critical techniques for complementing the topological band theory for spins and spin currents.

  16. Experimental electronic structure and Fermi-surface instability of the correlated 3d sulphide BaVS3 : High-resolution angle-resolved photoemission spectroscopy

    Science.gov (United States)

    Mitrovic, S.; Fazekas, P.; Søndergaard, C.; Ariosa, D.; Barišić, N.; Berger, H.; Cloëtta, D.; Forró, L.; Höchst, H.; Kupčić, I.; Pavuna, D.; Margaritondo, G.

    2007-04-01

    The correlated 3d sulphide BaVS3 exhibits an interesting coexistence of one-dimensional and three-dimensional properties. Our experiments determine the electronic band structure and shed light on this puzzle. High-resolution angle-resolved photoemission measurements in a 4-eV -wide range below the Fermi energy level uncover and investigate the coexistence of a1g wide-band and eg narrow-band d electrons, which lead to the complicated electronic properties of this material. We explore the effects of strong correlations and the Fermi surface instability associated with the metal-insulator transition.

  17. Doping Dependence of the $(\\pi,\\pi)$ Shadow Band in La-Based Cuprates Studied by Angle-Resolved Photoemission Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Z. X.

    2011-08-15

    The ({pi},{pi}) shadow band (SB) in La-based cuprate family (La214) was studied by angle-resolved photoemission spectroscopy (ARPES) over a wide doping range from x = 0.01 to x = 0.25. Unlike the well-studied case of the Bi-based cuprate family, an overall strong, monotonic doping dependence of the SB intensity at the Fermi level (E{sub F}) was observed. In contrast to a previous report for the presence of the SB only close to x = 1/8, we found it exists in a wide doping range, associated with a doping-independent ({pi},{pi}) wave vector but strongly doping-dependent intensity: It is the strongest at x {approx} 0.03 and systematically diminishes as the doping increases until it becomes negligible in the overdoped regime. This SB with the observed doping dependence of intensity can in principle be caused by the antiferromagnetic fluctuations or a particular form of low-temperature orthorhombic lattice distortion known to persist up to x {approx} 0.21 in the system, with both being weakened with increasing doping. However, a detailed binding energy dependent analysis of the SB at x = 0.07 does not appear to support the former interpretation, leaving the latter as a more plausible candidate, despite a challenge in quantitatively linking the doping dependences of the SB intensity and the magnitude of the lattice distortion. Our finding highlights the necessity of a careful and global consideration of the inherent structural complications for correctly understanding the cuprate Fermiology and its microscopic implication.

  18. Angle resolved photoemission from organic semiconductors: orbital imaging beyond the molecular orbital interpretation

    OpenAIRE

    Dauth, M.; Wiessner, M.; Feyer, V.; Schöll, A.; Puschnig, P.; Reinert, F.; Kümmel, S.

    2015-01-01

    Fascinating pictures that can be interpreted as showing molecular orbitals have been obtained with various imaging techniques. Among these, angle resolved photoemission spectroscopy (ARPES) has emerged as a particularly powerful method. Orbital images have been used to underline the physical credibility of the molecular orbital concept. However, from the theory of the photoemission process it is evident that imaging experiments do not show molecular orbitals, but Dyson orbitals. The latter ar...

  19. Angle-Resolved Spectroscopy of Parametric Fluorescence

    CERN Document Server

    Hsu, Feng-kuo

    2013-01-01

    The parametric fluorescence from a nonlinear crystal forms a conical radiation pattern. We measure the angular and spectral distributions of parametric fluorescence in a beta-barium borate crystal pumped by a 405-nm diode laser employing angle-resolved imaging spectroscopy. The experimental angle-resolved spectra and the generation efficiency of parametric down conversion are compared with a plane-wave theoretical analysis. The parametric fluorescence is used as a broadband light source for the calibration of the instrument spectral response function in the wavelength range from 450 to 1000 nm.

  20. Charge-density-wave partial gap opening in quasi-2D KMo{sub 6}O{sub 17} purple bronze studied by angle resolved photoemission spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Valbuena, M.A. [LURE, Centre Universitaire Paris-Sud, Bat. 209D, B.P. 34, 91898 Orsay Cedex (France); Avila, J. [Instituto de Ciencia de Materiales de Madrid, ICMM - CSIC, 28049 Madrid (Spain); Synchrotron SOLEIL, L' Orme des Merisiers, Saint-Aubin - B.P. 48, 91192 GIF-SUR-YVETTE Cedex (France); Pantin, V. [LURE, Centre Universitaire Paris-Sud, Bat. 209D, B.P. 34, 91898 Orsay Cedex (France); Drouard, S. [LEPES-CENES, B.P. 166x, 38042 Grenoble, Cedex 9 (France); Guyot, H. [LEPES-CENES, B.P. 166x, 38042 Grenoble, Cedex 9 (France); Asensio, M.C. [Instituto de Ciencia de Materiales de Madrid, ICMM - CSIC, 28049 Madrid (Spain) and Synchrotron SOLEIL, L' Orme des Merisiers, Saint-Aubin - B.P. 48, 91192 GIF-SUR-YVETTE Cedex (France)]. E-mail: asensio@synchrotron-soleil.fr

    2006-05-30

    Low dimensional (LD) metallic oxides have been a subject of continuous interest in the last two decades, mainly due to the electronic instabilities that they present at low temperatures. In particular, charge density waves (CDW) instabilities associated with a strong electron-phonon interaction have been found in Molybdenum metallic oxides such as KMo{sub 6}O{sub 17} purple bronze. We report an angle resolved photoemission (ARPES) study from room temperature (RT) to T {approx}40 K well below the Peierls transition temperature for this material, with CDW transition temperature T {sub CDW} {approx}120 K. We have focused on photoemission spectra along {gamma}M high symmetry direction as well as photoemission measurements were taken as a function of temperature at one representative k {sub F} point in the Brillouin zone in order to look for the characteristic gap opening after the phase transition. We found out a pseudogap opening and a decrease in the density of states near the Fermi energy, E {sub F}, consistent with the partial removal of the nested portions of the Fermi surface (FS) at temperature below the CDW transition. In order to elucidate possible Fermi liquid (FL) or non-Fermi liquid (NFL) behaviour we have compared the ARPES data with that one reported on quasi-1D K{sub 0.3}MoO{sub 3} blue bronze.

  1. Charge-density-wave partial gap opening in quasi-2D KMo 6O 17 purple bronze studied by angle resolved photoemission spectroscopy

    Science.gov (United States)

    Valbuena, M. A.; Avila, J.; Pantin, V.; Drouard, S.; Guyot, H.; Asensio, M. C.

    2006-05-01

    Low dimensional (LD) metallic oxides have been a subject of continuous interest in the last two decades, mainly due to the electronic instabilities that they present at low temperatures. In particular, charge density waves (CDW) instabilities associated with a strong electron-phonon interaction have been found in Molybdenum metallic oxides such as KMo 6O 17 purple bronze. We report an angle resolved photoemission (ARPES) study from room temperature (RT) to T ˜40 K well below the Peierls transition temperature for this material, with CDW transition temperature TCDW ˜120 K. We have focused on photoemission spectra along ΓM high symmetry direction as well as photoemission measurements were taken as a function of temperature at one representative kF point in the Brillouin zone in order to look for the characteristic gap opening after the phase transition. We found out a pseudogap opening and a decrease in the density of states near the Fermi energy, EF, consistent with the partial removal of the nested portions of the Fermi surface (FS) at temperature below the CDW transition. In order to elucidate possible Fermi liquid (FL) or non-Fermi liquid (NFL) behaviour we have compared the ARPES data with that one reported on quasi-1D K 0.3MoO 3 blue bronze.

  2. Charge-density-wave partial gap opening in quasi-2D KMo6O17 purple bronze studied by angle resolved photoemission spectroscopy

    International Nuclear Information System (INIS)

    Low dimensional (LD) metallic oxides have been a subject of continuous interest in the last two decades, mainly due to the electronic instabilities that they present at low temperatures. In particular, charge density waves (CDW) instabilities associated with a strong electron-phonon interaction have been found in Molybdenum metallic oxides such as KMo6O17 purple bronze. We report an angle resolved photoemission (ARPES) study from room temperature (RT) to T ∼40 K well below the Peierls transition temperature for this material, with CDW transition temperature T CDW ∼120 K. We have focused on photoemission spectra along ΓM high symmetry direction as well as photoemission measurements were taken as a function of temperature at one representative k F point in the Brillouin zone in order to look for the characteristic gap opening after the phase transition. We found out a pseudogap opening and a decrease in the density of states near the Fermi energy, E F, consistent with the partial removal of the nested portions of the Fermi surface (FS) at temperature below the CDW transition. In order to elucidate possible Fermi liquid (FL) or non-Fermi liquid (NFL) behaviour we have compared the ARPES data with that one reported on quasi-1D K0.3MoO3 blue bronze

  3. Electronic structure of transition metal dichalcogenides PdTe2 and Cu0.05PdTe2 superconductors obtained by angle-resolved photoemission spectroscopy

    Science.gov (United States)

    Liu, Yan; Zhao, Jian-Zhou; Yu, Li; Lin, Cheng-Tian; Hu, Cheng; Liu, De-Fa; Peng, Ying-Ying; Xie, Zhuo-Jin; He, Jun-Feng; Chen, Chao-Yu; Feng, Ya; Yi, He-Mian; Liu, Xu; Zhao, Lin; He, Shao-Long; Liu, Guo-Dong; Dong, Xiao-Li; Zhang, Jun; Chen, Chuang-Tian; Xu, Zu-Yan; Weng, Hong-Ming; Dai, Xi; Fang, Zhong; Zhou, Xing-Jiang

    2015-06-01

    The layered transition metal chalcogenides have been a fertile land in solid state physics for many decades. Various MX2-type transition metal dichalcogenides, such as WTe2, IrTe2, and MoS2, have triggered great attention recently, either for the discovery of novel phenomena or some extreme or exotic physical properties, or for their potential applications. PdTe2 is a superconductor in the class of transition metal dichalcogenides, and superconductivity is enhanced in its Cu-intercalated form, Cu0.05PdTe2. It is important to study the electronic structures of PdTe2 and its intercalated form in order to explore for new phenomena and physical properties and understand the related superconductivity enhancement mechanism. Here we report systematic high resolution angle-resolved photoemission (ARPES) studies on PdTe2 and Cu0.05PdTe2 single crystals, combined with the band structure calculations. We present in detail for the first time the complex multi-band Fermi surface topology and densely-arranged band structure of these compounds. By carefully examining the electronic structures of the two systems, we find that Cu-intercalation in PdTe2 results in electron-doping, which causes the band structure to shift downwards by nearly 16 meV in Cu0.05PdTe2. Our results lay a foundation for further exploration and investigation on PdTe2 and related superconductors. Project supported by the National Natural Science Foundation of China (Grant No. 11190022), the National Basic Research Program of China (Grant Nos. 2011CB921703 and 2011CBA00110), and the Strategic Priority Research Program (B) of the Chinese Academy of Sciences (Grant No. XDB07020300).

  4. Electronic structure, Dirac points and Fermi arc surface states in three-dimensional Dirac semimetal Na3Bi from angle-resolved photoemission spectroscopy

    Science.gov (United States)

    Aiji, Liang; Chaoyu, Chen; Zhijun, Wang; Youguo, Shi; Ya, Feng; Hemian, Yi; Zhuojin, Xie; Shaolong, He; Junfeng, He; Yingying, Peng; Yan, Liu; Defa, Liu; Cheng, Hu; Lin, Zhao; Guodong, Liu; Xiaoli, Dong; Jun, Zhang; M, Nakatake; H, Iwasawa; K, Shimada; M, Arita; H, Namatame; M, Taniguchi; Zuyan, Xu; Chuangtian, Chen; Hongming, Weng; Xi, Dai; Zhong, Fang; Xing-Jiang, Zhou

    2016-07-01

    The three-dimensional (3D) Dirac semimetals have linearly dispersive 3D Dirac nodes where the conduction band and valence band are connected. They have isolated 3D Dirac nodes in the whole Brillouin zone and can be viewed as a 3D counterpart of graphene. Recent theoretical calculations and experimental results indicate that the 3D Dirac semimetal state can be realized in a simple stoichiometric compound A 3Bi (A = Na, K, Rb). Here we report comprehensive high-resolution angle-resolved photoemission (ARPES) measurements on the two cleaved surfaces, (001) and (100), of Na3Bi. On the (001) surface, by comparison with theoretical calculations, we provide a proper assignment of the observed bands, and in particular, pinpoint the band that is responsible for the formation of the three-dimensional Dirac cones. We observe clear evidence of 3D Dirac cones in the three-dimensional momentum space by directly measuring on the k x –k y plane and by varying the photon energy to get access to different out-of-plane k z s. In addition, we reveal new features around the Brillouin zone corners that may be related with surface reconstruction. On the (100) surface, our ARPES measurements over a large momentum space raise an issue on the selection of the basic Brillouin zone in the (100) plane. We directly observe two isolated 3D Dirac nodes on the (100) surface. We observe the signature of the Fermi-arc surface states connecting the two 3D Dirac nodes that extend to a binding energy of ∼150 meV before merging into the bulk band. Our observations constitute strong evidence on the existence of the Dirac semimetal state in Na3Bi that are consistent with previous theoretical and experimental work. In addition, our results provide new information to clarify on the nature of the band that forms the 3D Dirac cones, on the possible formation of surface reconstruction of the (001) surface, and on the issue of basic Brillouin zone selection for the (100) surface. Project supported by the

  5. The electronic structure of spintronic materials as seen by spin-polarized angle-resolved photoemission

    International Nuclear Information System (INIS)

    Highlights: •Introduction of spin-dependent effects in modern angle-resolved photoemission from the point of view of potential applications in spintronics. •Review on modern spin-polarimeters, including the historical development of the field. •Several examples to illustrate the application of spin-polarized photoemission to ferromagnetic and non-ferromagnetic sample systems. -- Abstract: The key quantity in spintronic devices is the spin polarization of the current flowing through the various device components, which in turn is closely determined by the components’ electronic structure. Modern spin- and angle-resolved photoemission spectroscopy (spin-ARPES) can map the details of the spin-polarized electronic structure in many novel material systems – both magnetic and nonmagnetic. In order to separate close-lying electronic states, however, an improvement in energy and angular resolution as well as information depth is still mandatory. We review several types of modern photoemission spectrometers capable of spin analysis and discuss the application of the technique for several physical systems including ferromagnetic thin films and topological insulators

  6. Exploring the Electronic Structure and Chemical Homogeneity of Individual Bi2Te3 Nanowires by Nano-Angle-Resolved Photoemission Spectroscopy.

    Science.gov (United States)

    Krieg, Janina; Chen, Chaoyu; Avila, José; Zhang, Zeying; Sigle, Wilfried; Zhang, Hongbin; Trautmann, Christina; Asensio, Maria Carmen; Toimil-Molares, Maria Eugenia

    2016-07-13

    Due to their high surface-to-volume ratio, cylindrical Bi2Te3 nanowires are employed as model systems to investigate the chemistry and the unique conductive surface states of topological insulator nanomaterials. We report on nanoangle-resolved photoemission spectroscopy (nano-ARPES) characterization of individual cylindrical Bi2Te3 nanowires with a diameter of 100 nm. The nanowires are synthesized by electrochemical deposition inside channels of ion-track etched polymer membranes. Core level spectra recorded with submicron resolution indicate a homogeneous chemical composition along individual nanowires, while nano-ARPES intensity maps reveal the valence band structure at the single nanowire level. First-principles electronic structure calculations for chosen crystallographic orientations are in good agreement with those revealed by nano-ARPES. The successful application of nano-ARPES on single one-dimensional nanostructures constitutes a new avenue to achieve a better understanding of the electronic structure of topological insulator nanomaterials. PMID:27311702

  7. Angle-resolved photoemission study of Si electronic structure: Boron concentration dependence

    International Nuclear Information System (INIS)

    The boron concentration dependence of the Si electronic structure of Si(1 0 0)2 x 1 surfaces were investigated by angle-resolved photoemission spectroscopy (ARPES). The ARPES spectra exhibit rigid shifts toward lower binding energy as the boron concentration increases. The band dispersion was obtained from fitting procedure, and it is found that the top of the valence band does not exceed the Fermi level even with a boron concentration 35 times larger than the critical concentration of the metal-insulator transition.

  8. Angle Resolved Photoemission Spectroscopy Studies of the Mott Insulator to Superconductor Evolution in Ca2-xNaxCuO2Cl2

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Kyle Michael

    2005-09-02

    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 dissertation presents high-resolution, doping dependent angle-resolved photoemission (ARPES) studies of the cuprate superconductor Ca{sub 2-x}Na{sub x}CuO{sub 2}Cl{sub 2}, spanning from the undoped parent Mott insulator to a high-temperature superconductor with a T{sub c} of 22 K. A phenomenological model is proposed to explain how the spectral lineshape, the quasiparticle band dispersion, and the chemical potential all progress with doping in a logical and self-consistent framework. This model is based on Franck-Condon broadening observed in polaronic systems where strong electron-boson interactions cause the quasiparticle residue, Z, to be vanishingly small. Comparisons of the low-lying states to different electronic states in the valence band strongly suggest that the coupling of the photohole to the lattice (i.e. lattice polaron formation) is the dominant broadening mechanism for the lower Hubbard band states. Combining this polaronic framework with high-resolution ARPES measurements finally provides a resolution to the long-standing controversy over the behavior of the chemical potential in the high-T{sub c} cuprates. This scenario arises from replacing the conventional Fermi liquid quasiparticle interpretation of the features in the Mott insulator by a Franck-Condon model, allowing the reassignment of the position of the quasiparticle pole. As a function of hole doping, the chemical potential shifts smoothly into the valence band while spectral weight is transferred

  9. Spin-orbit-induced photoelectron spin polarization in angle-resolved photoemission from both atomic and condensed matter targets

    International Nuclear Information System (INIS)

    The existence of highly spin polarized photoelectrons emitted from non-magnetic solids as well as from unpolarized atoms and molecules has been found to be very common in many studies over the past 40 years. This so-called Fano effect is based upon the influence of the spin-orbit interaction in the photoionization or the photoemission process. In a non-angle-resolved photoemission experiment, circularly polarized radiation has to be used to create spin polarized photoelectrons, while in angle-resolved photoemission even unpolarized or linearly polarized radiation is sufficient to get a high spin polarization. In past years the Rashba effect has become very important in the angle-resolved photoemission of solid surfaces, also with an observed high photoelectron spin polarization. It is the purpose of the present topical review to cross-compare the spin polarization experimentally found in angle-resolved photoelectron emission spectroscopy of condensed matter with that of free atoms, to compare it with the Rashba effect and topological insulators to describe the influence and the importance of the spin-orbit interaction and to show and disentangle the matrix element and phase shift effects therein. The relationship between the energy dispersion of these phase shifts and the emission delay of photoelectron emission in attosecond-resolved photoemission is also discussed. Furthermore the influence of chiral structures of the photo-effect target on the spin polarization, the interferences of different spin components in coherent superpositions in photoemission and a cross-comparison of spin polarization in photoemission from non-magnetic solids with XMCD on magnetic materials are presented; these are all based upon the influence of the spin-orbit interaction in angle-resolved photoemission. (topical review)

  10. Valence-band dispersion in angle-resolved resonant photoemission from LaSb

    International Nuclear Information System (INIS)

    Angle-resolved photoemission spectra taken on single crystals of LaSb at the La 4d→4f resonance show dispersion of resonantly emitted valence-band electrons. This is the first direct demonstration that the Bloch component of valence states participates in resonant photoemission. copyright 1996 The American Physical Society

  11. Spin- and angle-resolved photoemission on the topological Kondo insulator candidate: SmB6

    Science.gov (United States)

    Xu, Nan; Ding, Hong; Shi, Ming

    2016-09-01

    Topological Kondo insulators are a new class of topological insulators in which metallic surface states protected by topological invariants reside in the bulk band gap at low temperatures. Unlike other 3D topological insulators, a truly insulating bulk state, which is critical for potential applications in next-generation electronic devices, is guaranteed by many-body effects in the topological Kondo insulator. Furthermore, the system has strong electron correlations that can serve as a testbed for interacting topological theories. This topical review focuses on recent advances in the study of SmB6, the most promising candidate for a topological Kondo insulator, from the perspective of spin- and angle-resolved photoemission spectroscopy with highlights of some important transport results.

  12. Spin- and angle-resolved photoemission on the topological Kondo insulator candidate: SmB6.

    Science.gov (United States)

    Xu, Nan; Ding, Hong; Shi, Ming

    2016-09-14

    Topological Kondo insulators are a new class of topological insulators in which metallic surface states protected by topological invariants reside in the bulk band gap at low temperatures. Unlike other 3D topological insulators, a truly insulating bulk state, which is critical for potential applications in next-generation electronic devices, is guaranteed by many-body effects in the topological Kondo insulator. Furthermore, the system has strong electron correlations that can serve as a testbed for interacting topological theories. This topical review focuses on recent advances in the study of SmB6, the most promising candidate for a topological Kondo insulator, from the perspective of spin- and angle-resolved photoemission spectroscopy with highlights of some important transport results. PMID:27391865

  13. Angle-resolved photoemission studies of the superconducting gap symmetry in Fe-based superconductors

    Directory of Open Access Journals (Sweden)

    Y.-B. Huang

    2012-12-01

    Full Text Available The superconducting gap is the fundamental parameter that characterizes the superconducting state, and its symmetry is a direct consequence of the mechanism responsible for Cooper pairing. Here we discuss about angle-resolved photoemission spectroscopy measurements of the superconducting gap in the Fe-based high-temperature superconductors. We show that the superconducting gap is Fermi surface dependent and nodeless with small anisotropy, or more precisely, a function of the momentum location in the Brillouin zone. We show that while this observation seems inconsistent with weak coupling approaches for superconductivity in these materials, it is well supported by strong coupling models and global superconducting gaps. We also suggest that a smaller lifetime of the superconducting Cooper pairs induced by the momentum dependent interband scattering inherent to these materials could affect the residual density of states at low energies, which is critical for a proper evaluation of the superconducting gap.

  14. Modeling angle-resolved photoemission of graphene and black phosphorus nano structures.

    Science.gov (United States)

    Park, Sang Han; Kwon, Soonnam

    2016-01-01

    Angle-resolved photoemission spectroscopy (ARPES) data on electronic structure are difficult to interpret, because various factors such as atomic structure and experimental setup influence the quantum mechanical effects during the measurement. Therefore, we simulated ARPES of nano-sized molecules to corroborate the interpretation of experimental results. Applying the independent atomic-center approximation, we used density functional theory calculations and custom-made simulation code to compute photoelectron intensity in given experimental setups for every atomic orbital in poly-aromatic hydrocarbons of various size, and in a molecule of black phosphorus. The simulation results were validated by comparing them to experimental ARPES for highly-oriented pyrolytic graphite. This database provides the calculation method and every file used during the work flow. PMID:27164313

  15. Commissioning Results Of Angle-Resolved Photoemission System At The Siam Photon Laboratory

    International Nuclear Information System (INIS)

    This report describes the first results obtained by the angle-resolved photoemission system at the Siam Photon Laboratory. Nickel single crystal with (111) surface was selected as the sample. Sample preparation methods as well as measurement procedures are described. The total energy resolution at photon energy of 35 eV was 370 MeV. Surface energy band structure of the nickel was obtained from angle-resolved photoemission spectra along two lines of symmetry: τto Τto Κand τto ΣtoΜ. The experimental energy band structure is qualitatively agreed with a theoretical calculation

  16. Angle resolved photoemission from organic semiconductors: orbital imaging beyond the molecular orbital interpretation

    International Nuclear Information System (INIS)

    Fascinating pictures that can be interpreted as showing molecular orbitals have been obtained with various imaging techniques. Among these, angle resolved photoemission spectroscopy (ARPES) has emerged as a particularly powerful method. Orbital images have been used to underline the physical credibility of the molecular orbital concept. However, from the theory of the photoemission process it is evident that imaging experiments do not show molecular orbitals, but Dyson orbitals. The latter are not eigenstates of a single-particle Hamiltonian and thus do not fit into the usual simple interpretation of electronic structure in terms of molecular orbitals. In a combined theoretical and experimental study we thus check whether a Dyson-orbital and a molecular-orbital based interpretation of ARPES lead to differences that are relevant on the experimentally observable scale. We discuss a scheme that allows for approximately calculating Dyson orbitals with moderate computational effort. Electronic relaxation is taken into account explicitly. The comparison reveals that while molecular orbitals are frequently good approximations to Dyson orbitals, a detailed understanding of photoemission intensities may require one to go beyond the molecular orbital picture. In particular we clearly observe signatures of the Dyson-orbital character for an adsorbed semiconductor molecule in ARPES spectra when these are recorded over a larger momentum range than in earlier experiments. (paper)

  17. Quasiparticle dynamics across the full Brillouin zone of Bi2Sr2CaCu2O8+δ traced with ultrafast time and angle-resolved photoemission spectroscopy

    Directory of Open Access Journals (Sweden)

    Georgi L. Dakovski

    2015-09-01

    Full Text Available A hallmark in the cuprate family of high-temperature superconductors is the nodal-antinodal dichotomy. In this regard, angle-resolved photoemission spectroscopy (ARPES has proven especially powerful, providing band structure information directly in energy-momentum space. Time-resolved ARPES (trARPES holds great promise of adding ultrafast temporal information, in an attempt to identify different interaction channels in the time domain. Previous studies of the cuprates using trARPES were handicapped by the low probing energy, which significantly limits the accessible momentum space. Using 20.15 eV, 12 fs pulses, we show for the first time the evolution of quasiparticles in the antinodal region of Bi2Sr2CaCu2O8+δ and demonstrate that non-monotonic relaxation dynamics dominates above a certain fluence threshold. The dynamics is heavily influenced by transient modification of the electron-phonon interaction and phase space restrictions, in stark contrast to the monotonic relaxation in the nodal and off-nodal regions.

  18. Imaging electron dynamics with time- and angle-resolved photoelectron spectroscopy

    CERN Document Server

    Popova-Gorelova, Daria; Santra, Robin

    2016-01-01

    We theoretically study how time- and angle-resolved photoemission spectroscopy can be applied for imaging coherent electron dynamics in molecules. We consider a process in which a pump pulse triggers coherent electronic dynamics in a molecule by creating a valence electron hole. An ultrashort extreme ultraviolet (XUV) probe pulse creates a second electron hole in the molecule. Information about the electron dynamics is accessed by analyzing angular distributions of photoemission probabilities at a fixed photoelectron energy. We demonstrate that a rigorous theoretical analysis, which takes into account the indistinguishability of transitions induced by the ultrashort, broadband probe pulse and electron hole correlation effects, is necessary for the interpretation of time- and angle-resolved photoelectron spectra. We show how a Fourier analysis of time- and angle-resolved photoelectron spectra from a molecule can be applied to follow its electron dynamics by considering photoelectron distributions from an indol...

  19. Invited Article: High resolution angle resolved photoemission with tabletop 11 eV laser

    Energy Technology Data Exchange (ETDEWEB)

    He, Yu; Vishik, Inna M.; Yi, Ming; Yang, Shuolong; Lee, James J.; Chen, Sudi; Rebec, Slavko N.; Leuenberger, Dominik; Shen, Zhi-Xun [SIMES, SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); Department of Applied Physics, Stanford University, Stanford, California 94305 (United States); Liu, Zhongkai [SIMES, SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); Department of Physics, Stanford University, Stanford, California 94305 (United States); Zong, Alfred [Department of Physics, Stanford University, Stanford, California 94305 (United States); Jefferson, C. Michael; Merriam, Andrew J. [Lumeras LLC, 207 McPherson St, Santa Cruz, California 95060 (United States); Moore, Robert G.; Kirchmann, Patrick S. [SIMES, SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States)

    2016-01-15

    We developed a table-top vacuum ultraviolet (VUV) laser with 113.778 nm wavelength (10.897 eV) and demonstrated its viability as a photon source for high resolution angle-resolved photoemission spectroscopy (ARPES). This sub-nanosecond pulsed VUV laser operates at a repetition rate of 10 MHz, provides a flux of 2 × 10{sup 12} photons/s, and enables photoemission with energy and momentum resolutions better than 2 meV and 0.012 Å{sup −1}, respectively. Space-charge induced energy shifts and spectral broadenings can be reduced below 2 meV. The setup reaches electron momenta up to 1.2 Å{sup −1}, granting full access to the first Brillouin zone of most materials. Control over the linear polarization, repetition rate, and photon flux of the VUV source facilitates ARPES investigations of a broad range of quantum materials, bridging the application gap between contemporary low energy laser-based ARPES and synchrotron-based ARPES. We describe the principles and operational characteristics of this source and showcase its performance for rare earth metal tritellurides, high temperature cuprate superconductors, and iron-based superconductors.

  20. Invited Article: High resolution angle resolved photoemission with tabletop 11 eV laser

    International Nuclear Information System (INIS)

    We developed a table-top vacuum ultraviolet (VUV) laser with 113.778 nm wavelength (10.897 eV) and demonstrated its viability as a photon source for high resolution angle-resolved photoemission spectroscopy (ARPES). This sub-nanosecond pulsed VUV laser operates at a repetition rate of 10 MHz, provides a flux of 2 × 1012 photons/s, and enables photoemission with energy and momentum resolutions better than 2 meV and 0.012 Å−1, respectively. Space-charge induced energy shifts and spectral broadenings can be reduced below 2 meV. The setup reaches electron momenta up to 1.2 Å−1, granting full access to the first Brillouin zone of most materials. Control over the linear polarization, repetition rate, and photon flux of the VUV source facilitates ARPES investigations of a broad range of quantum materials, bridging the application gap between contemporary low energy laser-based ARPES and synchrotron-based ARPES. We describe the principles and operational characteristics of this source and showcase its performance for rare earth metal tritellurides, high temperature cuprate superconductors, and iron-based superconductors

  1. High Resolution Angle Resolved Photoemission with Tabletop 11eV Laser

    CERN Document Server

    He, Yu; Yi, Ming; Yang, Shuolong; Liu, Zhongkai; Lee, James; Chen, Sudi; Rebec, Slavko; Leuenberger, Dominik; Zong, Alfred; Jefferson, Michael; Moore, Robert; Kirchmann, Patrick; Merriam, Andrew; Shen, Zhixun

    2015-01-01

    We developed a table-top vacuum ultraviolet (VUV) laser with $113.778$nm wavelength (10.897eV) and demonstrated its viability as a photon source for high resolution angle-resolved photoemission spectroscopy (ARPES). This sub-nanosecond pulsed VUV laser operates at a repetition rate of 10MHz, provides a flux of 2$\\times$10$^{12}$ photons/second, and enables photoemission with energy and momentum resolutions better than 2meV and 0.012\\AA$^{-1}$, respectively. Space-charge induced energy shifts and spectral broadenings can be reduced below 2meV. The setup reaches electron momenta up to 1.2\\AA$^{-1}$, granting full access to the first Brillouin zone of most materials. Control over the linear polarization, repetition rate, and photon flux of the VUV source facilitates ARPES investigations of a broad range of quantum materials, bridging the application gap between contemporary low energy laser-based ARPES and synchrotron-based ARPES. We describe the principles and operational characteristics of this source, and sho...

  2. Invited Article: High resolution angle resolved photoemission with tabletop 11 eV laser.

    Science.gov (United States)

    He, Yu; Vishik, Inna M; Yi, Ming; Yang, Shuolong; Liu, Zhongkai; Lee, James J; Chen, Sudi; Rebec, Slavko N; Leuenberger, Dominik; Zong, Alfred; Jefferson, C Michael; Moore, Robert G; Kirchmann, Patrick S; Merriam, Andrew J; Shen, Zhi-Xun

    2016-01-01

    We developed a table-top vacuum ultraviolet (VUV) laser with 113.778 nm wavelength (10.897 eV) and demonstrated its viability as a photon source for high resolution angle-resolved photoemission spectroscopy (ARPES). This sub-nanosecond pulsed VUV laser operates at a repetition rate of 10 MHz, provides a flux of 2 × 10(12) photons/s, and enables photoemission with energy and momentum resolutions better than 2 meV and 0.012 Å(-1), respectively. Space-charge induced energy shifts and spectral broadenings can be reduced below 2 meV. The setup reaches electron momenta up to 1.2 Å(-1), granting full access to the first Brillouin zone of most materials. Control over the linear polarization, repetition rate, and photon flux of the VUV source facilitates ARPES investigations of a broad range of quantum materials, bridging the application gap between contemporary low energy laser-based ARPES and synchrotron-based ARPES. We describe the principles and operational characteristics of this source and showcase its performance for rare earth metal tritellurides, high temperature cuprate superconductors, and iron-based superconductors. PMID:26827301

  3. Invited Article: High resolution angle resolved photoemission with tabletop 11 eV laser

    Science.gov (United States)

    He, Yu; Vishik, Inna M.; Yi, Ming; Yang, Shuolong; Liu, Zhongkai; Lee, James J.; Chen, Sudi; Rebec, Slavko N.; Leuenberger, Dominik; Zong, Alfred; Jefferson, C. Michael; Moore, Robert G.; Kirchmann, Patrick S.; Merriam, Andrew J.; Shen, Zhi-Xun

    2016-01-01

    We developed a table-top vacuum ultraviolet (VUV) laser with 113.778 nm wavelength (10.897 eV) and demonstrated its viability as a photon source for high resolution angle-resolved photoemission spectroscopy (ARPES). This sub-nanosecond pulsed VUV laser operates at a repetition rate of 10 MHz, provides a flux of 2 × 1012 photons/s, and enables photoemission with energy and momentum resolutions better than 2 meV and 0.012 Å-1, respectively. Space-charge induced energy shifts and spectral broadenings can be reduced below 2 meV. The setup reaches electron momenta up to 1.2 Å-1, granting full access to the first Brillouin zone of most materials. Control over the linear polarization, repetition rate, and photon flux of the VUV source facilitates ARPES investigations of a broad range of quantum materials, bridging the application gap between contemporary low energy laser-based ARPES and synchrotron-based ARPES. We describe the principles and operational characteristics of this source and showcase its performance for rare earth metal tritellurides, high temperature cuprate superconductors, and iron-based superconductors.

  4. Identification of Nodal Kink in Electron-Doped (Nd1.85Ce0.15CuO4 Superconductor from Laser-Based Angle-Resolved Photoemission Spectroscopy

    Directory of Open Access Journals (Sweden)

    Zhou X. J.

    2012-03-01

    Full Text Available High-resolution laser-based angle-resolved photoemission measurements have been carried out on the electron-doped (Nd1.85Ce0.15CuO4 high temperature superconductor. We have revealed a clear kink at ~60 meV in the dispersion along the (0,0–(π,π nodal direction, accompanied by a peak-dip-hump feature in the photoemission spectra. This indicates that the nodal electrons are coupled to collective excitations (bosons in electron-doped superconductors, with the phonons as the most likely candidate of the boson. This finding has established a universality of nodal electron coupling in both hole- and electron-doped high temperature cuprate superconductors.

  5. Angle-resolved photoemission spectroscopy of (Ca, Na) sub 2 CuO sub 2 Cl sub 2 crystals: Fingerprints of a magnetic insulator in a heavily underdoped superconductor

    CERN Document Server

    Kohsaka, Y; Ronning, F

    2003-01-01

    Electric evolution from an antiferromagnet to a high-T sub c superconductor is revealed by angle-resolved photoemission experiments on tetragonal Ca sub 1 sub . sub 9 Na sub 0 sub . sub 1 CuO sub 2 Cl sub 2 single crystals, which were successfully grown for the first time under high pressures. In this underdoped superconductor, we found clear fingerprints of the parent insulator: a shadow band and a large pseudogap. These observations are most likely described by a 'chemical potential shift', which contrasts clearly with the prevailing wisdom of the pinned chemical potential' learned from the prototype La sub 2 sub - sub x Sr sub x CuO sub 4 , demonstrating that the route to a high-T sub c superconductor is not unique. (author)

  6. Angle-resolved photoemission extended fine structure: Multiple layers of emitters and multiple initial states

    Energy Technology Data Exchange (ETDEWEB)

    Huff, W.R.A.; Kellar, S.A.; Moler, E.J. [Lawrence Berkeley Lab., CA (US)]|[California Univ., Berkeley, CA (US). Dept. of Chemistry; Chen, Y.; Wu, H.; Shirley, D.A. [Pennsylvania State Univ., University Park, PA (US). Dept. of Chemistry and Physics; Hussain, Z. [California Univ., Berkeley, CA (US). Dept. of Chemistry

    1995-08-01

    Recently, angle-resolved photoemission extended fine structure (ARPEFS) has been applied to experimental systems involving multiple layers of emitters and non-s core-level photoemission in an effort to broaden the utility of the technique. Most of the previous systems have been comprised of atomic or molecular overlayers adsorbed onto a single-crystal, metal surface and the photoemission data were taken from an s atomic core-level in the overlayer. For such a system, the acquired ARPEFS data is dominated by the p{sub o} final state wave backscattering from the substrate atoms and is well understood. In this study, we investigate ARPEFS as a surface-region structure determination technique when applied to experimental systems comprised of multiple layers of photoemitters and arbitrary initial state core-level photoemission. Understanding the data acquired from multiple layers of photoemitters is useful for studying multilayer interfaces, ''buried'' surfaces, and clean crystals in ultra- high vacuum. The ability to apply ARPEFS to arbitrary initial state core-level photoemission obviously opens up many systems to analysis. Efforts have been ongoing to understand such data in depth. We present clean Cu(111) 3s, 3p, and 3d core-level, normal photoemission data taken on a high resolution soft x-ray beamline 9.3.2 at the Advanced Light Source in Berkeley, California and clean Ni(111) 3p normal photoemission data taken at the National Synchrotron Light Source in Upton, New York, USA.

  7. Angle-resolved photoemission extended fine structure: Multiple layers of emitters and multiple initial states

    International Nuclear Information System (INIS)

    Recently, angle-resolved photoemission extended fine structure (ARPEFS) has been applied to experimental systems involving multiple layers of emitters and non-s core-level photoemission in an effort to broaden the utility of the technique. Most of the previous systems have been comprised of atomic or molecular overlayers adsorbed onto a single-crystal, metal surface and the photoemission data were taken from an s atomic core-level in the overlayer. For such a system, the acquired ARPEFS data is dominated by the po final state wave backscattering from the substrate atoms and is well understood. In this study, we investigate ARPEFS as a surface-region structure determination technique when applied to experimental systems comprised of multiple layers of photoemitters and arbitrary initial state core-level photoemission. Understanding the data acquired from multiple layers of photoemitters is useful for studying multilayer interfaces, ''buried'' surfaces, and clean crystals in ultra- high vacuum. The ability to apply ARPEFS to arbitrary initial state core-level photoemission obviously opens up many systems to analysis. Efforts have been ongoing to understand such data in depth. We present clean Cu(111) 3s, 3p, and 3d core-level, normal photoemission data taken on a high resolution soft x-ray beamline 9.3.2 at the Advanced Light Source in Berkeley, California and clean Ni(111) 3p normal photoemission data taken at the National Synchrotron Light Source in Upton, New York, USA

  8. Method to map one-dimensional electronic wave function by using multiple Brillouin zone angle resolved photoemission

    Directory of Open Access Journals (Sweden)

    Dong-Wook Lee

    2010-10-01

    Full Text Available Angle resolved photoemission spectroscopy (ARPES is a powerful tool to investigate electronic structures in solids and has been widely used in studying various materials. The electronic structure information by ARPES is obtained in the momentum space. However, in the case of one-dimensional system, we here show that we extract the real space information from ARPES data taken over multiple Brillouin zones (BZs. Intensities in the multiple BZs are proportional to the photoemission matrix element which contains information on the coefficient of the Bloch wave function. It is shown that the Bloch wave function coefficients can be extracted from ARPES data, which allows us to construct the real space wave function. As a test, we use ARPES data from proto-typical one-dimensional system SrCuO2 and construct the real space wave function.

  9. Charge density waves in 1T-TaS2: an angle-resolved photoemission study

    Energy Technology Data Exchange (ETDEWEB)

    Clerc, F. [Institut de Physique, Universite de Neuchatel, Rue A.L. Breguet 1, CH-2000 Neuchatel (Switzerland); Bovet, M. [Institut de Physique, Universite de Neuchatel, Rue A.L. Breguet 1, CH-2000 Neuchatel (Switzerland); Berger, H. [Institut de Physique Appliquee, EPFL, CH-1015 Lausanne (Switzerland); Despont, L. [Institut de Physique, Universite de Neuchatel, Rue A.L. Breguet 1, CH-2000 Neuchatel (Switzerland); Koitzsch, C. [Institut de Physique, Universite de Neuchatel, Rue A.L. Breguet 1, CH-2000 Neuchatel (Switzerland); Garnier, M.G. [Institut de Physique, Universite de Neuchatel, Rue A.L. Breguet 1, CH-2000 Neuchatel (Switzerland); Aebi, P. [Institut de Physique, Universite de Neuchatel, Rue A.L. Breguet 1, CH-2000 Neuchatel (Switzerland)]. E-mail: philipp.aebi@unine.ch

    2004-09-15

    The transition metal dichalcogenide 1T-TaS2 is a layered material exhibiting charge density waves. Based on angle-resolved photoemission experiments mapping spectral weight at the Fermi surface and density functional theory calculations we discuss possible mechanisms involved with the creation of charge density waves. At first the flat parts of the elliptically shaped Fermi surface appear to play an important role via Fermi surface nesting. A closer analysis of the charge density wave induced new Brillouin zones and the possible energy balance between elastic deformation energy and electronic energy points to a more complicated scenario.

  10. Charge density waves in 1T-TaS2: an angle-resolved photoemission study

    International Nuclear Information System (INIS)

    The transition metal dichalcogenide 1T-TaS2 is a layered material exhibiting charge density waves. Based on angle-resolved photoemission experiments mapping spectral weight at the Fermi surface and density functional theory calculations we discuss possible mechanisms involved with the creation of charge density waves. At first the flat parts of the elliptically shaped Fermi surface appear to play an important role via Fermi surface nesting. A closer analysis of the charge density wave induced new Brillouin zones and the possible energy balance between elastic deformation energy and electronic energy points to a more complicated scenario

  11. Simple surface structure determination from Fourier transforms of angle-resolved photoemission extended fine structure

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Y. [Pennsylvania State Univ., University Park, PA (United States)]|[Lawrence Berkeley Lab., CA (United States); Shirley, D.A. [Pennsylvania State Univ., University Park, PA (United States)

    1995-02-01

    The authors show by Fourier analyses of experimental data, with no further treatment, that the positions of all the strong peaks in Fourier transforms of angle-resolved photoemission extended fine structure (ARPEFS) from adsorbed surfaces can be explicitly predicted from a trial structure with an accuracy of about {+-} 0.3 {angstrom} based on a single-scattering cluster model together with the concept of a strong backscattering cone, and without any additional analysis. This characteristic of ARPEFS Fourier transforms can be developed as a simple method for determining the structures of adsorbed surfaces to an accuracy of about {+-} 0.1 {angstrom}.

  12. Angle-resolved photoemission from γ-Ce: Distinguishing band peaks from f-electron emission

    International Nuclear Information System (INIS)

    Angle-resolved photoemission spectra from single crystal γ-Ce(100) are presented and discussed. Valence-band peaks are observed for photon energies below 40 eV. These peaks disperse with electron exit angle and obey simple one-electron selection rules. For photon energies above 50 eV, two peaks, at the Fermi level and at 2-eV binding energy, dominate the spectra. These peaks do not disperse, and do not obey the one-electron selection rules. They are identified as atomiclike 4f emission

  13. Nodal Quasiparticle Meltdown in Ultra-High Resolution Pump-Probe Angle-Resolved Photoemission

    Energy Technology Data Exchange (ETDEWEB)

    Graf, Jeff; Jozwiak, Chris; Smallwood, Chris L.; Eisaki, H.; Kaindl, Robert A.; Lee, Dung-Hai; Lanzara, Alessandra

    2011-06-03

    High-T{sub c} cuprate superconductors are characterized by a strong momentum-dependent anisotropy between the low energy excitations along the Brillouin zone diagonal (nodal direction) and those along the Brillouin zone face (antinodal direction). Most obvious is the d-wave superconducting gap, with the largest magnitude found in the antinodal direction and no gap in the nodal direction. Additionally, while antin- odal quasiparticle excitations appear only below T{sub c}, superconductivity is thought to be indifferent to nodal excitations as they are regarded robust and insensitive to T{sub c}. Here we reveal an unexpected tie between nodal quasiparticles and superconductivity using high resolution time- and angle-resolved photoemission on optimally doped Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}}. We observe a suppression of the nodal quasiparticle spectral weight following pump laser excitation and measure its recovery dynamics. This suppression is dramatically enhanced in the superconducting state. These results reduce the nodal-antinodal dichotomy and challenge the conventional view of nodal excitation neutrality in superconductivity. The electronic structures of high-Tc cuprates are strongly momentum-dependent. This is one reason why the momentum-resolved technique of angle-resolved photoemission spectroscopy (ARPES) has been a central tool in the field of high-temperature superconductivity. For example, coherent low energy excitations with momenta near the Brillouin zone face, or antinodal quasiparticles (QPs), are only observed below T{sub c} and have been linked to superfluid density. They have therefore been the primary focus of ARPES studies. In contrast, nodal QPs, with momenta along the Brillouin zone diagonal, have received less attention and are usually regarded as largely immune to the superconducting transition because they seem insensitive to perturbations such as disorder, doping, isotope exchange, charge ordering, and temperature. Clearly

  14. Angle-resolved photoemission studies of the CdTe(110) surface

    Science.gov (United States)

    Qu, H.; Kanski, J.; Nilsson, P. O.; Karlsson, U. O.

    1991-06-01

    The electronic structure of the CdTe(110) surface has been studied with angle-resolved photoelectron spectroscopy using synchrotron radiation. An empirical tight-binding linar combination of atomic orbitals band structure has been derived, based on normal-emission spectra. Several, previously unreported, surface-related states have been observed in off-normal emission, and their dispersions have been mapped along symmetry directions of the surface Brillouin zone.

  15. Evidence of the nature of core-level photoemission satellites using angle-resolved photoemission extended fine structure

    Energy Technology Data Exchange (ETDEWEB)

    Moler, E.J.; Kellar, S.A.; Huff, W.R.A. [Lawrence Berkeley National Lab., CA (United States)] [and others

    1997-04-01

    The authors present a unique method of experimentally determining the angular momentum and intrinsic/extrinsic origin of core-level photoemission satellites by examining the satellite diffraction pattern in the Angle Resolved Photoemission Extended Fine Structure (ARPEFS) mode. They show for the first time that satellite peaks not associated with chemically differentiated atomic species display an ARPEFS intensity oscillation. They present ARPEFS data for the carbon 1s from ({radical}3x{radical}3)R30 CO/Cu(111) and p2mg(2xl)CO/Ni(110), nitrogen 1s from c(2x2) N{sub 2}/Ni(100), cobalt 1s from p(1x1)Co/Cu(100), and nickel 3p from clean nickel (111). The satellite peaks and tails of the Doniach-Sunjic line shapes in all cases exhibit ARPEFS curves which indicate an angular momentum identical to the main peak and are of an intrinsic nature.

  16. Fingerprints of entangled spin and orbital physics in itinerant ferromagnets via angle-resolved resonant photoemission

    Science.gov (United States)

    Da Pieve, F.

    2016-01-01

    A method for mapping the local spin and orbital nature of the ground state of a system via corresponding flip excitations is proposed based on angle-resolved resonant photoemission and related diffraction patterns, obtained here via an ab initio modified one-step theory of photoemission. The analysis is done on the paradigmatic weak itinerant ferromagnet bcc Fe, whose magnetism, a correlation phenomenon given by the coexistence of localized moments and itinerant electrons, and the observed non-Fermi-Liquid behavior at extreme conditions both remain unclear. The combined analysis of energy spectra and diffraction patterns offers a mapping of local pure spin-flip, entangled spin-flip-orbital-flip excitations and chiral transitions with vortexlike wave fronts of photoelectrons, depending on the valence orbital symmetry and the direction of the local magnetic moment. Such effects, mediated by the hole polarization, make resonant photoemission a promising tool to perform a full tomography of the local magnetic properties even in itinerant ferromagnets or macroscopically nonmagnetic systems.

  17. Angle resolved electron energy loss spectroscopy on graphite

    Science.gov (United States)

    Diebold, U.; Preisinger, A.; Schattschneider, P.; Varga, P.

    We report on angle resolved electron energy loss spectroscopy (EELS) in reflection mode with low primary energy on a graphite single crystal. Measurements with primary electron energy of 175 eV have been performed in off-Bragg-reflex geometry in two different directions within the (0001) surface plane of the graphite single crystal. In addition, EELS measurements in specular reflection mode with different primary energies and angles of incidence were done in order to distinguish between surface and bulk plasmon losses. The energy losses and the transferred momenta of the losses have been analyzed. The results are compared with the loss functions for bulk and surface excitations calculated from the dielectric function ɛ(ω, q) obtained from TEELS-data (EELS in transmission mode) [Springer Tracts Mod. Phys. 54 (1970) 77].

  18. Surface band structure of CdTe(111)-2 × 2 by angle-resolved photoemission

    Science.gov (United States)

    Janowitz, C.; Manzke, R.; Skibowski, M.; Orlowski, B. A.

    1991-05-01

    The surface band structure of non-cleavable CdTe(111)-2 × 2 reconstructed surfaces is determined by means of angle-resolved photoemission and constant-final-state (CFS) spectroscopy. The experiments were performed with He I radiation and synchrotron radiation from the DORIS II storage ring at HASYLAB. High-quality (111)-2 × 2 surfaces were prepared by sputtering and annealing controlled by electron diffraction (LEED and RHEED). In order to distinguish between surface and bulk related emissions in the spectra we utilized, besides the criteria that the k∥ dispersion of surface states should reveal the 2 × 2 periodicity of the surfac mesh, also photon energy dependent CFS series at several critical points of the surface Brillouin zone. The data on CdTe(111) will be compared with experimental and theoretical results which are available for the electronically similar GaAs(111) surface.

  19. Photoelectron spectroscopy at a free-electron laser. Investigation of space-charge effects in angle-resolved and core-level spectroscopy and realizaton of a time-resolved core-level photoemission experiment

    Energy Technology Data Exchange (ETDEWEB)

    Marczynski-Buehlow, Martin

    2012-01-30

    The free-electron laser (FEL) in Hamburg (FLASH) is a very interesting light source with which to perform photoelectron spectroscopy (PES) experiments. Its special characteristics include highly intense photon pulses (up to 100 J/pulse), a photon energy range of 30 eV to 1500 eV, transverse coherence as well as pulse durations of some ten femtoseconds. Especially in terms of time-resolved PES (TRPES), the deeper lying core levels can be reached with photon energies up to 1500 eV with acceptable intensity now and, therefore, element-specific, time-resolved core-level PES (XPS) is feasible at FLASH. During the work of this thesis various experimental setups were constructed in order to realize angle-resolved (ARPES), core-level (XPS) as well as time-resolved PES experiments at the plane grating monochromator beamline PG2 at FLASH. Existing as well as newly developed systems for online monitoring of FEL pulse intensities and generating spatial and temporal overlap of FEL and optical laser pulses for time-resolved experiments are successfully integrated into the experimental setup for PES. In order to understand space-charge effects (SCEs) in PES and, therefore, being able to handle those effects in future experiments using highly intense and pulsed photon sources, the origin of energetic broadenings and shifts in photoelectron spectra are studied by means of a molecular dynamic N-body simulation using a modified Treecode Algorithm for sufficiently fast and accurate calculations. It turned out that the most influencing parameter is the ''linear electron density'' - the ratio of the number of photoelectrons to the diameter of the illuminated spot on the sample. Furthermore, the simulations could reproduce the observations described in the literature fairly well. Some rules of thumb for XPS and ARPES measurements could be deduced from the simulations. Experimentally, SCEs are investigated by means of ARPES as well as XPS measurements as a function of

  20. Photoelectron spectroscopy at a free-electron laser. Investigation of space-charge effects in angle-resolved and core-level spectroscopy and realizaton of a time-resolved core-level photoemission experiment

    International Nuclear Information System (INIS)

    The free-electron laser (FEL) in Hamburg (FLASH) is a very interesting light source with which to perform photoelectron spectroscopy (PES) experiments. Its special characteristics include highly intense photon pulses (up to 100 J/pulse), a photon energy range of 30 eV to 1500 eV, transverse coherence as well as pulse durations of some ten femtoseconds. Especially in terms of time-resolved PES (TRPES), the deeper lying core levels can be reached with photon energies up to 1500 eV with acceptable intensity now and, therefore, element-specific, time-resolved core-level PES (XPS) is feasible at FLASH. During the work of this thesis various experimental setups were constructed in order to realize angle-resolved (ARPES), core-level (XPS) as well as time-resolved PES experiments at the plane grating monochromator beamline PG2 at FLASH. Existing as well as newly developed systems for online monitoring of FEL pulse intensities and generating spatial and temporal overlap of FEL and optical laser pulses for time-resolved experiments are successfully integrated into the experimental setup for PES. In order to understand space-charge effects (SCEs) in PES and, therefore, being able to handle those effects in future experiments using highly intense and pulsed photon sources, the origin of energetic broadenings and shifts in photoelectron spectra are studied by means of a molecular dynamic N-body simulation using a modified Treecode Algorithm for sufficiently fast and accurate calculations. It turned out that the most influencing parameter is the ''linear electron density'' - the ratio of the number of photoelectrons to the diameter of the illuminated spot on the sample. Furthermore, the simulations could reproduce the observations described in the literature fairly well. Some rules of thumb for XPS and ARPES measurements could be deduced from the simulations. Experimentally, SCEs are investigated by means of ARPES as well as XPS measurements as a function of FEL pulse

  1. Direct evidence for the nature of core-level photoemission satellites using angle-resolved photoemission extended fine structure

    International Nuclear Information System (INIS)

    Photoemission satellites from several systems have been found to exhibit exactly the same angle-resolved photoemission extended fine structure (ARPEFS) as found in the main peaks, when referred to the equivalent photoelectron wave number k for their own photoelectrons. This provides a direct and powerful method for experimentally determining the angular momentum parameters and the intrinsic/extrinsic nature of core-level photoemission satellites. We present ARPEFS satellite data for nitrogen 1s line in c(2x2)N2/Ni(100), the nickel 3p line in clean nickel (111), the carbon 1s lines in (√(3)x√(3))R30 CO/Cu(111) and p2mg(2x1)CO/Ni(110), and the cobalt 1s line in p(1x1) Co/Cu(100). For the last two cases the open-quotes satelliteclose quotes structure is actually the low-energy tail of a Doniach-Sunjic line shape. The satellite peaks and the tails of the Doniach-Sunjic line shapes exhibit ARPEFS curves that in all cases except one indicate angular-momentum parameters identical to the main peak and an intrinsic nature. copyright 1997 The American Physical Society

  2. Angle-Resolved Photoemission of Solvated Electrons in Sodium-Doped Clusters

    CERN Document Server

    West, Adam H C; Luckhaus, David; Saak, Clara-Magdalena; Doppelbauer, Maximilian; Signorell, Ruth

    2015-01-01

    Angle-resolved photoelectron spectroscopy of the unpaired electron in sodium-doped water, methanol, ammonia, and dimethyl ether clusters is presented. The experimental observations and the complementary calculations are consistent with surface electrons for the cluster size range studied. Evidence against internally solvated electrons is provided by the photoelectron angular distribution. The trends in the ionization energies seem mainly determined by the degree of hydrogen bonding in the solvent and the solvation of the ion core. The onset ionization energies of water and methanol clusters do not level off at small cluster sizes, but decrease slightly with increasing cluster size.

  3. Tetragonal and collapsed-tetragonal phases of CaFe2As2 : A view from angle-resolved photoemission and dynamical mean-field theory

    Science.gov (United States)

    van Roekeghem, Ambroise; Richard, Pierre; Shi, Xun; Wu, Shangfei; Zeng, Lingkun; Saparov, Bayrammurad; Ohtsubo, Yoshiyuki; Qian, Tian; Sefat, Athena S.; Biermann, Silke; Ding, Hong

    2016-06-01

    We present a study of the tetragonal to collapsed-tetragonal transition of CaFe2As2 using angle-resolved photoemission spectroscopy and dynamical mean field theory-based electronic structure calculations. We observe that the collapsed-tetragonal phase exhibits reduced correlations and a higher coherence temperature due to the stronger Fe-As hybridization. Furthermore, a comparison of measured photoemission spectra and theoretical spectral functions shows that momentum-dependent corrections to the density functional band structure are essential for the description of low-energy quasiparticle dispersions. We introduce those using the recently proposed combined "screened exchange + dynamical mean field theory" scheme.

  4. Angle resolved photoemission study of Fermi surfaces and single-particle excitations of quasi-low dimensional materials

    Science.gov (United States)

    Gweon, Gey-Hong

    Using angle resolved photoemission spectroscopy (ARPES) as the main experimental tool and the single particle Green's function as the main theoretical tool, materials of various degrees of low dimensionality and different ground states are studied. The underlying theme of this thesis is that of one dimensional physics, which includes charge density waves (CDW's) and the Luttinger liquid (LL). The LL is the prime example of a lattice non-Fermi liquid (non-FL) and CDW fluctuations also give non-FL behaviors. Non-FL physics is an emerging paradigm of condensed matter physics. It is thought by some researchers that one dimensional LL behavior is a key element in solving the high temperature superconductivity problem. TiTe2 is a quasi-2 dimensional (quasi-2D) Fermi liquid (FL) material very well suited for ARPES lineshape studies. I report ARPES spectra at 300 K which show an unusual behavior of a peak moving through the Fermi energy (EF). I also report a good fit of the ARPES spectra at 25 K obtained by using a causal Green's function proposed by K. Matho. SmTe3 is a quasi-2D CDW material. The near EF ARPES spectra and intensity map reveal rich details of an anisotropic gap and imperfectly nested Fermi surface (FS) for a high temperature CDW. A simple model of imperfect nesting can be constructed from these data and predicts a CDW wavevector in very good agreement with the value known from electron diffraction. NaMo6O17 and KMo 6O17 are also quasi-2D CDW materials. The "hidden nesting" or "hidden 1 dimensionality" picture for the CDW is confirmed very well by our direct image of the FS. K0.3MoO3, the so-called "blue bronze," is a quasi-1 dimensional (quasi-1D) CDW material. Even in its metallic phase above the CDW transition temperature, its photoemission spectra show an anomalously weak intensity at EF and no clear metallic Fermi edge. I compare predictions of an LL model and a CDW fluctuation model regarding these aspects, and find that the LL scenario explains them

  5. Electronic structure of HfN/sub 0.93/(100) studied by angle-resolved photoemission

    International Nuclear Information System (INIS)

    An experimental and theoretical study of the electronic structure of HfN is reported. Results from angle-resolved photoemission experiments on HfN/sub 0.93/(100) are presented and interpreted with use of calculated results. The bulk-band structure of stoichiometric HfN was calculated relativistically and nonrelativistically using the linear augmented-plane-wave method. Predicted band locations and dispersions along the Γ--X direction are compared with experimental results. In general the experiment indicates smaller bandwidths and locates the bands deeper below the Fermi level than the calculated values. Calculations of photoemission spectra, made nonrelativistically, are also reported and these spectra are found to reflect the recorded spectra fairly well

  6. Magnetic dichroism in angle-resolved hard x-ray photoemission from buried layers

    Science.gov (United States)

    Kozina, Xeniya; Fecher, Gerhard H.; Stryganyuk, Gregory; Ouardi, Siham; Balke, Benjamin; Felser, Claudia; Schönhense, Gerd; Ikenaga, Eiji; Sugiyama, Takeharu; Kawamura, Naomi; Suzuki, Motohiro; Taira, Tomoyuki; Uemura, Tetsuya; Yamamoto, Masafumi; Sukegawa, Hiroaki; Wang, Wenhong; Inomata, Koichiro; Kobayashi, Keisuke

    2011-08-01

    This work reports the measurement of magnetic dichroism in angular-resolved photoemission from in-plane magnetized buried thin films. The high bulk sensitivity of hard x-ray photoelectron spectroscopy (HAXPES) in combination with circularly polarized radiation enables the investigation of the magnetic properties of buried layers. HAXPES experiments with an excitation energy of 8 keV were performed on exchange-biased magnetic layers covered by thin oxide films. Two types of structures were investigated with the IrMn exchange-biasing layer either above or below the ferromagnetic layer: one with a CoFe layer on top and another with a Co2FeAl layer buried beneath the IrMn layer. A pronounced magnetic dichroism is found in the Co and Fe 2p states of both materials. The localization of the magnetic moments at the Fe site conditioning the peculiar characteristics of the Co2FeAl Heusler compound, predicted to be a half-metallic ferromagnet, is revealed from the magnetic dichroism detected in the Fe 2p states.

  7. High-resolution-angle resolved photoemission studies of high temperature superconductors

    International Nuclear Information System (INIS)

    This paper presents recent photoemission studies of Y 123 and Bi 2212 performed with high energy and angular resolution. They provide detailed information on the nature of the states near the Fermi level. Measurements of the superconducting gap, band dispersion, and the density of states near the Fermi level in the normal state all support a Fermi liquid description of these materials

  8. The orbital structure of {pi}-conjugated organic molecules on metal surfaces probed by angle-resolved photoemission

    Energy Technology Data Exchange (ETDEWEB)

    Ziroff, Johannes; Wiessner, Michael; Forster, Frank; Schoell, Achim [Universitaet Wuerzburg, Experimentelle Physik VII, D-97074 Wuerzburg (Germany); Puschnig, Peter [University of Leoben, Chair of Atomistic Modelling and Design of Materials, A-8700 Leoben (Austria); Reinert, Friedrich [Universitaet Wuerzburg, Experimentelle Physik VII, D-97074 Wuerzburg (Germany); FZ Karlsruhe, Gemeinschaftslabor fuer Nanoanalytik, D-76021 Karlsruhe (Germany)

    2010-07-01

    We present angle resolved photoemission spectra of monolayers of {pi}-conjugated molecules adsorbed on single-crystalline metal surfaces. Comparing the experimental k-dependant intensity distribution of the molecular states to DFT calculations for the free molecule allows to detect sophisticated modifications of the molecular orbitals at the interface. In case of the single-domain system PTCDA on Ag(110) the 2D emission pattern confirms that the now occupied interface state is mainly derived from the former LUMO-orbital. Moreover, a clear contribution of metal states is evident from additional intensity in normal emission. In the contrary, the structure of the molecular HOMO changes only slightly upon chemisorption on Ag surfaces. Additional data on other planar {pi}-conjugated organic molecules such as coronene or NTCDA demonstrates the potential of this approach in analysing the interaction at metal-organic interfaces in great detail.

  9. Observation of an ''extended'' Van Hove singularity in YBa2Cu4O8 by ultrahigh energy resolution angle-resolved photoemission

    International Nuclear Information System (INIS)

    We characterize the nature of the Van Hove singularity near the Fermi energy (EF) in YBa2Cu4O8 using ultrahigh energy resolution (10 meV) angle-resolved photoemission spectroscopy, together with corresponding first-principles spectra intensity computations. The singularity, related to CuO2 planes, is located about 19 meV below EF at the Y point in the Brillouin zone and arises from a band which is nearly dispersionless along the Γ to Y direction. Such an ''extended'' saddle point would render the band structure quasi-1D and yield a power law divergence in the density of states, allowing the occurrence of Tc's of order 100 K even in a weak coupling BCS scheme

  10. Gap anisotropy in Bi2Sr2CaCu2O8+δ by ultrahigh-resolution angle-resolved photoemission

    International Nuclear Information System (INIS)

    Ultrahigh-resolution (ΔE up to 10 meV) angle-resolved photoemission spectroscopy on single crystals of Bi2Sr2CaCu2O8+δ (Bi-2212) show a highly anisotropic superconducting energy gap: the gap is minimized, with a value close to zero, along the Γ-X and Γ-Y symmetry directions, while a large gap (Δ=22 meV) is observed along the Γ-bar M (Cu-O bond) direction. However, the observation of gap anisotropy may depend on sample conditions; in a few cases the gap becomes more isotropic. A dip in the spectral weight at 65 meV below the Fermi energy is clearly observed only in samples with an anisotropic gap

  11. Angle-resolved photoemission study and first-principles calculation of the electronic structure of LaSb2

    International Nuclear Information System (INIS)

    In this work we present valence band studies of LaSb2 using angle-resolved photoelectron spectroscopy with synchrotron radiation and compare these data with band structure calculations. Valence band spectra reveal that Sb 5p states are dominant near the Fermi level and are hybridized with the La 5d states just below. The calculations show a fair agreement with the experimentally determined valence band spectra, allowing an identification of the observed features. We measured some dispersion for kbar, especially for Sb 5p states; no significant dispersion was found for k||. (letter to the editor)

  12. A New Spin on Photoemission Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Jozwiak, Chris [Univ. of California, Berkeley, CA (United States)

    2008-12-01

    The electronic spin degree of freedom is of general fundamental importance to all matter. Understanding its complex roles and behavior in the solid state, particularly in highly correlated and magnetic materials, has grown increasingly desirable as technology demands advanced devices and materials based on ever stricter comprehension and control of the electron spin. However, direct and efficient spin dependent probes of electronic structure are currently lacking. Angle Resolved Photoemission Spectroscopy (ARPES) has become one of the most successful experimental tools for elucidating solid state electronic structures, bolstered by-continual breakthroughs in efficient instrumentation. In contrast, spin-resolved photoemission spectroscopy has lagged behind due to a lack of similar instrumental advances. The power of photoemission spectroscopy and the pertinence of electronic spin in the current research climate combine to make breakthroughs in Spin and Angle Resolved Photoemission Spectroscopy (SARPES) a high priority . This thesis details the development of a unique instrument for efficient SARPES and represents a radical departure from conventional methods. A custom designed spin polarimeter based on low energy exchange scattering is developed, with projected efficiency gains of two orders of magnitude over current state-of-the-art polarimeters. For energy analysis, the popular hemispherical analyzer is eschewed for a custom Time-of-Flight (TOF) analyzer offering an additional order of magnitude gain in efficiency. The combined instrument signifies the breakthrough needed to perform the high resolution SARPES experiments necessary for untangling the complex spin-dependent electronic structures central to today's condensed matter physics.

  13. Angle-resolved inverse photoemission of the H-etched 6H-SiC(0001) surface

    Energy Technology Data Exchange (ETDEWEB)

    Aghdassi, Nabi; Ostendorf, Ralf; Zacharias, Helmut [Physikalisches Institut, Westfaelische Wilhelms-Universitaet Muenster (Germany)

    2009-07-01

    The etching of 6H-SiC(0001) substrates in molecular hydrogen at elevated temperatures leads to an ordered silicate adlayer as it is confirmed by LEED and AES. LEED patterns clearly feature a ({radical}(3) x {radical}(3))R30 periodicity while AES spectra are evidence for the presence of Si-O bonds. The generated surfaces appear to be fully passivated and therefore stable in ambient air. After cleaning the samples by heating in UHV up to temperatures around 750 C angle-resolved inverse photoemission is performed on the SiO{sub 2}/SiC interface. The IPE spectra reveal five features above the Fermi level around 0.5 eV, 1.2 eV, 2.3 eV, 3.5 eV and 5.5 eV, respectively, which show only a weak dispersion along the {gamma} - M and {gamma} - K directions of the (1 x 1) surface Brillouin zone.

  14. Angle-Resolved Mid-Infrared Spectroscopy of Gyroid Photonic Crystals

    Science.gov (United States)

    Khabiboulline, Emil T.; Peng, Siying; Hon, Philip; Zhang, Runyu; Chen, Hongjie; Sweatlock, Luke A.; Braun, Paul; Atwater, Harry A.

    Photonic topological insulators form a new class of materials with exciting properties. Theory has indicated that gyroid photonic crystals are photonic topological insulators. In this paper, we experimentally characterize the photonic properties of gyroid photonic crystals at mid-infrared wavelengths, using angle-resolved spectroscopy with coherent light from a quantum cascade laser tuned from 7.7 μm to 11.1 μm and focused onto a 100 μm × 100 μm spot. From measurements of reflection and transmission spectra over incidence angles, we construct the band structure of the photonic crystals. In this study, the photonic crystals are single and double gyroid made of amorphous silicon, with unit cell size of 5 μm, sitting on an intrinsic silicon substrate. Simulations predict band gaps for the single gyroid and Weyl points for the double gyroid. We compare results of angle-resolved spectroscopy experiments with simulations for nanofabricated gyroid structures and discuss the topological features observable in angle-resolved scattering.

  15. Soft X-ray photoemission spectroscopy

    International Nuclear Information System (INIS)

    The main motivation behind this thesis has been to determine both the advantages and the disadvantages of the soft X-ray application of angle-resolved photoemission spectroscopy. The investigation of a well known system, Ag(001), enables us to discuss several questions such as the role of the photon momentum, the applicability of the free-electron-like final state approximation and the role of phonons. The polarisation of the incoming light has also been exploited. The choice of such a system also comes from our desire to compare the results with calculations of angle-resolved photoemission spectra in this energy range. The anomalous low temperature properties of Ce-based compounds are generally related to the Kondo effect. Original results have been obtained by investigating the valence band of three iso-structural single crystalline Ce compounds, CeCu2Ge2, CeNi2Ge2 and CeCo2Ge2. The location of the Ce M5 absorption edge within the soft X-ray energy range is exploited in order to isolate the 4f contribution to the spectra. Added to this, the use of relatively high incoming photon energies allows minimising the surface contribution. Temperature dependent, resonant, angle-resolved and angle-integrated photoemission measurements have been performed. The former are in qualitative agreement with the single impurity Anderson model, whereas the latter suggest the importance of taking the lattice into account. (author)

  16. Electronic and geometric structure of the PTCDA/Ag(110) interface probed by angle-resolved photoemission

    Science.gov (United States)

    Wießner, M.; Hauschild, D.; Schöll, A.; Reinert, F.; Feyer, V.; Winkler, K.; Krömker, B.

    2012-07-01

    The properties of molecular films are determined by the geometric structure of the first layers near the interface. These are in contact with the substrate and feel the effect of the interfacial bonding, which particularly, for metal substrates, can be substantial. For the model system 3,4,9,10-perylenetetracarboxylic dianhydride on Ag(110), the geometric structure of the first monolayer can be modified by preparation parameters. This leads to significant differences in the electronic structure of the first layer. Here, we show that, by combining angle-resolved photoelectron spectroscopy with low-energy electron diffraction, we cannot only determine the electronic structure of the interfacial layer and the unit cell of the adsorbate superstructure, but also the arrangement of the molecules in the unit cell. Moreover, in bilayer films, we can distinguish the first from the second layer and, thus, study the formation of the second layer and its influence on the buried interface.

  17. Depth- and momentum- resolved electronic structure at buried oxide interfaces from standing-wave angle-resolved photoemission

    Science.gov (United States)

    Fadley, Charles

    2015-03-01

    It is clear that interfaces in complex oxide heterostructures often represent emergent materials that possess surprising properties not associated with the parent oxides, such as two-dimensional electron gases (2DEGs), superconductivity, and magnetism. A detailed knowledge of the composition, atomic structure, and electronic structure through such interfaces is thus critical. Photomission (PES) and angle-resolved photoemission (ARPES) represent techniques of choice for such studies, but have certain limitations in being too surface sensitive and in not being able to focus specifically on buried interfaces or heterostructure layers. In this talk, I will discuss combining two newer elements of PES/ARPES to deal with this challenge: - the use of soft x-rays in the ca. few hundred-to-2000 eV regime, or even into the true hard x-ray regime, to probe more deeply into the structure, and - tailoring of the x-ray intensity profile into a strong standing wave (SW) through reflection from a multilayer heterostructure to provide much enhanced depth resolution. The relative advantages of soft/hard x-ray PES and ARPES and their complementarity to conventional VUV ARPES in the ca. 5-150 eV regime will be considered. As illustrative examples, by combining SW-PES and SW-ARPES, it has been possible to measure for the first time the detailed concentration profiles and momentum-resolved electronic structure at the SrTiO3/La0.67Sr0.33MnO3 interface and to directly measure the depth profile of the 2DEG at SrTiO3/GdTiO3 interfaces. Future directions for such measurements will also be discussed. Supported by US DOE Contract No. DE-AC02-05CH11231, ARO-MURI Grant W911-NF-09-1-0398, and the PALM-APTCOM Project (France).

  18. The Fermi surface and band folding in La2-xSrxCuO4, probed by angle-resolved photoemission

    International Nuclear Information System (INIS)

    A systematic angle-resolved photoemission study of the electronic structure of La2-xSrxCuO4 in a wide doping range is presented in this paper. In addition to the main energy band, we observed a weaker additional band, the (π, π) folded band, which shows unusual doping dependence. The appearance of the folded band suggests that a Fermi surface reconstruction is doping dependent and could already occur at zero magnetic field.

  19. The Fermi surface and band folding in La{sub 2-x}Sr{sub x}CuO{sub 4}, probed by angle-resolved photoemission

    Energy Technology Data Exchange (ETDEWEB)

    Razzoli, E; Radovic, M; Patthey, L; Shi, M [Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI (Switzerland); Sassa, Y; Chang, J [Laboratory for Neutron Scattering, Paul Scherrer Institut, CH-5232 Villigen PSI (Switzerland); Drachuck, G; Keren, A; Shay, M [Department of Physics, Technion-Israel Institute of Technology, Haifa 32000 (Israel); Maansson, M; Mesot, J [Laboratory for Synchrotron and Neutron Spectroscopy, EPF Lausanne, CH-1015 Lausanne (Switzerland); Berntsen, M H; Tjernberg, O [Materials Physics, KTH Royal Institute of Technology, S-16440 Kista (Sweden); Pailhes, S [CEA, CNRS, CE Saclay, Laboratoire Leon Brillouin, F-91191 Gif Sur Yvette (France); Momono, N [Department of Applied Sciences, Muroran Institute of Technology, Muroran 050-8585 (Japan); Oda, M; Ido, M [Department of Physics, Hokkaido University, Sapporo 060-0810 (Japan); Lipscombe, O J; Hayden, S M, E-mail: ming.shi@psi.c [H H Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL (United Kingdom)

    2010-12-15

    A systematic angle-resolved photoemission study of the electronic structure of La{sub 2-x}Sr{sub x}CuO{sub 4} in a wide doping range is presented in this paper. In addition to the main energy band, we observed a weaker additional band, the ({pi}, {pi}) folded band, which shows unusual doping dependence. The appearance of the folded band suggests that a Fermi surface reconstruction is doping dependent and could already occur at zero magnetic field.

  20. Angle-resolved photoemission studies of lattice polaron formation in the cuprate Ca2CuO2Cl2

    Energy Technology Data Exchange (ETDEWEB)

    Shen, K.M.

    2010-05-03

    To elucidate the nature of the single-particle excitations in the undoped parent cuprates, we have performed a detailed study of Ca{sub 2}CuO{sub 2}Cl{sub 2} using photoemission spectroscopy. The photoemission lineshapes of the lower Hubbard band are found to be well-described by a polaron model. By comparing the lineshape and temperature dependence of the lower Hubbard band with additional O 2p and Ca 3p states, we conclude that the dominant broadening mechanism arises from the interaction between the photohole and the lattice. The strength of this interaction was observed to be strongly anisotropic and may have important implications for the momentum dependence of the first doped hole states.

  1. Energy and angle resolved ion scattering spectroscopy: new possibilities for surface analysis

    International Nuclear Information System (INIS)

    In this thesis the design and development of a novel, very sensitive and high-resolving spectrometer for surface analysis is described. This spectrometer is designed for Energy and Angle Resolved Ion Scattering Spectroscopy (EARISS). There are only a few techniques that are sensitive enough to study the outermost atomic layer of surfaces. One of these techniques, Low-Energy Ion Scattering (LEIS), is discussed in chapter 2. Since LEIS is destructive, it is important to make a very efficient use of the scattered ions. This makes it attractive to simultaneously carry out energy and angle dependent measurements (EARISS). (Auth.)

  2. Size Effects in Angle-Resolved Photoelectron Spectroscopy of Free Rare-Gas Clusters

    Energy Technology Data Exchange (ETDEWEB)

    Rolles, D.; Zhang, H.; Pesic, Z.D.; Bilodeau, R.C.; Wills, A.; Kukk, E.; Rude, B.S.; Ackerman, G.D.; Bozek, J.D.; Muino, R.D.; de Abajo, F.J.G.; Berrah, N.; /Western

    2007-05-23

    The photoionization of free Xe clusters is investigated by angle-resolved time-of-flight photoelectron spectroscopy. The measurements probe the evolution of the photoelectron angular distribution parameter as a function of photon energy and cluster size. While the overall photon-energy-dependent behavior of the photoelectrons from the clusters is very similar to that of the free atoms, distinct differences in the angular distribution point at cluster-size-dependent effects. Multiple scattering calculations trace their origin to elastic photoelectron scattering.

  3. Electronic structure of single crystal UPd3, UGe2, and USb2 from hard X-ray and angle-resolved photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Highlights: → Electronic structure of single crystal UPd3, UGe2, and USb2 was measured by hard X-ray and angle-resolved photoemission spectroscopy. → Angle resolved photoemission results demonstrate hybridization between U 5f and Pd 4d electrons within UPd3. → HAXPES probing of bulk features within of UPd3, UGe2, and USb2 samples with native oxide contamination demonstrated. → Two distinct spectral features identified for Sb I and Sb II sites within USb2 HAXPES spectrum. → Line shape analysis reveals correlations between Doniach-Sunjic asymmetry coefficients and 5f localization. - Abstract: Electronic structure of single crystal UPd3, UGe2, and USb2 has been measured from hard X-ray photoelectron spectroscopy (HAXPES) with 7.6 keV photons at the European Synchrotron Radiation Facility (ESRF). Lower photon energy angle-resolved photoelectron spectroscopy (ARPES) was also performed at the Synchrotron Radiation Center (SRC). Herein the following results are presented: (i) ARPES results demonstrate hybridization between the U 5f and Pd 4d electrons within UPd3. (ii) The greatly reduced surface sensitivity of HAXPES enabled observation of the bulk core levels in spite of surface oxidation. Photoelectron mean-free-path versus oxide layer thickness considerations were used to model the effectiveness of HAXPES for probing bulk features of in-air cleaved samples. (iii) Two distinct features separated by 800 meV were observed for the Sb 3d core level. These two features are attributed to manifestations of two distinct Sb sites within the USb2 single crystal as supported by consideration of interatomic distances and enthalpy-of-formation. (iv) Doniach-Sunjic line shape analysis of core level spectral features revealed correlations between asymmetry coefficients and 5f localization.

  4. Probing the momentum-dependent response of the charge density wave phase in TbTe3 by ultrafast time- and angle-resolved photoemission

    International Nuclear Information System (INIS)

    Charge density wave (CDW) systems such as TbTe3 offer fascinating options for studying the correlation of electrons and the lattice. We investigate the ultrafast response of the charge density wave (CDW) phase in TbTe3 after femtosecond IR excitation using time- and angle-resolved photoemission. The time-dependent photoemission intensity at the Fermi level yields a characteristic time for the closing of the CDW bandgap. With increasing laser fluence the bandgap closes faster, pointing to an increasing slope of the excited potential energy surface. As function of electron momentum the amplitude of the response increases strongly at the position of the Fermi wave vector kF. These results vividly demonstrate that the CDW system is most susceptible to electronic excitations near kF and that these electronic perturbations drive collective excitations of the coupled electron-lattice system.

  5. Angle resolved ion-electron spectroscopy (ARIES), a new technique to study surface structural features

    International Nuclear Information System (INIS)

    Angle Resolved Ion-Electron Spectroscopy (ARIES), combined with Low Energy Ion Scattering (LEIS), is presented as a new technique with a wide applicability to study solid surfaces. Energy and angular distribution of secondary electrons emitted due to the ionization of (ad)-sorbates on a Cu(001) surface upon bombardment with 10 keV He+ are examined. When sulphur atoms - diffused from the bulk to the surface upon a 6000C anneal - are involved in the emission process, a strongly anisotropical emission is found. The anisotropy is related only to the incoming beam direction and appears to be fully independent of the copper target orientation. Some points of importance for a theoretical description are discussed. The anisotropy effect can effectively be used to determine the relative position of contaminant and substrate atoms in the uppermost surface layers. Thus, it is found that (1) sulphur atoms diffused to positions just below the surface occupy substitutional sites and (2) in this situation surface relaxation for the copper atoms in the first layer is negligible. (author)

  6. Angle-resolved photoemission study of untwinned PrBa2Cu3O7: Undoped CuO2 plane and doped CuO3 chain

    International Nuclear Information System (INIS)

    We have performed an angle-resolved photoemission study on untwinned PrBa2Cu3O7, which has low resistivity but does not show superconductivity. We have observed a dispersive feature with a band maximum around (π/2,π/2), indicating that this band is derived from the undoped CuO2 plane. We have observed another dispersive band exhibiting one-dimensional character, which we attribute to signals from the doped CuO3 chain. The overall band dispersion of the one-dimensional band agrees with the prediction of the t-J model calculation with parameters relevant to cuprates except that the intensity near the Fermi level is considerably suppressed in the experiment. copyright 1999 The American Physical Society

  7. Effects of symmetry on circular and linear magnetic dichroism in angle-resolved photoemission spectra of Gd/Y (0001) and Fe-Ni//Cu (001)

    Energy Technology Data Exchange (ETDEWEB)

    Goodman, K.W.; Tobin, J.G.; Schumann, F.O. [Pennsylvania State Univ., University Park, PA (United States); Willis, R.F. [Pennsylvania State Univ., University Park, PA (United States); Gammon, J.W. [Virginia Commonwealth Univ., Richmond, VA (United States); Pappas, D.P. [Virginia Commonwealth Univ., Richmond, VA (United States); Kortright, J.B. [Lawrence Berkeley National Lab., CA (United States); Denlinger, J.D. [Lawrence Berkeley National Lab., CA (United States); Rotenberg, E. [Lawrence Berkeley National Lab., CA (United States); Warwick, A. [Lawrence Berkeley National Lab., CA (United States); Smith, N.V. [Lawrence Berkeley National Lab., CA (United States)

    1997-03-26

    We have observed circular and linear magnetic dichroism in angle- resolved photoemission spectra of 50-monolayer Gd film grown on Y(0001) and 6-monolayer Fe-Ni alloy films grown on Cu(001). The 4f level of Gd and the Fe 3p level of the Fe-Ni alloy were measured. A different geometry was used for the magnetic circular dichroism than was used to measure the magnetic linear dichroism. The geometries were chosen so that the shape of the magnetic circular dichroism is predicted to be equal to the shape of the magnetic linear dichroism for four-fold symmetric Fe-Ni/Cu(001) but not for three-fold symmetric Gd/Y(0001). Experimental results are presented. In this paper we examine the effect of symmetry (experimental geometry and sample geometry) on magnetic linear and circular dichroism in angle- resolved photoemission. In particular we chose separate geometries for measuring magnetic circular and magnetic linear dichroism. The geometries were chosen such that samples with four-fold symmetry about the sample normal may have magnetic circular and magnetic linear dichroism of the same shape. But samples with three-fold symmetry should not exhibit circular and magnetic linear dichroism of the same shape. The samples studied are three-fold symmetric Gd films grown on Y(0001) and four-fold symmetric Fe-Ni alloy grown on Cu(001). After presenting the methods of the experiment, we briefly review parts of a model of magnetic dichroism developed by Venus and coworkers and our specialization and extension of it, particularly for FeNi/Cu(001). We then show the results of our measurements.

  8. Metal-insulator transition and tunable Dirac-cone surface state in the topological insulator TlBi1 -xSbxTe2 studied by angle-resolved photoemission

    Science.gov (United States)

    Trang, Chi Xuan; Wang, Zhiwei; Yamada, Keiko; Souma, Seigo; Sato, Takafumi; Takahashi, Takashi; Segawa, Kouji; Ando, Yoichi

    2016-04-01

    We report a systematic angle-resolved photoemission spectroscopy on topological insulator (TI) TlBi1 -xSbxTe2 which is bulk insulating at 0.5 ≲x ≲0.9 and undergoes a metal-insulator-metal transition with the Sb content x . We found that this transition is characterized by a systematic hole doping with increasing x , which results in the Fermi-level crossings of the bulk conduction and valence bands at x ˜0 and x ˜1 , respectively. The Dirac point of the topological surface state is gradually isolated from the valence-band edge, accompanied by a sign reversal of Dirac carriers. We also found that the Dirac velocity is the largest among known solid-solution TI systems. The TlBi1 -xSbxTe2 system thus provides an excellent platform for Dirac-cone engineering and device applications of TIs.

  9. Angle-resolved scattering spectroscopy of explosives using an external cavity quantum cascade laser

    Energy Technology Data Exchange (ETDEWEB)

    Suter, Jonathan D.; Bernacki, Bruce E.; Phillips, Mark C.

    2012-04-01

    Investigation of angle-resolved scattering from solid explosives residues on a car door for non-contact sensing geometries. Illumination with a mid-infrared external cavity quantum cascade laser tuning between 7 and 8 microns was detected both with a sensitive single point detector and a hyperspectral imaging camera. Spectral scattering phenomena were discussed and possibilities for hyperspectral imaging at large scattering angles were outlined.

  10. Angle-resolved and core-level photoemission study of interfacing the topological insulator Bi1.5Sb0.5Te1.7Se1.3 with Ag, Nb, and Fe

    NARCIS (Netherlands)

    N. de Jong; E. Frantzeskakis; B. Zwartsenberg; Y.K. Huang; D. Wu; P. Hlawenka; J. Sanchez-Barriga; A. Varykhalov; E. van Heumen; M.S. Golden

    2015-01-01

    Interfaces between a bulk-insulating topological insulator (TI) and metallic adatoms have been studied using high-resolution, angle-resolved, and core-level photoemission. Fe, Nb, and Ag were evaporated onto Bi1.5Sb0.5Te1.7Se1.3 (BSTS) surfaces both at room temperature and 38 K. The coverage and tem

  11. Angle - resolved photoemission study of two phases of the GaAs(100)-c(4x4) surface

    Czech Academy of Sciences Publication Activity Database

    Cukr, Miroslav; Jiříček, Petr; Bartoš, Igor; Sadowski, J.

    2008-01-01

    Roč. 100, - (2008), 072017/1-072017/4. ISSN 1742-6588 R&D Projects: GA AV ČR IAA100100628; GA ČR GA202/07/0601 Institutional research plan: CEZ:AV0Z10100521 Keywords : gallium arsenide * molecular beam epitaxy * photoelectron spectroscopy * surface reconstruction * surface phases * electron states Subject RIV: BM - Solid Matter Physics ; Magnetism

  12. Adsorption site and structure determination of c(2x2) N{sub 2}/Ni(100) using angle-resolved photoemission extended fine structure

    Energy Technology Data Exchange (ETDEWEB)

    Moler, E.J.; Kellar, S.A.; Huff, W.R.A. [Lawrence Berkeley National Lab., CA (United States)] [and others

    1997-04-01

    The authors have determined the atomic spatial structure of c(2x2) N2Ni(100) with Angle-Resolved Photoemission Extended Fine Structure (ARPEFS) from the nitrogen 1s core level using monochromatized x-rays from beamline 6.1 at SSRL and beamline 9.3.2 at the ALS. The chemically shifted N 1s peak intensities were summed together to obtain ARPEFS curves for both nitrogen atoms in the molecule. They used a new, highly-optimized program based on the Rehr-Albers scattering matrix formalism to find the adsorption site and to quantitatively determine the bond-lengths. The nitrogen molecule stands upright at an atop site, with a N-Ni bond length of 2.25(1) {angstrom}, a N-N bond length of 1.10(7) {angstrom}, and a first layer Ni-Ni spacing of 1.76(4) {angstrom}. The shake-up peak shows an identical ARPEFS diffraction pattern, confirming its intrinsic nature and supporting a previous use of this feature to decompose the peak into contributions from the chemically inequivalent nitrogen atoms. Comparison to a previously published theoretical treatment of N-N-Ni and experimental structures of analogous adsorbate systems demonstrates the importance of adsorbate-adsorbate interactions in weakly chemisorbed systems.

  13. Electronic structure as a function of doping in YBa2Cu3Ox(6.2≤x≤6.9) studied by angle-resolved photoemission

    International Nuclear Information System (INIS)

    We report angle-resolved photoemission studies on YBa2Cu3Ox with oxygen stoichiometry varied in the range 6.2≤x≤6.9. The distinct 1-eV peak, observed with hν=24 eV at the X(Y) point(s), shifts monotonically toward higher binding energies (as much as 0.20 eV) as oxygen stoichiometry is reduced from x=6.9 to 6.3. The direction and the magnitude of the shift are consistent with a simple rigid-band filling picture. However, another distinct peak observed at the X(Y) point(s), but with energy very close to EF, remains at nearly the same energy when the oxygen stoichiometry is varied from 6.9 to 6.4. This behavior is not consistent with a rigid-band picture. The intensities of the 1-eV peak and the peak at EF are significantly attenuated when the material becomes insulating

  14. Shape resonances in the angle-resolved photoelectron spectroscopy of the Si 2p shell of SiCl4

    International Nuclear Information System (INIS)

    The partial cross sections and angular distribution parameters, β, have been determined for the 2p subshell in SiCl4. These data were obtained with angle-resolved photoelectron spectroscopy and the use of synchrotron radiation for a range of photon energies from 114 to 150 eV. The same quantities were calculated by use of a multiple scattering Xα method, and the agreement between experiment and theory is very good. In particular, the behavior of shape resonances was well predicted. The nature of shape resonances as a function of molecular orbitals in SiCl4 is discussed, and the importance of such intercomparison is emphasized

  15. Fourier transform photoemission spectroscopy

    NARCIS (Netherlands)

    Meinders, M.B J; Drabe, K.E.; Jonkman, H.T.; Sawatzky, G.A

    1996-01-01

    It is shown that photoemission spectra can be obtained by exciting the electrons with two phase-correlated wave trains. The phase-correlated wave trains are obtained by sending broad-band ultra-violet light, coming from a deuterium lamp, through a Michelson interferometer. It is possible to stabiliz

  16. CuPc/Au(1 1 0): Determination of the azimuthal alignment by a combination of angle-resolved photoemission and density functional theory

    International Nuclear Information System (INIS)

    Highlights: • Complete structural determination of a Copper-Phthalocyanice monolayer on Au(1 1 0). • Orbital tomography method identifies emission at 1.2 eV as the HOMO of CuPc. • Retain correct orbital order by using hybrid functional calculations. - Abstract: Here we report on a combined experimental and theoretical study on the structural and electronic properties of a monolayer of Copper-Phthalocyanine (CuPc) on the Au(1 1 0) surface. Low-energy electron diffraction reveals a commensurate overlayer unit cell containing one adsorbate species. The azimuthal alignment of the CuPc molecule is revealed by comparing experimental constant binding energy (kxky)-maps using angle-resolved photoelectron spectroscopy with theoretical momentum maps of the free molecule's highest occupied molecular orbital (HOMO). This structural information is confirmed by total energy calculations within the framework of van-der-Waals corrected density functional theory. The electronic structure is further analyzed by computing the molecule-projected density of states, using both a semi-local and a hybrid exchange-correlation functional. In agreement with experiment, the HOMO is located about 1.2 eV below the Fermi-level, while there is no significant charge transfer into the molecule and the CuPc LUMO remains unoccupied on the Au(1 1 0) surface

  17. Angle-resolved photoemission analysis on electronic structures and thermoelectric properties of off-stoichiometric Fe2-xV1+xAl

    International Nuclear Information System (INIS)

    The electronic states of Heusler (L21)-type off-stoichiometric Fe2-xV1+xAl have been investigated by soft X-ray angle-resolved photoelectron spectroscopy (ARPES) in order to clarify the origin of their large thermoelectric powers, which cannot be explained in terms of the rigid band model. In off-normal and normal ARPES, Fe2.05V0.95Al shows a weakly dispersive bulk band around the binding energy of 0.3 eV in the Γ-X direction and an almost dispersion-less one around 0.3 eV in a gap of dispersive bulk bands in the Γ-L direction, which is attributed to the anti-site Fe defect. At the Γ point, the bulk band does not appear to cross the Fermi level EF, consistent with the rigid band model for the excess Fe content bringing about the increase in the valence electrons, but no band crossing EF down is found at the X point. The anti-site Fe defect states near EF might push up the band at the X point and cause the p-type thermoelectric properties, unexpected with the rigid band picture. The change in the electronic structures and thermoelectric properties are discussed on the off-stoichiometry and substitution of the forth element. (author)

  18. Angle Resolved X-ray Photoelectron Spectroscopy Study of Pd/NbOx/Nb Interfaces

    Czech Academy of Sciences Publication Activity Database

    Thiam, Michel Malick; Bastl, Zdeněk

    507-510, - (2002), s. 678-682. ISSN 0039-6028 R&D Projects: GA ČR GA202/99/1714; GA ČR GV202/98/K002 Institutional research plan: CEZ:AV0Z4040901 Keywords : photoelectron spectroscopy * palladium * metallic films Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.140, year: 2002

  19. Development of a high-resolution soft x-ray (30--1500 eV) beamline at the Advanced Light Source and its use for the study of angle-resolved photoemission extended fine structure

    International Nuclear Information System (INIS)

    ALS Bending magnet beamline 9.3.2 is for high resolution spectroscopy, with circularly polarized light. Fixed included-angle SGM uses three gratings for 30--1500 eV photons; circular polarization is produced by an aperture for selecting the beam above or below the horizontal plane. Photocurrent from upper and lower jaws of entrance slit sets a piezoelectric drive feedback loop on the vertically deflecting mirror for stable beam. End station has a movable platform. With photomeission data from Stanford, structure of c(2x2)P/Fe(100) was determined using angle-resolved photoemission extended fine structure (ARPEFS). Multiple-scattering spherical-wave (MSSW) calculations indicate that P atoms adsorb in fourfold hollow sites 1.02A above the first Fe layer. Self-consistent-field Xα scattered wave calculation confirm that the Fe1-Fe2 space is contracted for S/Fe but not for P/Fe; comparison is made to atomic N and O on Fe(100). Final-state effects on ARPEFS curves used literature data from the S 1s and 2p core levels of c(2x2)S/Ni(001); a generalized Ramsauer-Townsend splitting is present in the 1s but not 2p data. An approximate method for analyzing ARPEFS data from a non-s initial state using only the higher-ell partial wave was tested successfully. ARPEFS data from clean surfaces were collected normal to Ni(111) (3p core levels) and 5 degree off-normal from Cu(111)(3s, 3p). Fourier transforms (FT) resemble adsorbate systems, showing backscattering signals from atoms up to 4 layers below emitters. 3p FTs show scattering from 6 nearest neighbors in the same crystal layer as the emitters. MSSW calulation indicate that Cu 3p photoemission is mostly d-wave. FTs also indicate double-scattering and single-scattering from laterally distant atoms; calculations indicate that the signal is dominated by photoemission from the first 2 crystal layers

  20. Accessing Phonon Polaritons in Hyperbolic Crystals by Angle-Resolved Photoemission Spectroscopy

    OpenAIRE

    Tomadin, Andrea; Principi, Alessandro; Song, Justin C. W.; Levitov, Leonid S.; Polini, Marco

    2015-01-01

    Recently studied hyperbolic materials host unique phonon-polariton (PP) modes. The ultrashort wavelengths of these modes, as well as their low damping, hold promise for extreme subdiffraction nanophotonics schemes. Polar hyperbolic materials such as hexagonal boron nitride can be used to realize long-range coupling between PP modes and extraneous charge degrees of freedom. The latter, in turn, can be used to control and probe PP modes. Here we analyze coupling between PP modes and plasmons in...

  1. Electronic structure of ion arsenic high temperature superconductors studied by angle resolved photoemission spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Chang [Iowa State Univ., Ames, IA (United States)

    2011-01-01

    The main purpose of the present thesis is to present our ARPES results on the iron arsenic superconductors. As revealed by a series of ARPES measurements on both the AEFe2As2 and the RFeAs(O,F) families (parent compound and carrier-doped systems), the electronic structures of the pnictides are complicated, three dimensional, and closely linked to their superconducting behavior (13; 14; 15; 16; 17; 18; 19). Parent compounds of these materials exhibit the basic hole-electron pocket dual plus an apparent Fermi surface reconstruction caused by long range antiferromagnetism (13; 15). When carriers are introduced, the chemical potential shifts in accordance with the Luttinger theorem and the rigid band shifting picture (13). Importantly, both the appearance and disappearance of the superconducting dome at low and high doping levels have intimate relation with topological changes at the Fermi surfaces, resulting in a specific Fermi topology being favored by superconductivity (15; 16). On the low doping side, superconductivity emerges in the phase diagram once the antiferromagnetic reconstruction disappears below the Fermi level, returning the Fermi surface to its paramagnetic-like appearance. On the high doping side, superconductivity disappears around a doping level at which the central hole pocket vanishes due to increasing electron concentration. Such phenomena are evidence for the governing role the electronic structure plays in their superconducting behavior.

  2. Dual analyzer system for surface analysis dedicated for angle-resolved photoelectron spectroscopy at liquid surfaces and interfaces

    Science.gov (United States)

    Niedermaier, Inga; Kolbeck, Claudia; Steinrück, Hans-Peter; Maier, Florian

    2016-04-01

    The investigation of liquid surfaces and interfaces with the powerful toolbox of ultra-high vacuum (UHV)-based surface science techniques generally has to overcome the issue of liquid evaporation within the vacuum system. In the last decade, however, new classes of liquids with negligible vapor pressure at room temperature—in particular, ionic liquids (ILs)—have emerged for surface science studies. It has been demonstrated that particularly angle-resolved X-ray Photoelectron Spectroscopy (ARXPS) allows for investigating phenomena that occur at gas-liquid and liquid-solid interfaces on the molecular level. The results are not only relevant for IL systems but also for liquids in general. In all of these previous ARXPS studies, the sample holder had to be tilted in order to change the polar detection angle of emitted photoelectrons, which restricted the liquid systems to very thin viscous IL films coating a flat solid support. We now report on the concept and realization of a new and unique laboratory "Dual Analyzer System for Surface Analysis (DASSA)" which enables fast ARXPS, UV photoelectron spectroscopy, imaging XPS, and low-energy ion scattering at the horizontal surface plane of macroscopically thick non-volatile liquid samples. It comprises a UHV chamber equipped with two electron analyzers mounted for simultaneous measurements in 0° and 80° emission relative to the surface normal. The performance of DASSA on a first macroscopic liquid system will be demonstrated.

  3. Spin orbit splitting in the valence bands of ZrSxSe2−x: Angle resolved photoemission and density functional theory

    International Nuclear Information System (INIS)

    Highlights: ► We performed high resolution ARPES on 1T–ZrSxSe2−x. ► A characteristic splitting of the chalcogen p-derived VB along high symmetry directions was observed. ► The splitting size at the A point of the BZ is found to increase from 0.06 to 0.31 eV from ZrS2 towards ZrSe2. ► Electronic structure calculations based on the DFT were performed using the model of TB–MBJ. ► The calculations show that the splitting is due to SO coupling of the valence bands. -- Abstract: Angle-resolved photoelectron spectroscopy using synchrotron radiation has been performed on 1T–ZrSxSe2−x, where x varies from 0 to 2, in order to study the influence of the spin-orbit interaction in the valence bands. The crystals were grown by chemical vapour transport technique using Iodine as transport agent. A characteristic splitting of the chalcogen p-derived valence bands along high symmetry directions has been observed experimentally. The size of the splitting increases with the increase of the atomic number of the chalcogenide, e.g. at the A point of the Brillouin zone from 0.06 eV to 0.31 eV with an almost linear dependence with x, as progressing from ZrS2 towards ZrSe2, respectively. Electronic structure calculations based on the density functional theory have been performed using the model of Tran–Blaha [1] and the modified version of the exchange potential proposed by Becke and Johnson [2] (TB–MBJ) both with and without spin-orbit (SO) coupling. The calculations show that the splitting is mainly due to spin-orbit coupling and the degeneracy of the valance bands is lifted

  4. Anisotropy of chemical bonding in semifluorinated graphite C2F revealed with angle-resolved X-ray absorption spectroscopy.

    Science.gov (United States)

    Okotrub, Alexander V; Yudanov, Nikolay F; Asanov, Igor P; Vyalikh, Denis V; Bulusheva, Lyubov G

    2013-01-22

    Highly oriented pyrolytic graphite characterized by a low misorientation of crystallites is fluorinated using a gaseous mixture of BrF(3) with Br(2) at room temperature. The golden-colored product, easily delaminating into micrometer-size transparent flakes, is an intercalation compound where Br(2) molecules are hosted between fluorinated graphene layers of approximate C(2)F composition. To unravel the chemical bonding in semifluorinated graphite, we apply angle-resolved near-edge X-ray absorption fine structure (NEXAFS) spectroscopy and quantum-chemical modeling. The strong angular dependence of the CK and FK edge NEXAFS spectra on the incident radiation indicates that room-temperature-produced graphite fluoride is a highly anisotropic material, where half of the carbon atoms are covalently bonded with fluorine, while the rest of the carbon atoms preserve π electrons. Comparison of the experimental CK edge spectrum with theoretical spectra plotted for C(2)F models reveals that fluorine atoms are more likely to form chains. This conclusion agrees with the atomic force microscopy observation of a chain-like pattern on the surface of graphite fluoride layers. PMID:23214423

  5. Spin orbit splitting in the valence bands of ZrS{sub x}Se{sub 2−x}: Angle resolved photoemission and density functional theory

    Energy Technology Data Exchange (ETDEWEB)

    Moustafa, Mohamed, E-mail: moustafa@physik.hu-berlin.de [Institut für Physik, Humboldt Universität zu Berlin, Newtonstr. 15, D-12489 Berlin (Germany); Faculty of Engineering, Pharos University in Alexandria, Canal El Mahmoudia Str., Alexandria (Egypt); Ghafari, Aliakbar; Paulheim, Alexander; Janowitz, Christoph; Manzke, Recardo [Institut für Physik, Humboldt Universität zu Berlin, Newtonstr. 15, D-12489 Berlin (Germany)

    2013-08-15

    Highlights: ► We performed high resolution ARPES on 1T–ZrS{sub x}Se{sub 2−x}. ► A characteristic splitting of the chalcogen p-derived VB along high symmetry directions was observed. ► The splitting size at the A point of the BZ is found to increase from 0.06 to 0.31 eV from ZrS{sub 2} towards ZrSe{sub 2}. ► Electronic structure calculations based on the DFT were performed using the model of TB–MBJ. ► The calculations show that the splitting is due to SO coupling of the valence bands. -- Abstract: Angle-resolved photoelectron spectroscopy using synchrotron radiation has been performed on 1T–ZrS{sub x}Se{sub 2−x}, where x varies from 0 to 2, in order to study the influence of the spin-orbit interaction in the valence bands. The crystals were grown by chemical vapour transport technique using Iodine as transport agent. A characteristic splitting of the chalcogen p-derived valence bands along high symmetry directions has been observed experimentally. The size of the splitting increases with the increase of the atomic number of the chalcogenide, e.g. at the A point of the Brillouin zone from 0.06 eV to 0.31 eV with an almost linear dependence with x, as progressing from ZrS{sub 2} towards ZrSe{sub 2}, respectively. Electronic structure calculations based on the density functional theory have been performed using the model of Tran–Blaha [1] and the modified version of the exchange potential proposed by Becke and Johnson [2] (TB–MBJ) both with and without spin-orbit (SO) coupling. The calculations show that the splitting is mainly due to spin-orbit coupling and the degeneracy of the valance bands is lifted.

  6. An experimental setup for high resolution 10.5 eV laser-based angle-resolved photoelectron spectroscopy using a time-of-flight electron analyzer.

    Science.gov (United States)

    Berntsen, M H; Götberg, O; Tjernberg, O

    2011-09-01

    We present an experimental setup for laser-based angle-resolved time-of-flight photoemission. Using a picosecond pulsed laser, photons of energy 10.5 eV are generated through higher harmonic generation in xenon. The high repetition rate of the light source, variable between 0.2 and 8 MHz, enables high photoelectron count rates and short acquisition times. By using a time-of-flight analyzer with angle-resolving capabilities, electrons emitted from the sample within a circular cone of up to ±15° can be collected. Hence, simultaneous acquisition of photoemission data for a complete area of the Brillouin zone is possible. The current photon energy enables bulk sensitive measurements, high angular resolution, and the resulting covered momentum space is large enough to enclose the entire Brillouin zone in cuprate high-T(c) superconductors. Fermi edge measurements on polycrystalline Au shows an energy resolution better than 5 meV. Data from a test measurement of the Au(111) surface state are presented along with measurements of the Fermi surface of the high-T(c) superconductor Bi(2)Sr(2)CaCu(2)O(8 + δ) (Bi2212). PMID:21974625

  7. Angle resolved x-ray photoelectron spectroscopy (ARXPS) analysis of lanthanum oxide for micro-flexography printing

    Energy Technology Data Exchange (ETDEWEB)

    Hassan, S., E-mail: suhaimihas@uthm.edu.my; Yusof, M. S., E-mail: mdsalleh@uthm.edu.my; Maksud, M. I., E-mail: midris1973@gmail.com [Faculty of Mechanical and Manufacturing Engineering, Universiti Tun Hussein Onn Malaysia, 86400 Batu Pahat, Johor (Malaysia); Embong, Z., E-mail: zaidi@uthm.edu.my [Faculty of Science, Technology and Human Development, Universiti Tun Hussein Onn Malaysia, 86400 Batu Pahat, Johor (Malaysia)

    2016-01-22

    Micro-flexography printing was developed in patterning technique from micron to nano scale range to be used for graphic, electronic and bio-medical device on variable substrates. In this work, lanthanum oxide (La{sub 2}O{sub 3}) has been used as a rare earth metal candidate as depositing agent. This metal deposit was embedded on Carbon (C) and Silica (Si) wafer substrate using Magnetron Sputtering technique. The choose of Lanthanum as a target is due to its wide application in producing electronic devices such as thin film battery and printed circuit board. The La{sub 2}O{sub 3} deposited on the surface of Si wafer substrate was then analyzed using Angle Resolve X-Ray Photoelectron Spectroscopy (ARXPS). The position for each synthetic component in the narrow scan of Lanthanum (La) 3d and O 1s are referred to the electron binding energy (eV). The La 3d narrow scan revealed that the oxide species of this particular metal is mainly contributed by La{sub 2}O{sub 3} and La(OH){sub 3}. The information of oxygen species, O{sup 2-} component from O 1s narrow scan indicated that there are four types of species which are contributed from the bulk (O{sup 2−}), two chemisorb component (La{sub 2}O{sub 3}) and La(OH){sub 3} and physisorp component (OH). Here, it is proposed that from the adhesive and surface chemical properties of La, it is suitable as an alternative medium for micro-flexography printing technique in printing multiple fine solid lines at nano scale. Hence, this paper will describe the capability of this particular metal as rare earth metal for use in of micro-flexography printing practice. The review of other parameters contributing to print fine lines will also be described later.

  8. Angle resolved x-ray photoelectron spectroscopy (ARXPS) analysis of lanthanum oxide for micro-flexography printing

    Science.gov (United States)

    Hassan, S.; Yusof, M. S.; Embong, Z.; Maksud, M. I.

    2016-01-01

    Micro-flexography printing was developed in patterning technique from micron to nano scale range to be used for graphic, electronic and bio-medical device on variable substrates. In this work, lanthanum oxide (La2O3) has been used as a rare earth metal candidate as depositing agent. This metal deposit was embedded on Carbon (C) and Silica (Si) wafer substrate using Magnetron Sputtering technique. The choose of Lanthanum as a target is due to its wide application in producing electronic devices such as thin film battery and printed circuit board. The La2O3 deposited on the surface of Si wafer substrate was then analyzed using Angle Resolve X-Ray Photoelectron Spectroscopy (ARXPS). The position for each synthetic component in the narrow scan of Lanthanum (La) 3d and O 1s are referred to the electron binding energy (eV). The La 3d narrow scan revealed that the oxide species of this particular metal is mainly contributed by La2O3 and La(OH)3. The information of oxygen species, O2- component from O 1s narrow scan indicated that there are four types of species which are contributed from the bulk (O2-), two chemisorb component (La2O3) and La(OH)3 and physisorp component (OH). Here, it is proposed that from the adhesive and surface chemical properties of La, it is suitable as an alternative medium for micro-flexography printing technique in printing multiple fine solid lines at nano scale. Hence, this paper will describe the capability of this particular metal as rare earth metal for use in of micro-flexography printing practice. The review of other parameters contributing to print fine lines will also be described later.

  9. Angle resolved x-ray photoelectron spectroscopy (ARXPS) analysis of lanthanum oxide for micro-flexography printing

    International Nuclear Information System (INIS)

    Micro-flexography printing was developed in patterning technique from micron to nano scale range to be used for graphic, electronic and bio-medical device on variable substrates. In this work, lanthanum oxide (La2O3) has been used as a rare earth metal candidate as depositing agent. This metal deposit was embedded on Carbon (C) and Silica (Si) wafer substrate using Magnetron Sputtering technique. The choose of Lanthanum as a target is due to its wide application in producing electronic devices such as thin film battery and printed circuit board. The La2O3 deposited on the surface of Si wafer substrate was then analyzed using Angle Resolve X-Ray Photoelectron Spectroscopy (ARXPS). The position for each synthetic component in the narrow scan of Lanthanum (La) 3d and O 1s are referred to the electron binding energy (eV). The La 3d narrow scan revealed that the oxide species of this particular metal is mainly contributed by La2O3 and La(OH)3. The information of oxygen species, O2- component from O 1s narrow scan indicated that there are four types of species which are contributed from the bulk (O2−), two chemisorb component (La2O3) and La(OH)3 and physisorp component (OH). Here, it is proposed that from the adhesive and surface chemical properties of La, it is suitable as an alternative medium for micro-flexography printing technique in printing multiple fine solid lines at nano scale. Hence, this paper will describe the capability of this particular metal as rare earth metal for use in of micro-flexography printing practice. The review of other parameters contributing to print fine lines will also be described later

  10. A study of angle-resolved photoemission extended fine structure as applied to the Ni 3p, Cu 3s, and Cu 3p core levels of the respective clean (111) surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Huff, W.R.A.; Moler, E.J.; Kellar, S.A. [Lawrence Berkeley National Lab., CA (United States)] [and others

    1997-04-01

    The first non-s initial state angle-resolved photoemission extended fine structure (ARPEFS) study of clean surfaces for the purpose of further understanding the technique is reported. The surface structure sensitivity of ARPEFS applied to clean surfaces and to arbitrary initial states is studied using normal photoemission data taken from the Ni 3p core levels of a Ni(111) single crystal and the Cu 3s and the Cu 3p core-levels of a Cu(111) single crystal. The Fourier transforms of these clean surface data are dominated by backscattering. Unlike the s initial state data, the p initial state data show a peak in the Fourier transform corresponding to in-plane scattering from the six nearest-neighbors to the emitter. Evidence was seen for single-scattering events from in the same plane as the emitters and double-scattering events. Using a newly developed, multiple-scattering calculation program, ARPEFS data from clean surfaces and from p initial states can be modeled to high precision. Although there are many layers of emitters when measuring photoemission from a clean surface, test calculations show that the ARPEFS signal is dominated by photoemission from atoms in the first two crystal layers. Thus, ARPEFS applied to clean surfaces is sensitive to surface reconstruction. The known contraction of the first two Cu(111) layers is confirmed. The best-fit calculation for clean Ni(111) indicates an expansion of the first two layers. To better understand the ARPEFS technique, the authors studied s and non-s initial state photoemission from clean metal surfaces.

  11. A study of angle-resolved photoemission extended fine structure as applied to the Ni 3p, Cu 3s, and Cu 3p core levels of the respective clean (111) surfaces

    International Nuclear Information System (INIS)

    The first non-s initial state angle-resolved photoemission extended fine structure (ARPEFS) study of clean surfaces for the purpose of further understanding the technique is reported. The surface structure sensitivity of ARPEFS applied to clean surfaces and to arbitrary initial states is studied using normal photoemission data taken from the Ni 3p core levels of a Ni(111) single crystal and the Cu 3s and the Cu 3p core-levels of a Cu(111) single crystal. The Fourier transforms of these clean surface data are dominated by backscattering. Unlike the s initial state data, the p initial state data show a peak in the Fourier transform corresponding to in-plane scattering from the six nearest-neighbors to the emitter. Evidence was seen for single-scattering events from in the same plane as the emitters and double-scattering events. Using a newly developed, multiple-scattering calculation program, ARPEFS data from clean surfaces and from p initial states can be modeled to high precision. Although there are many layers of emitters when measuring photoemission from a clean surface, test calculations show that the ARPEFS signal is dominated by photoemission from atoms in the first two crystal layers. Thus, ARPEFS applied to clean surfaces is sensitive to surface reconstruction. The known contraction of the first two Cu(111) layers is confirmed. The best-fit calculation for clean Ni(111) indicates an expansion of the first two layers. To better understand the ARPEFS technique, the authors studied s and non-s initial state photoemission from clean metal surfaces

  12. Pump laser-induced space-charge effects in HHG-driven time- and angle-resolved photoelectron spectroscopy

    Science.gov (United States)

    Oloff, L.-P.; Hanff, K.; Stange, A.; Rohde, G.; Diekmann, F.; Bauer, M.; Rossnagel, K.

    2016-06-01

    With the advent of ultrashort-pulsed extreme ultraviolet sources, such as free-electron lasers or high-harmonic-generation (HHG) sources, a new research field for photoelectron spectroscopy has opened up in terms of femtosecond time-resolved pump-probe experiments. The impact of the high peak brilliance of these novel sources on photoemission spectra, so-called vacuum space-charge effects caused by the Coulomb interaction among the photoemitted probe electrons, has been studied extensively. However, possible distortions of the energy and momentum distributions of the probe photoelectrons caused by the low photon energy pump pulse due to the nonlinear emission of electrons have not been studied in detail yet. Here, we systematically investigate these pump laser-induced space-charge effects in a HHG-based experiment for the test case of highly oriented pyrolytic graphite. Specifically, we determine how the key parameters of the pump pulse—the excitation density, wavelength, spot size, and emitted electron energy distribution—affect the measured time-dependent energy and momentum distributions of the probe photoelectrons. The results are well reproduced by a simple mean-field model, which could open a path for the correction of pump laser-induced space-charge effects and thus toward probing ultrafast electron dynamics in strongly excited materials.

  13. High-resolution soft-X-ray beamline ADRESS at Swiss Light Source for resonant inelastic X-ray scattering and angle-resolved photoelectron spectroscopies

    OpenAIRE

    Strocov, V. N.; Schmitt, T; U. Flechsig; Schmidt, T.; Imhof, A; Q. Chen; J. Raabe; Betemps, R.; Zimoch, D.; Krempasky, J.; A. Piazzalunga; X Wang; Grioni, M.; Patthey, L.

    2009-01-01

    We describe the concepts and technical realization of the high-resolution soft-X-ray beamline ADRESS operating in the energy range from 300 to 1600 eV and intended for Resonant Inelastic X-ray Scattering (RIXS) and Angle-Resolved Photoelectron Spectroscopy (ARPES). The photon source is an undulator of novel fixed-gap design where longitudinal movement of permanent magnetic arrays controls not only the light polarization (including circular and 0-180 deg rotatable linear polarizations) but als...

  14. High-resolution soft X-ray beamline ADRESS at the Swiss Light Source for resonant inelastic X-ray scattering and angle-resolved photoelectron spectroscopies

    OpenAIRE

    Strocov, V. N.; Schmitt, T; U. Flechsig; Schmidt, T.; Imhof, A; Q. Chen; J. Raabe; Betemps, R.; Zimoch, D.; Krempasky, J.; X Wang; Grioni, M.; A. Piazzalunga; Patthey, L.

    2010-01-01

    The concepts and technical realisation of the high-resolution soft X-ray beamline ADRESS operating in the energy range from 300 to 1600 eV and intended for resonant inelastic X-ray scattering (RIXS) and angle-resolved photoelectron spectroscopy (ARPES) are described. The photon source is an undulator of novel fixed-gap design where longitudinal movement of permanent magnetic arrays controls not only the light polarization (including circular and 0–180° rotatable linear polarizations) but also...

  15. Improvements in the contemporary photoemission spectroscopy implementation: A message to the ARPES community

    CERN Document Server

    Patil, Swapnil

    2015-01-01

    In this short communication, we highlight the deficiencies within the contemporary angle resolved photoemission spectroscopy (ARPES) implementations and point out few remedies towards their resolution. These deficiencies prohibit the current version of the ARPES technique from revealing the many-body physics of solids in its entirety. It is believed that the origin of these deficiencies lie within the prevailing data acquisition methods used for registering information from the photoelectron. It is argued that a slight change in the data acquisition methods would remedy the situation.

  16. Observation by resonant angle-resolved photoemission of a critical thickness for 2-dimensional electron gas formation in SrTiO{sub 3} embedded in GdTiO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Nemšák, S. [Department of Physics, University of California, 1 Shields Ave, Davis, California 95616 (United States); Materials Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Rd., Berkeley, California 94720 (United States); Peter-Grünberg-Institut PGI-6, Forschungszentrum Jülich, 52425 Jülich (Germany); Conti, G.; Palsson, G. K.; Conlon, C.; Fadley, C. S. [Department of Physics, University of California, 1 Shields Ave, Davis, California 95616 (United States); Materials Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Rd., Berkeley, California 94720 (United States); Cho, S.; Rault, J. E.; Avila, J.; Asensio, M.-C. [Synchrotron SOLEIL, L' Orme des Merisiers, Saint-Aubin, 91192 Gif sur Yvette Cedex (France); Jackson, C. A.; Moetakef, P.; Janotti, A.; Bjaalie, L.; Himmetoglu, B.; Van de Walle, C. G.; Stemmer, S. [Materials Department, University of California, Santa Barbara, California 93106-5050 (United States); Balents, L. [Department of Physics, University of California, Santa Barbara, California 93106-9530 (United States); Schneider, C. M. [Peter-Grünberg-Institut PGI-6, Forschungszentrum Jülich, 52425 Jülich (Germany)

    2015-12-07

    For certain conditions of layer thickness, the interface between GdTiO{sub 3} (GTO) and SrTiO{sub 3} (STO) in multilayer samples has been found to form a two-dimensional electron gas (2DEG) with very interesting properties including high mobilities and ferromagnetism. We have here studied two trilayer samples of the form [2 nm GTO/1.0 or 1.5 unit cells STO/10 nm GTO] as grown on (001) (LaAlO{sub 3}){sub 0.3}(Sr{sub 2}AlTaO{sub 6}){sub 0.7}, with the STO layer thicknesses being at what has been suggested is the critical thickness for 2DEG formation. We have studied these with Ti-resonant angle-resolved and angle-integrated photoemission and find that the spectral feature in the spectra associated with the 2DEG is present in the 1.5 unit cell sample, but not in the 1.0 unit cell sample. We also observe through core-level spectra additional states in Ti and Sr, with the strength of a low-binding-energy state for Sr being associated with the appearance of the 2DEG, and we suggest it to have an origin in final-state core-hole screening.

  17. Spatial structure determination of ({radical}3 x {radical}3)R30{degrees} and (1.5 x 1.5)R18{degrees}CO on Cu(111) using angle-resolved photoemission extended fine structure

    Energy Technology Data Exchange (ETDEWEB)

    Moler, E.J.; Kellar, S.A.; Huff, W.R.A. [Lawrence Berkeley National Lab., CA (United States)] [and others

    1997-04-01

    The authors report a study of the spatial structure of ({radical}3 x {radical}3)R30{degrees} (low coverage) and (1.5 x 1.5)R18{degrees} (intermediate coverage) CO adsorbed on Cu(111), using the Angle-Resolved Photoemission Extended Fine Structure (ARPEFS) technique at beamline 9.3.2 at the Advanced Light Source. The CO molecule adsorbs on an atop site for both adsorption phases. Full multiple-scattering spherical-wave (MSSW) calculations were used to extract the C-Cu. bond length and the first Cu-Cu layer spacing for each adsorption phase. The authors find that the C-Cu bond length remains unchanged with increasing coverage, but the 1st Cu-Cu layer spacing contracts at the intermediate coverage. They calculate the bending mode force constant in the (1.5 x 1.5)R18{degrees} phase to be K{sub {delta}} = 2.2 (1) x 10{sup {minus}12} dyne-cm/rad from their experimentally determined bond lengths combined with previously published infra-red absorption frequencies.

  18. Coexistence of two sharp-mode couplings and their unusual momentum dependence in the superconducting state of Bi2Sr2CaCu2O(8+δ) revealed by laser-based angle-resolved photoemission.

    Science.gov (United States)

    He, Junfeng; Zhang, Wentao; Bok, Jin Mo; Mou, Daixiang; Zhao, Lin; Peng, Yingying; He, Shaolong; Liu, Guodong; Dong, Xiaoli; Zhang, Jun; Wen, J S; Xu, Z J; Gu, G D; Wang, Xiaoyang; Peng, Qinjun; Wang, Zhimin; Zhang, Shenjin; Yang, Feng; Chen, Chuangtian; Xu, Zuyan; Choi, H-Y; Varma, C M; Zhou, X J

    2013-09-01

    High-resolution laser-based angle-resolved photoemission measurements have been carried out on Bi2Sr2CaCu2O(8+δ) (Bi2212) superconductors to investigate momentum dependence of electron coupling with collective excitations (modes). Two coexisting energy scales are clearly revealed over a large momentum space for the first time in the superconducting state of the overdoped Bi2212 superconductor. These two energy scales exhibit distinct momentum dependence: one keeps its energy near 78 meV over a large momentum space while the other changes its energy from ∼40  meV near the antinodal region to ∼70  meV near the nodal region. These observations provide a new picture on momentum evolution of electron-boson coupling in Bi2212 that electrons are coupled with two sharp modes simultaneously over a large momentum space in the superconducting states. Their unusual momentum dependence poses a challenge to our current understanding of electron-mode-coupling and its role for high-temperature superconductivity in cuprate superconductors. PMID:25166699

  19. Observation by resonant angle-resolved photoemission of a critical thickness for 2-dimensional electron gas formation in SrTiO3 embedded in GdTiO3

    International Nuclear Information System (INIS)

    For certain conditions of layer thickness, the interface between GdTiO3 (GTO) and SrTiO3 (STO) in multilayer samples has been found to form a two-dimensional electron gas (2DEG) with very interesting properties including high mobilities and ferromagnetism. We have here studied two trilayer samples of the form [2 nm GTO/1.0 or 1.5 unit cells STO/10 nm GTO] as grown on (001) (LaAlO3)0.3(Sr2AlTaO6)0.7, with the STO layer thicknesses being at what has been suggested is the critical thickness for 2DEG formation. We have studied these with Ti-resonant angle-resolved and angle-integrated photoemission and find that the spectral feature in the spectra associated with the 2DEG is present in the 1.5 unit cell sample, but not in the 1.0 unit cell sample. We also observe through core-level spectra additional states in Ti and Sr, with the strength of a low-binding-energy state for Sr being associated with the appearance of the 2DEG, and we suggest it to have an origin in final-state core-hole screening

  20. Phenomenological model for the normal-state angle-resolved photoemission spectroscopy line shapes of high-temperature superconductors.

    Science.gov (United States)

    Matsuyama, Kazue; Gweon, G-H

    2013-12-13

    Providing a full theoretical description of the single-particle spectral function observed for high-temperature superconductors in the normal state is an important goal, yet unrealized. Here, we present a phenomenological model approaching towards this goal. The model results from implementing key phenomenological improvement in the so-called extremely correlated Fermi-liquid model. The model successfully describes the dichotomy of the spectral function as functions of momentum and energy and fits data for different materials (Bi2Sr2CaCu2O8+δ and La2-xSrxCuO4), with an identical set of intrinsic parameters. The current analysis goes well beyond the prevalent analysis of the spectral function as a function of momentum alone. PMID:24483680

  1. Molar concentration-depth profiles at the solution surface of a cationic surfactant reconstructed with angle resolved X-ray photoelectron spectroscopy

    International Nuclear Information System (INIS)

    In the current work, we first reconstructed the molar fraction-depth profiles of cation and anion near the surface of tetrabutylammonium iodide dissolved in formamide by a refined calculation procedure, based on angle resolved X-ray photoelectron spectroscopy experiments. In this calculation procedure, both the transmission functions of the core levels and the inelastic mean free paths of the photoelectrons have been taken into account. We have evaluated the partial molar volumes of surfactant and solvent by the densities of such solutions with different bulk concentrations. With those partial molar volumes, the molar concentration-depth profiles of tetrabutylammonium ion and iodide ion were determined. The surface excesses of both surfactant ions were then achieved directly by integrating these depth profiles. The anionic molar concentration-depth profiles and surface excesses have been compared with their counterparts determined by neutral impact ion scattering spectroscopy. The comparisons exhibit good agreements. Being capable of determining molar concentration-depth profiles of surfactant ions by core levels with different kinetic energies may extend the applicable range of ARXPS in investigating solution surfaces.

  2. Angle-resolved photoelectron spectroscopy of the valence orbitals of SiCl4 as a function of photon energy from 14 to 80 eV

    International Nuclear Information System (INIS)

    Angle-resolved photoelectron spectroscopy coupled with synchrotron radiation have been used to measure partial cross sections and angular distribution parameters, β, from a photon energy of 14 to 80 eV for SiCl4. Parallel to these measurements, calculations have been made using the continuum multiple scattering Xα method. The results have been examined, primarily in terms of the phenomena of the Cooper minimum and shape resonances. Minima in both the cross sections and β values were found for each of the first five orbitals of SiCl4: 2t1, 8t2, 2e, 7t2, and 7a1. These minima were examined for their energy positions and, in the case of the β values, the depth of the minimum. Shape resonances were calculated in the photoionization of each of the orbitals, and a number of experimental features due to shape resonances are identified. The results, both experimental and theoretical, are compared with earlier work on CC14

  3. Angle-resolved photoelectron spectroscopy of Cl2 as a function of photon energy from 18 to 70 eV

    International Nuclear Information System (INIS)

    Angle-resolved photoelectron spectroscopy using synchrotron radiation has been carried out on gaseous chlorine as a function of photon energy from 18 to 70 eV. From this data the partial cross sections and angular distribution parameter ν have been derived for the first three orbitals. For the lone pair orbitals 2π/sub g/ and 2π/sub u/, distinct minima are found in both the partial cross sections and ν values in the region of photoelectron energies from 30 to 40 eV. Less well-defined minima are also seen in the case photoionization for the nonlone pair orbital 5sigma/sub g/. These features are believed related to the Cooper minimum that arises from an atomic 3p subshell. Calculations have also been carried out on the partial cross sections and ν values using the multiple scattering Xα method. Comparison with experiment gives excellent qualitative agreement with regard to the ''Cooper minimum.'' The nature of the Cooper minimum in molecules and its usefulness in understanding photoelectron dynamics is discussed

  4. High-resolution soft-X-ray beamline ADRESS at Swiss Light Source for resonant inelastic X-ray scattering and angle-resolved photoelectron spectroscopies

    CERN Document Server

    Strocov, V N; Flechsig, U; Schmidt, T; Imhof, A; Chen, Q; Raabe, J; Betemps, R; Zimoch, D; Krempasky, J; Piazzalunga, A; Wang, X; Grioni, M; Patthey, L

    2009-01-01

    We describe the concepts and technical realization of the high-resolution soft-X-ray beamline ADRESS operating in the energy range from 300 to 1600 eV and intended for Resonant Inelastic X-ray Scattering (RIXS) and Angle-Resolved Photoelectron Spectroscopy (ARPES). The photon source is an undulator of novel fixed-gap design where longitudinal movement of permanent magnetic arrays controls not only the light polarization (including circular and 0-180 deg rotatable linear polarizations) but also the energy without changing the gap. The beamline optics is based on the well-established scheme of plane grating monochromator (PGM) operating in collimated light. The ultimate resolving power E/dE is above 33000 at 1 keV photon energy. The choice of blazed vs lamellar gratings and optimization of their profile parameters is described. Due to glancing angles on the mirrors as well as optimized groove densities and profiles of the gratings, high photon flux is achieved up to 1.0e13 photons/s/0.01%BW at 1 keV. Ellipsoida...

  5. Photoemission spectroscopy of composition and doping of high-temperature superconductors

    International Nuclear Information System (INIS)

    The authors present a systematic study of compositional and doping effects in Bi2Sr2CaCu2Oy high-Tc superconductors performed with photoemission spectroscopy. The study has been extended to Y-doping and I-intercalation of Bi-2212 high quality single crystals. The main results is that each type of dopant affects the crystal composition in its own way. Yttrium affects the Ca and Sr planes, producing a charge transfer into the CuO planes. For I-doping, they find that the main effect is a change in the interplanar distance, but X-ray Photoemission Spectroscopy (XPS) allows to see that the decrease of the critical temperature is not caused only by a structure parameter, but by a over-doping of copper planes (hole doping). They performed also a comparative study by Angle Resolved Ultraviolet Photoemission Spectroscopy [ARUPS] between this sample and an oxygen annealed specimen. XPS Cu2p core level data establish that the hole concentration in the CuO2 planes is essentially the same for these two kinds of samples. ARUPS measurements show that electronic structure of the normal states near the Fermi level has been strongly affected by iodine intercalation

  6. High-resolution soft X-ray beamline ADRESS at the Swiss Light Source for resonant inelastic X-ray scattering and angle-resolved photoelectron spectroscopies.

    Science.gov (United States)

    Strocov, V N; Schmitt, T; Flechsig, U; Schmidt, T; Imhof, A; Chen, Q; Raabe, J; Betemps, R; Zimoch, D; Krempasky, J; Wang, X; Grioni, M; Piazzalunga, A; Patthey, L

    2010-09-01

    The concepts and technical realisation of the high-resolution soft X-ray beamline ADRESS operating in the energy range from 300 to 1600 eV and intended for resonant inelastic X-ray scattering (RIXS) and angle-resolved photoelectron spectroscopy (ARPES) are described. The photon source is an undulator of novel fixed-gap design where longitudinal movement of permanent magnetic arrays controls not only the light polarization (including circular and 0-180 degrees rotatable linear polarizations) but also the energy without changing the gap. The beamline optics is based on the well established scheme of plane-grating monochromator operating in collimated light. The ultimate resolving power E/DeltaE is above 33000 at 1 keV photon energy. The choice of blazed versus lamellar gratings and optimization of their profile parameters is described. Owing to glancing angles on the mirrors as well as optimized groove densities and profiles of the gratings, the beamline is capable of delivering high photon flux up to 1 x 10(13) photons s(-1) (0.01% BW)(-1) at 1 keV. Ellipsoidal refocusing optics used for the RIXS endstation demagnifies the vertical spot size down to 4 microm, which allows slitless operation and thus maximal transmission of the high-resolution RIXS spectrometer delivering E/DeltaE > 11000 at 1 keV photon energy. Apart from the beamline optics, an overview of the control system is given, the diagnostics and software tools are described, and strategies used for the optical alignment are discussed. An introduction to the concepts and instrumental realisation of the ARPES and RIXS endstations is given. PMID:20724785

  7. Signature of quantum criticality in photoemission spectroscopy.

    Science.gov (United States)

    Klein, M; Nuber, A; Reinert, F; Kroha, J; Stockert, O; van Löhneysen, H

    2008-12-31

    A quantum phase transition in a heavy-fermion compound may destroy the Fermi-liquid ground state. However, the conditions for this breakdown have remained obscure. We report the first direct investigation of heavy quasiparticle formation and breakdown in the canonical system CeCu(6-x)Au(x) by ultraviolet photoemission spectroscopy at elevated temperatures without the complications of lattice coherence. Surprisingly, the single-ion Kondo energy scale T(K) exhibits an abrupt step near the quantum critical Au concentration of x(c) = 0.1. We show theoretically that this step is expected from a highly nonlinear renormalization of the local spin coupling at each Ce site, induced by spin fluctuations on neighboring sites. It provides a general high-temperature indicator for heavy-fermion quasiparticle breakdown at a quantum phase transition. PMID:19437657

  8. Internal Photoemission Spectroscopy of 2-D Materials

    Science.gov (United States)

    Nguyen, Nhan; Li, Mingda; Vishwanath, Suresh; Yan, Rusen; Xiao, Shudong; Xing, Huili; Cheng, Guangjun; Hight Walker, Angela; Zhang, Qin

    Recent research has shown the great benefits of using 2-D materials in the tunnel field-effect transistor (TFET), which is considered a promising candidate for the beyond-CMOS technology. The on-state current of TFET can be enhanced by engineering the band alignment of different 2D-2D or 2D-3D heterostructures. Here we present the internal photoemission spectroscopy (IPE) approach to determine the band alignments of various 2-D materials, in particular SnSe2 and WSe2, which have been proposed for new TFET designs. The metal-oxide-2-D semiconductor test structures are fabricated and characterized by IPE, where the band offsets from the 2-D semiconductor to the oxide conduction band minimum are determined by the threshold of the cube root of IPE yields as a function of photon energy. In particular, we find that SnSe2 has a larger electron affinity than most semiconductors and can be combined with other semiconductors to form near broken-gap heterojunctions with low barrier heights which can produce a higher on-state current. The details of data analysis of IPE and the results from Raman spectroscopy and spectroscopic ellipsometry measurements will also be presented and discussed.

  9. Angle-resolved photoelectron spectroscopy studies of the many-body effects in the electronic structure of high-Tc cuprates

    International Nuclear Information System (INIS)

    In the present work some steps are done towards understanding the anomalous effects observed in the single-particle excitation spectra of cuprates. First, the electronic properties of BSCCO are considered. The main result of this part of the work is a model of the Green's function that is later used for calculating the two-particle excitation spectrum. Then, the matrix element effects in the photoemission spectra of cuprates are discussed. After a general introduction to the problem, the thesis focuses on the recently discovered anomalous behavior of the ARPES spectra that partially originates from the momentum-dependent photoemission matrix element. The momentum- and excitation energy dependence of the anomalous high-energy dispersion, termed ''waterfalls'', is covered in full detail. Understanding the role of the matrix element effects in this phenomenon proves crucial, as they obstruct the view of the underlying excitation spectrum that is of indisputable interest. For the optimally doped bilayer Bi-based cuprate, the renormalized two-particle correlation function in the superconducting state is calculated from ARPES data within an itinerant model based on the random phase approximation (RPA). (orig.)

  10. Angle-resolved photoelectron spectroscopy studies of the many-body effects in the electronic structure of high-T{sub c} cuprates

    Energy Technology Data Exchange (ETDEWEB)

    Inosov, Dmytro S.

    2008-06-18

    In the present work some steps are done towards understanding the anomalous effects observed in the single-particle excitation spectra of cuprates. First, the electronic properties of BSCCO are considered. The main result of this part of the work is a model of the Green's function that is later used for calculating the two-particle excitation spectrum. Then, the matrix element effects in the photoemission spectra of cuprates are discussed. After a general introduction to the problem, the thesis focuses on the recently discovered anomalous behavior of the ARPES spectra that partially originates from the momentum-dependent photoemission matrix element. The momentum- and excitation energy dependence of the anomalous high-energy dispersion, termed ''waterfalls'', is covered in full detail. Understanding the role of the matrix element effects in this phenomenon proves crucial, as they obstruct the view of the underlying excitation spectrum that is of indisputable interest. For the optimally doped bilayer Bi-based cuprate, the renormalized two-particle correlation function in the superconducting state is calculated from ARPES data within an itinerant model based on the random phase approximation (RPA). (orig.)

  11. Angle-resolved X-ray photoelectron spectroscopy of topmost surface for LaNiO 3 thin film grown on SrTiO 3 substrate by laser molecular beam epitaxy

    Science.gov (United States)

    Chen, P.; Xu, S. Y.; Lin, J.; Ong, C. K.; Cui, D. F.

    1999-01-01

    The LaNiO 3 thin film was grown on SrTiO 3 (001) substrate by computer-controlled laser molecular beam epitaxy (laser MBE). In situ monitoring of the growing film surface was performed with a reflection high energy electron diffraction (RHEED). Angle-resolved X-ray photoelectron spectroscopy (ARXPS) indicated that the terminating plane of the LaNiO 3 film was the LaO atomic plane, and the SrTiO 3 (001) surfaces of as-supplied substrate as well as HF-pretreated substrate were predominantly terminated with TiO atomic plane. The structural conversion of the topmost atomic layer from NiO to LaO occurred during the LaNiO 3 epitaxial growth process.

  12. Complete Fermi Surface and Surface State in WTe2 Revealed by High-Resolution Laser-Based Angle-Resolved Photoemission Spectroscopy

    Science.gov (United States)

    Wang, Chenlu; Zhang, Yan; Liu, Guodong; Mao, Zhiqiang; He, Shaolong; Zhao, Lin; Chen, Chuangtian; Xu, Zuyan; Zhou, Xingjiang

    WTe2, an unique transition metal dichalcogenide, attracts considerable attention recently, which shows an extremely large magnetoresistance (MR) with no saturation under very high field. In this talk, we will present our high resolution laser-ARPES study on WTe2. Our distinctive ARPES system is equipped with the VUV laser and the time-of-flight (TOF) electron energy analyzer, being featured by super-high energy resolution, simultaneous data acquisition for two-dimensional momentum space and much reduced nonlinearity effect. With this advanced apparatus, the very high quality of electronic structure data are obtained for WTe2 which gives a full picture of the Fermi surface. Meanwhile, the obtained systematic temperature dependence of its electronic state leads us to a better understanding on the origin of large magnetoresistance in WTe2.

  13. Electronic Structure of Transition Metal Dichalcogenides PdTe2 and Cu0.05PdTe2 Superconductors Obtained by Angle-Resolved Photoemission Spectroscopy

    OpenAIRE

    Liu, Yan; Zhao, Jianzhou; Yu, Li; Lin, Chengtian; Hu, Cheng; Liu, Defa; Peng, Yingying; Xie, Zhuojin; He, Junfeng; Chen, Chaoyu; Feng, Ya; Yi, Hemian; Liu, Xu; Zhao, Lin; He, Shaolong

    2015-01-01

    The layered transition metal chalcogenides have been a fertile land in solid state physics for many decades. Various MX2-type transition metal dichalcogenides, such as WTe2, IrTe2, and MoS2, have triggered great attention recently, either for the discovery of novel phenomena or some extreme or exotic physical properties, or for their potential applications. PdTe2 is a superconductor in the class of transition metal dichalcogenides, and superconductivity is enhanced in its Cu-intercalated form...

  14. A spin- and angle-resolving photoelectron spectrometer

    International Nuclear Information System (INIS)

    A new type of hemispherical electron energy analyzer that permits angle and spin resolved photoelectron spectroscopy has been developed. The analyzer permits standard angle resolved spectra to be recorded with a two-dimensional detector in parallel with spin detection using a mini-Mott polarimeter. General design considerations as well as technical solutions are discussed and test results from the Au(111) surface state are presented.

  15. Attosecond angle-resolved photoelectron spectroscopy

    International Nuclear Information System (INIS)

    We report experiments on the characterization of a train of attosecond pulses obtained by high-harmonic generation, using mixed-color (XUV+IR) atomic two-photon ionization and electron detection on a velocity map imaging detector. We demonstrate that the relative phase of the harmonics is encoded both in the photoelectron yield and the angular distribution as a function of XUV-IR time delay, thus making the technique suitable for the detection of single attosecond pulses. The timing of the attosecond pulse with respect to the field oscillation of the driving laser critically depends on the target gas used to generate the harmonics

  16. X-ray photoemission spectroscopy study of zirconium hydride

    International Nuclear Information System (INIS)

    X-ray photoemission spectroscopy (XPS) measurements are reported for ZrH/sub 1.65/ and Zr metal. The valence-band measurements are compared with available band-theory density-of-states calculations for the metal and hydride. The hydride spectrum differs significantly from the metal spectrum. Most important, a strong peak associated with hydrogen s electrons appears approximately 7 eV below the Fermi level. XPS measurements of Zr 4p core levels show a binding-energy shift of 1 eV between Zr metal and ZrH/sub 1.65/. It is argued that this shift results from charge readjustment in the vicinity of the Zr site. With the addition of hydrogen, net charge must be transferred from the Zr site to the hydrogen site. A charge-density analysis based on simplified cluster calculations is presented

  17. X-ray photoemission spectroscopy study of hexavalent uranium compounds

    International Nuclear Information System (INIS)

    The electronic structure of the outer occupied levels of a series of hexavalent uranium (predominately uranyl) compounds was studied using x-ray photoemission spectroscopy (XPS). The changes in the spectral features of the outer occupied levels with the variation of the uranium-oxygen bond lengths (1.7--2.1 A) are systematically investigated. Previously unexplained spectral structure has been found to result from ligand-field splitting of the occupied U 6p3/2 levels. The XPS results are compared with predictions of a relativistic molecular-cluster calculation and with the results of a simple point-charge crystal-field model. When the crystalline electric fields generated by both the primary and secondary ligands are taken into consideration, excellent quantitative agreement is obtained between the XPS data and the molecular-cluster results with no parameter adjustment

  18. Transmission function calibration of an angular resolved analyzer for X-ray photoemission spectroscopy: Theory vs experiment

    International Nuclear Information System (INIS)

    Highlights: • A calibration method for the transmission function of modern XPS analyser is shown. • This method can be applied to any soft X-ray photoemission setup. • Ray tracing calculations well agree with experimental results. • A fine calibration is carried out through variable photon energy XPS. • An escape depth correction must be included in the calibration process. - Abstract: In order to achieve the most accurate quantification results in an X-ray photoelectron spectroscopy (XPS) experiment, a fine calibration of the analyzer response is required. In this work an experimental characterization of a modern angle-resolved analyzer, carried out with a unfocused and a highly collimated synchrotron source, is shown. The transmission function is extrapolated from the discrepancy between experimental and theoretically predicted XPS peak areas; the influence of different sensitivity factors and of the escape depth correction on the expected values is also discussed. The analyzer response and the theoretical approach are then tested against energy dispersive XPS measurements (EDXPS). These results are finally compared with TF calculated on the basis of an high accuracy electron ray tracing code, also described in this work

  19. A high-efficiency spin-resolved photoemission spectrometer combining time-of-flight spectroscopy with exchange-scattering polarimetry

    Energy Technology Data Exchange (ETDEWEB)

    Jozwiak, Chris M.; Graff, Jeff; Lebedev, Gennadi; Andresen, Nord; Schmid, Andreas; Fedorov, Alexei; El Gabaly, Farid; Wan, Weishi; Lanzara, Alessandra; Hussain, Zahid

    2010-04-13

    We describe a spin-resolved electron spectrometer capable of uniquely efficient and high energy resolution measurements. Spin analysis is obtained through polarimetry based on low-energy exchange scattering from a ferromagnetic thin-film target. This approach can achieve a similar analyzing power (Sherman function) as state-of-the-art Mott scattering polarimeters, but with as much as 100 times improved efficiency due to increased reflectivity. Performance is further enhanced by integrating the polarimeter into a time-of-flight (TOF) based energy analysis scheme with a precise and flexible electrostatic lens system. The parallel acquisition of a range of electron kinetic energies afforded by the TOF approach results in an order of magnitude (or more) increase in efficiency compared to hemispherical analyzers. The lens system additionally features a 90 degrees bandpass filter, which by removing unwanted parts of the photoelectron distribution allows the TOF technique to be performed at low electron drift energy and high energy resolution within a wide range of experimental parameters. The spectrometer is ideally suited for high-resolution spin- and angle-resolved photoemission spectroscopy (spin-ARPES), and initial results are shown. The TOF approach makes the spectrometer especially ideal for time-resolved spin-ARPES experiments.

  20. X-ray Photoemission Spectroscopy Studies of Cesium Antimonide Photocathodes for Photoinjector Applications

    Science.gov (United States)

    Martini, Irene; Chevallay, Eric; Fedosseev, Valentin; Hessler, Christoph; Neupert, Holger; Nistor, Valentin; Taborelli, Mauro

    Within the CLIC (Compact Linear Collider) project, feasibility studies of a photoinjector option for the drive beam as an alternative to its baseline design using a thermionic electron gun (Geschonke et al. [1]) are on-going. This R&D program covers both the laser and the photocathode side. Cesium antimonide cathodes were produced at CERN by co-deposition onto copper substrates and characterized by photoemission and by XPS (X-ray Photoemission Spectroscopy) analysis. A systematic study on newly produced and used photocathodes was conducted in order to correlate the surface composition to the photoemissive properties.

  1. Low-Temperature and High-Energy-Resolution Laser Photoemission Spectroscopy

    Science.gov (United States)

    Shimojima, Takahiro; Okazaki, Kozo; Shin, Shik

    2015-07-01

    We present a review on the developments in the photoemission spectrometer with a vacuum ultraviolet laser at Institute for Solid State Physics at the University of Tokyo. The advantages of high energy resolution, high cooling ability, and bulk sensitivity enable applications with a wide range of materials. We introduce some examples of fine electronic structures detected by laser photoemission spectroscopy and discuss the prospects of research on low-transition-temperature superconductors exhibiting unconventional superconductivity.

  2. Low-Temperature and High-Energy-Resolution Laser Photoemission Spectroscopy

    OpenAIRE

    Shimojima, Takahiro; Okazaki, Kozo; Shin, Shik

    2016-01-01

    We present a review on the developments in the photoemission spectrometer with a vacuum ultraviolet laser at Institute for Solid State Physics at the University of Tokyo. The advantages of high energy resolution, high cooling ability, and bulk sensitivity enable applications with a wide range of materials. We introduce some examples of fine electronic structures detected by laser photoemission spectroscopy and discuss the prospects of research on low-transition-temperature superconductors exh...

  3. Characterization of Catechins in Water by Photoemission Yield Spectroscopy in Air.

    Science.gov (United States)

    Yamashita, Daisuke; Ishizaki, Atsushi

    2016-01-01

    Photoemission yield spectroscopy in air (PYSA) was applied for the characterization of catechins in water in ambient conditions. According to the results of measurements on aqueous solutions of epigallocatechin gallate (EGCg) of various concentrations, the photoemission yield is almost proportional to the concentration of EGCg. Contrarily, the threshold energy of photoemission, EPET, is almost constant at 5.46 ± 0.02 eV. Moreover, we measured aqueous solutions of epicatechin (EC), epigallocatechin (EGC), and epicatechin gallate (ECg). The values of EPET of EC, EGC, ECg were estimated to be 5.72 ± 0.02, 5.68 ± 0.01, and 5.45 ± 0.02 eV, respectively, and a dependence on the molecular structure was found. Furthermore, changes in the photoemission yield spectra of heated EGCg were well explained by molecular orbital calculations on the basis of an assumption of epimerization. PMID:27169659

  4. Vacuum space charge effect in laser-based solid-state photoemission spectroscopy

    OpenAIRE

    Graf, J; Hellmann, S; Jozwiak, C.; Smallwood, C. L.; Hussain, Z.; Kaindl, R. A.; Kipp, L.; Rossnagel, K.; Lanzara, A.

    2010-01-01

    We report a systematic measurement of the space charge effect observed in the few-ps laser pulse regime in laser-based solid-state photoemission spectroscopy experiments. The broadening and the shift of a gold Fermi edge as a function of spot size, laser power, and emission angle are characterized for pulse lengths of 6 ps and 6 eV photon energy. The results are used as a benchmark for an $N$-body numerical simulation and are compared to different regimes used in photoemission spectroscopy. T...

  5. Vacuum space charge effect in laser-based solid-state photoemission spectroscopy

    OpenAIRE

    Graf, Jeff

    2010-01-01

    We report a systematic measurement of the space charge effect observed in the few-ps laser pulse regime in laser-based solid-state photoemission spectroscopy experiments. The broadening and the shift of a gold Fermi edge as a function of spot size, laser power, and emission angle are characterized for pulse lengths of 6 ps and 6 eV photon energy. The results are used as a benchmark for an N-body numerical simulation and are compared to different regimes used in photoemission spectroscopy. The...

  6. Tachometer Derived From Brushless Shaft-Angle Resolver

    Science.gov (United States)

    Howard, David E.; Smith, Dennis A.

    1995-01-01

    Tachometer circuit operates in conjunction with brushless shaft-angle resolver. By performing sequence of straightforward mathematical operations on resolver signals and utilizing simple trigonometric identity, generates voltage proportional to rate of rotation of shaft. One advantage is use of brushless shaft-angle resolver as main source of rate signal: no brushes to wear out, no brush noise, and brushless resolvers have proven robustness. No switching of signals to generate noise. Another advantage, shaft-angle resolver used as shaft-angle sensor, tachometer input obtained without adding another sensor. Present circuit reduces overall size, weight, and cost of tachometer.

  7. Angle-resolved cathodoluminescence imaging polarimetry

    CERN Document Server

    Osorio, Clara I; Brenny, Benjamin; Polman, Albert; Koenderink, A Femius

    2015-01-01

    Cathodoluminescence spectroscopy (CL) allows characterizing light emission in bulk and nanostructured materials and is a key tool in fields ranging from materials science to nanophotonics. Previously, CL measurements focused on the spectral content and angular distribution of emission, while the polarization was not fully determined. Here we demonstrate a technique to access the full polarization state of the cathodoluminescence emission, that is the Stokes parameters as a function of the emission angle. Using this technique, we measure the emission of metallic bullseye nanostructures and show that the handedness of the structure as well as nanoscale changes in excitation position induce large changes in polarization ellipticity and helicity. Furthermore, by exploiting the ability of polarimetry to distinguish polarized from unpolarized light, we quantify the contributions of different types of coherent and incoherent radiation to the emission of a gold surface, silicon and gallium arsenide bulk semiconductor...

  8. Bulk-Sensitive Photoemission Spectroscopy of TlFe2Se2

    International Nuclear Information System (INIS)

    We have investigated the electronic structures of the parent compound of an iron chalcogenide superconductor TlFe2Se2 by bulk-sensitive photoemission spectroscopy (PES). Valence-band PES demonstrates the energy gap opening at the Fermi level due to the shift of Fe 3d state to the higher binding energy side as compared to the calculated density of states, being consistent with the insulating behaviour in transport measurements.

  9. Retention Characteristics of CBTi144 Thin Films Explained by Means of X-Ray Photoemission Spectroscopy

    OpenAIRE

    G. Biasotto; A.Z. Simões; C. S. Riccardi; M.A. Zaghete; E. Longo; J. A. Varela

    2010-01-01

    CaBi4Ti4O15 (CBTi144) thin films were grown on Pt/Ti/SiO2/Si substrates using a soft chemical solution and spin-coating method. Structure and morphology of the films were characterized by the X-ray Diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), Raman analysis, X-ray photoemission spectroscopy (XPS), and transmission electron microscopy (TEM). The films present a single phase of layered-structured perovskite with polar axis orient. The a/b-axis orientation of the ferroelec...

  10. Rb-intercalated C{sub 60} compounds studied by photoemission spectroscopies

    Energy Technology Data Exchange (ETDEWEB)

    Brambilla, A. [INFM - Dipartimento di Fisica, Politecnico di Milano, p.za L. da Vinci 32, I-20133 Milan (Italy)]. E-mail: alberto.brambilla@polimi.it; Giovanelli, L. [Sincrotrone Trieste S.C.p.A., Strada Statale 14, Km 163.5, I-34012 Basovizza, Trieste (Italy); Vilmercati, P. [Sincrotrone Trieste S.C.p.A., Strada Statale 14, Km 163.5, I-34012 Basovizza, Trieste (Italy); Cattoni, A. [INFM - Dipartimento di Fisica, Politecnico di Milano, p.za L. da Vinci 32, I-20133 Milan (Italy); Biagioni, P. [INFM - Dipartimento di Fisica, Politecnico di Milano, p.za L. da Vinci 32, I-20133 Milan (Italy); Goldoni, A. [Sincrotrone Trieste S.C.p.A., Strada Statale 14, Km 163.5, I-34012 Basovizza, Trieste (Italy); Finazzi, M. [INFM - Dipartimento di Fisica, Politecnico di Milano, p.za L. da Vinci 32, I-20133 Milan (Italy); Duo, L. [INFM - Dipartimento di Fisica, Politecnico di Milano, p.za L. da Vinci 32, I-20133 Milan (Italy)

    2005-06-15

    We report on a combined photoemission and inverse photoemission spectroscopy analysis on Rb{sub x}C{sub 60} compounds with different stoichiometries (0-bar x-bar 6). Apart from shifts and broadening of the spectral features associated to the different phase formed, we observe in the RbC{sub 60} phase the presence of the highest occupied molecular orbital (HOMO) shoulder and of its symmetric (with respect to the Fermi level) empty state. According to calculations, the metallicity of this phase and the presence of these electronic states may be taken as a fingerprint of the interplay between electron-electron and electron-phonon interactions in determining the electronic behavior of alkali metal fullerides.

  11. Photoemission Spectroscopy Characterization of Attempts to Deposit MoO2 Thin Film

    Directory of Open Access Journals (Sweden)

    Irfan

    2011-01-01

    Full Text Available Attempts to deposit molybdenum dioxide (MoO2 thin films have been described. Electronic structure of films, deposited by thermal evaporation of MoO2 powder, had been investigated with ultraviolet photoemission and X-ray photoemission spectroscopy (UPS and XPS. The thermally evaporated films were found to be similar to the thermally evaporated MoO3 films at the early deposition stage. XPS analysis of MoO2 powder reveals presence of +5 and +6 oxidation states in Mo 3d core level along with +4 state. The residue of MoO2 powder indicates substantial reduction in higher oxidation states while keeping +4 oxidation state almost intact. Interface formation between chloroaluminum phthalocyanine (AlPc-Cl and the thermally evaporated film was also investigated.

  12. Photoemission and ferromagnetism

    International Nuclear Information System (INIS)

    Photoemission is a well established technique for the study of the electronic structure of atoms and solids. In particular, angle-resolved photoemission has been used extensively to map the band structure of clean and adsorbate covered surfaces, both metal and semiconductor. Extending the technique by measuring the spin of the photoemitted electrons allows the possibility of examining the exchange split band structures characterizing ferromagnetic systems. Here the technique becomes particularly useful in the study of the magnetic properties of surfaces, thin films and associated interfaces

  13. Common Electronic Features and Electronic Nematicity in Parent Compounds of Iron-Based Superconductors and FeSe/SrTiO3 Films Revealed by Angle-Resolved Photoemission Spectroscopy

    Science.gov (United States)

    De-Fa, Liu; Lin, Zhao; Shao-Long, He; Yong, Hu; Bing, Shen; Jian-Wei, Huang; Ai-Ji, Liang; Yu, Xu; Xu, Liu; Jun-Feng, He; Dai-Xiang, Mou; Shan-Yu, Liu; Hai-Yun, Liu; Guo-Dong, Liu; Wen-Hao, Zhang; Fang-Sen, Li; Xu-Cun, Ma; Qi-Kun, Xue; Xian-Hui, Chen; Gen-Fu, Chen; Li, Yu; Jun, Zhang; Zu-Yan, Xu; Chuang-Tian, Chen; Xing-Jiang, Zhou

    2016-07-01

    Not Available Supported by the National Natural Science Foundation of China under Grant Nos 11190022, 11334010 and 11534007, the National Basic Research Program of China under Grant No 2015CB921000, and the Strategic Priority Research Program (B) of Chinese Academy of Sciences under Grant No XDB07020300.

  14. Photoelectron yield spectroscopy and inverse photoemission spectroscopy evaluations of p-type amorphous silicon carbide films prepared using liquid materials

    Directory of Open Access Journals (Sweden)

    Tatsuya Murakami

    2016-05-01

    Full Text Available Phosphorus-doped amorphous silicon carbide films were prepared using a polymeric precursor solution. Unlike conventional polymeric precursors, this polymer requires neither catalysts nor oxidation for its synthesis and cross-linkage, providing semiconducting properties in the films. The valence and conduction states of resultant films were determined directly through the combination of inverse photoemission spectroscopy and photoelectron yield spectroscopy. The incorporated carbon widened energy gap and optical gap comparably in the films with lower carbon concentrations. In contrast, a large deviation between the energy gap and the optical gap was observed at higher carbon contents because of exponential widening of the band tail.

  15. Photoelectron spectroscopy and the dipole approximation

    Energy Technology Data Exchange (ETDEWEB)

    Hemmers, O.; Hansen, D.L.; Wang, H. [Univ. of Nevada, Las Vegas, NV (United States)] [and others

    1997-04-01

    Photoelectron spectroscopy is a powerful technique because it directly probes, via the measurement of photoelectron kinetic energies, orbital and band structure in valence and core levels in a wide variety of samples. The technique becomes even more powerful when it is performed in an angle-resolved mode, where photoelectrons are distinguished not only by their kinetic energy, but by their direction of emission as well. Determining the probability of electron ejection as a function of angle probes the different quantum-mechanical channels available to a photoemission process, because it is sensitive to phase differences among the channels. As a result, angle-resolved photoemission has been used successfully for many years to provide stringent tests of the understanding of basic physical processes underlying gas-phase and solid-state interactions with radiation. One mainstay in the application of angle-resolved photoelectron spectroscopy is the well-known electric-dipole approximation for photon interactions. In this simplification, all higher-order terms, such as those due to electric-quadrupole and magnetic-dipole interactions, are neglected. As the photon energy increases, however, effects beyond the dipole approximation become important. To best determine the range of validity of the dipole approximation, photoemission measurements on a simple atomic system, neon, where extra-atomic effects cannot play a role, were performed at BL 8.0. The measurements show that deviations from {open_quotes}dipole{close_quotes} expectations in angle-resolved valence photoemission are observable for photon energies down to at least 0.25 keV, and are quite significant at energies around 1 keV. From these results, it is clear that non-dipole angular-distribution effects may need to be considered in any application of angle-resolved photoelectron spectroscopy that uses x-ray photons of energies as low as a few hundred eV.

  16. Evaluation of the fluorinated antisticking layer by using photoemission and NEXAFS spectroscopies

    Energy Technology Data Exchange (ETDEWEB)

    Haruyama, Yuichi; Nakai, Yasuki; Matsui, Shinji [University of Hyogo, Graduate School of Science, Laboratory of Advanced Science and Technology for Industry, Ako, Hyogo (Japan)

    2015-11-15

    The electronic structures of four kinds of fluorinated self-assembled monolayers (F-SAMs) with different chain length, which were used for an antisticking layer, were investigated by the photoemission and the near-edge X-ray absorption fine structure (NEXAFS) spectroscopies. From the photoemission spectra in the wide and in the C 1s core-level regions, chemical compositions and components of the F-SAMs with different chain length were evaluated. By using the curve fitting analysis of the photoemission spectra in C 1s core-level region, it was found that the CF{sub 3} site is located at the top of the surface in the C sites of the F-SAM. From the C K-edge NEXAFS spectra of the F-SAMs as a function of the incidence angle of the excitation photon, it was shown that the σ*(C-F) and σ*(C-C) orbitals in the F-SAMs are parallel and perpendicular to the surface, respectively. This indicates that the C-C chain in (CF{sub 2}){sub n} part of the F-SAMs is perpendicular to the surface. Based on these results, the electronic structures of the F-SAMs are discussed. (orig.)

  17. Vacuum ultraviolet photon detector with continuously adjustable resolution for inverse photoemission spectroscopy

    OpenAIRE

    Liu, Shu-Hu; Hong, Cai-Hao; Zhao, Yi-Dong; Geng, Dong-Ping; Zheng, Lei; Zhao, Xiao-Liang; Li, Hua-Peng

    2014-01-01

    We present a vacuum ultraviolet (VUV) band-pass photon detector for inverse photoemission spectroscopy. A SrF2 window is used due to its high-energy cutoff of the optical transmission being 9.7eV, and acetone is selected as filling gas with the photoionization threshold also being 9.7eV. The structure of the detector described in detail is based on a Geiger-M\\"uller type counter with an MgF2 window and argon as amplification gas. Its energy resolution can be tuned continuously from 46meV with...

  18. Hard and soft X-ray photoemission spectroscopies of ferromagnetic Sm4As3

    International Nuclear Information System (INIS)

    We have investigated the bulk and surface electronic structures of Sm4As3 by using hard and soft X-ray photoemission spectroscopies (PESs). The valence band spectral shape changes much with photon energies (hν s) due to the variation of both photoionization cross sections and bulk sensitivity. PES with the wide range of hν s between 220 and 2450-bar eV demonstrates that the valence of the Sm ions is definitely trivalent in the bulk and divalent at the surface

  19. Laser-excited photoemission spectroscopy study of superconducting boron-doped diamond

    Directory of Open Access Journals (Sweden)

    K. Ishizaka, R. Eguchi, S. Tsuda, T. Kiss, T. Shimojima, T. Yokoya, S. Shin, T. Togashi, S. Watanabe, C.-T. Chen, C.Q. Zhang, Y. Takano, M. Nagao, I. Sakaguchi, T. Takenouchi and H. Kawarada

    2006-01-01

    Full Text Available We have investigated the low-energy electronic state of boron-doped diamond thin film by the laser-excited photoemission spectroscopy. A clear Fermi-edge is observed for samples doped above the semiconductor–metal boundary, together with the characteristic structures at 150×n meV possibly due to the strong electron–lattice coupling effect. In addition, for the superconducting sample, we observed a shift of the leading edge below Tc indicative of a superconducting gap opening. We discuss the electron–lattice coupling and the superconductivity in doped diamond.

  20. Magnetism and electronic properties of Mn:Ge(111) interfaces probed by core level photoemission spectroscopy

    International Nuclear Information System (INIS)

    The electronic and magnetic properties of Mn:Ge(111) interfaces have been investigated by photoelectron spectroscopy and SQUID magnetometry. An ordered, metallic and ferromagnetic, Mn:Ge(111) interface and a disordered, semiconducting and paramagnetic, MnxGe1-x surface alloy have been considered. An analysis of the Mn 2p X-ray photoemission core line shows that the former interface can be described by a single-configuration Mn 3d6 initial state, while the latter presents satellite features typical of Mn-based diluted magnetic semiconductors, characterized by relevant ligand-to-metal charge transfer effects.

  1. Properties of La2-xSrxCuO4 under epitaxial strain: photoemission on ultra thin films grown by pulsed laser deposition

    OpenAIRE

    Cloëtta, Dominique; Pavuna, Davor

    2007-01-01

    The subject of this thesis is the growth and analysis of high temperature superconductor (HTSC) films and the study of their electronic structure and properties. In particular, the effect of epitaxial strain is investigated, predominantly by means of in-situ angle resolved photoemission spectroscopy (ARPES), as well as X-ray diffraction, resistivity and susceptibility measurements. In order to achieve that goal we have developed a unique experimental set-up at the Synchrotron Radiation Center...

  2. Angle-resolved diffraction grating biosensor based on porous silicon

    Science.gov (United States)

    Lv, Changwu; Jia, Zhenhong; Liu, Yajun; Mo, Jiaqing; Li, Peng; Lv, Xiaoyi

    2016-03-01

    In this study, an optical biosensor based on a porous silicon composite structure was fabricated using a simple method. This structure consists of a thin, porous silicon surface diffraction grating and a one-dimensional porous silicon photonic crystal. An angle-resolved diffraction efficiency spectrum was obtained by measuring the diffraction efficiency at a range of incident angles. The angle-resolved diffraction efficiency of the 2nd and 3rd orders was studied experimentally and theoretically. The device was sensitive to the change of refractive index in the presence of a biomolecule indicated by the shift of the diffraction efficiency spectrum. The sensitivity of this sensor was investigated through use of an 8 base pair antifreeze protein DNA hybridization. The shifts of the angle-resolved diffraction efficiency spectrum showed a relationship with the change of the refractive index, and the detection limit of the biosensor reached 41.7 nM. This optical device is highly sensitive, inexpensive, and simple to fabricate. Using shifts in diffraction efficiency spectrum to detect biological molecules has not yet been explored, so this study establishes a foundation for future work.

  3. Orbital tomography: Deconvoluting photoemission spectra of organic molecules

    Science.gov (United States)

    Puschnig, Peter; Reinisch, Eva-Maria; Ules, Thomas; Koller, Georg; Soubatch, Sergey; Ostler, Markus; Romaner, Lorenz; Tautz, F. Stefan; Ambrosch-Draxl, Claudia; Ramsey, Michael G.

    2012-02-01

    We study the interface of an organic monolayer with a metallic surface, i. e., PTCDA (3,4,9,10-perylene-tetracarboxylic-dianhydride) on Ag(110), by means of angle-resolved photoemission spectroscopy (ARPES) and ab initio electronic structure calculations. We present a tomographic method which uses the energy and momentum dependence of ARPES data to deconvolute spectra into individual orbital contributions beyond the limits of energy resolution. This provides an orbital-by-orbital characterization of large adsorbate systems without the need to invoke sophisticated theory of photoemission, allowing us to directly estimate the effects of bonding on individual orbitals. Moreover, this experimental data serves as a most stringent test necessary for the further development of ab initio electronic structure theory.

  4. Retention Characteristics of CBTi144 Thin Films Explained by Means of X-Ray Photoemission Spectroscopy

    Directory of Open Access Journals (Sweden)

    G. Biasotto

    2010-01-01

    Full Text Available CaBi4Ti4O15 (CBTi144 thin films were grown on Pt/Ti/SiO2/Si substrates using a soft chemical solution and spin-coating method. Structure and morphology of the films were characterized by the X-ray Diffraction (XRD, Fourier-transform infrared spectroscopy (FT-IR, Raman analysis, X-ray photoemission spectroscopy (XPS, and transmission electron microscopy (TEM. The films present a single phase of layered-structured perovskite with polar axis orient. The a/b-axis orientation of the ferroelectric film is considered to be associated with the preferred orientation of the Pt bottom electrode. XPS measurements were employed to understand the nature of defects on the retention behavior of CBTi144 films. We have observed that the main source of retention-free characteristic of the capacitors is the oxygen environment in the CBTi144 lattice.

  5. Origin of localized states in graphite: Indirect photoemission processes or impurities?

    Energy Technology Data Exchange (ETDEWEB)

    Davila, M.E. [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Cientificas (CSIC), C/ Sor Juana Ines de la Cruz, 3, 28049 Madrid (Spain)], E-mail: mdavila@icmm.csic.es; Valbuena, M.A.; Pantin, V. [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Cientificas (CSIC), C/ Sor Juana Ines de la Cruz, 3, 28049 Madrid (Spain); Avila, J. [Synchrotron SOLEIL, Orme des Merisiers, Saint Aubin BP 48, 91192 Gif sur Yvette Cedex (France); Esquinazi, P. [Department of Superconductivity and Magnetism, Leipzig University (Germany); Asensio, M.C. [Synchrotron SOLEIL, Orme des Merisiers, Saint Aubin BP 48, 91192 Gif sur Yvette Cedex (France)

    2007-10-31

    The electronic band structure of different types of graphite samples have been investigated in order to identify the origin of non-dispersive density of states recently reported in the literature. A systematic series of synchrotron radiation angle resolved photoemission spectroscopy (ARPES) measurements on graphite single crystal, highly oriented graphite (HOPG) and epitaxial grown graphite single crystal on 6H-SiC(0 0 0 1) samples, have been carried out as well as compared with theoretical tight binding calculations. Our results indicate that these localized states are present in all the graphite-investigated samples showing the same non-dispersive character and at the same binding energies. The photoemission data taken at several photon energies demonstrate that these states are not surface states nor due to indirect photoemission processes. It seems that they are closely related to the level of impurities present in the studied samples.

  6. Vacuum ultraviolet photon detector with continuously adjustable resolution for inverse photoemission spectroscopy

    CERN Document Server

    Liu, Shu-Hu; Zhao, Yi-Dong; Geng, Dong-Ping; Zhen, Lei; Zhao, Xiao-Liang; Li, Hua-Peng

    2014-01-01

    We present a vacuum ultraviolet (VUV) band-pass photon detector for inverse photoemission spectroscopy. A SrF2 window is used due to its high-energy cutoff of the optical transmission being 9.7eV, and acetone is selected as filling gas with the photoionization threshold also being 9.7eV. The structure of the detector described in detail is based on a Geiger-M\\"uller type counter with an MgF2 window and argon as amplification gas. Its energy resolution can be tuned continuously from 46meV with a normal temperature situation to 105meV at 215K. Meanwhile, the signal intensity of the detector is adjusted accordingly to find an optimal operation program for our inverse photoemission system which is being constructed. The ratio of acetone vapor and argon is varied carefully. Background signals and the response of time are analyzed. The detector is normalized by deuterium lamp in combination with a grating monochromator.

  7. Electronic structure of Mo1-x Re x alloys studied through resonant photoemission spectroscopy.

    Science.gov (United States)

    Sundar, Shyam; Banik, Soma; Sharath Chandra, L S; Chattopadhyay, M K; Ganguli, Tapas; Lodha, G S; Pandey, Sudhir K; Phase, D M; Roy, S B

    2016-08-10

    We studied the electronic structure of Mo-rich Mo1-x Re x alloys ([Formula: see text]) using valence band photoemission spectroscopy in the photon energy range 23-70 eV and density of states calculations. Comparison of the photoemission spectra with the density of states calculations suggests that, with respect to the Fermi level E F, the d states lie mostly in the binding energy range 0 to  -6 eV, whereas s states lie in the binding energy range  -4 to  -10 eV. We observed two resonances in the photoemission spectra of each sample, one at about 35 eV photon energy and the other at about 45 eV photon energy. Our analysis suggests that the resonance at 35 eV photon energy is related to the Mo 4p-5s transition and the resonance at 45 eV photon energy is related to the contribution from both the Mo 4p-4d transition (threshold: 42 eV) and the Re 5p-5d transition (threshold: 46 eV). In the constant initial state plot, the resonance at 35 eV incident photon energy for binding energy features in the range E F (BE  =  0) to  -5 eV becomes progressively less prominent with increasing Re concentration x and vanishes for x  >  0.2. The difference plots obtained by subtracting the valence band photoemission spectrum of Mo from that of Mo1-x Re x alloys, measured at 47 eV photon energy, reveal that the Re d-like states appear near E F when Re is alloyed with Mo. These results indicate that interband s-d interaction, which is weak in Mo, increases with increasing x and influences the nature of the superconductivity in alloys with higher x. PMID:27301550

  8. Electronic structure of Mo1‑x Re x alloys studied through resonant photoemission spectroscopy

    Science.gov (United States)

    Sundar, Shyam; Banik, Soma; Sharath Chandra, L. S.; Chattopadhyay, M. K.; Ganguli, Tapas; Lodha, G. S.; Pandey, Sudhir K.; Phase, D. M.; Roy, S. B.

    2016-08-01

    We studied the electronic structure of Mo-rich Mo1‑x Re x alloys (0≤slant x≤slant 0.4 ) using valence band photoemission spectroscopy in the photon energy range 23–70 eV and density of states calculations. Comparison of the photoemission spectra with the density of states calculations suggests that, with respect to the Fermi level E F, the d states lie mostly in the binding energy range 0 to  ‑6 eV, whereas s states lie in the binding energy range  ‑4 to  ‑10 eV. We observed two resonances in the photoemission spectra of each sample, one at about 35 eV photon energy and the other at about 45 eV photon energy. Our analysis suggests that the resonance at 35 eV photon energy is related to the Mo 4p–5s transition and the resonance at 45 eV photon energy is related to the contribution from both the Mo 4p–4d transition (threshold: 42 eV) and the Re 5p–5d transition (threshold: 46 eV). In the constant initial state plot, the resonance at 35 eV incident photon energy for binding energy features in the range E F (BE  =  0) to  ‑5 eV becomes progressively less prominent with increasing Re concentration x and vanishes for x  >  0.2. The difference plots obtained by subtracting the valence band photoemission spectrum of Mo from that of Mo1‑x Re x alloys, measured at 47 eV photon energy, reveal that the Re d-like states appear near E F when Re is alloyed with Mo. These results indicate that interband s–d interaction, which is weak in Mo, increases with increasing x and influences the nature of the superconductivity in alloys with higher x.

  9. Angle-resolved effective potentials for disk-shaped molecules

    International Nuclear Information System (INIS)

    We present an approach for calculating coarse-grained angle-resolved effective pair potentials for uniaxial molecules. For integrating out the intramolecular degrees of freedom we apply umbrella sampling and steered dynamics techniques in atomistically-resolved molecular dynamics (MD) computer simulations. Throughout this study we focus on disk-like molecules such as coronene. To develop the methods we focus on integrating out the van der Waals and intramolecular interactions, while electrostatic charge contributions are neglected. The resulting coarse-grained pair potential reveals a strong temperature and angle dependence. In the next step we fit the numerical data with various Gay-Berne-like potentials to be used in more efficient simulations on larger scales. The quality of the resulting coarse-grained results is evaluated by comparing their pair and many-body structure as well as some thermodynamic quantities self-consistently to the outcome of atomistic MD simulations of many-particle systems. We find that angle-resolved potentials are essential not only to accurately describe crystal structures but also for fluid systems where simple isotropic potentials start to fail already for low to moderate packing fractions. Further, in describing these states it is crucial to take into account the pronounced temperature dependence arising in selected pair configurations due to bending fluctuations

  10. Angle-resolved effective potentials for disk-shaped molecules

    Energy Technology Data Exchange (ETDEWEB)

    Heinemann, Thomas, E-mail: thomas.heinemann@tu-berlin.de; Klapp, Sabine H. L., E-mail: klapp@physik.tu-berlin.de [Institut für Theoretische Physik, Technische Universität Berlin, Hardenbergstr. 36, 10623 Berlin (Germany); Palczynski, Karol, E-mail: karol.palczynski@helmholtz-berlin.de; Dzubiella, Joachim, E-mail: joachim.dzubiella@helmholtz-berlin.de [Institut für Physik, Humboldt Universität zu Berlin, Newtonstraße 15, 12489 Berlin (Germany); Helmholtz Zentrum Berlin (HZB), Institute of Soft Matter and Functional Materials, Hahn-Meitner Platz 1, 14109 Berlin (Germany)

    2014-12-07

    We present an approach for calculating coarse-grained angle-resolved effective pair potentials for uniaxial molecules. For integrating out the intramolecular degrees of freedom we apply umbrella sampling and steered dynamics techniques in atomistically-resolved molecular dynamics (MD) computer simulations. Throughout this study we focus on disk-like molecules such as coronene. To develop the methods we focus on integrating out the van der Waals and intramolecular interactions, while electrostatic charge contributions are neglected. The resulting coarse-grained pair potential reveals a strong temperature and angle dependence. In the next step we fit the numerical data with various Gay-Berne-like potentials to be used in more efficient simulations on larger scales. The quality of the resulting coarse-grained results is evaluated by comparing their pair and many-body structure as well as some thermodynamic quantities self-consistently to the outcome of atomistic MD simulations of many-particle systems. We find that angle-resolved potentials are essential not only to accurately describe crystal structures but also for fluid systems where simple isotropic potentials start to fail already for low to moderate packing fractions. Further, in describing these states it is crucial to take into account the pronounced temperature dependence arising in selected pair configurations due to bending fluctuations.

  11. Electronic structure investigation of atomic layer deposition ruthenium(oxide) thin films using photoemission spectroscopy

    Science.gov (United States)

    Schaefer, Michael; Schlaf, Rudy

    2015-08-01

    Analyzing and manipulating the electronic band line-up of interfaces in novel micro- and nanoelectronic devices is important to achieve further advancement in this field. Such band alignment modifications can be achieved by introducing thin conformal interfacial dipole layers. Atomic layer deposition (ALD), enabling angstrom-precise control over thin film thickness, is an ideal technique for this challenge. Ruthenium (Ru0) and its oxide (RuO2) have gained interest in the past decade as interfacial dipole layers because of their favorable properties like metal-equivalent work functions, conductivity, etc. In this study, initial results of the electronic structure investigation of ALD Ru0 and RuO2 films via photoemission spectroscopy are presented. These experiments give insight into the band alignment, growth behavior, surface structure termination, and dipole formation. The experiments were performed in an integrated vacuum system attached to a home-built, stop-flow type ALD reactor without exposing the samples to the ambient in between deposition and analysis. Bis(ethylcyclopentadienyl)ruthenium(II) was used as precursor and oxygen as reactant. The analysis chamber was outfitted with X-ray photoemission spectroscopy (LIXPS, XPS). The determined growth modes are consistent with a strong growth inhibition situation with a maximum average growth rate of 0.21 Å/cycle for RuO2 and 0.04 Å/cycle for Ru.0 An interface dipole of up to -0.93 eV was observed, supporting the assumption of a strongly physisorbed interface. A separate experiment where the surface of a RuO film was sputtered suggests that the surface is terminated by an intermediate, stable, non-stoichiometric RuO2/OH compound whose surface is saturated with hydroxyl groups.

  12. Electronic structure investigation of atomic layer deposition ruthenium(oxide) thin films using photoemission spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Schaefer, Michael, E-mail: mvschaefer@mail.usf.edu, E-mail: schlaf@mail.usf.edu [Department of Physics, University of South Florida, Tampa, Florida 33620 (United States); Schlaf, Rudy, E-mail: mvschaefer@mail.usf.edu, E-mail: schlaf@mail.usf.edu [Department of Electrical Engineering, University of South Florida, Tampa, Florida 33620 (United States)

    2015-08-14

    Analyzing and manipulating the electronic band line-up of interfaces in novel micro- and nanoelectronic devices is important to achieve further advancement in this field. Such band alignment modifications can be achieved by introducing thin conformal interfacial dipole layers. Atomic layer deposition (ALD), enabling angstrom-precise control over thin film thickness, is an ideal technique for this challenge. Ruthenium (Ru{sup 0}) and its oxide (RuO{sub 2}) have gained interest in the past decade as interfacial dipole layers because of their favorable properties like metal-equivalent work functions, conductivity, etc. In this study, initial results of the electronic structure investigation of ALD Ru{sup 0} and RuO{sub 2} films via photoemission spectroscopy are presented. These experiments give insight into the band alignment, growth behavior, surface structure termination, and dipole formation. The experiments were performed in an integrated vacuum system attached to a home-built, stop-flow type ALD reactor without exposing the samples to the ambient in between deposition and analysis. Bis(ethylcyclopentadienyl)ruthenium(II) was used as precursor and oxygen as reactant. The analysis chamber was outfitted with X-ray photoemission spectroscopy (LIXPS, XPS). The determined growth modes are consistent with a strong growth inhibition situation with a maximum average growth rate of 0.21 Å/cycle for RuO{sub 2} and 0.04 Å/cycle for Ru.{sup 0} An interface dipole of up to −0.93 eV was observed, supporting the assumption of a strongly physisorbed interface. A separate experiment where the surface of a RuO film was sputtered suggests that the surface is terminated by an intermediate, stable, non-stoichiometric RuO{sub 2}/OH compound whose surface is saturated with hydroxyl groups.

  13. Electronic structure investigation of atomic layer deposition ruthenium(oxide) thin films using photoemission spectroscopy

    International Nuclear Information System (INIS)

    Analyzing and manipulating the electronic band line-up of interfaces in novel micro- and nanoelectronic devices is important to achieve further advancement in this field. Such band alignment modifications can be achieved by introducing thin conformal interfacial dipole layers. Atomic layer deposition (ALD), enabling angstrom-precise control over thin film thickness, is an ideal technique for this challenge. Ruthenium (Ru0) and its oxide (RuO2) have gained interest in the past decade as interfacial dipole layers because of their favorable properties like metal-equivalent work functions, conductivity, etc. In this study, initial results of the electronic structure investigation of ALD Ru0 and RuO2 films via photoemission spectroscopy are presented. These experiments give insight into the band alignment, growth behavior, surface structure termination, and dipole formation. The experiments were performed in an integrated vacuum system attached to a home-built, stop-flow type ALD reactor without exposing the samples to the ambient in between deposition and analysis. Bis(ethylcyclopentadienyl)ruthenium(II) was used as precursor and oxygen as reactant. The analysis chamber was outfitted with X-ray photoemission spectroscopy (LIXPS, XPS). The determined growth modes are consistent with a strong growth inhibition situation with a maximum average growth rate of 0.21 Å/cycle for RuO2 and 0.04 Å/cycle for Ru.0 An interface dipole of up to −0.93 eV was observed, supporting the assumption of a strongly physisorbed interface. A separate experiment where the surface of a RuO film was sputtered suggests that the surface is terminated by an intermediate, stable, non-stoichiometric RuO2/OH compound whose surface is saturated with hydroxyl groups

  14. Phonon contribution to quasiparticle lifetimes in Cu measured by angle-resolved photoemission

    International Nuclear Information System (INIS)

    The line shape of the photoelectron spectrum emitted from the sp-derived surface state at bar Γ on Cu(111) is investigated. The line shape is Lorentzian, and the temperature dependence of the width is linear, varying from 30 meV at 30 K to 75 meV at 625 K. Less than 5-meV variation with binding energy is observed. The temperature dependence is explained as the phonon contribution to the inverse hole lifetime, predicted to be 2πλkbT allowing the determination that the electron-phonon mass enhancement parameter λ=0.14±0.02 for this surface state at bar Γ. This is compared to λ=0.15 reported as an average over the bulk Fermi surface

  15. Low-energy electro- and photo-emission spectroscopy of GaN materials and devices

    International Nuclear Information System (INIS)

    In hot-electron semiconductor devices, carrier transport extends over a wide range of conduction states, which often includes multiple satellite valleys. Electrical measurements can hardly give access to the transport processes over such a wide range without resorting to models and simulations. An alternative experimental approach however exists which is based on low-energy electron spectroscopy and provides, in a number of cases, very direct and selective information on hot-electron transport mechanisms. Recent results obtained in GaN crystals and devices by electron emission spectroscopy are discussed. Using near-band-gap photoemission, the energy position of the first satellite valley in wurtzite GaN is directly determined. By electro-emission spectroscopy, we show that the measurement of the electron spectrum emitted from a GaN p-n junction and InGaN/GaN light-emitting diodes (LEDs) under electrical injection of carriers provides a direct observation of transport processes in these devices. In particular, at high injected current density, high-energy features appear in the electro-emission spectrum of the LEDs showing that Auger electrons are being generated in the active region. These measurements allow us identifying the microscopic mechanism responsible for droop which represents a major hurdle for widespread adoption of solid-state lighting

  16. Inner-shell photoemission from atoms and molecules using synchrotron radiation

    International Nuclear Information System (INIS)

    Photoelectron spectroscopy, in conjunction with synchrotron radiation, has been used to study inner-shell photoemission from atoms and molecules. The time structure of the synchrotron radiation permits the measurements of time-of-flight (TOF) spectra of Auger and photoelectrons, thereby increasing the electron collection efficiency. The double-angle TOF method yielded angle-resolved photoelectron intensities, which were used to determine photoionization cross sections and photoelectron angular distributions in several cases. Comparison to theoretical calculations has been made where possible to help explain observed phenomena in terms of the electronic structure and photoionization dynamics of the systems studied. 154 references, 23 figures, 7 tables

  17. orbital selective correlation reduce in collapse tetragonal phase of CaFe2(As0.935P0.065)2 and electronic structure reconstruction studied by angel resolved photoemission spectroscopy

    Science.gov (United States)

    Zeng, Lingkun

    We performed an angle-resolved photoemission spectroscopy (ARPES) study of the CaFe2(As0.935P0.065)2 in the collapse tetragonal(CT) phase and uncollapse tetragonal(UCT) phase. We find in the CT phase the electronic correlation dramatically reduces respective to UCT phase. Meanwhile, the reduction of correlation in CT phase show an orbital selective effect: correlation in dxy reduces the most, and then dxz/yz, while the one in dz2-r2 almost keeps the same. In CT phase, almost all bands sink downwards to higher binding energy, leading to the hole like bands around Brillouin zone(BZ) center sink below EF compared with UCT phase. However, the electron pocket around Brillouin Zone(BZ) corner(M) in UCT phase, forms a hole pocket around BZ center(Z point) in CT phase. Moreover, the dxy exhibits larger movement down to higher binding energy, resulting in farther away from dyz/xz and closer to dxy.We propose the electron filling ,namely high spin state in UCT phase to low spin state in CT phase(due to competing between crystal structure field and Hund's coupling), other than the Fermi surface nesting might be responsible for the absent of magnetic ordering.

  18. Imaging the wave functions of adsorbed molecules using angle-resolved photoemmision data

    Science.gov (United States)

    Lüftner, Daniel; Ules, Thomas; Reinisch, Eva Maria; Koller, Georg; Soubatch, Serguei; Tautz, F. Stefan; Ramsey, Michael G.; Puschnig, Peter

    2014-03-01

    The frontier electronic orbitals of molecules are the prime determinants of the respective compounds' chemical, electronic, and optical properties. Although orbitals are very powerful concepts, experimentally only the electron densities and energy levels are directly observable. As has been shown in recent publications, angle-resolved photoemission (ARPES) intensity maps of organic molecular layers are related to the absolute value of the Fourier transform of the initial state molecular orbital. However, the lost phase information impedes the back-transformation of the orbital into real space. Here, we show how molecular orbital images as well as the absent phase information can be retrieved by applying an iterative procedure which takes experimental ARPES maps as input and only assumes spatial confinement of the orbital. The method is demonstrated for several molecular orbitals of two proto-typical pi-conjugated molecules: the LUMO, HOMO, and HOMO-1 of pentacene, and the LUMO and HOMO of PTCDA. The technique is simple and robust and further emphasizes the capabilities of ARPES looking at spatial distributions of wave functions of adsorbed molecules thereby complementing data obtained from scanning probe methods.

  19. Interface characterization of metal-HfO2-InAs gate stacks using hard x-ray photoemission spectroscopy

    Directory of Open Access Journals (Sweden)

    O. Persson

    2013-07-01

    Full Text Available MOS devices based on III-V semiconductors and thin high-k dielectric layers offer possibilities for improved transport properties. Here, we have studied the interface structure and chemical composition of realistic MOS gate stacks, consisting of a W or Pd metal film and a 6- or 12-nm-thick HfO2 layer deposited on InAs, with Hard X-ray Photoemission Spectroscopy. In and As signals from InAs buried more than 18 nm below the surface are clearly detected. The HfO2 layers are found to be homogeneous, and no influence of the top metal on the sharp InAs-HfO2 interface is observed. These results bridge the gap between conventional photoemission spectroscopy studies on various metal-free model samples with very thin dielectric layers and realistic MOS gate stacks.

  20. Angle-Resolved Plasmonic Properties of Single Gold Nanorod Dimers

    Institute of Scientific and Technical Information of China (English)

    Jian Wu; Xuxing Lu; Qiannan Zhu; Junwei Zhao; Qishun Shen; Li Zhan; Weihai Ni

    2014-01-01

    Through wet-chemical assembly methods, gold nanorods were placed close to each other and formed a dimer with a gap distance*1 nm, and hence degenerated plasmonic dipole modes of individual nanorods coupled together to produce hybridized bonding and antibonding resonance modes. Previous studies using a condenser for illumination result in averaged signals over all excitation angles. By exciting an individual dimer obliquely at different angles, we demonstrate that these two new resonance modes are highly tunable and sensitive to the angle between the excitation polarization and the dimer orientation, which follows cos2u dependence. Moreover, for dimer structures with various structure angles, the resonance wavelengths as well as the refractive index sensitivities were found independent of the structure angle. Cal-culated angle-resolved plasmonic properties are in good agreement with the measurements. The assembled nanostructures investigated here are important for fundamental researches as well as potential applications when they are used as building blocks in plasmon-based optical and optoelectronic devices.

  1. Direct comparison of photoemission spectroscopy and in situ Kelvin probe work function measurements on indium tin oxide films

    International Nuclear Information System (INIS)

    The work function of commercially available indium tin oxide (ITO) films on glass substrates was measured using photoemission spectroscopy (PES) and ultra-high vacuum (UHV) Kelvin probe in direct comparison. Absolute Kelvin probe work function values were determined via calibration of the measured contact potential difference (CPD) using an in situ sputtered Au reference sample. The Kelvin probe data confirmed that ultraviolet photoemission spectroscopy (UPS) measurements change the work function of ITO surfaces previously exposed to ambient environment, when measured without in situ surface cleaning procedures. The results also demonstrate that both Kelvin probe and PES yield virtually identical work function values, as long as the Kelvin probe data are calibrated against a known standard. As a consequence, previously reported higher work function values determined with Kelvin probe as compared to values obtained with UPS on similar samples are likely related to a photochemically generated surface dipole during UPS measurements. Comparison between Kelvin probe and low intensity X-ray photoemission spectroscopy (LIXPS) work function measurements demonstrated that accurate work function measurements on ITO previously exposed to the ambient are possible with PES

  2. First-principles photoemission spectroscopy in DNA and RNA nucleobases from Koopmans-compliant functionals

    Science.gov (United States)

    Nguyen, Ngoc Linh; Borghi, Giovanni; Ferretti, Andrea; Marzari, Nicola

    The determination of spectral properties of the DNA and RNA nucleobases from first principles can provide theoretical interpretation for experimental data, but requires complex electronic-structure formulations that fall outside the domain of applicability of common approaches such as density-functional theory. In this work, we show that Koopmans-compliant functionals, constructed to enforce piecewise linearity in energy functionals with respect to fractional occupation-i.e., with respect to charged excitations-can predict not only frontier ionization potentials and electron affinities of the nucleobases with accuracy comparable or superior with that of many-body perturbation theory and high-accuracy quantum chemistry methods, but also the molecular photoemission spectra are shown to be in excellent agreement with experimental ultraviolet photoemsision spectroscopy data. The results highlight the role of Koopmans-compliant functionals as accurate and inexpensive quasiparticle approximations to the spectral potential, which transform DFT into a novel dynamical formalism where electronic properties, and not only total energies, can be correctly accounted for.

  3. Ion bombardment of Ni(110) studied with inverse photoemission spectroscopy and low-energy electron diffraction

    Science.gov (United States)

    Young, Benjamin; Warner, James; Heskett, David

    2016-02-01

    Inverse photoemission spectroscopy (IPES) performed on clean Ni(110) reveals an unoccupied electronic surface state with energy ~ 2.5 eV above the Fermi level for emission near the Ȳ point of the Surface Brillouin Zone. Ion bombardment of the sample creates defects that reduce the intensity of the peak in IPES spectra. Sharp, intense diffraction spots in low-energy electron diffraction (LEED) patterns taken of the clean surface become dimmer after bombardment. Results of these measurements are compared to Monte Carlo simulations of the sputtering process to ascertain the approximate size of clean patches on the sample necessary to sustain the IPES and LEED features. At 170 K, the IPES surface state peak appears closely associated with the population of surface atomic sites contained in clean circular patches of about 50 atoms. The LEED patterns persist to greater degrees of sputtering and are associated with smaller clean patches. Both measurements performed at 300 K indicate significant self-annealing of the sputtering damage.

  4. Study of neutralization kinetics in charged polymer-metal nanocomposite systems by photoemission spectroscopy

    International Nuclear Information System (INIS)

    In case of photoelectron spectroscopy of an insulating material the data obtained from the charged surface are often distorted due to differentially charged surface domains. Recently we have developed a controlled surface neutralization technique to study the kinetics of the surface charging. Here we demonstrate the application of the technique to study the neutralization kinetics of both thick and thin films of charged polymer-metal nanocomposite material using photoemission. Neutralization kinetics of grounded and floated pure polymer thin films was also studied. It was observed that for the thick sample the transition of positively charged domains to overcompensated ones occurs through percolation. In case of grounded thin films the growth of overcompensated domains exhibit a linear behavior followed by saturation. When electrons appear at both surfaces of a floated thin film, the neutralization kinetics show a completely different behavior. Present investigation indicates that for thin films of insulating materials appearing to be neutral in presence of an electron source, controlled neutralization technique may be an important tool to distinguish between presence of multiple chemical species and differential charging.

  5. Photo-induced charge-orbital switching in transition-metal compounds probed by photoemission spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Takubo, K; Mizokawa, T [Department of Physics and Department of Complexity Science and Engineering, University of Tokyo, Kashiwa, Chiba 277-8561 (Japan); Takubo, N; Miyano, K [Research Center for Advanced Science and Technology (RCAST), University of Tokyo, Tokyo 153-8904 (Japan); Matsumoto, N; Nagata, S, E-mail: takubo@sces.k.u-tokyo.ac.j [Department of Materials Science and Engineering, Muroran Institute of Technology, 27-1 Mizumoto-cho, Muroran, Hokkaido, 050-8585 Japan (Japan)

    2009-02-01

    Transition-metal compounds with spin, charge, and orbital degrees of freedom tend to have frustrated electronic states coupled with local lattice distortions and to show drastic response to external stimuli such as photo-excitation. We have studied the charge-orbital states in perovskite-type Pr{sub 0.55}(Ca{sub 1-y}Sr{sub y}){sub 0.45}MnO{sub 3} thin films (PCSMO) and spinel-type CuIr{sub 2}S{sub 4} using photoemission spectroscopy combined with additional laser illumination. PCSMO and CuIr{sub 2}S{sub 4} are clear-cut examples of transition-metal compounds showing photo-induced metallic conductivities but the charge-orbital states in the two systems show contrasting responses to the photo-excitation. The charge-orbital states in PCSMO are stabilized by Jahn-Teller or Breathing-type lattice distortions and can be destroyed by photo-excitation. On the other hand, the charge-orbital states in CuIr{sub 2}S{sub 4} are stabilized by dimer formation and tend to be robust against photo-excitation.

  6. Visualizing the chiral anomaly in Dirac and Weyl semimetals with photoemission spectroscopy

    Science.gov (United States)

    Behrends, Jan; Grushin, Adolfo G.; Ojanen, Teemu; Bardarson, Jens H.

    2016-02-01

    Quantum anomalies are the breaking of a classical symmetry by quantum fluctuations. They dictate how physical systems of diverse nature, ranging from fundamental particles to crystalline materials, respond topologically to external perturbations, insensitive to local details. The anomaly paradigm was triggered by the discovery of the chiral anomaly that contributes to the decay of pions into photons and influences the motion of superfluid vortices in 3He-A. In the solid state, it also fundamentally affects the properties of topological Weyl and Dirac semimetals, recently realized experimentally. In this work we propose that the most identifying consequence of the chiral anomaly, the charge density imbalance between fermions of different chirality induced by nonorthogonal electric and magnetic fields, can be directly observed in these materials with the existing technology of photoemission spectroscopy. With angle resolution, the chiral anomaly is identified by a characteristic note-shaped pattern of the emission spectra, originating from the imbalanced occupation of the bulk states and a previously unreported momentum dependent energy shift of the surface state Fermi arcs. We further demonstrate that the chiral anomaly likewise leaves an imprint in angle averaged emission spectra, facilitating its experimental detection. Thereby, our work provides essential theoretical input to foster the direct visualization of the chiral anomaly in condensed matter, in contrast to transport properties, such as negative magnetoresistance, which can also be obtained in the absence of a chiral anomaly.

  7. Band alignments in Fe/graphene/Si(001) junctions studied by x-ray photoemission spectroscopy

    Science.gov (United States)

    Le Breton, J.-C.; Tricot, S.; Delhaye, G.; Lépine, B.; Turban, P.; Schieffer, P.

    2016-08-01

    The control of tunnel contact resistance is of primary importance for semiconductor-based spintronic devices. This control is hardly achieved with conventional oxide-based tunnel barriers due to deposition-induced interface states. Manipulation of single 2D atomic crystals (such as graphene sheets) weakly interacting with their substrate might represent an alternative and efficient way to design new heterostructures for a variety of different purposes including spin injection into semiconductors. In the present paper, we study by x-ray photoemission spectroscopy the band alignments and interface chemistry of iron-graphene-hydrogenated passivated silicon (001) surfaces for a low and a high n-doping concentration. We find that the hydrogen passivation of the Si(001) surface remains efficient even with a graphene sheet on the Si(001) surface. For both doping concentrations, the semiconductor is close to flat-band conditions which indicates that the Fermi level is unpinned on the semiconductor side of the Graphene/Si(001):H interface. When iron is deposited on the graphene/Si(001):H structures, the Schottky barrier height remains mainly unaffected by the metallic overlayer with a very low barrier height for electrons, a sought-after property in semiconductor based spintronic devices. Finally, we demonstrate that the graphene layer intercalated between the metal and semiconductor also serves as a protection against iron-silicide formation even at elevated temperatures preventing from the formation of a Si-based magnetic dead layer.

  8. Precision angle-resolved autoionization resonances in Ar and Ne

    Energy Technology Data Exchange (ETDEWEB)

    Berrah, N.; Langer, B.; Gorczyca, T.W. [Western Michigan Univ., Kalamazoo, MI (United States)] [and others

    1997-04-01

    Theoretical work has shown that the electron angular distribution and the shape of the autoionization resonances are crucial to the understanding of certain types of electron-electron correlation. Autoionization resonances in Ne (Ar) result from the decay of the excited discrete state Ne{sup *} 2s2p{sup 6} np (Ar{sup *} 3s3p{sup 6} np) into the continuum state Ne{sup +} 2s{sup 2}2p{sup 5} + e{sup {minus}} (ks,kd) (Ar{sup +} 3s{sup 2}3p{sup 5} + e{sup {minus}} (ks,kd)). Since the continuum can also be reached by direct photoionization, both paths add coherently, giving rise to interferences that produce the characteristic Beutler-Fano line shape. In this work, the authors report on quantitative angle-resolved electron spectrometry studies of (a) the Ne 2s{sup 2}2p{sup 6} {r_arrow} 2s2p{sup 6} np (n=3-5) autoionizing resonances and the 2s{sup 2}2p{sup 6} {r_arrow} 2p{sup 4}3s3p doubly excited resonance, (b) the Ar 3s{sup 2}3p{sup 6} {r_arrow} 3s3p{sup 6} np (n=4-9) autoionization resonances and extended R-matrix calculations of the angular-distribution parameters for both Ne and Ar measurements. Their results are compared with previous theoretical work by Taylor.

  9. Band structure of Heusler compounds studied by photoemission and tunneling spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Arbelo Jorge, Elena

    2011-07-01

    Heusler compounds are key materials for spintronic applications. They have attracted a lot of interest due to their half-metallic properties predicted by band structure calculations. The aim of this work is to evaluate experimentally the validity of the predictions of half metallicity by band structure calculations for two specific Heusler compounds, Co{sub 2}FeAl{sub 0.3}Si{sub 0.7} and Co{sub 2}MnGa. Two different spectroscopy methods for the analysis of the electronic properties were used: Angular Resolved Ultraviolet Photoemission Spectroscopy (ARUPS) and Tunneling Spectroscopy. Heusler compounds are prepared as thin films by RF-sputtering in an ultra high vacuum system. For the characterization of the samples, bulk and surface crystallographic and magnetic properties of Co{sub 2}FeAl{sub 0.3}Si{sub 0.7} and Co{sub 2}MnGa are studied. X-ray and electron diffraction reveal a bulk and surface crossover between two different types of sublattice order (from B2 to L2{sub 1}) with increasing annealing temperature. X-ray magnetic circular dichroism results show that the magnetic properties in the surface and bulk are identical, although the magnetic moments obtained are 5 % below from the theoretically predicted. By ARUPS evidence for the validity of the predicted total bulk density of states (DOS) was demonstrated for both Heusler compounds. Additional ARUPS intensity contributions close to the Fermi energy indicates the presence of a specific surface DOS. Moreover, it is demonstrated that the crystallographic order, controlled by annealing, plays an important role on broadening effects of DOS features. Improving order resulted in better defined ARUPS features. Tunneling magnetoresistance measurements of Co{sub 2}FeAl{sub 0.3}Si{sub 0.7} and Co{sub 2}MnGa based MTJ's result in a Co{sub 2}FeAl{sub 0.3}Si{sub 0.7} spin polarization of 44 %, which is the highest experimentally obtained value for this compound, although it is lower than the 100 % predicted. For Co

  10. First-principles photoemission spectroscopy of DNA and RNA nucleobases from Koopmans-compliant functionals

    CERN Document Server

    Nguyen, Ngoc Linh; Ferretti, Andrea; Marzari, Nicola

    2016-01-01

    The need to interpret ultraviolet photoemission data strongly motivates the refinement of first-principles techniques able to accurately predict spectral properties. In this work we employ Koopmans-compliant functionals, constructed to enforce piecewise linearity in approximate density functionals, to calculate the structural and electronic properties of DNA and RNA nucleobases. Our results show that not only ionization potentials and electron affinities are accurately predicted with mean absolute errors < 0.1 eV, but also that calculated photoemission spectra are in excellent agreement with experimental ultraviolet photoemission spectra. In particular, the role and contribution of different tautomers to the photoemission spectra are highlighted and discussed in detail. The structural properties of nucleobases are also investigated, showing an improved description with respect to local and semilocal density-functional theory. Methodologically, our results further consolidate the role of Koopmans-compliant ...

  11. Electronic states of solids probed by bulk-sensitive high-resolution soft X-ray photoemission spectroscopy

    CERN Document Server

    Sekiyama, A

    2003-01-01

    High-energy and high-resolution soft x-ray photoemission studies have been performed on strongly correlated Ce compounds and vanadium oxides at BL25SU of SPring-8. The bulk spectra of CeRu sub 2 are explained by a band-structure calculation (itinerant model) whereas the other Ce 4f spectra are well reproduced by calculations based on the single impurity Anderson model (model from a localized limit). In a strong contrast to so far reported results, the bulk spectral functions are revealed to be insensitive to x for Sr sub 1 sub - sub x Ca sub x VO sub 3. Our study has demonstrated the importance of high-energy and high-resolution photoemission spectroscopy for revealing detailed bulk electronic states of strongly correlated systems. (author)

  12. Direct characterization of the energy level alignments and molecular components in an organic hetero-junction by integrated photoemission spectroscopy and reflection electron energy loss spectroscopy analysis

    Science.gov (United States)

    Yun, Dong-Jin; Shin, Weon-Ho; Bulliard, Xavier; Park, Jong Hwan; Kim, Seyun; Chung, Jae Gwan; Kim, Yongsu; Heo, Sung; Kim, Seong Heon

    2016-08-01

    A novel, direct method for the characterization of the energy level alignments at bulk-heterojunction (BHJ)/electrode interfaces on the basis of electronic spectroscopy measurements is proposed. The home-made in situ photoemission system is used to perform x-ray/ultraviolet photoemission spectroscopy (XPS/UPS), reflection electron energy loss spectroscopy (REELS) and inverse photoemission spectroscopy of organic-semiconductors (OSCs) deposited onto a Au substrate. Through this analysis system, we are able to obtain the electronic structures of a boron subphthalocyanine chloride:fullerene (SubPC:C60) BHJ and those of the separate OSC/electrode structures (SubPC/Au and C60/Au). Morphology and chemical composition analyses confirm that the original SubPC and C60 electronic structures remain unchanged in the electrodes prepared. Using this technique, we ascertain that the position and area of the nearest peak to the Fermi energy (EF = 0 eV) in the UPS (REELS) spectra of SubPC:C60 BHJ provide information on the highest occupied molecular orbital level (optical band gap) and combination ratio of the materials, respectively. Thus, extracting the adjusted spectrum from the corresponding SubPC:C60 BHJ UPS (REELS) spectrum reveals its electronic structure, equivalent to that of the C60 materials. This novel analytical approach allows complete energy-level determination for each combination ratio by separating its electronic structure information from the BHJ spectrum.

  13. Direct characterization of the energy level alignments and molecular components in an organic hetero-junction by integrated photoemission spectroscopy and reflection electron energy loss spectroscopy analysis.

    Science.gov (United States)

    Yun, Dong-Jin; Shin, Weon-Ho; Bulliard, Xavier; Park, Jong Hwan; Kim, Seyun; Chung, Jae Gwan; Kim, Yongsu; Heo, Sung; Kim, Seong Heon

    2016-08-26

    A novel, direct method for the characterization of the energy level alignments at bulk-heterojunction (BHJ)/electrode interfaces on the basis of electronic spectroscopy measurements is proposed. The home-made in situ photoemission system is used to perform x-ray/ultraviolet photoemission spectroscopy (XPS/UPS), reflection electron energy loss spectroscopy (REELS) and inverse photoemission spectroscopy of organic-semiconductors (OSCs) deposited onto a Au substrate. Through this analysis system, we are able to obtain the electronic structures of a boron subphthalocyanine chloride:fullerene (SubPC:C60) BHJ and those of the separate OSC/electrode structures (SubPC/Au and C60/Au). Morphology and chemical composition analyses confirm that the original SubPC and C60 electronic structures remain unchanged in the electrodes prepared. Using this technique, we ascertain that the position and area of the nearest peak to the Fermi energy (EF = 0 eV) in the UPS (REELS) spectra of SubPC:C60 BHJ provide information on the highest occupied molecular orbital level (optical band gap) and combination ratio of the materials, respectively. Thus, extracting the adjusted spectrum from the corresponding SubPC:C60 BHJ UPS (REELS) spectrum reveals its electronic structure, equivalent to that of the C60 materials. This novel analytical approach allows complete energy-level determination for each combination ratio by separating its electronic structure information from the BHJ spectrum. PMID:27420635

  14. ANTARES, a scanning photoemission microscopy beamline at SOLEIL

    CERN Document Server

    Avila, Jose; Lorcy, Stehane; Lagarde, Bruno; Giorgetta, Jean-Luc; Polack, François; Asensio, Maria C

    2013-01-01

    As one of the latest beamline built at the SOLEIL synchrotron source, ANTARES beamline offers a spectroscopic non-destructive nano-probe to study advanced materials. This innovative scanning photoemission microscopy combines linear and angle sweeps to perform precise electronic band structure determination by Nano Angle Resolved Photoelectron Spectroscopy (nanoARPES) and chemical imaging by core level detection. The beamline integrates effectively insertion devices and a high transmission beamline optics. This photon source has been combined with an advanced microscope, which has precise sample handling abilities. Moreover, it is fully compatible with a high resolution R4000 Scienta hemispherical analyzer and a set of Fresnel Zone Plates (FZP) able to focalize the beam spot up to a few tenths of nanometers, depending on the spatial resolution of the selected FZP. We present here the main conceptual design of the beamline and endstation, together with some of the firsts commissioning results.

  15. Widespread spin polarization effects in photoemission from topological insulators

    Energy Technology Data Exchange (ETDEWEB)

    Jozwiak, C.; Chen, Y. L.; Fedorov, A. V.; Analytis, J. G.; Rotundu, C. R.; Schmid, A. K.; Denlinger, J. D.; Chuang, Y.-D.; Lee, D.-H.; Fisher, I. R.; Birgeneau, R. J.; Shen, Z.-X.; Hussain, Z.; Lanzara, A.

    2011-06-22

    High-resolution spin- and angle-resolved photoemission spectroscopy (spin-ARPES) was performed on the three-dimensional topological insulator Bi{sub 2}Se{sub 3} using a recently developed high-efficiency spectrometer. The topological surface state's helical spin structure is observed, in agreement with theoretical prediction. Spin textures of both chiralities, at energies above and below the Dirac point, are observed, and the spin structure is found to persist at room temperature. The measurements reveal additional unexpected spin polarization effects, which also originate from the spin-orbit interaction, but are well differentiated from topological physics by contrasting momentum and photon energy and polarization dependencies. These observations demonstrate significant deviations of photoelectron and quasiparticle spin polarizations. Our findings illustrate the inherent complexity of spin-resolved ARPES and demonstrate key considerations for interpreting experimental results.

  16. X-ray photoemission spectroscopy determination of the InN/yttria stabilized cubic-zirconia valence band offset

    International Nuclear Information System (INIS)

    The valence band offset of wurtzite InN(0001)/yttria stabilized cubic-zirconia (YSZ)(111) heterojunctions is determined by x-ray photoemission spectroscopy to be 1.19±0.17 eV giving a conduction band offset of 3.06±0.20 eV. Consequently, a type-I heterojunction forms between InN and YSZ in the straddling arrangement. The low lattice mismatch and high band offsets suggest potential for use of YSZ as a gate dielectric in high-frequency InN-based electronic devices

  17. Alkaline Earth Core Level Photoemission Spectroscopy of High-Temperature Superconductors

    Science.gov (United States)

    Vasquez, R.

    1993-01-01

    This paper examines photoemission measurements of the alkaline Earth core levels of high-temperature superconductors and related materials, models that seek to explain the large negative shifts observed relative to the corresponding alkaline Earth metals, and the effect of lattice site disorder on the core level spectra and the presence or absence of intrinsic surface peaks.

  18. Angle-resolved photoelectron spectrometry: new electron optics and detection system

    International Nuclear Information System (INIS)

    A new spectrometer system is described, designed to measure angle-resolved energy distributions of photoemitted electrons efficiently. Some results are presented of measurements on a Si(001) surface. (Auth.)

  19. Electronic properties of Mn-phthalocyanine–C{sub 60} bulk heterojunctions: Combining photoemission and electron energy-loss spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Roth, Friedrich [Center for Free-Electron Laser Science/DESY, Notkestraße 85, D-22607 Hamburg (Germany); Herzig, Melanie; Knupfer, Martin [FW Dresden, P.O. Box 270116, D-01171 Dresden (Germany); Lupulescu, Cosmin [Institute of Optics and Atomic Physics, TU Berlin, Straße des 17. Juni 135, D-10623 Berlin (Germany); Darlatt, Erik; Gottwald, Alexander [Physikalisch-Technische Bundesanstalt (PTB), Abbestraße 2-12, D-10587 Berlin (Germany); Eberhardt, Wolfgang [Center for Free-Electron Laser Science/DESY, Notkestraße 85, D-22607 Hamburg (Germany); Institute of Optics and Atomic Physics, TU Berlin, Straße des 17. Juni 135, D-10623 Berlin (Germany)

    2015-11-14

    The electronic properties of co-evaporated mixtures (blends) of manganese phthalocyanine and the fullerene C{sub 60} (MnPc:C{sub 60}) have been studied as a function of the concentration of the two constituents using two supplementary electron spectroscopic methods, photoemission spectroscopy (PES) and electron energy-loss spectroscopy (EELS) in transmission. Our PES measurements provide a detailed picture of the electronic structure measured with different excitation energies as well as different mixing ratios between MnPc and C{sub 60}. Besides a relative energy shift, the occupied electronic states of the two materials remain essentially unchanged. The observed energy level alignment is different compared to that of the related CuPc:C{sub 60} bulk heterojunction. Moreover, the results from our EELS investigations show that, despite the rather small interface interaction, the MnPc related electronic excitation spectrum changes significantly by admixing C{sub 60} to MnPc thin films.

  20. Measurements of Schottky barrier at the low-k SiOC:H/Cu interface using vacuum ultraviolet photoemission spectroscopy

    International Nuclear Information System (INIS)

    The band alignment between copper interconnects and their low-k interlayer dielectrics is critical to understanding the fundamental mechanisms involved in electrical leakage in low-k/Cu interconnects. In this work, vacuum-ultraviolet (VUV) photoemission spectroscopy is utilized to determine the potential of the Schottky barrier present at low-k a-SiOC:H/Cu interfaces. By examining the photoemission spectra before and after VUV exposure of a low-k a-SiOC:H (k = 3.3) thin film fabricated by plasma-enhanced chemical-vapor deposition on a polished Cu substrate, it was found that photons with energies of 4.9 eV or greater can deplete accumulated charge in a-SiOC:H films, while VUV photons with energies of 4.7 eV or less, did not have this effect. These critical values were identified to relate the electric potential of the interface barrier between the a-SiOC:H and the Cu layers. Using this method, the Schottky barrier at the low-k a-SiOC:H (k = 3.3)/Cu interface was determined to be 4.8 ± 0.1 eV

  1. Measurements of Schottky barrier at the low-k SiOC:H/Cu interface using vacuum ultraviolet photoemission spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Guo, X.; Pei, D.; Zheng, H.; Shohet, J. L. [Plasma Processing and Technology Laboratory and Department of Electrical and Computer Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); King, S. W. [Logic Technology Development, Intel Corporation, Hillsboro, Oregon 97124 (United States); Lin, Y.-H.; Fung, H.-S.; Chen, C.-C. [National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan (China); Nishi, Y. [Department of Electrical Engineering, Stanford University, Stanford, California 94305 (United States)

    2015-12-07

    The band alignment between copper interconnects and their low-k interlayer dielectrics is critical to understanding the fundamental mechanisms involved in electrical leakage in low-k/Cu interconnects. In this work, vacuum-ultraviolet (VUV) photoemission spectroscopy is utilized to determine the potential of the Schottky barrier present at low-k a-SiOC:H/Cu interfaces. By examining the photoemission spectra before and after VUV exposure of a low-k a-SiOC:H (k = 3.3) thin film fabricated by plasma-enhanced chemical-vapor deposition on a polished Cu substrate, it was found that photons with energies of 4.9 eV or greater can deplete accumulated charge in a-SiOC:H films, while VUV photons with energies of 4.7 eV or less, did not have this effect. These critical values were identified to relate the electric potential of the interface barrier between the a-SiOC:H and the Cu layers. Using this method, the Schottky barrier at the low-k a-SiOC:H (k = 3.3)/Cu interface was determined to be 4.8 ± 0.1 eV.

  2. Chemical potential landscape in band filling and bandwidth-control of manganites: Photoemission spectroscopy measurements

    OpenAIRE

    Ebata, K.; Takizawa, M.; A. Fujimori; Kuwahara, H; Tomioka, Y.; Y. Tokura

    2008-01-01

    We have studied the effects of band filling and bandwidth control on the chemical potential in perovskite manganites $R_{1-x}A_x$MnO$_3$ ($R$ : rare earth, $A$ : alkaline earth) by measurements of core-level photoemission spectra. A suppression of the doping-dependent chemical potential shift was observed in and around the CE-type charge-ordered composition range, indicating that there is charge self-organization such as stripe formation or its fluctuations. As a function of bandwidth, we obs...

  3. X-ray photoemission spectroscopy and ion backscattering analysis of leached simulated waste glass containing UO/sub 3/

    Energy Technology Data Exchange (ETDEWEB)

    Karim, D.P.; Lam, D.J.

    1980-01-01

    UO/sub 3/ has been dissolved into several complex borosilicate glasses including Battelle simulated waste glasses 76-68, 3008, and 76-101. The glass surfaces were examined before and after leaching using x-ray photoemission spectroscopy and backscattered ion beam profiling. Samples leached in distilled water showed enhanced surface layer concentrations of several elements including uranium, titanium, zinc, iron and rare earths. For the case of uranium in 76-101, a simple experiment involving leaching two glasses in the same container showed that this surface enhancement is probably not due to redeposition from solution. Similar samples behaved quite differently when leached in a pH = 3.5 nitric acid solution, showing a surface layer high in SiO/sub 2/.

  4. Analysis of the injection layer of PTCDA in OLEDs using x-ray photoemission spectroscopy and atomic force microscopy

    Institute of Scientific and Technical Information of China (English)

    Ou Gu-Ping; Song Zhen; Wu You-Yu; Chen Xiao-Qiang; Zhang Fu-Jia

    2006-01-01

    Through the investigation of the sample surface and interface of 3, 4, 9, 10-perylenetetracarboxylic dianhydride(PTCDA)/indium-tin-oxide (ITO) thin films using atomic force microscopy, it has been found that the surface is complanate, the growth is uniform and the defects cover basically the surface of ITO. Furthermore, the number of pinholes is small. The analysis of the sample surface and interface further verifies this result by using x-ray photoemission spectroscopy. At the same time, PTCDA is found to have the ability of restraining the diffusion of chemical constituents from ITO to the hole transport layer, which is beneficial to the improvement of the performance and the useful lifetime of the organic light emitting diodes (OLEDs).

  5. Photoemission Study of the Rare Earth Intermetallic Compounds: RNi2Ge2 (R=Eu, Gd)

    International Nuclear Information System (INIS)

    EuNi2Ge2 and GdNi2Ge2 are two members of the RT2X2 (R = rare earth, T = transition metal and X = Si, Ge) family of intermetallic compounds, which has been studied since the early 1980s. These ternary rare-earth intermetallic compounds with the tetragonal ThCr2Si2 structure are known for their wide variety of magnetic properties, Extensive studies of the RT2X2 series can be found in Refs [ 1,2,3]. The magnetic properties of the rare-earth nickel germanides RNi2Ge2 were recently studied in more detail [4]. The purpose of this dissertation is to investigate the electronic structure (both valence band and shallow core levels) of single crystals of EuNi2Ge2 and GdNi2Ge2 and to check the assumptions that the f electrons are non-interacting and, consequently, the rigid-band model for these crystals would work [11], using synchrotron radiation because, to the best of our knowledge, no photoemission measurements on those have been reported. Photoemission spectroscopy has been widely used to study the detailed electronic structure of metals and alloys, and especially angle-resolved photoemission spectroscopy (ARPES) has proven to be a powerful technique for investigating Fermi surfaces (FSs) of single-crystal compounds

  6. Angular distribution and atomic effects in condensed phase photoelectron spectroscopy

    International Nuclear Information System (INIS)

    A general concept of condensed phase photoelectron spectroscopy is that angular distribution and atomic effects in the photoemission intensity are determined by different mechanisms, the former being determined largely by ordering phenomena such as crystal momentum conservation and photoelectron diffraction while the latter are manifested in the total (angle-integrated) cross section. In this work, the physics of the photoemission process is investigated in several very different experiments to elucidate the mechanisms of, and correlation between, atomic and angular distribution effects. Theoretical models are discussed and the connection betweeen the two effects is clearly established. The remainder of this thesis, which describes experiments utilizing both angle-resolved and angle-integrated photoemission in conjunction with synchrotron radiation in the energy range 6 eV less than or equal to h ν less than or equal to 360 eV and laboratory sources, is divided into three parts

  7. Use of angle-resolved XPS to determine depth profiles based on Fick's second law of diffusion: description of method and simulation study

    International Nuclear Information System (INIS)

    An iterative algorithm is proposed to extract depth profiles based on Fick's second law of diffusion in a multi-element system from data supplied by angle-resolved X-ray photoelectron spectroscopy (ARXPS). Parameters related to the concentration profiles are obtained by fitting the experimental angle-dependent relative photoelectron intensities to predictions from the algorithm. The use of relative instead of absolute photoelectron intensities eliminates error due to changes in absolute photoelectron intensities resulting from the change of system geometries in angle-resolved experiments. Simulations using an infinite source diffusion model have been conducted to study the influence of errors in the raw data and to demonstrate the robustness of the algorithm. The algorithm is tested based on preliminary experimental ARXPS data from a chemically treated polymer film

  8. Photoemission spectroscopy investigations of silicon organic dye interfaces for photovoltaic applications

    Energy Technology Data Exchange (ETDEWEB)

    Decker, Andreas; Mayer, Thomas; Jaegermann, Wolfram [Fachgebiet Oberflaechenforschung, Fachbereich Materialwissenschaften, Technische Universitaet Darmstadt (Germany); Suraru, Sabin; Wuerthner, Frank [Institut fuer Organische Chemie, Universitaet Wuerzburg (Germany)

    2010-07-01

    In a new solar cell concept, organic dyes (small molecules) are embedded in the hydrogenated microcrystalline i-layer of a silicon p-i-n structure to enhance the optical absorption. This approach aims at an increase in efficiency and a decreased silicon absorber layer thickness, thus potentially lowering deposition time and production cost. The electrical lineup of the dye orbitals versus the silicon band edges plays a vital role for this sensitization process because a driving force is needed for the transfer of photogenerated electrons and holes from the dye molecules to the silicon matrix. For the two dyes Cl{sub 4}MePTCDI and CuPc the electrical lineup on our model substrate, hydrogen terminated n-type Si(111), was investigated with photoemission interface experiments. Si(111):H was prepared from wafers with a native oxide by two-step wet-chemical etching in NH{sub 4}F which leads to clean and flat terraces as shown in AFM measurements. By comparison of calculations with XPS measurements the Si(111):H surface was found to have flat bands, i. e. showing no Fermi level pinning due to dangling bonds or fresh adsorbates originating from the sample transport through air to the UHV system, thus being a suitable substrate for interface experiments.

  9. Interferometer-controlled soft X-ray scanning photoemission microscope at SOLEIL

    CERN Document Server

    Avila, José; Lorcy, Stephane; Giorgetta, Jean-Luc; Polack, François; Asensio, María C

    2013-01-01

    ANTARES beamline (BL), a new soft X-ray scanning photoemission microscope located at the SOLEIL synchrotron storage ring has been recently designed, built and commissioned. The implemented interferometer control allows the accurate measurement of the transverse position of the Fresnel zone plate (FZP) relative to the sample. An effective sample position feedback has been achieved during experiments in static mode, with a fixed FZP position required to perform nano Angle-Resolved Photoelectron Spectroscopy (Nano-ARPES) measurements. Likewise, long-term stability has been attained for the FZP position relative to the sample during the translation of the FZP when performing typical X-ray absorption experiments around the absorption edges of light elements. Moreover, a fully automatic feedback digital control of the interferometric system provides extremely low orthogonal distortion of the recorded two-dimensional images. The microscope is diffraction limited with the resolution set to several tens of nanometers ...

  10. Probing the exciton condensate phase in 1T-TiSe{sub 2} with photoemission

    Energy Technology Data Exchange (ETDEWEB)

    Monney, C; Schwier, E F; Garnier, M G; Mariotti, N; Didiot, C; Beck, H; Aebi, P [Departement de Physique and Fribourg Center for Nanomaterials, Universite de Fribourg, CH-1700 Fribourg (Switzerland); Cercellier, H; Marcus, J [Institut Neel, CNRS-UJF, BP 166, 38042 Grenoble (France); Berger, H [EPFL, Institut de Physique de la Matiere Condensee, CH-1015 Lausanne (Switzerland); Titov, A N, E-mail: philipp.aebi@unifr.ch [Institute of Metal Physics UrD RAS, Ekaterinburg 620219 (Russian Federation)

    2010-12-15

    We present recent results obtained using angle-resolved photoemission spectroscopy performed on 1T-TiSe{sub 2}. Emphasis is put on the peculiarity of the bandstructure of TiSe{sub 2} compared to other transition metal dichalcogenides, which suggests that this system is an excellent candidate for the realization of the excitonic insulator phase. This exotic phase is discussed in relation to the BCS theory, and its spectroscopic signature is computed via a model adapted to the particular bandstructure of 1T-TiSe{sub 2}. A comparison between photoemission intensity maps calculated with the spectral function derived for this model and experimental results is shown, giving strong support for the exciton condensate phase as the origin of the charge density wave transition observed in 1T-TiSe{sub 2}. The temperature-dependent order parameter characterizing the exciton condensate phase is discussed, both on a theoretical and an experimental basis, as well as the chemical potential shift occurring in this system. Finally, the transport properties of 1T-TiSe{sub 2} are analyzed in the light of the photoemission results.

  11. Electronic properties of atomic layer deposition films, anatase and rutile TiO2 studied by resonant photoemission spectroscopy

    Science.gov (United States)

    Das, C.; Richter, M.; Tallarida, M.; Schmeisser, D.

    2016-07-01

    The TiO2 films are prepared by atomic layer deposition (ALD) method using titanium isopropoxide precursors at 250 °C and analyzed using resonant photoemission spectroscopy (resPES). We report on the Ti2p and O1s core levels, on the valence band (VB) spectra and x-ray absorption spectroscopy (XAS) data, and on the resonant photoelectron spectroscopy (resPES) profiles at the O1s and the Ti3p absorption edges. We determine the elemental abundance, the position of the VB maxima, the partial density of states (PDOS) in the VB and in the conduction band (CB) and collect these data in a band scheme. In addition, we analyze the band-gap states as well as the intrinsic states due to polarons and charge-transfer excitations. These states are found to cause multiple Auger decay processes upon resonant excitation. We identify several of these processes and determine their relative contribution to the Auger signal quantitatively. As our resPES data allow a quantitative analysis of these defect states, we determine the relative abundance of the PDOS in the VB and in CB and also the charge neutrality level. The anatase and rutile polymorphs of TiO2 are analyzed in the same way as the TiO2 ALD layer. The electronic properties of the TiO2 ALD layer are compared with the anatase and rutile polymorphs of TiO2. In our comparative study, we find that ALD has its own characteristic electronic structure that is distinct from that of anatase and rutile. However, many details of the electronic structure are comparable and we benefit from our spectroscopic data and our careful analysis to find these differences. These can be attributed to a stronger hybridization of the O2p and Ti3d4s states for the ALD films when compared to the anatase and rutile polymorphs.

  12. The development of photoemission spectroscopy and its application to the study of semiconductor interfaces Observations on the interplay between basic and applied research (Welch Memorial Lecture)

    Science.gov (United States)

    Spicer, W. E.

    1985-01-01

    A sketch is given of the development of photoemission electron spectroscopy (PES) with emphasis on the author's own experience. Emphasis is placed: (1) on the period between 1958-1970; (2) on the various developments which were required for PES to emerge; and (3) on the strong interactions between applied/fundamental and knowledge/empirically based research. A more detailed discussion is given of the recent (1975-present) application of PES to study the interfaces of III-V semiconductors.

  13. Photoemission with high-order harmonics: A tool for time-resolved core-level spectroscopy

    DEFF Research Database (Denmark)

    Christensen, Bjarke Holl; Raarup, Merete Krog; Balling, Peter

    2010-01-01

    A setup for femtosecond time-resolved photoelectron spectroscopy of solid surfaces is presented. The photon energies for core-level spectroscopy experiments are created by high-order harmonic generation from infrared 120-femtosecond laser pulses focused in a Ne gas jet. The present experimental r...... from the sample are collected by a large-solid-angle time-of-flight electron spectrometer based on a parabolic-grid reflector. Results from experiments probing the Bi 5d core-levels are presented, and the results of preliminary pump-probe experiments are described....

  14. Electronic structure of YbNiX3 (X =Si, Ge) studied by hard X-ray photoemission spectroscopy

    International Nuclear Information System (INIS)

    lectronic structure of the Kondo lattices YbNiX3 (X =Si, Ge) has been investigated by means of hard x-ray photoemission spectroscopy (HAXPES) with hν = 5.95 keV. From the Yb 3d HAXPES spectra, the Yb valence in YbNiSi3 is estimated to be ∝ 2.92, which is almost temperature-independent. On the other hand, the valence in YbNiGe3 is estimated to be 2.48 at 300 K, showing significant valence fluctuation, and gradually decreases to 2.41 at 20 K on cooling. The Ni 2p3/2 and Yb3+ 4f peaks exhibit opposite energy shifts amounting to ∝ 0.6 eV between YbNiSi3 and YbNiGe3. We propose a simple model for the electronic structure of YbNiX3 based on the HAXPES results. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  15. Electronic structure of YbNiX{sub 3} (X =Si, Ge) studied by hard X-ray photoemission spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Sato, Hitoshi; Shimada, Kenya; Namatame, Hirofumi [Hiroshima Synchrotron Radiation Center, Hiroshima University, Kagamiyama 2-313, Higashi-Hiroshima 739-0046 (Japan); Utsumi, Yuki [Max-Planck Institute for Chemical Physics of Solids, 01187 Dresden (Germany); Kodama, Junichi; Nagata, Heisuke [Graduate School of Science, Hiroshima University, Kagamiyama 1-3-1, Higashi-Hiroshima 739-8526 (Japan); Avila, Marcos A.; Ribeiro, Raquel A. [Centro de Ciencias Naturais e Humanas, Universidade Federal do ABC, Santo Andre - SP, 09210-580 (Brazil); Umeo, Kazunori [Cryogenics and Instrumental Analysis Division, N-BARD, Hiroshima University, Higashi-Hiroshima 739-8526 (Japan); Takabatake, Toshiro [Department of Quantum Matter, AdSM, Hiroshima University, Higashi-Hiroshima 739-8530 (Japan); Institute for Advanced Materials Research, Hiroshima University, Higashi-Hiroshima 739-8530 (Japan); Mimura, Kojiro; Motonami, Satoru; Anzai, Hiroaki [Graduate School of Engineering, Osaka Prefecture University, Sakai 599-8531 (Japan); Ueda, Shigenori [Synchrotron X-ray Station at SPring-8, National Institute for Materials Science, Hyogo 679-5148 (Japan); Taniguchi, Masaki [Hiroshima Synchrotron Radiation Center, Hiroshima University, Kagamiyama 2-313, Higashi-Hiroshima 739-0046 (Japan); Graduate School of Science, Hiroshima University, Kagamiyama 1-3-1, Higashi-Hiroshima 739-8526 (Japan)

    2015-06-15

    lectronic structure of the Kondo lattices YbNiX{sub 3} (X =Si, Ge) has been investigated by means of hard x-ray photoemission spectroscopy (HAXPES) with hν = 5.95 keV. From the Yb 3d HAXPES spectra, the Yb valence in YbNiSi{sub 3} is estimated to be ∝ 2.92, which is almost temperature-independent. On the other hand, the valence in YbNiGe{sub 3} is estimated to be 2.48 at 300 K, showing significant valence fluctuation, and gradually decreases to 2.41 at 20 K on cooling. The Ni 2p{sub 3/2} and Yb{sup 3+} 4f peaks exhibit opposite energy shifts amounting to ∝ 0.6 eV between YbNiSi{sub 3} and YbNiGe{sub 3}. We propose a simple model for the electronic structure of YbNiX{sub 3} based on the HAXPES results. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  16. Structure analysis of thin corrosion products film on hot-dip Zn-Al coatings by synchrotron radiation photoemission spectroscopy

    International Nuclear Information System (INIS)

    Structure of thin corrosion products film (CPF) on hot-dip Zn-Al alloy coated steel sheets were investigated by means of photoemission spectroscopy using synchrotron radiation of 160 eV and μ-FT-IR method, and were compared with those on Zn and Al pure metal sheets. CPF was prepared by 1 h and 16 h exposure in air saturated with water vapor at 323 K under the presence of NaCl particles. As a result, the dominant component of the CPF on the Zn-0.2%Al coating changed from Zn (OH)2 to 2ZnCO3·3Zn (OH)2, while the CPF of Zn-55%Al alloy coating was consisted mainly of ZnCl2·4Zn (OH)2. And it was found that the structure near the surface of CPF, which was composed mainly of Al oxide, was transformed into the surface structure covered with Al chloride by humid exposure under the presence of NaCl. (author)

  17. Methods in angle-resolved photoelectron diffraction: Slab method versus separable propagator cluster approach

    OpenAIRE

    H. Wu; Chu, TP; Tong, SY; Ng, CY

    1998-01-01

    We have compared multiple-scattering results of angle-resolved photoelectron diffraction spectra between the exact slab method and the separable propagator perturbation cluster method. In the slab method, the source wave and multiple scattering within strongly scattering layers are expanded in spherical waves while the scattering among different layers is expressed in plane waves. The transformation between spherical waves and plane waves is done exactly. The plane waves are then matched acro...

  18. Angle-resolved x-ray circular and magnetic circular dichroisms: Definitions and applications

    OpenAIRE

    Tong, DSY; X Guo; Tobin, JG; Waddill, GD

    1996-01-01

    We introduce definitions of angle-resolved x-ray circular dichroism (ARXCD) and magnetic x-ray circular dichroism (ARMXCD). As defined, the much larger effect of circular dichroism (ARXCD) is separated from the smaller magnetic (ARMXCD) effect. In all materials, ARXCD is zero along mirror planes while nonzero elsewhere. ARMXCD is nonzero only in magnetic materials. The measurement and analysis of ARMXCD allow element specific surface magnetism and surface structure as well as their inter-rela...

  19. Angle-resolved ion TOF spectrometer with a position sensitive detector

    Energy Technology Data Exchange (ETDEWEB)

    Saito, Norio [Electrotechnical Lab., Tsukuba, Ibaraki (Japan); Heiser, F.; Wieliczec, K.; Becker, U.

    1996-07-01

    A angle-resolved ion time-of-flight mass spectrometer with a position sensitive anode has been investigated. Performance of this spectrometer has been demonstrated by measuring an angular distribution of a fragment ion pair, C{sup +} + O{sup +}, from CO at the photon energy of 287.4 eV. The obtained angular distribution is very close to the theoretically expected one. (author)

  20. Cellular organization and substructure measured using angle-resolved low-coherence interferometry.

    OpenAIRE

    Wax, Adam; Yang, Changhuei; Backman, Vadim; Badizadegan, Kamran; Boone, Charles W.; Dasari, Ramachandra R.; Feld, Michael S.

    2002-01-01

    We measure the organization and substructure of HT29 epithelial cells in a monolayer using angle-resolved low-coherence interferometry. This new technique probes cellular structure by measuring scattered light, as in flow cytometry, but offers an advantage in that the structure can be examined in situ, avoiding the need to disrupt the cell monolayer. We determine the size distribution of the cell nuclei by fitting measured light-scattering spectra to the predictions of Mie theory. In addition...

  1. Electron mean free path from angle-dependent photoelectron spectroscopy of aerosol particles

    CERN Document Server

    Goldmann, Maximilian; West, Adam H C; Yoder, Bruce L; Signorell, Ruth

    2015-01-01

    We propose angle-resolved photoelectron spectroscopy of aerosol particles as an alternative way to determine the electron mean free path of low energy electrons in solid and liquid materials. The mean free path is obtained from fits of simulated photoemission images to experimental ones over a broad range of different aerosol particle sizes. The principal advantage of the aerosol approach is twofold. Firstly, aerosol photoemission studies can be performed for many different materials, including liquids. Secondly, the size-dependent anisotropy of the photoelectrons can be exploited in addition to size-dependent changes in their kinetic energy. These finite size effects depend in different ways on the mean free path and thus provide more information on the mean free path than corresponding liquid jet, thin film, or bulk data. The present contribution is a proof of principle employing a simple model for the photoemission of electrons and preliminary experimental data for potassium chloride aerosol particles.

  2. Electron mean free path from angle-dependent photoelectron spectroscopy of aerosol particles

    International Nuclear Information System (INIS)

    We propose angle-resolved photoelectron spectroscopy of aerosol particles as an alternative way to determine the electron mean free path of low energy electrons in solid and liquid materials. The mean free path is obtained from fits of simulated photoemission images to experimental ones over a broad range of different aerosol particle sizes. The principal advantage of the aerosol approach is twofold. First, aerosol photoemission studies can be performed for many different materials, including liquids. Second, the size-dependent anisotropy of the photoelectrons can be exploited in addition to size-dependent changes in their kinetic energy. These finite size effects depend in different ways on the mean free path and thus provide more information on the mean free path than corresponding liquid jet, thin film, or bulk data. The present contribution is a proof of principle employing a simple model for the photoemission of electrons and preliminary experimental data for potassium chloride aerosol particles

  3. Development of transmission-type polarized electron source for inverse photoemission spectroscopy

    International Nuclear Information System (INIS)

    Transmission type (NEA-GaAs) spin-polarized electron sources, in which pumped laser light is injected from the back side of the photocathodes and the polarize beam is extracted from the front side, have been developed. By using this type photocathode, the high brightness of ∼2×107A.cm-2.sr-1 and the high polarization of ∼90% were achieved. In UVSOR, we are planning to apply these types of photocathodes to the inverse photoelectron spectroscopy, and started to design compact 90° bend spin rotator. (author)

  4. Soft X-ray photoemission spectroscopy of selected neurotransmitters in the gas phase

    Energy Technology Data Exchange (ETDEWEB)

    Maris, Assimo; Melandri, Sonia; Evangelisti, Luca; Caminati, Walther [Dipartimento di Chimica ' G. Ciamician' dell' Universita, Via Selmi 2, I-40126 Bologna (Italy); Giuliano, Barbara M. [Departamento de Quimica da Universidade de Coimbra, 3004-535 Coimbra (Portugal); Plekan, Oksana [Sincrotrone Trieste, in Area Science Park, I-34149 Basovizza, Trieste (Italy); Feyer, Vitaliy [Sincrotrone Trieste, in Area Science Park, I-34149 Basovizza, Trieste (Italy); Electronic Properties (PGI-6), Peter Gruenberg Institute, Forschungszentrum Juelich GmbH, Leo-Brandt-Strasse, 52428 Juelich (Germany); Richter, Robert [Sincrotrone Trieste, in Area Science Park, I-34149 Basovizza, Trieste (Italy); Coreno, Marcello [CNR-IMIP, Montelibretti, I-00016 Rome (Italy); Prince, Kevin C., E-mail: kevin.prince@elettra.trieste.it [Sincrotrone Trieste, in Area Science Park, I-34149 Basovizza, Trieste (Italy); CNR-IOM, Laboratorio TASC, I-34149 Basovizza, Trieste (Italy)

    2012-09-15

    Highlights: Black-Right-Pointing-Pointer Neurotransmitter molecules. Black-Right-Pointing-Pointer Photoelectron spectroscopy. Black-Right-Pointing-Pointer Electronic structure. Black-Right-Pointing-Pointer Weak hydrogen bonding. -- Abstract: The valence molecular orbitals and core levels of tyramine, tryptamine and tryptophol in the gas phase have been studied using X-ray photoelectron spectroscopy (XPS) and theoretical methods. The energies of the outer valence region spectrum are found to be in agreement with previously reported He I spectra, while new data on the inner valence molecular orbitals are reported. The structures in the carbon, nitrogen and oxygen core level spectra of these molecules have been identified and assigned. These compounds are characterised by conformers with hydrogen bonding in which the {pi} systems of the phenol and indole groups act as hydrogen acceptors, but a spectroscopic signature of this hydrogen bond was not observed. This is in contrast with our previous spectra of amino acids, where conformers with specific hydrogen bonding showed strong effects in core level spectra. We attribute the difference to the weaker strength of the {pi}-hydrogen bonding.

  5. Dynamic High Pressure: a novel approach toward near ambient pressure photoemission spectroscopy and spectromicroscopy

    International Nuclear Information System (INIS)

    A Dynamic High Pressure (DHP) system has been developed, tested and implemented in the scanning photoelectron microscope (SPEM) operated at ESCAmicroscopy beamline at Elettra synchrotron. The system consists of a compact gas injection set up that allows experiments with local pressure near the sample several orders of magnitude higher that the allowable pressure for X-ray photoelectron spectroscopy setups. The DHP setup controls the amount of gas injected toward the sample by fine tuning the time and spatial profiles using a pulsed valve and a nozzle, respectively. The DHP functionality and effectiveness has been demonstrated by in operando oxidation experiments of Ru and Si. The obtained results confirmed that using the DHP the gas exposure onto the sample is equivalent to a static pressure between 10−3 and 10−2 mbar, about 3 orders of magnitude higher than the maximum gas pressure for the XPS machines under operation.

  6. Electronic structure of the Ga1-xCrxN studied by high-energy photoemission spectroscopy

    International Nuclear Information System (INIS)

    Full text: It is predicted based on hole-mediated ferromagnetism (FM) that GaMnN may have Curie temperature (Tc) higher than room temperature if doped with high hole concentration (ca 1020 cm-3 ). The hole-mediated ferromagnetism (FM) can produce reliable estimate of Tc for diluted magnetic semiconductor (DMS) such as GaMnAs due to the shallow Mn-associated energy states in the GaAs system. Since the energy states of doped transition metals exist as a deep level in a wide band semiconductor like GaN and carriers are localized in these states, different mechanisms for magnetism will play a role in GaN rather than the hole-mediated one. This conjecture is partly supported by the recent report of FM in n-type GaN doped with Cr, although the mechanism of the observed FM has not been elucidated yet. In order to get insight into the mechanism of the FM, we have studied the electronic structure of GaN doped with Cr exploiting bulk-sensitive hard X-ray photoemission spectroscopy at a photon energy of 5.95keV at SPring-8. We have observed that Cr-doping does introduce new electronic levels in the band gap and causes some change in the valence band structure. Based on the first principle calculation, the Cr-associated electronic levels in the band gap are assigned to nonbonding and anti-bonding d states, the latter of which pins the Fermi level, while the change of the valence band suggests that the Ga 4s originated states are significantly modified through hybridization with the Cr 3d orbital. The present result evidences that the Ga valence electrons are considerably modified through the interaction with second neighbor Cr atoms. Such hybridization between Ga 4s and Cr 3d may play a significant role in the observed ferromagnetism in Ga1-xCrxN

  7. Combined Photoemission Spectroscopy and Electrochemical Study of a Mixture of (Oxy)carbides as Potential Innovative Supports and Electrocatalysts.

    Science.gov (United States)

    Calvillo, Laura; Valero-Vidal, Carlos; Agnoli, Stefano; Sezen, Hikmet; Rüdiger, Celine; Kunze-Liebhäuser, Julia; Granozzi, Gaetano

    2016-08-01

    Active and stable non-noble metal materials, able to substitute Pt as catalyst or to reduce the Pt amount, are vitally important for the extended commercialization of energy conversion technologies, such as fuel cells and electrolyzers. Here, we report a fundamental study of nonstoichiometric tungsten carbide (WxC) and its interaction with titanium oxycarbide (TiOxCy) under electrochemical working conditions. In particular, the electrochemical activity and stability of the WxC/TiOxCy system toward the ethanol electrooxidation reaction (EOR) and hydrogen evolution reaction (HER) are investigated. The chemical changes caused by the applied potential are established by combining photoemission spectroscopy and electrochemistry. WxC is not active toward the ethanol electrooxidation reaction at room temperature but it is highly stable under these conditions thanks to the formation of a passive thin film on the surface, consisting mainly of WO2 and W2O5, which prevents the full oxidation of WxC. In addition, WxC is able to adsorb ethanol, forming ethoxy groups on the surface, which constitutes the first step for the ethanol oxidation. The interaction between WxC and TiOxCy plays an important role in the electrochemical stability of WxC since specific orientations of the substrate are able to stabilize WxC and prevent its corrosion. The beneficial interaction with the substrate and the specific surface chemistry makes tungsten carbide a good electrocatalyst support or cocatalyst for direct ethanol fuel cells. However, WxC is active toward the HER and chemically stable under hydrogen reduction conditions, since no changes in the chemical composition or dissolution of the film are observed. This makes tungsten carbide a good candidate as electrocatalyst support or cocatalyst for the electrochemical production of hydrogen. PMID:27399154

  8. Time dependence of FEL-induced surface photovoltage on semiconductor interfaces measured with synchroton radiation photoemission spectroscopy

    International Nuclear Information System (INIS)

    During the last year, the first surface science experiments simultaneously using a Free Electron Laser (FEL) and Synchrotron Radiation (SR) have been performed on SuperACO at LURE (Orsay, France). These open-quotes two colorclose quotes experiments studied the surface photovoltage (SPV) induced on semiconductor surfaces and interfaces by the SuperACO FEL, a storage ring FEL delivering 350 nm photons which am naturally synchronized with the SR; the SPV was measured by synchrotron radiation core-level photoemission spectroscopy on the high-resolution SU3 undulator beamline. We will describe the experimental setup, which allowed us to convey the FEL light onto the samples sitting in the SU3 experimental station by means of a series of mirrors, and show the results we obtained for prototypical systems such as Ag/GaAs(110) and Si(111) 2 x 1. The dependence of the SPV was studied in function of various parameters, changing sample doping and photon flux; but our efforts were mainly devoted to studying its dependence on the time delay between the FEL pump and the SR probe. On SuperACO, such delay can be varied between 1 and 120 ns, the limits being given by the time duration of a SR pulse and by the interval between two consecutive positron bunches, respectively. The results show a clear temporal dependence of the amount of SPV on cleaved Si surfaces, where as the Ag/GaAs(110) does not show any difference on the ns time scale. We will discuss these results in terms of the role of surface recombination in the dynamics of the photoinduced electron-hole pairs. These studies follow the evolution of the density of electrostatic charge at surfaces and interfaces on a nanosecond time scale, and might pave the way for a new series of experiments: for example, one might explore what are the physical mechanisms limiting the time response of Schottky diodes

  9. The Use of XPS and Angle Resolved XPS for the Characterization of Self Assembled Monolayer Grown on Substrate Surfaces for Specific Biological Applications

    International Nuclear Information System (INIS)

    The techniques of X-Ray Photoelectron Spectroscopy (XPS) and angle resolved XPS have been utilised to characterise the chemistry and structure of SAMs grown on gold surfaces for biological applications. A study of a series of alkane thiol SAMs on gold showed that the film thickness is proportional to alkane chain length and that changes in the sulphur chemistry indicate different bonding modes at low and high overlayer coverage. It is determined that a well ordered matrix thiol has a SAM film thickness confirming that the molecules are aligned at a 27 degree tilt angle to the surface normal and bond to the gold surface via the sulphur group. (author)

  10. Electronic properties of metal-organic and organic-organic interfaces studied by photoemission and photoabsorption spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Molodtsova, Olga

    2006-07-01

    In this work systematic studies of the organic semiconductor CuPc have been presented. In general the investigation can be devided in three parts. In the first one we have studied the electronic structure of clean CuPc thin film. The next two parts are devoted to organic-organic and metal-organic interface formation, where one of the interface components is CuPc thin film. The main results of this thesis are: - The electronic structure of the pristine organic semiconductor CuPc has been obtained by a combination of conventional and resonant photoemission, near-edge X-ray absorption, as well as by theoretical ab initio quantum-chemical calculations. The contributions of different atomic species as well as sites of the CuPc molecule to the electronic DOS has been established. A combined experimental and theoretical study of the unoccupied electronic density of states of CuPc was presented. - The electronic properties of the organic heterointerfaces between fullerite and pristine copper phthalocyanine were studied. Both interfaces, CuPc/C{sub 60} and C{sub 60}/CuPc, were found to be non-reactive with pronounced shifts of the vacuum level pointing to the formation of an interfacial dipole mainly at the CuPc side of the heterojunctions. The dipole values are close to the difference of the work functions of the two materials. Important interface parameters and hole-injection barriers were obtained. The sequence of deposition does not influence the electronic properties of the interfaces. - CuPc doped with potassium was studied by means of photoemission and photoabsorption spectroscopy. A detailed analysis of the core-level PE spectra allows one to propose possible lattice sites, which harbor the potassium ions. The films prepared in this thesis showed no finite electronic density of states at the Fermi level. - Two stages of the In/CuPc interface formation have been distinguished. The low-coverage stage is characterized by a strong diffusion of the In atoms into the

  11. Angle-resolved analysis of magnetic hysteresis for micro-magnetic clusters with local deformations

    International Nuclear Information System (INIS)

    Magnetic dynamic process for an octagonal micro-magnetic cluster with one dislocation loop was simulated by pseudo-nonequilibrial Monte Carlo method including pseudo-dipole interaction. The results showed that the magnetic hysteresis curves of micro-magnetic clusters with one dislocation loop and of those without any deformation differ. The difference is more clearly shown for noise pattern of magnetization process, which depends on dynamic behavior of spin ensemble. A series of snapshots for spin ensemble displays that the magnetization process depends on the direction of the applied magnetic field. We propose usefulness of angle-resolved analysis of magnetic dynamic process to evaluate magnetic clusters

  12. Photoemission spectroscopy study of the hole-doped Haldane chain Y2-xSrxBaNiO5

    International Nuclear Information System (INIS)

    In this paper, we present photoemission experiments on the hole-doped Haldane chain compound Y2-xSrxBaNiO5. By using the photon energy dependence of the photoemission cross section, we identified the symmetry of the first ionisation states (d type). Hole doping in this system leads to a significant increase in the spectral weight at the top of the valence band without any change in the vicinity of the Fermi energy. This behavior, never observed in other charge transfer oxides, could result from the Ni3d-O2p hybridization enhancement due to the shortening of the relevant Ni-O distance with doping

  13. Introductory Lecture. Probing wavepacket dynamics with femtosecond energy- and angle-resolved photoelectron spectroscopy

    OpenAIRE

    Takatsuka, Kazuo; Arasaki, Yasuki; Wang, Kwanghsi; McKoy, Vincent

    2000-01-01

    Several recent studies have demonstrated how well-suited femtosecond time-resolved photoelectron spectra are for mapping wavepacket dynamics in molecular systems. Theoretical studies of femtosecond photoelectron spectra which incorporate a robust description of the underlying photoionization dynamics should enhance the utility of such spectra as a probe of wavepackets and of the evolution of electronic structure. This should be particularly true in regions of avoided crossings where the photo...

  14. Charge transfer dynamics of 3,4,9,10-perylene-tetracarboxylic-dianhydride molecules on Au(111) probed by resonant photoemission spectroscopy.

    Science.gov (United States)

    Cao, Liang; Wang, Yu-Zhan; Chen, Tie-Xin; Zhang, Wen-Hua; Yu, Xiao-Jiang; Ibrahim, Kurash; Wang, Jia-Ou; Qian, Hai-Jie; Xu, Fa-Qiang; Qi, Dong-Chen; Wee, Andrew T S

    2011-11-01

    Charge transfer dynamics across the lying-down 3,4,9,10-perylene-tetracarboxylic-dianhydride (PTCDA) organic semiconductor molecules on Au(111) interface has been investigated using the core-hole clock implementation of resonant photoemission spectroscopy. It is found that the charge transfer time scale at the PTCDA∕Au(111) interface is much larger than the C 1s core-hole lifetime of 6 fs, indicating weak electronic coupling between PTCDA and the gold substrate due to the absence of chemical reaction and∕or bonding. PMID:22070311

  15. On the X-ray induced chemical reduction of CeO2 as seen with X-ray photoemission spectroscopy

    International Nuclear Information System (INIS)

    A recent X-ray photoemission spectroscopy (XPS) study (M.V. Rama Rao and T. Shripathi, J. Electron Spectrosc. Relat. Phenom., 87 (1997) 121) on X-ray irradiated ceria stated that hydroxyl groups play a meaningful role in enhancing the chemical reduction of this oxide and that chemical damage mainly involves layers lying at depths that are larger than photoelectron attenuation lengths. We comment upon this paper, and show that the experimental evidence therein presented by the authors does not warrant these conclusions. (Copyright (c) 1998 Elsevier Science B.V., Amsterdam. All rights reserved.)

  16. High resolution photoemission spectroscopy: Evidence for strong chemical interaction between Mg and 3,4,9,10-perylene-tetracarboxylic dianhydride

    International Nuclear Information System (INIS)

    The interface formation between Mg and 3,4,9,10-perylene-tetracarboxylic dianhydride (PTCDA) was investigated by high resolution soft x-ray photoemission spectroscopy. The interface chemistry was obtained after fitting the core level spectra as a function of Mg thickness. At the initial stage of deposition, a strong chemical interaction between Mg and the single bonded oxygen atoms of PTCDA is observed leading to the formation of MgO and a modified organic molecule. Based on the experimental evidence, the molecular structure of the modified molecule is proposed. Moreover, the changes observed in the measured C1s core level spectra are supported by density functional theory calculations

  17. Electronic structure of C and N co-doped TiO2: A combined hard x-ray photoemission spectroscopy and density functional theory study

    International Nuclear Information System (INIS)

    We have studied the electronic structure of C and N co-doped TiO2 using hard x-ray photoelectron spectroscopy and first-principles density functional theory calculations. Our results reveal overlap of the 2p states of O, N, and C in the system which shifts the valence band maximum towards the Fermi level. Combined with optical data we show that co-doping is an effective route for band gap reduction in TiO2. Comparison of the measured valence band with theoretical photoemission density of states reveals the possibility of C on Ti and N on O site

  18. Angle-resolved multioctave supercontinua from mid-infrared laser filaments.

    Science.gov (United States)

    Mitrofanov, A V; Voronin, A A; Sidorov-Biryukov, D A; Mitryukovsky, S I; Rozhko, M V; Pugžlys, A; Fedotov, A B; Panchenko, V Ya; Baltuška, A; Zheltikov, A M

    2016-08-01

    Angle-resolved spectral analysis of a multioctave high-energy supercontinuum output of mid-infrared laser filaments is shown to provide a powerful tool for understanding intricate physical scenarios behind laser-induced filamentation in the mid-infrared. The ellipticity of the mid-infrared driver beam breaks the axial symmetry of filamentation dynamics, offering a probe for a truly (3+1)-dimensional spatiotemporal evolution of mid-IR pulses in the filamentation regime. With optical harmonics up to the 15th order contributing to supercontinuum generation in such filaments alongside Kerr-type and ionization-induced nonlinearities, the output supercontinuum spectra span over five octaves from the mid-ultraviolet deep into the mid-infrared. Full (3+1)-dimensional field evolution analysis is needed for an adequate understanding of this regime of laser filamentation. Supercomputer simulations implementing such analysis articulate the critical importance of angle-resolved measurements for both descriptive and predictive power of filamentation modeling. Strong enhancement of ionization-induced blueshift is shown to offer new approaches in filamentation-assisted pulse compression, enabling the generation of high-power few- and single-cycle pulses in the mid-infrared. PMID:27472598

  19. High-resolution three-dimensional spin- and angle-resolved photoelectron spectrometer using vacuum ultraviolet laser light

    Science.gov (United States)

    Yaji, Koichiro; Harasawa, Ayumi; Kuroda, Kenta; Toyohisa, Sogen; Nakayama, Mitsuhiro; Ishida, Yukiaki; Fukushima, Akiko; Watanabe, Shuntaro; Chen, Chuangtian; Komori, Fumio; Shin, Shik

    2016-05-01

    We describe a spin- and angle-resolved photoelectron spectroscopy (SARPES) apparatus with a vacuum-ultraviolet (VUV) laser (hν = 6.994 eV) developed at the Laser and Synchrotron Research Center at the Institute for Solid State Physics, The University of Tokyo. The spectrometer consists of a hemispherical photoelectron analyzer equipped with an electron deflector function and twin very-low-energy-electron-diffraction-type spin detectors, which allows us to analyze the spin vector of a photoelectron three-dimensionally with both high energy and angular resolutions. The combination of the high-performance spectrometer and the high-photon-flux VUV laser can achieve an energy resolution of 1.7 meV for SARPES. We demonstrate that the present laser-SARPES machine realizes a quick SARPES on the spin-split band structure of a Bi(111) film even with 7 meV energy and 0.7∘ angular resolutions along the entrance-slit direction. This laser-SARPES machine is applicable to the investigation of spin-dependent electronic states on an energy scale of a few meV.

  20. Instrument developments for inverse photoemission

    International Nuclear Information System (INIS)

    Experimental developments principally concerning electron sources for inverse photoemission are presented. The specifications of the electron beam are derived from experiment requirements, taking into account the limitations encountered (space charge divergence). For a wave vector resolution of 0.2 A-1, the maximum current is 25 microA at 20 eV. The design of a gun providing such a beam in the range 5 to 50 eV is presented. Angle-resolved inverse photoemission experiments show angular effects at 30 eV. For an energy of 10 eV, angular effects should be stronger, but the low efficiency of the spectrometer in this range makes the experiments difficult. The total energy resolution of 0.3 eV is the result mainly of electron energy spread, as expected. The electron sources are based on field effect electron emission from a cathode consisting of a large number of microtips. The emission arises from a few atomic cells for each tip. The ultimate theoretical energy spread is 0.1 eV. This value is not attained because of an interface resistance problem. A partial solution of this problem allows measurement of an energy spread of 0.9 eV for a current of 100 microA emitted at 60 eV. These cathodes have a further advantage in that emission can occur at a low temperature

  1. Exploring three-dimensional orbital imaging with energy-dependent photoemission tomography

    Science.gov (United States)

    Weiß, S.; Lüftner, D.; Ules, T.; Reinisch, E. M.; Kaser, H.; Gottwald, A.; Richter, M.; Soubatch, S.; Koller, G.; Ramsey, M. G.; Tautz, F. S.; Puschnig, P.

    2015-10-01

    Recently, it has been shown that experimental data from angle-resolved photoemission spectroscopy on oriented molecular films can be utilized to retrieve real-space images of molecular orbitals in two dimensions. Here, we extend this orbital tomography technique by performing photoemission initial state scans as a function of photon energy on the example of the brickwall monolayer of 3,4,9,10-perylene tetracarboxylic dianhydride (PTCDA) on Ag(110). The overall dependence of the photocurrent on the photon energy can be well accounted for by assuming a plane wave for the final state. However, the experimental data, both for the highest occupied and the lowest unoccupied molecular orbital of PTCDA, exhibits an additional modulation attributed to final state scattering effects. Nevertheless, as these effects beyond a plane wave final state are comparably small, we are able, with extrapolations beyond the attainable photon energy range, to reconstruct three-dimensional images for both orbitals in agreement with calculations for the adsorbed molecule.

  2. Growth and structure of CrN nanoislands on Cu(001) studied by scanning tunneling microscopy and X-ray photoemission spectroscopy

    International Nuclear Information System (INIS)

    We report a method for the fabrication of high structural quality CrN nanoislands on Cu(001). The CrN nanoislands can be fabricated in ultrahigh vacuum conditions by means of Cr atoms deposition on saturated Cu(001)c(2 × 2)-N surface and subsequent annealing at 500 °C. Existence of two types of nanoislands is shown by scanning tunneling microscopy investigations with atomic resolution for different CrN nanoislands formed on surface with 0.35 monolayer Cr coverage. The measured in-plane lattice constant (a = 0.39 ± 0.01 nm) of the CrN nanoislands is 8% larger than the Cu substrate lattice. X-ray photoemission spectroscopy investigations reveal chromium nitride phase transition from CrN to Cr2N associated with changes of Cr concentration. - Highlights: ► We develop a method for the fabrication of CrN nanoislands on Cu(001). ► Growth of two types of CrN nanoislands is shown by scanning tunneling microscopy. ► Chromium nitride phase transition is shown by X-ray photoemission spectroscopy

  3. Effects of the electron–hole pair in Auger and X-ray photoemission spectroscopy from surfaces of Fe–Si

    Energy Technology Data Exchange (ETDEWEB)

    Gervasoni, J.L. [Centro Atomico Bariloche and Instituto Balseiro, Comision Nacional de Energia Atomica, Universidad Nacional de Cuyo, R8402AGP S. C. de Bariloche, Rio Negro (Argentina); Jenko, M.; Poniku, B.; Belič, I. [Institute of Metals and Technology, Lepi pot 11, 1000 Ljubljana (Slovenia); Juan, A. [Departamento de Física, Universidad Nacional del Sur, Bahia Blanca (Argentina)

    2015-07-01

    In this work, we investigate in detail the effects due to the interaction between an electron and a stationary positive ion (or atomic hole) in the neighborhood of a surface of Fe–Si, having a strong plasmon peak in their electron energy loss spectra, when it is excited with synchrotron radiation. We take into account the effects due to the sudden creation of an electron and the residual holes, one in the case of X-ray photoemission spectroscopy (XPS) and two in the case of Auger electron spectroscopy (AES). We use a semi classical dielectric formulation for the photoelectron trajectory, and we estimated the parameter r{sub s}, the radius of the sphere occupied by one electron in the solid, which is critical in order to define the electron density of the alloy. With the cited formulation, we have obtained a detailed behavior of the different contributions of the collective excitations in both processes.

  4. The triple correlation function as a tool for angle resolved structural analysis of spherical clusters

    International Nuclear Information System (INIS)

    Complete text of publication follows. Finite charged particle ensembles in externally controlled confinement geometries allow for a systematic investigation of correlation effects over broad ranges of plasma parameters. Additionally, the formation of distinct shells emerges as a governing finite-size effect in systems of trapped ions and dusty plasma as well. As a sensitive tool to study the internal cluster structure, we introduce the 'Triple Correlations Function' (TCF), which allows for an angle resolved structure analysis. The TCF can not only resolve the transition probability of particles between shells, but also structural modifications within the shells during dynamic processes, e.g. melting or excitation. In particular this quantity is not affected by rotational invariance (i.e. rotation of the entire cluster). Using the TCF we study the effect of Coulomb screening, temperature, and special symmetries of different ground and metastable states with respect to the exact particle number as well as the limiting case of large N.

  5. Angle-resolved spin wave band diagrams of square antidot lattices studied by Brillouin light scattering

    International Nuclear Information System (INIS)

    The Brillouin light scattering technique has been exploited to study the angle-resolved spin wave band diagrams of squared Permalloy antidot lattice. Frequency dispersion of spin waves has been measured for a set of fixed wave vector magnitudes, while varying the wave vector in-plane orientation with respect to the applied magnetic field. The magnonic band gap between the two most dispersive modes exhibits a minimum value at an angular position, which exclusively depends on the product between the selected wave vector magnitude and the lattice constant of the array. The experimental data are in very good agreement with predictions obtained by dynamical matrix method calculations. The presented results are relevant for magnonic devices where the antidot lattice, acting as a diffraction grating, is exploited to achieve multidirectional spin wave emission

  6. Angle-resolved Beutler-Fano profile and dynamics for the predissociation of H2

    Science.gov (United States)

    Meng, Qingnan; Wang, Jie; Mo, Yuxiang

    2016-05-01

    The asymmetric photoabsorption line profile (Beutler-Fano profile) arising from two interacting channels has applications in atomic, molecular, and condensed matter physics. In this work, the angle-resolved and fully-rotationally-resolved Beutler-Fano profiles for the predissociation of H2,H2+h v →H ( 1 s )+H ( 2 s )/H (2 p ) , have been measured. It is found that the Beutler-Fano profiles display different shapes for the fragments H(2 s ,2 p ) recoiling at the parallel and perpendicular directions relative to the polarization direction of the dissociation laser. Tuning the excitation photon energy from the resonance center to the lower energies within the Beutler-Fano profile, the branching ratios H(2 s )/[H(2 s )+H(2 p )] decrease, and the fragment angular distributions change in a trend indicating the presence of more components of direct dissociation channels in comparison with the predissociation channel.

  7. Angle-resolved spin wave band diagrams of square antidot lattices studied by Brillouin light scattering

    Energy Technology Data Exchange (ETDEWEB)

    Gubbiotti, G.; Tacchi, S. [Istituto Officina dei Materiali del Consiglio Nazionale delle Ricerche (IOM-CNR), Sede di Perugia, c/o Dipartimento di Fisica e Geologia, Via A. Pascoli, I-06123 Perugia (Italy); Montoncello, F.; Giovannini, L. [Dipartimento di Fisica e Scienze della Terra, Università di Ferrara, Via G. Saragat 1, I-44122 Ferrara (Italy); Madami, M.; Carlotti, G. [Dipartimento di Fisica e Geologia, Università di Perugia, Via A. Pascoli, I-06123 Perugia (Italy); Ding, J.; Adeyeye, A. O. [Information Storage Materials Laboratory, Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117576 (Singapore)

    2015-06-29

    The Brillouin light scattering technique has been exploited to study the angle-resolved spin wave band diagrams of squared Permalloy antidot lattice. Frequency dispersion of spin waves has been measured for a set of fixed wave vector magnitudes, while varying the wave vector in-plane orientation with respect to the applied magnetic field. The magnonic band gap between the two most dispersive modes exhibits a minimum value at an angular position, which exclusively depends on the product between the selected wave vector magnitude and the lattice constant of the array. The experimental data are in very good agreement with predictions obtained by dynamical matrix method calculations. The presented results are relevant for magnonic devices where the antidot lattice, acting as a diffraction grating, is exploited to achieve multidirectional spin wave emission.

  8. Angle resolved XPS of monomolecular layer of 5-chlorobenzotriazole on oxidized metallic surface

    Science.gov (United States)

    Kazansky, L. P.; Selyaninov, I. A.; Kuznetsov, Yu. I.

    2012-10-01

    Angle resolved XPS is used to study adsorption of 5-chlorobenzotriazole (5-chloroBTAH) on surfaces of the oxidized metals: mild steel, copper and zinc from borate buffer solution (pH 7.4). It is shown that for the metals studied the 5-chloroBTA anions, when adsorbed, form a monomolecular layer whose thickness is ∼6 Å comparable with the size of BTA. As XPS evidences adsorption proceeds with deprotonation of 5-chloroBTAH and formation of the coordination bonds between the lone pair of nitrogens and cation of a metal. Measuring XPS at two different angles unequivocally points out almost vertical arrangement of the anions toward the sample surface, when chlorine atoms form outmost virtual layer.

  9. Electronic Properties of Layered Oxides:. Pulsed Laser Deposition of YBCO Films for In-Situ Studies by Photoemission Spectroscopy

    Science.gov (United States)

    Pavuna, D.; Ariosa, D.; Berger, H.; Christensen, S.; Frazer, B.; Gatt, R.; Grioni, M.; Margaritondo, G.; Misra, S.; Onellion, M.; Schmauder, T.; Vobornik, I.; Xi, X.; Zacchigna, M.; Zwick, F.

    Due to imperfect surfaces of most cuprate samples, almost all Photoemission studies in the past decade were performed on Bi2Sr2CaCu2O8+x, even though a large fraction of other studies and electronic applications was reported for YBa2Cu3O7-δ (YBCO) family of superconducting compounds. In order to systematically study the gap parameter and the Fermi surface variation in high symmetry directions of YBCO and related oxide films we have constructed a new facility at the Wisconsin Synchrotron Radiation Center. We use the pulsed laser ablation (PLD) system that is directly linked to the photoemission chamber. In our unique approach, the samples never leave the controlled ambient and we oxidize our films, either by molecular oxygen or by ozone. In this paper, we, summarize some of the most relevant recent results on electronic properties of layered oxides and describe our new facility for the study of YBCO and related oxide films.

  10. Electronic properties of layered oxides: Pulsed laser deposition of YBCO films for in-situ studies by photoemission spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Pavuna, D.; Ariosa, D. (Ecole Polytechnique, Lausanne (Switzerland)); Berger, H. (and others)

    1998-12-20

    Due to imperfect surfaces of most cuprate samples, almost all photoemission studies in the past decade were performed on Bi[sub 2]Sr[sub 2]CaCu[sub 2]O[sub 8+x], even though a large fraction of other studies and electronic applications was reported for YBa[sub 2]Cu[sub 3]O[sub 7[minus][delta

  11. Improving the measurement performance of angle-resolved scattermetry by use of pupil optimization

    Science.gov (United States)

    Wang, Fan; Zhang, Qingyun; Lu, Hailiang; Duan, Lifeng; Li, Xiaoping

    2012-03-01

    As feature sizes decrease, requirements on critical dimension uniformity have become very strict. To monitor variations in lithography process and perform advanced process control it is important to establish a fast and accurate measurement technique for characterizing critical dimension, sidewall angle and height of the resist profile. Various techniques for feature measurement such as CD-SEM, AFM, FE-SEM, and scatterometry have been developed. Among these techniques, scatterometry has both high accuracy and a non-deconstructive measurement modality. It thus provides advantages of low-cost, high throughput, and robustness. Angle-resolved scatterometry has already been shown to provide in-line feedback information necessary for tight process control. In present paper, we introduce a novel angle-resolved scatterometer with pupil optimization. The intensity distribution of the incident light in the pupil plane is optimized considering the feature and the image sensor response properties, which improve the measurement performance of the scatterometer. A first order analysis of measurement sensitivity at different polarization conditions is carried out on resist-coated wafers with 45nm and 22nm features using Rigorous Coupled- Wave analysis (RCWA). Based on the criteria defined as the sum of the absolute difference of the relative intensity values between the nominal and varied conditions in the pupil, the sensitivity of the new technique and traditional scatterometer is compared. Simulation results show that, for 45nm feature, the sensitivity in s and p-polarization is increased by 400% and 300% respectively. While for 22nm feature, the sensitivity is increased by 200% and 130%. Reproducibility of measurement is also analyzed on 45nm and 22nm features using a Monte Carlo method and models for detector noise. Comparison of reproducibility for CD, sidewall angle, and resist height measurement is demonstrated.

  12. Comparison of the electronic structure of anatase and rutile TiO2 single-crystal surfaces using resonant photoemission and x-ray absorption spectroscopy

    Science.gov (United States)

    Thomas, A. G.; Flavell, W. R.; Mallick, A. K.; Kumarasinghe, A. R.; Tsoutsou, D.; Khan, N.; Chatwin, C.; Rayner, S.; Smith, G. C.; Stockbauer, R. L.; Warren, S.; Johal, T. K.; Patel, S.; Holland, D.; Taleb, A.; Wiame, F.

    2007-01-01

    A comparison of the electronic structure of rutile (110), anatase (101), and anatase (001) single-crystal surfaces has been made using resonant photoemission and x-ray absorption spectroscopy. Under identical preparative conditions, the anatase (101) surface shows the lowest Ti3d and 4sp hybridization in the states close to the valence-band maximum of the three surfaces. It also shows the highest concentration of surface-oxygen vacancies. The effect on the electronic structure of modifying the surface preparative route and thus the concentration of surface-oxygen vacancies is examined. The σ -antibonding Ti3deg/O2p hybridization (probed by XAS) is reduced by the removal of surface-oxygen. Photoemission shows that as the number of surface-defects is increased, the O2p-Ti3dt2gπ -bonding interaction is disrupted. For the anatase (101) surface it is found that as the number of surface-oxygen vacancies is increased, the Ti3d and 4sp contributions at the valence-band maximum are reduced. We discuss the correlation between electronic structure and photocatalytic activity of the different polymorphs of TiO2 .

  13. Investigation of the potassium fluoride post deposition treatment on the CIGSe/CdS interface using hard X-ray photoemission spectroscopy - a comparative study.

    Science.gov (United States)

    Ümsür, Bünyamin; Calvet, Wolfram; Steigert, Alexander; Lauermann, Iver; Gorgoi, Mihaela; Prietzel, Karsten; Greiner, Dieter; Kaufmann, Christian A; Unold, Thomas; Lux-Steiner, Martha Ch

    2016-05-18

    The impact of the potassium fluoride post deposition treatment on CIGSe chalcopyrite absorbers is investigated by means of depth resolved hard X-ray photoemission spectroscopy of the near surface region. Two similar, slightly Cu-poor CIGSe absorbers were used with one being treated by potassium fluoride prior to the chemical bath deposition of an ultrathin CdS layer. The thickness of the CdS layer was chosen to be in the range of about 10 nm in order to allow the investigation of the CIGSe/CdS interface by the application of hard X-rays, increasing the information depth up to 30 nm. Besides strong intermixing on both samples, an increased Cu depletion of the KF treated absorber was observed in combination with an increased accumulation of Cd and S. In addition, a general shift of about 0.15 eV to higher binding energies of the CIGSe valence band at the absorber surface as well as the CIGSe and CdS related core levels was measured on the KF treated sample. This phenomenon is attributed to the impact of additional cadmium which acts as donor and releases further electrons into the conduction band of the absorber. Finally, the electrons accumulate at the CdS surface after having passed the interface region. This additional surface charge leads to a pronounced shift in the photoemission spectra as observed on the KF treated CIGSe absorber compared to the non-treated absorber. PMID:27160389

  14. High-kinetic-energy photoemission spectroscopy of Ni at 1s : 6-eV satellite at 4 eV

    Science.gov (United States)

    Karis, O.; Svensson, S.; Rusz, J.; Oppeneer, P. M.; Gorgoi, M.; Schäfers, F.; Braun, W.; Eberhardt, W.; Mårtensson, N.

    2008-12-01

    Electron correlations are responsible for many profound phenomena in solid-state physics. A classical example is the 6-eV satellite in the photoelectron spectrum of Ni. Until now the satellite structure has only been investigated at the L shell and more shallow levels. Here we report a high-kinetic-energy photoemission spectroscopy (HIKE) investigation of Ni metal. We present 1s and 2p photoelectron spectra, obtained using excitation energies up to 12.6 keV. Our investigation demonstrates that the energy position of the satellite relative to the main line is different for the 1s and the 2p levels. In combination with electronic structure calculations, we show that this energy shift is attributed to unique differences in the core-valence coupling for the K and L2,3 shells in 3d transition metals, resulting in different screening of the core holes.

  15. Effect of antiferromagnetic ordering on temperature dependent superconducting gap in ErNi2B2C: Laser-photoemission spectroscopy

    International Nuclear Information System (INIS)

    We have performed temperature (T)-dependent laser-photoemission spectroscopy of antiferromagnetic (AF) superconductor ErNi2B2C to study the electronic structure, especially the effect of AF ordering in T-dependent superconducting (SC) gap. To estimate the values of T-dependent SC gap, we fitted the experimental data by Dynes function having an anisotropic s-wave SC gap. From the fitting results, we find a sudden deviation from the BCS prediction just below TN. This observation can be well explained by the theoretical model, indicating that the origin of anomalous T-dependence is competition between rapid evolution of AF molecular field and SC condensation energy.

  16. X-ray photoemission spectroscopy investigation of the early stages of the oxygen aided Cr growth on Fe(0 0 1)

    International Nuclear Information System (INIS)

    We report on an X-ray photoemission spectroscopy investigation of the early stages of growth of ultra-thin Cr films on the oxygen-passivated Fe(0 0 1)–p(1 × 1)O surface. The Cr coverages ranged from sub-monolayer up to a few atomic layers. Cr has been grown either at 380 K or at 570 K. Our investigation reveals that during the Cr film growth oxygen floats toward the free surface. The presence of a metallic Cr signal from the very beginning of film growth is discussed in relation to Cr–Fe intermixing and alloy formation at the interface. Our findings are independent from the growth temperature, indicating that it has a very little influence on the chemical interactions at the interface, at variance with the oxygen-free Cr/Fe interface.

  17. X-ray photoemission spectroscopy investigation of the early stages of the oxygen aided Cr growth on Fe(0 0 1)

    Energy Technology Data Exchange (ETDEWEB)

    Brambilla, A., E-mail: alberto.brambilla@polimi.it [CNISM and Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo Da Vinci 32, 20133 Milano (Italy); Calloni, A.; Picone, A.; Finazzi, M.; Duò, L.; Ciccacci, F. [CNISM and Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo Da Vinci 32, 20133 Milano (Italy)

    2013-02-15

    We report on an X-ray photoemission spectroscopy investigation of the early stages of growth of ultra-thin Cr films on the oxygen-passivated Fe(0 0 1)–p(1 × 1)O surface. The Cr coverages ranged from sub-monolayer up to a few atomic layers. Cr has been grown either at 380 K or at 570 K. Our investigation reveals that during the Cr film growth oxygen floats toward the free surface. The presence of a metallic Cr signal from the very beginning of film growth is discussed in relation to Cr–Fe intermixing and alloy formation at the interface. Our findings are independent from the growth temperature, indicating that it has a very little influence on the chemical interactions at the interface, at variance with the oxygen-free Cr/Fe interface.

  18. In-situ X-ray Photoemission Spectroscopy Study of Atomic Layer Deposition of TiO2 on Silicon Substrate

    Science.gov (United States)

    Youb Lee, Seung; Jeon, Cheolho; Kim, Seok Hwan; Kim, Yooseok; Jung, Woosung; An, Ki-Seok; Park, Chong-Yun

    2012-03-01

    In-situ X-ray photoemission spectroscopy (XPS) has been used to investigate the initial stages of TiO2 growth on a Si(001) substrate by atomic layer deposition (ALD). The core level spectra of Si 2p, C 1s, O 1s, and Ti 2p were measured at every half reaction in the titanium tetra-isopropoxide (TTIP)-H2O ALD process. The ligand exchange reactions were verified using the periodic oscillation of the C 1s concentration, as well as changes in the hydroxyl concentration. XPS analysis revealed that Ti2O3 and Si oxide were formed at the initial stages of TiO2 growth. A stoichiometric TiO2 layer was dominantly formed after two cycles and was chemically saturated after four cycles.

  19. Probing the energy levels of perovskite solar cells via Kelvin probe and UV ambient pressure photoemission spectroscopy.

    Science.gov (United States)

    Harwell, J R; Baikie, T K; Baikie, I D; Payne, J L; Ni, C; Irvine, J T S; Turnbull, G A; Samuel, I D W

    2016-07-20

    The field of organo-lead halide perovskite solar cells has been rapidly growing since their discovery in 2009. State of the art devices are now achieving efficiencies comparable to much older technologies like silicon, while utilising simple manufacturing processes and starting materials. A key parameter to consider when optimising solar cell devices or when designing new materials is the position and effects of the energy levels in the materials. We present here a comprehensive study of the energy levels present in a common structure of perovskite solar cell using an advanced macroscopic Kelvin probe and UV air photoemission setup. By constructing a detailed map of the energy levels in the system we are able to predict the importance of each layer to the open circuit voltage of the solar cell, which we then back up through measurements of the surface photovoltage of the cell under white illumination. Our results demonstrate the effectiveness of air photoemission and Kelvin probe contact potential difference measurements as a method of identifying the factors contributing to the open circuit voltage in a solar cell, as well as being an excellent way of probing the physics of new materials. PMID:27384817

  20. A flexible setup for angle-resolved X-ray fluorescence spectrometry with laboratory sources

    Science.gov (United States)

    Spanier, M.; Herzog, C.; Grötzsch, D.; Kramer, F.; Mantouvalou, I.; Lubeck, J.; Weser, J.; Streeck, C.; Malzer, W.; Beckhoff, B.; Kanngießer, B.

    2016-03-01

    X-ray fluorescence (XRF) analysis is one of the standard tools for the analysis of stratified materials and is widely applied for the investigation of electronics and coatings. The composition and thickness of the layers can be determined quantitatively and non-destructively. Recent work showed that these capabilities can be extended towards retrieving stratigraphic information like concentration depth profiles using angle-resolved XRF (ARXRF). This paper introduces an experimental sample chamber which was developed as a multi-purpose tool enabling different measurement geometries suited for transmission measurements, conventional XRF, ARXRF, etc. The chamber was specifically designed for attaching all kinds of laboratory X-ray sources for the soft and hard X-ray ranges as well as various detection systems. In detail, a setup for ARXRF using an X-ray tube with a polycapillary X-ray lens as source is presented. For such a type of setup, both the spectral and lateral characterizations of the radiation field are crucial for quantitative ARXRF measurements. The characterization is validated with the help of a stratified validation sample.

  1. Angle resolved XPS of monomolecular layer of 5-chlorobenzotriazole on oxidized metallic surface

    International Nuclear Information System (INIS)

    Highlights: ► Adsorption of 5-chloroBTA on oxidized metals is studied by ARXPS. ► When adsorbed, 5-chloroBTA forms a monolayer whose thickness is close to molecule size. ► According to ARXPS, the planes of 5-chloroBTA anions are vertical to a metal oxide surface. ► Metal cations of the surface coordinate nitrogen atoms of 5-chloroBTA. ► Chlorine atoms forming outmost virtual layer. - Abstract: Angle resolved XPS is used to study adsorption of 5-chlorobenzotriazole (5-chloroBTAH) on surfaces of the oxidized metals: mild steel, copper and zinc from borate buffer solution (pH 7.4). It is shown that for the metals studied the 5-chloroBTA anions, when adsorbed, form a monomolecular layer whose thickness is ∼6 Å comparable with the size of BTA. As XPS evidences adsorption proceeds with deprotonation of 5-chloroBTAH and formation of the coordination bonds between the lone pair of nitrogens and cation of a metal. Measuring XPS at two different angles unequivocally points out almost vertical arrangement of the anions toward the sample surface, when chlorine atoms form outmost virtual layer.

  2. Comparison of models and measurements of angle-resolved scatter from irregular aerosols

    International Nuclear Information System (INIS)

    We have developed and validated a method for modeling the elastic scattering properties of biological and inert aerosols of irregular shape at near- and mid-wave infrared wavelengths. The method, based on Gaussian random particles, calculates the ensemble-average optical cross section and Mueller scattering matrix, using the measured aerodynamic size distribution and previously-reported refractive index as inputs. The utility of the Gaussian particle model is that it is controlled by only two parameters (σ and Γ) which we have optimized such that the model best reproduces the full angle-resolved Mueller scattering matrices measured at λ=1.55 µm in the Standoff Aerosol Active Signature Testbed (SAAST). The method has been applied to wet-generated singlet biological spore samples, dry-generated biological spore clusters, and kaolin. The scattering computation is performed using the Discrete Dipole Approximation (DDA), which requires significant computational resources, and is thus implemented on LLGrid, a large parallel grid computer. For the cases presented, the best fit Gaussian particle model is in good qualitative correspondence with microscopy images of the corresponding class of particles. The measured and computed cross sections agree well within a factor of two overall, with certain cases bearing closer correspondence. In particular, the DDA reproduces the shape of the measured scatter function more accurately than Mie predictions. The DDA-computed depolarization factors are also in good agreement with measurement. - Highlights: • We model elastic scattering of biological and inert aerosols of irregular shape. • We calculate cross sections and Mueller matrix using random particle shape model. • Scatter models employ refractive index and measured size distribution as inputs. • Discrete dipole approximation (DDA) with parallelization enables model calculations. • DDA-modeled cross section and Mueller matrix agree well with measurements at 1.55 μm

  3. Two-photon Photo-emission of Ultrathin Film PTCDA Morphologies on Ag(111)

    OpenAIRE

    Yang, Aram

    2008-01-01

    Morphology- and layer-dependent electronic structure and dynamics at the PTCDA/Ag(111) interface have been studied with angle-resolved two-photon photoemission. In Stranski-Krastanov growth modes, the exposed wetting layer inhibited the evolution of the vacuum level and valence band to bulk values. For layer-by-layer growth, we observed the transition of electron structure from monolayer to bulk values within eight monolayers. Effective masses and lifetimes of the conduction band and the n=1 ...

  4. Characterization of heterojunctions via x-ray and uv photoemission spectroscopy: energy level implications for single and mixed monolayer SAMs, cadmium selenide nanoparticle films, and organic semiconductor depositions

    Science.gov (United States)

    Graham, Amy L.

    This work has centered on the interface dipoles arising at heterojunctions between metals, semiconductor nanoparticles, self-assembled monolayers, and organic semiconductor materials. Alkanethiol self-assembled monolayers, CdSe nanocrystals, and the organic semiconductors zinc phthalocyanine (ZnPc) and Buckminster fullerene (C60) were the basis of these investigations. UV photoemission spectroscopy has proven to be an invaluable tool to observe the vacuum level shifts for these analyses while using XPS to corroborate surface structure. With a full evaluation of these surfaces, the shifts in the vacuum level, valence ionizations, and core ionizations, the impact of these interfaces, as well as their influence on the subsequent deposition of organic semiconductor layers is established. Alkanethiols possessing varying dipole moments were examined on gold and silver substrates. The viability of these alkanethiols was demonstrated to predictively adjust the work function of these metals as a function of their intrinsic dipole moments projected to surface normal, and established differences between Ag---S and Au---S bonds. The capability of the SAMs to modify the work function of gold provided an opportunity for mixed monolayers of the alkanethiols to produce a precise range of work functions by minimal adjustments of solution concentration, which were examined with a simple point dipole model. Photoemission spectroscopy offers a thorough analysis of CdSe nanoparticle films. Despite a plethora of research on these nanocrystals, there still is controversy on the magnitude of the shift in the valence band with diameter. In our research we found the majority of the valence band shift could be attributed to the interface dipole, ignored previously. Meanwhile, the valence band tethered films was obscured by the sulfur of the thiol tether. Finally, organic semiconductor layers deposited on SAMs on gold exhibited various interface dipole effects at these heterojunctions. Charge

  5. Hard X-ray photoemission with angular resolution and standing-wave excitation

    Energy Technology Data Exchange (ETDEWEB)

    Fadley, Charles S., E-mail: fadley@physics.ucdavis.edu [Department of Physics, University of California Davis, Davis, CA 95616 (United States); Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States)

    2013-10-15

    Highlights: •Hard X-ray photoemission with angle resolution and standing-waves is discussed. •Hard X-ray angle-resolved photoemission yields k{sup →}-resolved bulk electronic structure. •Hard X-ray photoelectron diffraction provides element-specific atomic structure. •Multilayer standing-wave measurements add depth-resolved composition. •Standing-wave excitation also yields element-specific densities of states. -- Abstract: Several aspects of hard X-ray photoemission that make use of angular resolution and/or standing-wave excitation are discussed. These include hard X-ray angle-resolved photoemission (HARPES) from valence levels, which has the capability of determining bulk electronic structure in a momentum-resolved way; hard X-ray photoelectron diffraction (HXPD), which shows promise for studying element-specific bulk atomic structure, including dopant site occupations; and standing wave studies of the composition and chemical states of buried layers and interfaces. Beyond this, standing wave photoemission can be used to derive element-specific densities of states. Some recent examples relevant to all of these aspects are discussed.

  6. Spin polarization and magnetic dichroism in core-level photoemission from ferromagnets

    Energy Technology Data Exchange (ETDEWEB)

    Menchero, J G [Univ. of California, Berkeley, CA (United States). Dept. of Physics

    1997-05-01

    In this thesis we present a theoretical investigation of angle- and spin-resolved core-level photoemission from ferromagnetic Fe and Ni. We also consider magneto-dichroic effects due to reversal of the photon helicity or reversal of the sample magnetization direction. In chapter 1, we provide a brief outline of the history of photoemission, and show how it has played an important role in the development of modern physics. We then review the basic elements of the theory of core-level photoemission, and discuss the validity of the some of the commonly-used approximations. In chapter 2, we present a one-electron theory to calculate spin- and angle-resolved photoemission spectra for an arbitrary photon polarization. The Hamiltonian includes both spin-orbit and exchange interactions. As test cases for the theory, we calculate the spin polarization and magnetic dichroism for the Fe 2p core level, and find that agreement with experiment is very good.

  7. Direct comparative study on the energy level alignments in unoccupied/occupied states of organic semiconductor/electrode interface by constructing in-situ photoemission spectroscopy and Ar gas cluster ion beam sputtering integrated analysis system

    International Nuclear Information System (INIS)

    Through the installation of electron gun and photon detector, an in-situ photoemission and damage-free sputtering integrated analysis system is completely constructed. Therefore, this system enables to accurately characterize the energy level alignments including unoccupied/occupied molecular orbital (LUMO/HOMO) levels at interface region of organic semiconductor/electrode according to depth position. Based on Ultraviolet Photoemission Spectroscopy (UPS), Inverse Photoemission Spectroscopy (IPES), and reflective electron energy loss spectroscopy, the occupied/unoccupied state of in-situ deposited Tris[4-(carbazol-9-yl)phenyl]amine (TCTA) organic semiconductors on Au (ELUMO: 2.51 eV and EHOMO: 1.35 eV) and Ti (ELUMO: 2.19 eV and EHOMO: 1.69 eV) electrodes are investigated, and the variation of energy level alignments according to work function of electrode (Au: 4.81 eV and Ti: 4.19 eV) is clearly verified. Subsequently, under the same analysis condition, the unoccupied/occupied states at bulk region of TCTA/Au structures are characterized using different Ar gas cluster ion beam (Ar GCIB) and Ar ion sputtering processes, respectively. While the Ar ion sputtering process critically distorts both occupied and unoccupied states in UPS/IPES spectra, the Ar GCIB sputtering process does not give rise to damage on them. Therefore, we clearly confirm that the in-situ photoemission spectroscopy in combination with Ar GCIB sputtering allows of investigating accurate energy level alignments at bulk/interface region as well as surface region of organic semiconductor/electrode structure.

  8. Photoemission studies of mixed valent systems

    International Nuclear Information System (INIS)

    Photoemission spectroscopy has been used to study a number of aspects of the mixed valent state (corresponding to non-integral 4f occupation) in rare earth systems. Deep core photoemission (e.g., from 3d or 4d levels) allows the measurement of the 4f occupancy and surface valence shifts, and, as well, the indirect measurement of the effect of solid state environment on the energy of hybridization between 4f electrons and conduction electrons. 4f-Derived photoemission has been used to study surface valance and chemical shifts and to infer the nature of the mixed valent ground state. A combination of 4f-derived photoemission and add-electron spectroscopy provides a measurement of the rf Coulomb correlation energy, an important parameter in the mixed valent problem. A review of these approaches will be presented, with emphasis on Ce-based systems, whose behavior falls outside the usual description of 4f-unstable systems

  9. Determination of the surface band bending in InxGa1−xN films by hard x-ray photoemission spectroscopy

    Directory of Open Access Journals (Sweden)

    Mickael Lozac'h, Shigenori Ueda, Shitao Liu, Hideki Yoshikawa, Sang Liwen, Xinqiang Wang, Bo Shen, Kazuaki Sakoda, Keisuke Kobayashi and Masatomo Sumiya

    2013-01-01

    Full Text Available Core-level and valence band spectra of InxGa1−xN films were measured using hard x-ray photoemission spectroscopy (HX-PES. Fine structure, caused by the coupling of the localized Ga 3d and In 4d with N 2s states, was experimentally observed in the films. Because of the large detection depth of HX-PES (~20 nm, the spectra contain both surface and bulk information due to the surface band bending. The InxGa1−xN films (x = 0–0.21 exhibited upward surface band bending, and the valence band maximum was shifted to lower binding energy when the mole fraction of InN was increased. On the other hand, downward surface band bending was confirmed for an InN film with low carrier density despite its n-type conduction. Although the Fermi level (EF near the surface of the InN film was detected inside the conduction band as reported previously, it can be concluded that EF in the bulk of the film must be located in the band gap below the conduction band minimum.

  10. Growth Mode Investigation of 3,4,9,10-perylenetetra-carboxylic Dianhydride on p-Si Substrates by X-ray Photoemission Spectroscopy

    Institute of Scientific and Technical Information of China (English)

    SONG Zhen; OU Gu-ping

    2007-01-01

    The growth mode of 3,4,9,10-perylenetetra-carboxylic dianhydride(PTCDA) deposited on p-Si substrates can be deduced by X-ray Photoemission Spectroscopy(XPS). The spectrum and fine spectrum at the surface of specimen are studied. Firstly, PTCDA molecules assemble at the defects to form lots of three-dimensional island-like PTCDA crystal nucleuses, and then by the action of delocalized big π bond, two adjacent layers of PTCDA molecules overlap to some extent and finally island-like structure forms. PTCDA molecules of benzene ring combine with Si atoms at the defects, and that of acid anhydride radicals combine with Si atoms at the perfect fraction of the surface. In the course of combination, although the structure of benzene ring doesn't change, the chemical reaction of acid anhydride radicals and Si occurs to break off C=O bond in acid anhydride, and then C-Si-O and silicon oxide might be produced.

  11. Intrinsic spin polarized electronic structure of CrO{sub 2} epitaxial film revealed by bulk-sensitive spin-resolved photoemission spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Fujiwara, Hirokazu; Sunagawa, Masanori; Kittaka, Tomoko [Research Laboratory for Surface Science and Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530 (Japan); Terashima, Kensei; Wakita, Takanori; Muraoka, Yuji; Yokoya, Takayoshi [Research Laboratory for Surface Science and Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530 (Japan); Research Center of New Functional Materials for Energy Production, Storage, and Transport, Okayama University, Okayama 700-8530 (Japan)

    2015-05-18

    We have performed bulk-sensitive spin-resolved photoemission spectroscopy in order to clarify the intrinsic spin-resolved electronic states of half-metallic ferromagnet CrO{sub 2}. We used CrO{sub 2} epitaxial films on TiO{sub 2}(100), which shows a peak at 1 eV with a clear Fermi edge, consistent with the bulk-sensitive PES spectrum for CrO{sub 2}. In spin-resolved spectra at 40 K, while the Fermi edge was observed in the spin up (majority spin) state, no states at the Fermi level (E{sub F}) with an energy gap of 0.5 eV below E{sub F} were observed in the spin down (minority spin) state. At 300 K, the gap in the spin down state closes. These results are consistent with resistivity measurements and magnetic hysteresis curves of the fabricated CrO{sub 2} film, constituting spectroscopic evidence for the half-metallicity of CrO{sub 2} at low temperature and reducing the spin polarization at room temperature. We also discuss the electron correlation effects of Cr 3d.

  12. Epitaxial growth of CeO{sub 2}(111) film on Ru(0001): Scanning tunneling microscopy (STM) and x-ray photoemission spectroscopy (XPS) study

    Energy Technology Data Exchange (ETDEWEB)

    Hasegawa, Tomo; Shahed, Syed Mohammad Fakruddin; Sainoo, Yasuyuki [Institute of Multidisciplinary Research for Advanced Materials (IMRAM, Tagen), Tohoku University, 2-1-1, Katahira, Aoba-Ku, Sendai 980-0877 (Japan); Beniya, Atsushi; Isomura, Noritake; Watanabe, Yoshihide [Toyota Central R and D Labs., Inc., 41-1 Yokomichi, Nagakute, Aichi 480-1192 (Japan); Komeda, Tadahiro, E-mail: komeda@tagen.tohoku.ac.jp [Institute of Multidisciplinary Research for Advanced Materials (IMRAM, Tagen), Tohoku University, 2-1-1, Katahira, Aoba-Ku, Sendai 980-0877 (Japan); JST, CREST, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012 (Japan)

    2014-01-28

    We formed an epitaxial film of CeO{sub 2}(111) by sublimating Ce atoms on Ru(0001) surface kept at elevated temperature in an oxygen ambient. X-ray photoemission spectroscopy measurement revealed a decrease of Ce{sup 4+}/Ce{sup 3+} ratio in a small temperature window of the growth temperature between 1070 and 1096 K, which corresponds to the reduction of the CeO{sub 2}(111). Scanning tunneling microscope image showed that a film with a wide terrace and a sharp step edge was obtained when the film was grown at the temperatures close to the reduction temperature, and the terrace width observed on the sample grown at 1060 K was more than twice of that grown at 1040 K. On the surface grown above the reduction temperature, the surface with a wide terrace and a sharp step was confirmed, but small dots were also seen in the terrace part, which are considerably Ce atoms adsorbed at the oxygen vacancies on the reduced surface. This experiment demonstrated that it is required to use the substrate temperature close to the reduction temperature to obtain CeO{sub 2}(111) with wide terrace width and sharp step edges.

  13. Intrinsic spin polarized electronic structure of CrO2 epitaxial film revealed by bulk-sensitive spin-resolved photoemission spectroscopy

    International Nuclear Information System (INIS)

    We have performed bulk-sensitive spin-resolved photoemission spectroscopy in order to clarify the intrinsic spin-resolved electronic states of half-metallic ferromagnet CrO2. We used CrO2 epitaxial films on TiO2(100), which shows a peak at 1 eV with a clear Fermi edge, consistent with the bulk-sensitive PES spectrum for CrO2. In spin-resolved spectra at 40 K, while the Fermi edge was observed in the spin up (majority spin) state, no states at the Fermi level (EF) with an energy gap of 0.5 eV below EF were observed in the spin down (minority spin) state. At 300 K, the gap in the spin down state closes. These results are consistent with resistivity measurements and magnetic hysteresis curves of the fabricated CrO2 film, constituting spectroscopic evidence for the half-metallicity of CrO2 at low temperature and reducing the spin polarization at room temperature. We also discuss the electron correlation effects of Cr 3d

  14. Design of an ultrahigh vacuum transfer mechanism to interconnect an oxide molecular beam epitaxy growth chamber and an x-ray photoemission spectroscopy analysis system

    International Nuclear Information System (INIS)

    We designed a mechanism and the accompanying sample holders to transfer between a VEECO 930 oxide molecular beam epitaxy (MBE) and a PHI Versa Probe X-ray photoemission spectroscopy (XPS) chamber within a multiple station growth, processing, and analysis system through ultrahigh vacuum (UHV). The mechanism consists of four parts: (1) a platen compatible with the MBE growth stage, (2) a platen compatible with the XPS analysis stage, (3) a sample coupon that is transferred between the two platens, and (4) the accompanying UHV transfer line. The mechanism offers a robust design that enables transfer back and forth between the growth chamber and the analysis chamber, and yet is flexible enough to allow transfer between standard sample holders for thin film growth and masked sample holders for making electrical contacts and Schottky junctions, all without breaking vacuum. We used this mechanism to transfer a barium strontium titanate thin film into the XPS analysis chamber and performed XPS measurements before and after exposing the sample to the air. After air exposure, a thin overlayer of carbon was found to form and a significant shift (∼1 eV) in the core level binding energies was observed.

  15. Electrochemical, high-resolution photoemission spectroscopy and vdW-DFT study of the thermal stability of benzenethiol and benzeneselenol monolayers on Au(111).

    Science.gov (United States)

    Cometto, F P; Patrito, E M; Paredes Olivera, P; Zampieri, G; Ascolani, H

    2012-09-25

    The preparation and thermal stability of benzenethiol and benzeneselenol self-assembled monolayers (SAMs) grown on Au(111) have been investigated by electrochemical experiments and high-resolution photoemission spectroscopy. Both techniques confirm the formation of monolayers with high packing densities (θ = 0.27-0.29 ML) and good degrees of order in both cases. Despite many similarities between the two SAMs, the thermal desorption is distinctly different: whereas the benzenethiol SAM desorbs in a single steplike process, the desorption of the benzeneselenol SAM occurs with a much lower activation energy and involves the cleavage of some Se-C bonds and a change in molecular configuration from standing up to lying down. This behavior is explained by considering the different nature of the bonding of the headgroup with the metal surface and with the phenyl ring. Density functional theory calculations show that the breakage of the Se-C bond has a lower activation energy barrier than the breakage of the S-C bond. PMID:22946792

  16. X-ray excited optical luminescence, photoluminescence, photostimulated luminescence and x-ray photoemission spectroscopy studies on BaFBr:Eu

    CERN Document Server

    Subramanian, N; Govinda-Rajan, K; Mohammad-Yousuf; Santanu-Bera; Narasimhan, S V

    1997-01-01

    The results of x-ray excited optical luminescence (XEOL), photoluminescence (PL), photostimulated luminescence (PSL) and x-ray photoemission spectroscopy (XPS) studies on the x-ray storage phosphor BaFBr:Eu are presented in this paper. Analyses of XEOL, PL and PSL spectra reveal features corresponding to the transitions from 4f sup 6 td sup 1 to 4f sup 7 configurations in different site symmetries of Eu sup 2 sup +. Increasing x-ray dose is seen to lead to a red shift in the maximum of the PL excitation spectrum for the 391 nm emission. The XEOL and XPS spectra do not show any signature of Eu sup 3 sup + in the samples studied by us, directly raising doubts about the model of Takahashi et al in which Eu sup 2 sup + is expected to ionize to Eu sup 3 sup + upon x-ray irradiation and remain stable until photostimulation. XEOL and PSL experiments with simultaneous x-ray irradiation and He - Ne laser excitation as well as those with sequential x-ray irradiation and laser stimulation bring out the competition betwe...

  17. Influence of the contact potential and space-charge effect on the performance of a Stoffel-Johnson design electron source for inverse photoemission spectroscopy

    International Nuclear Information System (INIS)

    By imaging the spatial intensity distribution of the electrons from a Stoffel-Johnson (SJ) type low energy electron source for inverse photoemission spectroscopy (IPES), we find that the focus is distorted when the beam current exceeds the limiting value due to space charge effect. The space charge effect and the contact potential difference suppress the beam current at low energies (<10 eV). In this work, we show that these limitations of the SJ source can be overcome by compensation of the contact potential difference between the cathode and the lens electrodes and an uniform well focused electron beam with the set kinetic energy can be obtained. The size of the electron beam is around 1 mm full width at half maximum over the whole energy range of 5 to 30 eV generally used for IPES. The compensation of the contact potential difference also enhances the beam current substantially at low energies (<10 eV) and uniform beam current is achieved for the whole energy range. We find that the drift in the electron beam position is sensitive to the lens electrode separation and it is about 1 mm over the whole energy range. By measuring the n = 1 image potential state on Cu(100), we show that the resolution is better when the cathode filament current is set to lower values

  18. The electronic and chemical structure of the a-B3CO0.5:Hy-to-metal interface from photoemission spectroscopy: implications for Schottky barrier heights.

    Science.gov (United States)

    Driver, M Sky; Paquette, Michelle M; Karki, S; Nordell, B J; Caruso, A N

    2012-11-01

    The electronic and chemical structure of the metal-to-semiconductor interface was studied by photoemission spectroscopy for evaporated Cr, Ti, Al and Cu overlayers on sputter-cleaned as-deposited and thermally treated thin films of amorphous hydrogenated boron carbide (a-B(x)C:H(y)) grown by plasma-enhanced chemical vapor deposition. The films were found to contain ~10% oxygen in the bulk and to have approximate bulk stoichiometries of a-B(3)CO(0.5):H(y). Measured work functions of 4.7/4.5 eV and valence band maxima to Fermi level energy gaps of 0.80/0.66 eV for the films (as-deposited/thermally treated) led to predicted Schottky barrier heights of 1.0/0.7 eV for Cr, 1.2/0.9 eV for Ti, 1.2/0.9 eV for Al, and 0.9/0.6 eV for Cu. The Cr interface was found to contain a thick partial metal oxide layer, dominated by the wide-bandgap semiconductor Cr(2)O(3), expected to lead to an increased Schottky barrier at the junction and the formation of a space-charge region in the a-B(3)CO(0.5):H (y) layer. Analysis of the Ti interface revealed a thick layer of metal oxide, comprising metallic TiO and Ti (2)O (3), expected to decrease the barrier height. A thinner, insulating Al(2)O(3) layer was observed at the Al-to-a-B(3)CO(0.5):H(y) interface, expected to lead to tunnel junction behavior. Finally, no metal oxides or other new chemical species were evident at the Cu-to-a-B(3)CO(0.5):H(y) interface in either the core level or valence band photoemission spectra, wherein characteristic metallic Cu features were observed at very thin overlayer coverages. These results highlight the importance of thin-film bulk oxygen content on the metal-to-semiconductor junction character as well as the use of Cu as a potential Ohmic contact material for amorphous hydrogenated boron carbide semiconductor devices such as high-efficiency direct-conversion solid-state neutron detectors. PMID:22976833

  19. The electronic and chemical structure of the a-B3CO0.5:Hy-to-metal interface from photoemission spectroscopy: implications for Schottky barrier heights

    International Nuclear Information System (INIS)

    The electronic and chemical structure of the metal-to-semiconductor interface was studied by photoemission spectroscopy for evaporated Cr, Ti, Al and Cu overlayers on sputter-cleaned as-deposited and thermally treated thin films of amorphous hydrogenated boron carbide (a-BxC:Hy) grown by plasma-enhanced chemical vapor deposition. The films were found to contain ∼10% oxygen in the bulk and to have approximate bulk stoichiometries of a-B3CO0.5:Hy. Measured work functions of 4.7/4.5 eV and valence band maxima to Fermi level energy gaps of 0.80/0.66 eV for the films (as-deposited/thermally treated) led to predicted Schottky barrier heights of 1.0/0.7 eV for Cr, 1.2/0.9 eV for Ti, 1.2/0.9 eV for Al, and 0.9/0.6 eV for Cu. The Cr interface was found to contain a thick partial metal oxide layer, dominated by the wide-bandgap semiconductor Cr2O3, expected to lead to an increased Schottky barrier at the junction and the formation of a space-charge region in the a-B3CO0.5:H y layer. Analysis of the Ti interface revealed a thick layer of metal oxide, comprising metallic TiO and Ti 2O 3, expected to decrease the barrier height. A thinner, insulating Al2O3 layer was observed at the Al-to-a-B3CO0.5:Hy interface, expected to lead to tunnel junction behavior. Finally, no metal oxides or other new chemical species were evident at the Cu-to-a-B3CO0.5:Hy interface in either the core level or valence band photoemission spectra, wherein characteristic metallic Cu features were observed at very thin overlayer coverages. These results highlight the importance of thin-film bulk oxygen content on the metal-to-semiconductor junction character as well as the use of Cu as a potential Ohmic contact material for amorphous hydrogenated boron carbide semiconductor devices such as high-efficiency direct-conversion solid-state neutron detectors.

  20. Multi-atom resonant photoemission and the development of next-generation software and high-speed detectors for electron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Kay, Alexander William

    2000-09-01

    This dissertation has involved the exploration of a new effect in photoelectron emission, multi-atom resonant photoemission (MARPE), as well as the development of new software, data analysis techniques, and detectors of general use in such research. We present experimental and theoretical results related to MARPE, in which the photoelectron intensity from a core level on one atom is influenced by a core-level absorption resonance on another. We point out that some of our and others prior experimental data has been strongly influenced by detector non-linearity and that the effects seen in new corrected data are smaller and of different form. Corrected data for the MnO(001) system with resonance between the O 1s and Mn 2p energy levels are found to be well described by an extension of well-known intraatomic resonant photoemission theory to the interatomic case, provided that interactions beyond the usual second-order Kramers-Heisenberg treatment are included. This theory is also found to simplify under certain conditions so as to yield results equivalent to a classical x-ray optical approach, with the latter providing an accurate and alternative, although less detailed and general, physical picture of these effects. Possible future applications of MARPE as a new probe of near-neighbor identities and bonding and its relationship to other known effects are also discussed. We also consider in detail specially written data acquisition software that has been used for most of the measurements reported here. This software has been used with an existing experimental system to develop the method of detector characterization and then data correction required for the work described above. The development of a next generation one-dimensional, high-speed, electron detector is also discussed. Our goal has been to design, build and test a prototype high-performance, one-dimensional pulse-counting detector that represents a significant advancement in detector technology and is well

  1. Multi-atom resonant photoemission and the development of next-generation software and high-speed detectors for electron spectroscopy

    International Nuclear Information System (INIS)

    This dissertation has involved the exploration of a new effect in photoelectron emission, multi-atom resonant photoemission (MARPE), as well as the development of new software, data analysis techniques, and detectors of general use in such research. We present experimental and theoretical results related to MARPE, in which the photoelectron intensity from a core level on one atom is influenced by a core-level absorption resonance on another. We point out that some of our and others prior experimental data has been strongly influenced by detector non-linearity and that the effects seen in new corrected data are smaller and of different form. Corrected data for the MnO(001) system with resonance between the O 1s and Mn 2p energy levels are found to be well described by an extension of well-known intraatomic resonant photoemission theory to the interatomic case, provided that interactions beyond the usual second-order Kramers-Heisenberg treatment are included. This theory is also found to simplify under certain conditions so as to yield results equivalent to a classical x-ray optical approach, with the latter providing an accurate and alternative, although less detailed and general, physical picture of these effects. Possible future applications of MARPE as a new probe of near-neighbor identities and bonding and its relationship to other known effects are also discussed. We also consider in detail specially written data acquisition software that has been used for most of the measurements reported here. This software has been used with an existing experimental system to develop the method of detector characterization and then data correction required for the work described above. The development of a next generation one-dimensional, high-speed, electron detector is also discussed. Our goal has been to design, build and test a prototype high-performance, one-dimensional pulse-counting detector that represents a significant advancement in detector technology and is well

  2. Growth and photoemission spectroscopic studies of ultrathin noble metal films on graphite

    Indian Academy of Sciences (India)

    S K Mahatha; Krishnakumar S R Menon

    2015-06-01

    Growth of Cu, Ag and Au thin films on graphite(0 0 0 1)surface and possible formation of quantum well (QW) states originating due to the confinement of thin film sp electrons within the band gap of graphite along M symmetry direction are investigated using low-energy electron diffraction (LEED) and angle-resolved photoemission spectroscopy (ARPES). Higher surface diffusivity and surface energy of Cu on graphite surface led to cluster growth and does not reveal any quantum size effect, while Ag and Au films grow epitaxially in spite of large lattice mismatch. However, better surface ordering has been achieved by growing Ag and Au at low temperature (LT), followed by room-temperature (RT) annealing which are evident from LEED and the presence of sharp Shockley-type surface state (SS) at Fermi level (F). ARPES study of Ag films on graphite does not show any QW states, whereas Au films demonstrate a very sharp SS, Au bulk bands and well-resolved QW states or resonances. The observed low in-plane dispersions of these Au QW states or resonances are compared with the dispersions obtained in the previous Au QW state studies as well as for free-standing Au films.

  3. New ambient pressure photoemission endstation at Advanced Light Source beamline 9.3.2

    International Nuclear Information System (INIS)

    During the past decade, the application of ambient pressure photoemission spectroscopy (APPES) has been recognized as an important in situ tool to study environmental and materials science, energy related science, and many other fields. Several APPES endstations are currently under planning or development at the USA and international light sources, which will lead to a rapid expansion of this technique. The present work describes the design and performance of a new APPES instrument at the Advanced Light Source beamline 9.3.2 at Lawrence Berkeley National Laboratory. This new instrument, Scienta R4000 HiPP, is a result of collaboration between Advanced Light Source and its industrial partner VG-Scienta. The R4000 HiPP provides superior electron transmission as well as spectromicroscopy modes with 16 μm spatial resolution in one dimension and angle-resolved modes with simulated 0.5 deg. angular resolution at 24 deg. acceptance. Under maximum transmission mode, the electron detection efficiency is more than an order of magnitude better than the previous endstation at beamline 9.3.2. Herein we describe the design and performance of the system, which has been utilized to record spectra above 2 mbar.

  4. Interferometer-controlled soft X-ray scanning photoemission microscope at SOLEIL

    International Nuclear Information System (INIS)

    ANTARES beamline (BL), a new soft X-ray scanning photoemission microscope located at the SOLEIL synchrotron storage ring has been recently designed, built and commissioned. The implemented interferometer control allows the accurate measurement of the transverse position of the Fresnel zone plate (FZP) relative to the sample. An effective sample position feedback has been achieved during experiments in static mode, with a fixed FZP position required to perform nano Angle-Resolved Photoelectron Spectroscopy (Nano-ARPES) measurements. Likewise, long-term stability has been attained for the FZP position relative to the sample during the translation of the FZP when performing typical X-ray absorption experiments around the absorption edges of light elements. Moreover, a fully automatic feedback digital control of the interferometric system provides extremely low orthogonal distortion of the recorded two-dimensional images. The microscope is diffraction limited with the resolution set to several tens of nanometers by the quality of the zone plates. Details on the design of the interferometric system and a brief description of the first commissioning results are presented here.

  5. New ambient pressure photoemission endstation at Advanced Light Source beamline 9.3.2

    KAUST Repository

    Grass, Michael E.

    2010-01-01

    During the past decade, the application of ambient pressure photoemission spectroscopy (APPES) has been recognized as an important in situ tool to study environmental and materials science, energy related science, and many other fields. Several APPES endstations are currently under planning or development at the USA and international light sources, which will lead to a rapid expansion of this technique. The present work describes the design and performance of a new APPES instrument at the Advanced Light Source beamline 9.3.2 at Lawrence Berkeley National Laboratory. This new instrument, Scienta R4000 HiPP, is a result of collaboration between Advanced Light Source and its industrial partner VG-Scienta. The R4000 HiPP provides superior electron transmission as well as spectromicroscopy modes with 16 μm spatial resolution in one dimension and angle-resolved modes with simulated 0.5° angular resolution at 24° acceptance. Under maximum transmission mode, the electron detection efficiency is more than an order of magnitude better than the previous endstation at beamline 9.3.2. Herein we describe the design and performance of the system, which has been utilized to record spectra above 2 mbar. © 2010 American Institute of Physics.

  6. Investigation of the dipole formation and growth behavior at In2O3|TiO2 heterojunctions using photoemission spectroscopy and atomic force microscopy

    Science.gov (United States)

    Schaefer, Michael; Halpegamage, Sandamali; Batzill, Matthias; Schlaf, Rudy

    2016-02-01

    This paper discusses the investigation of the dipole formation at In2O3|TiO2 heterojunctions depending on preparation conditions, i.e., cleaning methods. In2O3 films were deposited using atomic layer deposition (ALD) onto solvent and in situ cleaned anatase and rutile film substrates. The interface dipole strength and film thickness were evaluated by photoemission spectroscopy. Our results indicate the formation of a large intrinsic and film thickness dependent interface dipole that reaches its maximum strength at monolayer thick ALD films. In addition, it was observed that UV photoelectron spectroscopy measurements introduced UV induced surface hydroxylation, which resulted in dipole potentials of -0.70 eV and -0.50 eV on solvent cleaned anatase and rutile, respectively. The overlayers also introduced small amounts of band bending (˜0.10 eV) at the interfaces. Taking these effects into account, the total dipole strength at monolayer thick In2O3 films was determined to be -0.96 eV for solvent cleaned anatase and rutile and -0.81 eV for in situ cleaned rutile. The deposition of single ALD cycles on differently cleaned rutile substrates resulted in similar work function values, suggesting little influence of the sample preparation method prior to ALD deposition on the dipole formation. This was assigned to the fact that ALD oxides benefit from ambient water related contamination by integrating the molecules into the growing ALD layer. Highest initial growth was observed on solvent cleaned rutile, followed by in-situ cleaned rutile and solvent cleaned anatase. The In2O3 growth converged at 0.3 Å/c past the nucleation regime.

  7. Electronic structure of Na/sub x/WO3: A photoemission study covering the entire concentration range

    International Nuclear Information System (INIS)

    Angle-resolved and angle-integrated ultraviolet-photoemission-spectroscopy (UPS) investigations have been carried out over the entire concentration range 03. The results indicate that the rigid-band model used by several authors fails to explain the x dependence of the electronic structure. For the metallic samples with x> or =0.3, the top of the valence band and the bottom of the conduction band remain at 3 and 1 eV, respectively, and the width of the occupied part of the conduction band is independent of x. The peak amplitude at the Fermi level varies linearly with x and does not follow the predicted dependence. A detailed comparison is made between the experimental results and the band-structure calculation of Kopp et al. Both the width of the valence band and the separation between the valence and conduction bands are too small in the calculation. Angle-resolved UPS measurements reveal a peak in the gap region for the metallic samples which disperses from 2.1 eV for k/sub parallel/ = 0 to 1.2 eV for k/sub parallel/ along Gamma-arrow-right-M. This feature is assigned to a surface state. The failure to detect localized gap states for the semiconducting samples is explained by band bending and a charge depletion layer caused by oxygen acceptor states at the surface. The fact that the work function phi decreases linearly with increasing x indicates that there is no surface depletion of sodium as has been claimed earlier

  8. Electronic structure of Na/sub x/WO/sub 3/: A photoemission study covering the entire concentration range

    Energy Technology Data Exchange (ETDEWEB)

    Hoechst, H.; Bringans, R.D.; Shanks, H.R.

    1982-08-15

    Angle-resolved and angle-integrated ultraviolet-photoemission-spectroscopy (UPS) investigations have been carried out over the entire concentration range 0 or =0.3, the top of the valence band and the bottom of the conduction band remain at 3 and 1 eV, respectively, and the width of the occupied part of the conduction band is independent of x. The peak amplitude at the Fermi level varies linearly with x and does not follow the predicted dependence. A detailed comparison is made between the experimental results and the band-structure calculation of Kopp et al. Both the width of the valence band and the separation between the valence and conduction bands are too small in the calculation. Angle-resolved UPS measurements reveal a peak in the gap region for the metallic samples which disperses from 2.1 eV for k/sub parallel/ = 0 to 1.2 eV for k/sub parallel/ along Gamma-arrow-right-M. This feature is assigned to a surface state. The failure to detect localized gap states for the semiconducting samples is explained by band bending and a charge depletion layer caused by oxygen acceptor states at the surface. The fact that the work function phi decreases linearly with increasing x indicates that there is no surface depletion of sodium as has been claimed earlier.

  9. Photoemission from stepped W(110): Umklapp or superlattice effect?

    International Nuclear Information System (INIS)

    Full text: Vicinal W(110) is an important substrate for the growth of metallic and magnetic nanostructures. In order to explore its potential to support nanostructures that lead to quantization of electronic states, the behavior of electrons on the pure stepped W(110) is studied. Using angle-resolved photoemission, we compare the electronic structure of the (110)-oriented terraces of stepped W(331) and W(551). We discover a surface-localized state which leads in [110]-terrace-normal emission to a large energy shift (∼0.8 eV) between W(110) and W(331). Away from normal emission it develops in the direction perpendicular to the steps into a repeated band dispersion. The measured periodicity agrees well with the step widths of W(331) and W(551), respectively, and is, principally, in agreement with both an initial-state superlattice effect and a final-state umklapp process. We discuss the role of the W bulk band gap and use the energy dependence in angle-resolved photoemission and low-energy electron diffraction to show that the observed behavior is due to a final-state umklapp effect at the step superlattice, as has recently been observed for carbon nanostripes on stepped Ni(771)[3] and independently on vicinal Au(111)

  10. Energy-band alignment of II-VI/Zn3P2 heterojunctions from x-ray photoemission spectroscopy

    OpenAIRE

    Watson, Graeme

    2013-01-01

    PUBLISHED The energy-band alignments for zb-ZnSe(001)/ a -Zn 3 P 2 (001), w-CdS(0001)/ a -Zn 3 P 2 (001), and w-ZnO(0001)/ a -Zn 3 P 2 (001) heterojunctions have been determined using high-resolution x-ray photoelectron spectroscopy via the Kraut method. Ab initio hybrid density functional theory calculations of the valence-band density of states were used to determine the energy differences between the core level and ...

  11. Angle-resolved photoemission study of the evolution of band structure and charge density wave properties in RTe3 (R= Y, La, Ce, Sm, Gd, Tb and Dy)

    Energy Technology Data Exchange (ETDEWEB)

    Brouet, V.; Yang, W.L.; Zhou, X.J.; Hussain, Z.; Moore, R.G.; He, R.; Lu, D.H.; Shen, Z.X.; Laverock, J.; Dugdale, S.; Ru, N.; Fisher, I.R.

    2010-02-15

    We present a detailed ARPES investigation of the RTe{sub 3} family, which sets this system as an ideal 'textbook' example for the formation of a nesting driven Charge Density Wave (CDW). This family indeed exhibits the full range of phenomena that can be associated to CDW instabilities, from the opening of large gaps on the best nested parts of Fermi Surface (FS) (up to 0.4eV), to the existence of residual metallic pockets. ARPES is the best suited technique to characterize these features, thanks to its unique ability to resolve the electronic structure in k-space. An additional advantage of RTe{sub 3} is that the band structure can be very accurately described by a simple 2D tight-binding (TB) model, which allows one to understand and easily reproduce many characteristics of the CDW. In this paper, we first establish the main features of the electronic structure, by comparing our ARPES measurements with Linear Muffin-Tin Orbital band calculations. We use this to define the validity and limits of the TB model. We then present a complete description of the CDW properties and, for the first time, of their strong evolution as a function of R. Using simple models, we are able to reproduce perfectly the evolution of gaps in k-space, the evolution of the CDW wave vector with R and the shape of the residual metallic pockets. Finally, we give an estimation of the CDW interaction parameters and find that the change in the electronic density of states n(Ef), due to lattice expansion when different R ions are inserted, has the correct order of magnitude to explain the evolution of the CDW properties.

  12. In situ hard x-ray photoemission spectroscopy of barrier-height control at metal/PMN-PT interfaces

    Science.gov (United States)

    Kröger, E.; Petraru, A.; Quer, A.; Soni, R.; Kalläne, M.; Pertsev, N. A.; Kohlstedt, H.; Rossnagel, K.

    2016-06-01

    Metal-ferroelectric interfaces form the basis of novel electronic devices. A key effect determining the device functionality is the bias-dependent change of the electronic energy-level alignment at the interface. Here, hard x-ray photoelectron spectroscopy (HAXPES) is used to determine the energy-level alignment at two metal-ferroelectric interfaces—Au versus SrRuO3 on the relaxor ferroelectric Pb (Mg1 /3Nb2 /3 )0.72Ti0.28O3 (PMN-PT)—directly in situ as a function of electrical bias. The bias-dependent average shifts of the PMN-PT core levels are found to have two dominant contributions on the 0.1 -1-eV energy scale: one depending on the metal electrode and the remanent electric polarization and the other correlated with electric-field-induced strain. Element-specific deviations from the average shifts are smaller than 0.1 eV and appear to be related to predicted dynamical charge variations in PMN-PT. In addition, the efficiency of ferroelectric polarization switching is shown to be reduced near the coercive field under x-ray irradiation. The results establish HAXPES as a tool for the in operando investigation of metal-ferroelectric interfaces and suggest electric-field-induced modifications of the polarization distribution as a novel way to control the barrier height at such interfaces.

  13. Cation profiling of passive films on stainless steel formed in sulphuric and acetic acid by deconvolution of angle-resolved X-ray photoelectron spectra

    International Nuclear Information System (INIS)

    An approach for determining depth gradients of metal-ion concentrations in passive films on stainless steel using angle-resolved X-ray photoelectron spectroscopy (ARXPS) is described. The iterative method, which is based on analyses of the oxidised metal peaks, provides increased precision and hence allows faster ARXPS measurements to be carried out. The method was used to determine the concentration depth profiles for molybdenum, iron and chromium in passive films on 316L/EN 1.4432 stainless steel samples oxidised in 0.5 M H2SO4 and acetic acid diluted with 0.02 M Na2B4O7 · 10H2O and 1 M H2O, respectively. The molybdenum concentration in the film is pin-pointed to the oxide/metal interface and the films also contained an iron-ion-enriched surface layer and a chromium-ion-dominated middle layer. Although films of similar composition and thickness (i.e., about 2 nm) were formed in the two electrolytes, the corrosion currents were found to be three orders of magnitude larger in the acetic acid solution. The differences in the layer composition, found for the two electrolytes as well as different oxidation conditions, can be explained based on the oxidation potentials of the metals and the dissolution rates of the different metal ions.

  14. Temperature-dependent photoemission features for overdoped Bi2Sr2CaCu2O8+x cuprates

    International Nuclear Information System (INIS)

    We report temperature-dependent angle-resolved photoemission spectra for overdoped Bi2Sr2CaCu2O8+x single-crystal samples. The data indicate that there is a special temperature (T+) where the spectral function changes intensity, and where the energy difference between the peak and dip features changes. The data also demonstrate that immediately above the superconducting transition temperature, the system exhibits a non-Lorentzian lineshape. We discuss implications of the data. (orig.)

  15. Temperature-dependent photoemission features for overdoped Bi2Sr2CaCu2O8 + x cuprates

    Science.gov (United States)

    Rast, S.; Frazer, B. H.; Onellion, M.; Schmauder, T.; Abrecht, M.; Touzelet, O.; Berger, H.; Margaritondo, G.; Pavuna, D.

    2000-07-01

    We report temperature-dependent angle-resolved photoemission spectra for overdoped Bi2Sr2CaCu2O8 + x single-crystal samples. The data indicate that there is a special temperature (T+) where the spectral function changes intensity, and where the energy difference between the peak and dip features changes. The data also demonstrate that immediately above the superconducting transition temperature, the system exhibits a non-Lorentzian lineshape. We discuss implications of the data.

  16. Inverse photoemission and resonant photoemission characterization of semimagnetic semiconductors

    International Nuclear Information System (INIS)

    The new magnetotransport and magneto-optical properties of the semimagnetic Cd/sub 1-//sub x/Mn/sub x/Te semiconductor alloy series depend critically on the nature of the Mn-derived d states. We examine here the electronic structure of these alloys with a combination of inverse photoemission spectroscopy, core-level photoemission line-shape analysis, valence-band resonant photoemission, and local density pseudofunction theory. The spectroscopic data reflect the local Mn--Te coordination and are in remarkable agreement with our one-electron calculations. We see no evidence of Mn-derived d states in the gap, and observe an experimental dup-arrow--darrow-down exchange splitting of 8.4 +- 0.4 eV, i.e., almost twice as large as expected from earlier theoretical estimates. The ground-state configuration of Mn in the solid is primarily (dup-arrow)(sup-arrow)(pup-arrow), and the super-exchange interaction has an important role in determining the stability of such a configuration relative to (dup-arrow)5s2

  17. X-ray-photoemission-spectroscopy evidence for anomalous oxidation states of silicon after exposure of hydrogen-terminated single-crystalline (100) silicon to a diluted N2:N2O atmosphere

    International Nuclear Information System (INIS)

    The early oxidation stages of hydrogen-terminated single-crystalline (100) silicon exposed to a diluted N2 : N2O atmosphere at 8500C for different durations have been studied by x-ray photoemission spectroscopy, following the evolution of the Si 2p signal. Evidence is given that the usual analysis, in terms of five pairs of peaks attributed to silicon in the oxidation states from 0 to +4, does not account for the observed Si 2p signal. An explanation for silicon in unusual oxidation states is proposed. (author)

  18. Direct angle resolved photoelectron spectroscopy (DARPES) on high-Tc films: doping, strains, Fermi surface topology and superconductivity

    Science.gov (United States)

    Pavuna, D.; Ariosa, D.; Cancellieri, C.; Cloetta, D.; Abrecht, M.

    2008-03-01

    Since 1997 we systematically perform Direct ARPES ( = DARPES) on in-situ grown, non-cleaved, ultra-thin (<25nm) cuprate films. Specifically, we probe low energy electronic structure and properties of high-Tc films under different degree of epitaxial (compressive vs tensile) strain. In overdoped in-plane compressed La2-xSrxCuO4 (LSCO) thin films we double Tc from 20K to 40K, yet the Fermi surface (FS) remains essentially 2-dimensional (2D). In contrast, tensile strained films show 3-dimensional (3D) dispersion, while Tc is drastically reduced. It seems that the in-plane compressive strain tends to push the apical oxygen far away from the CuO2 plane, enhances the 2D character of the dispersion and increases Tc, while the tensile strain seems to act exactly in the opposite direction and the resulting dispersion is 3D. We have the FS topology for both cases. As the actual lattice of cuprates is 'Napoleon-cake' -like i.e. rigid CuO2 planes alternate with softer 'reservoir' (that strains distort differently) our results tend to rule out 2D rigid lattice mean field models. Finally, we briefly discuss recent successful determination of the FS topology from the observed wavevector quantization by DARPES in cuprate films thinner than 18 units cells (<24nm). Such an approach is of broader interest as it can be extended to other similar confined (ultra-thin) functional oxide systems.

  19. Direct angle resolved photoelectron spectroscopy (DARPES) on high-Tc films: doping, strains, Fermi surface topology and superconductivity

    International Nuclear Information System (INIS)

    Since 1997 we systematically perform Direct ARPES ( = DARPES) on in-situ grown, non-cleaved, ultra-thin (c films under different degree of epitaxial (compressive vs tensile) strain. In overdoped in-plane compressed La2-xSrxCuO4 (LSCO) thin films we double Tc from 20K to 40K, yet the Fermi surface (FS) remains essentially 2-dimensional (2D). In contrast, tensile strained films show 3-dimensional (3D) dispersion, while Tc is drastically reduced. It seems that the in-plane compressive strain tends to push the apical oxygen far away from the CuO2 plane, enhances the 2D character of the dispersion and increases Tc, while the tensile strain seems to act exactly in the opposite direction and the resulting dispersion is 3D. We have the FS topology for both cases. As the actual lattice of cuprates is 'Napoleon-cake' -like i.e. rigid CuO2 planes alternate with softer 'reservoir' (that strains distort differently) our results tend to rule out 2D rigid lattice mean field models. Finally, we briefly discuss recent successful determination of the FS topology from the observed wavevector quantization by DARPES in cuprate films thinner than 18 units cells (<24nm). Such an approach is of broader interest as it can be extended to other similar confined (ultra-thin) functional oxide systems

  20. Direct angle resolved photoelectron spectroscopy (DARPES) on high-T{sub c} films: doping, strains, Fermi surface topology and superconductivity

    Energy Technology Data Exchange (ETDEWEB)

    Pavuna, D; Ariosa, D; Cancellieri, C; Cloetta, D; Abrecht, M [Institute of Physics of Complex Matter, FSB, Ecole Polytechnique Federale de Lausanne (EPFL), CH-1015 Lausanne (Switzerland)], E-mail: davor.pavuna@epfl.ch

    2008-03-15

    Since 1997 we systematically perform Direct ARPES ( = DARPES) on in-situ grown, non-cleaved, ultra-thin (<25nm) cuprate films. Specifically, we probe low energy electronic structure and properties of high-T{sub c} films under different degree of epitaxial (compressive vs tensile) strain. In overdoped in-plane compressed La{sub 2-x}Sr{sub x}CuO{sub 4} (LSCO) thin films we double T{sub c} from 20K to 40K, yet the Fermi surface (FS) remains essentially 2-dimensional (2D). In contrast, tensile strained films show 3-dimensional (3D) dispersion, while T{sub c} is drastically reduced. It seems that the in-plane compressive strain tends to push the apical oxygen far away from the CuO{sub 2} plane, enhances the 2D character of the dispersion and increases T{sub c}, while the tensile strain seems to act exactly in the opposite direction and the resulting dispersion is 3D. We have the FS topology for both cases. As the actual lattice of cuprates is 'Napoleon-cake' -like i.e. rigid CuO{sub 2} planes alternate with softer 'reservoir' (that strains distort differently) our results tend to rule out 2D rigid lattice mean field models. Finally, we briefly discuss recent successful determination of the FS topology from the observed wavevector quantization by DARPES in cuprate films thinner than 18 units cells (<24nm). Such an approach is of broader interest as it can be extended to other similar confined (ultra-thin) functional oxide systems.

  1. Symmetric and anti-symmetric magnetic resonances in double-triangle nanoparticle arrays fabricated via angle-resolved nanosphere lithography

    Directory of Open Access Journals (Sweden)

    Jian Pan

    2011-12-01

    Full Text Available We report experimentally that for a particular high-symmetry planar periodic arrangement of metal double-triangle nanoparticle arrays fabricated via angle resolved nanosphere lithography, both anti-symmetric and symmetric magnetic resonances can be explicitly excited at off-normal incidence. Further, we demonstrate that the underlying mechanism for the formation of these two modes is a result of direct interactions with the incident electric and magnetic fields, respectively. As a consequence, with increasing the incident angle there is a relatively small blue-shift in the transmission for the electric-field induced anti-symmetric mode, while a remarkable red-shift is observed for the magnetic-field induced symmetric mode.

  2. Depth profile analysis of polymerized fluorine compound on photo-resist film with angle-resolved XPS

    International Nuclear Information System (INIS)

    Angle-resolved XPS (ARXPS) is an observation technique which is very effective in chemical depth analysis method less than photoelectron detected depth. For the analysis of depth profile, several analysis methods have been proposed to calculate the depth profile using the ARXPS method. The present report is the measurements of depth profile of the fluorine in a fluorine-containing photo-resist film using the ARXPS method and the depth profile of concentration have been successfully determined using the ARCtick 1.0 software. It has been observed that thickness of the fluorocarbon enriched surface layer of the photo-resist was 2.7 nm, and so that the convert of the ARXPS data from the angle profile to the depth profile was proved to be useful analysis method for the ultrathin layer depth. (author)

  3. Role of ytterbium and ytterbium/cesium fluoride on the chemistry of poly(9,9-dioctylfluorene-co-benzothiadiazole) as investigated by photoemission spectroscopy

    International Nuclear Information System (INIS)

    Since ytterbium (Yb) possesses a low work function of 2.6 eV and Yb fluoride generally has a high negative free energy of formation, it is conceivable to use Yb, either directly or parasitically, with a metal fluoride, as a cathode in organic light-emitting diodes (OLEDs). In this work, the electronic structure and chemistry at the interface of Yb/poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT) were investigated by ultraviolet and x-ray photoemission spectroscopy (UPS and XPS, respectively). We found that the deposition of Yb on top of F8BT foremost formed organometallic complexes with the sulfur but interacted partly with the nitrogen of F8BT, and eventually formed a Yb-C complex at higher Yb coverages. In the UPS spectra, Yb deposition increased the relative peak intensities corresponding to the σ-bonds originated from the aliphatic side chains, implying that some of the π-conjugated carbons in the polymer backbone may be destroyed. These results agree well with the disappearance of the π-to-π* transition as observed from the shake-up peaks of the carbon 1s core level in the XPS. The chemistry at the interfaces of Yb/CsF/Au and Yb/CsF/F8BT was also examined by XPS. In both cases, Cs was liberated from the CsF upon Yb deposition and the Yb reacted with the liberated F to form YbF3. In the Yb/CsF/F8BT system, the dissociated Cs did not exist in the metallic state, but reacted with the N atoms and carbon backbone in the F8BT. The low work function of Cs (2.2 eV) may further enhance the injection of electrons into the polymer layer. More importantly, the utilization of Yb/CsF as an electrode is polymer independent, and the CsF layer between the Yb and F8BT could retard Yb diffusion into the bulk polymer. The present results are supported by a calculation of the free energy needed to liberate the Cs in the metal/CsF system using a simple thermodynamic model. It is suggested that the use of Yb/CsF cathode in the polymer offers an advantage over most other

  4. CdS and Cd-Free Buffer Layers on Solution Phase Grown Cu2ZnSn(SxSe1- x)4 :Band Alignments and Electronic Structure Determined with Femtosecond Ultraviolet Photoemission Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Haight, Richard; Barkhouse, Aaron; Wang, Wei; Yu, Luo; Shao, Xiaoyan; Mitzi, David; Hiroi, Homare; Sugimoto, Hiroki

    2013-12-02

    The heterojunctions formed between solution phase grown Cu2ZnSn(SxSe1- x)4(CZTS,Se) and a number of important buffer materials including CdS, ZnS, ZnO, and In2S3, were studied using femtosecond ultraviolet photoemission spectroscopy (fs-UPS) and photovoltage spectroscopy. With this approach we extract the magnitude and direction of the CZTS,Se band bending, locate the Fermi level within the band gaps of absorber and buffer and measure the absorber/buffer band offsets under flatband conditions. We will also discuss two-color pump/probe experiments in which the band bending in the buffer layer can be independently determined. Finally, studies of the bare CZTS,Se surface will be discussed including our observation of mid-gap Fermi level pinning and its relation to Voc limitations and bulk defects.

  5. Detection of ultrashort VUV radiation pulses using photoelectron spectroscopy at DELTA

    International Nuclear Information System (INIS)

    At the 1.5-GeV electron storage ring DELTA operated by the TU-Dortmund University, coherent VUV radiation is generated in a short-pulse facility based on the Coherent Harmonic Generation (CHG) scheme. In this scheme, a femtosecond laser pulse is used to induce a periodic modulation of the electron energy in an undulator. The energy modulation is converted to a density modulation in a dispersive section. The resulting electron microbunches radiate coherently at higher harmonics of the laser wavelength in a second undulator. The VUV beamline operated by the Forschungszentrum Juelich will be employed for pump-probe experiments. It comprises a plane-grating monochromator and a photoelectron spectrometer optimized for angle-resolved photoemission spectroscopy. While a dedicated setup was initially used during commissioning of the short-pulse facility, the CHG-generated pulses can now be characterized directly in the VUV beamline.

  6. Inverse photoemission and photoemission spectroscopic studies on sputter-annealed Ni–Mn–Sn and Ni–Mn–In surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Maniraj, M., E-mail: mr.maniraj@gmail.com [UGC-DAE Consortium for Scientific Research, Khandwa Road, Indore 452001, Madhya Pradesh (India); D' Souza, S.W. [UGC-DAE Consortium for Scientific Research, Khandwa Road, Indore 452001, Madhya Pradesh (India); Singh, Sandeep; Biswas, C. [Department of Condensed Matter Physics and Materials Science, SN Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata 700098, West Bengal (India); Majumdar, S. [Indian Association for the Cultivation of Science, Raja S.C. Mullick Road, Jadavpur, Kolkata 700032, West Bengal (India); Barman, S.R. [UGC-DAE Consortium for Scientific Research, Khandwa Road, Indore 452001, Madhya Pradesh (India)

    2014-12-15

    Highlights: • Inverse photoemission spectra dominated by Mn 3d-like states. • Photoemission spectra show change in Ni 3d-Mn 3d hybridization with composition. • Rigid band shift is observed between Ni{sub 2}MnIn and Ni{sub 2}MnSn. • Mn 2p and 3s core-level spectra exhibit existence of exchange splitting. - Abstract: The electronic structure of nearly stoichiometric Ni–Mn–Sn and Ni–Mn–In surface is investigated by inverse photoemission and photoemission spectroscopy. Comparison of the experimental and calculated inverse photoemission spectra shows that the dominant feature is related to Mn 3d-like states. The overall shape and peak position of the theoretically obtained spectra show good agreement with the experimental ultraviolet photoemission valence band spectra. The changes in the composition dependent ultraviolet photoemission spectra reveal the change in degree of Ni 3d and Mn 3d band hybridization. Both inverse photoemission and ultraviolet photoemission study show a rigid band shift between Ni{sub 2}MnIn and Ni{sub 2}MnSn because of band filling, due to increase in the number of 5p electrons from In to Sn. Mn 2p and 3s core-level reveal unambiguous existence of exchange splitting in both the materials.

  7. Nanofocusing, shadowing, and electron mean free path in the photoemission from aerosol droplets

    Science.gov (United States)

    Signorell, Ruth; Goldmann, Maximilian; Yoder, Bruce L.; Bodi, Andras; Chasovskikh, Egor; Lang, Lukas; Luckhaus, David

    2016-08-01

    Angle-resolved photoelectron spectroscopy of aerosol droplets is a promising method for the determination of electron mean free paths in liquids. It is particularly attractive for volatile liquids, such as water. Here we report the first angle-resolved photoelectron images of droplets with defined sizes, viz. of water, glycerol, and dioctyl phthalate droplets. Simulations of water droplet photoelectron images and data for electron mean free paths for liquid water at low kinetic energy (<3 eV) are provided. We present an approach that allows one to gradually vary the conditions from shadowing to nanofocusing to optimize the information content contained in the photoelectron images.

  8. Nanofocusing, shadowing, and electron mean free path in the photoemission from aerosol droplets

    CERN Document Server

    Signorell, Ruth; Yoder, Bruce L; Bodi, Andras; Chasovskikh, Egor; Lang, Lukas; Luckhaus, David

    2016-01-01

    Angle-resolved photoelectron spectroscopy of aerosol droplets is a promising method for the determination of electron mean free paths in liquids. It is particularly attractive for volatile liquids, such as water. Here we report the first angle-resolved photoelectron images of droplets with defined sizes, viz. of water, glycerol, and dioctyl phthalate droplets. We present an approach that allows one to gradually vary the conditions from dominant shadowing to dominant nanofocusing to optimize the information content contained in the photoelectron images. Example simulations of water droplet photoelectron images and preliminary data for electron mean free paths for liquid water at low kinetic energy (<3eV) are provided.

  9. Quantitative angle-resolved small-spot reflectance measurements on plasmonic perfect absorbers: impedance matching and disorder effects.

    Science.gov (United States)

    Tittl, Andreas; Harats, Moshe G; Walter, Ramon; Yin, Xinghui; Schäferling, Martin; Liu, Na; Rapaport, Ronen; Giessen, Harald

    2014-10-28

    Plasmonic devices with absorbance close to unity have emerged as essential building blocks for a multitude of technological applications ranging from trace gas detection to infrared imaging. A crucial requirement for such elements is the angle independence of the absorptive performance. In this work, we develop theoretically and verify experimentally a quantitative model for the angular behavior of plasmonic perfect absorber structures based on an optical impedance matching picture. To achieve this, we utilize a simple and elegant k-space measurement technique to record quantitative angle-resolved reflectance measurements on various perfect absorber structures. Particularly, this method allows quantitative reflectance measurements on samples where only small areas have been nanostructured, for example, by electron-beam lithography. Combining these results with extensive numerical modeling, we find that matching of both the real and imaginary parts of the optical impedance is crucial to obtain perfect absorption over a large angular range. Furthermore, we successfully apply our model to the angular dispersion of perfect absorber geometries with disordered plasmonic elements as a favorable alternative to current array-based designs. PMID:25251075

  10. A model-based approach for the calibration and traceability of the angle resolved scattering light sensor

    Science.gov (United States)

    Seewig, Jörg; Eifler, Matthias; Schneider, Frank; Kirsch, Benjamin; Aurich, Jan C.

    2016-06-01

    Within the field of geometric product specification there is a growing need for the application of inline measurement systems. The use of inline measurement requires robust and fast measurement principles. A very robust optical measurement principle is the angle resolved scattering light (ARS) sensor. The ARS sensor provides high precision and high resolution measurement data of technical surfaces because the surface angles are measured as an intensity distribution on a detector instead of measuring a series of discrete height values. However, until now, there were no specific measurement standards for the calibration of the ARS sensor and no traceability was ensured. In this paper, new strategies for the calibration of an ARS sensor are proposed. A new mathematical model for the ARS sensor is introduced. Based on this, two new measurement standards for the calibration of the sensor parameters are derived. These standards are designed with a model-based approach and can calibrate sensor-specific properties of the ARS sensor. The manufacturing of the standards is described and measurement results are provided.

  11. Soft X-ray synchrotron radiation photoemission study on uranium compounds

    International Nuclear Information System (INIS)

    We have carried out the angle-resolved photoemission experiments on some uranium compounds using soft X-ray synchrotron radiation. Bulk- and U 5f-sensitive band structure and Fermi surface were obtained for paramagnetic uranium compound UFeGa5. Although the agreement between the experimental band structure and the LDA calculation treating U 5f electrons as being itinerant is qualitative, the topology of the Fermi surface is well explained by the calculation, suggesting that the U 5f states can be essentially understood within the itinerant-electron model

  12. Study of III-V semiconductor band structure by synchrotron photoemission

    International Nuclear Information System (INIS)

    Angle-resolved synchrotron photoemission studies of six III-V semiconductors have been carried out. For emission normal to the (110) plane of these materials, peaks in the experimental spectra were identified with the bands involved in the transitions, and the critical point energies X3, X5, and Σ1/sup min/, were determined. The data indicate that k perpendicular is conserved in the transitions. Comparison of the data with theoretical bands permits an evaluation of k perpendicular associated with the experimentally observed transition, and from this information the bands were plotted out

  13. Observation of strontium segregation in LaAlO3/SrTiO3 and NdGaO3/SrTiO3 oxide heterostructures by X-ray photoemission spectroscopy

    International Nuclear Information System (INIS)

    LaAlO3 and NdGaO3 thin films of different thicknesses have been grown by pulsed laser deposition on TiO2-terminated SrTiO3 single crystals and investigated by soft X-ray photoemission spectroscopy. The surface sensitivity of the measurements has been tuned by varying photon energy hν and emission angle Θ. In contrast to the core levels of the other elements, the Sr 3d line shows an unexpected splitting for higher surface sensitivity, signaling the presence of a second strontium component. From our quantitative analysis we conclude that during the growth process Sr atoms diffuse away from the substrate and segregate at the surface of the heterostructure, possibly forming strontium oxide

  14. Electronic structure of Li1+x[Mn0.5Ni0.5]1−xO2 studied by photoemission and x-ray absorption spectroscopy

    International Nuclear Information System (INIS)

    We have studied the electronic structure of Li1+x[Mn0.5Ni0.5]1−xO2 (x = 0.00 and 0.05), one of the promising cathode materials for Li ion battery, by means of x-ray photoemission and absorption spectroscopy. The results show that the valences of Mn and Ni are basically 4+ and 2+, respectively. However, the Mn3+ component in the x = 0.00 sample gradually increases with the bulk sensitivity of the experiment, indicating that the Jahn-Teller active Mn3+ ions are introduced in the bulk due to the site exchange between Li and Ni. The Mn3+ component gets negligibly small in the x = 0.05 sample, which indicates that the excess Li suppresses the site exchange and removes the Jahn-Teller active Mn3+

  15. Observation of strontium segregation in LaAlO{sub 3}/SrTiO{sub 3} and NdGaO{sub 3}/SrTiO{sub 3} oxide heterostructures by X-ray photoemission spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Treske, Uwe; Heming, Nadine; Knupfer, Martin; Büchner, Bernd; Koitzsch, Andreas, E-mail: a.koitzsch@ifw-dresden.de [Institute for Solid State Research, IFW-Dresden, P.O. Box 270116, DE-01171 Dresden (Germany); Di Gennaro, Emiliano; Scotti di Uccio, Umberto; Miletto Granozio, Fabio [CNR-SPIN and Dipartimento di Fisica, Complesso Universitario di Monte S. Angelo, Via Cintia, 80126 Naples (Italy); Krause, Stefan [Helmholtz-Zentrum Berlin, BESSY, Albert-Einstein-Str. 15, 12489 Berlin (Germany)

    2014-01-01

    LaAlO{sub 3} and NdGaO{sub 3} thin films of different thicknesses have been grown by pulsed laser deposition on TiO{sub 2}-terminated SrTiO{sub 3} single crystals and investigated by soft X-ray photoemission spectroscopy. The surface sensitivity of the measurements has been tuned by varying photon energy hν and emission angle Θ. In contrast to the core levels of the other elements, the Sr 3d line shows an unexpected splitting for higher surface sensitivity, signaling the presence of a second strontium component. From our quantitative analysis we conclude that during the growth process Sr atoms diffuse away from the substrate and segregate at the surface of the heterostructure, possibly forming strontium oxide.

  16. Observation of strontium segregation in LaAlO3/SrTiO3 and NdGaO3/SrTiO3 oxide heterostructures by X-ray photoemission spectroscopy

    Science.gov (United States)

    Treske, Uwe; Heming, Nadine; Knupfer, Martin; Büchner, Bernd; Koitzsch, Andreas; Di Gennaro, Emiliano; Scotti di Uccio, Umberto; Miletto Granozio, Fabio; Krause, Stefan

    2014-01-01

    LaAlO3 and NdGaO3 thin films of different thicknesses have been grown by pulsed laser deposition on TiO2-terminated SrTiO3 single crystals and investigated by soft X-ray photoemission spectroscopy. The surface sensitivity of the measurements has been tuned by varying photon energy hν and emission angle Θ. In contrast to the core levels of the other elements, the Sr 3d line shows an unexpected splitting for higher surface sensitivity, signaling the presence of a second strontium component. From our quantitative analysis we conclude that during the growth process Sr atoms diffuse away from the substrate and segregate at the surface of the heterostructure, possibly forming strontium oxide.

  17. Observation of strontium segregation in LaAlO3/SrTiO3 and NdGaO3/SrTiO3 oxide heterostructures by X-ray photoemission spectroscopy

    Directory of Open Access Journals (Sweden)

    Uwe Treske

    2014-01-01

    Full Text Available LaAlO3 and NdGaO3 thin films of different thicknesses have been grown by pulsed laser deposition on TiO2-terminated SrTiO3 single crystals and investigated by soft X-ray photoemission spectroscopy. The surface sensitivity of the measurements has been tuned by varying photon energy hν and emission angle Θ. In contrast to the core levels of the other elements, the Sr 3d line shows an unexpected splitting for higher surface sensitivity, signaling the presence of a second strontium component. From our quantitative analysis we conclude that during the growth process Sr atoms diffuse away from the substrate and segregate at the surface of the heterostructure, possibly forming strontium oxide.

  18. Characterization of electronic structure of Cu{sub 2}ZnSn(S{sub x}Se{sub 1−x}){sub 4} absorber layer and CdS/Cu{sub 2}ZnSn(S{sub x}Se{sub 1−x}){sub 4} interfaces by in-situ photoemission and inverse photoemission spectroscopies

    Energy Technology Data Exchange (ETDEWEB)

    Terada, Norio, E-mail: terada@eee.kagoshima-u.ac.jp [Kagoshima University, 1-21-40 Korimoto, Kagoshima, Kagoshima 890-0065 (Japan); Advanced Industrial Science and Technology, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568 (Japan); Yoshimoto, Sho, E-mail: k0754754@kadai.jp [Kagoshima University, 1-21-40 Korimoto, Kagoshima, Kagoshima 890-0065 (Japan); Chochi, Kosuke, E-mail: k3024406@kadai.jp [Kagoshima University, 1-21-40 Korimoto, Kagoshima, Kagoshima 890-0065 (Japan); Fukuyama, Takayuki, E-mail: k9483803@kadai.jp [Kagoshima University, 1-21-40 Korimoto, Kagoshima, Kagoshima 890-0065 (Japan); Mitsunaga, Masahiro, E-mail: mistunaga@eee.kagoshima-u.ac.jp [Kagoshima University, 1-21-40 Korimoto, Kagoshima, Kagoshima 890-0065 (Japan); Tampo, Hitoshi, E-mail: tampo-21@aist.go.jp [Advanced Industrial Science and Technology, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568 (Japan); Shibata, Hajime, E-mail: h.shibata@aist.go.jp [Advanced Industrial Science and Technology, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568 (Japan); Matsubara, Koji, E-mail: koji.matsubara@aist.go.jp [Advanced Industrial Science and Technology, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568 (Japan); Niki, Shigeru, E-mail: shigeru-niki@aist.go.jp [Advanced Industrial Science and Technology, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568 (Japan); Sakai, Noriyuki, E-mail: Noriyuki.Sakai@solar-frontier.com [Showa Shell Sekiyu K. K., 123-1 Shimokawairi, Atsugi, Kanagawa 243-0206 (Japan); Katou, Takuya, E-mail: Takuya.Katou@solar-frontier.com [Showa Shell Sekiyu K. K., 123-1 Shimokawairi, Atsugi, Kanagawa 243-0206 (Japan); Sugimoto, Hiroki, E-mail: Hiroki.Sugimoto@solar-frontier.com [Showa Shell Sekiyu K. K., 123-1 Shimokawairi, Atsugi, Kanagawa 243-0206 (Japan)

    2015-05-01

    The dependences of electronic structure of CZTS{sub x}Se{sub 1−x} (CZTSSe) layers synthesized by sulfurization and/or selenization of the vacuum-deposited metal precursors on the anion mixing ratio x = S/(S + Se) have been studied by in-situ ultraviolet and X-ray photoemission spectroscopies (UPS, XPS) and inverse photoemission spectroscopy (IPES). The band alignment at interfaces between the CdS buffer by the sequential evaporation and the CZTSSe (x = 0.28 and 1.0) has also been investigated by the in-situ measurements of these spectroscopies. The UPS/IPES results of the CZTSSe surfaces have revealed linear expansion of band gap energy E{sub g} with an increase of x: E{sub g(CZTSe;x=0)} = 0.9-1.0 eV and E{sub g(CZTS;x=1)} = 1.5-1.6 eV. This expansion mainly originates in the rise of conduction band minimum CBM: CBM{sub (CZTSe;x=0)} = 0.45-0.50 eV and CBM{sub (CZTS;x=1)} = 0.95-1.05 eV. The in-situ measurements of the interface electronic structure have revealed that the CdS/CZTSSe (x = 0.28) interface has a so-called “type I” band alignment with a conduction band offset CBO about + 0.2 eV which is favorable to high cell performance. A negative CBO was distinguished for the CdS/CZTS (x = 1.0) interface, and the observed change in the band alignment with the anion mixing ratio was consistent with that of the variation in cell-performances. - Highlights: • The variation of electronic structure of CZTSSe films with S/(S + Se) ratio x is studied. • The monotonous rise of the conduction band minimum with x is clarified. • The band alignment at the CdS/CZTSSe interface is clarified by in-situ PES/IPES. • The change of the conduction band offset from positive to negative as an increase of x is observed. • The consistency between the band alignment and the cell performance is confirmed.

  19. Photocathode tunability: The photoemissive properties of ultra-thin multilayered MgO/Ag/MgO films synthesized by pulsed laser deposition

    Science.gov (United States)

    Velazquez, Daniel Gomez

    Much of the early development of photocathode materials was aimed at the growth of photoemissive thin films with low work function, and high quantum efficiency (QE). It has been shown, both theoretically and experimentally, that metal-insulator junctions can lead to the modification of the work function and QE for coverages of a few monolayers of metal oxides on metallic substrates. However, the production of electron beams suitable for new photoinjector technologies often requires low emittance beams from the cathode itself. A theoretical model [Phys. Rev. Lett. 104, 046801 (2010)] based on a multilayered structure of MgO/Ag(001)/MgO with 4 monolayers of Ag(001) flanked by n monolayers (ML) of MgO indicates the possibility to reduce the surface work function and photoelectron beam emittance when the thickness n of the MgO layers is 2 or 3 monolayers. These predictions were tested experimentally. Synthesis of multilayered MgO/Ag/MgO films was performed using a custom-built pulsed laser deposition (PLD) system. In-situ growth monitoring was carried out by Reflection High-Energy Electron Diffraction (RHEED). Ex-situ techniques such as Scanning Tunneling Microscopy (STM), Scanning Electron Microscopy/Energy Dispersive Spectroscopy (EDS) and Photoelectron Spectroscopy (PES) were used to show the formation of the crystalline and chemical structure. A custom-built Kelvin Probe/photocurrent-detector system was used to measure the work function and QE of the samples. Angle Resolved Photoelectron Spectroscopy was used to measure the angular photoelectron yield. Simultaneous reduction of work function and increase of QE was observed for (001) oriented multilayers of various thicknesses with respect to that of a bare Ag/MgO(001) surface. Work function measurements of multilayers of various thicknesses in the (111) orientation also showed a monotonic reduction with respect to that of a bare Ag/Si(111) surface. Angular emission was compared for a MgO/Ag/MgO multilayer

  20. Room temperature redox reaction by oxide ion migration at carbon/Gd-doped CeO2 heterointerface probed by an in situ hard x-ray photoemission and soft x-ray absorption spectroscopies

    Directory of Open Access Journals (Sweden)

    Takashi Tsuchiya, Shogo Miyoshi, Yoshiyuki Yamashita, Hideki Yoshikawa, Kazuya Terabe, Keisuke Kobayashi and Shu Yamaguchi

    2013-01-01

    Full Text Available In situ hard x-ray photoemission spectroscopy (HX-PES and soft x-ray absorption spectroscopy (SX-XAS have been employed to investigate a local redox reaction at the carbon/Gd-doped CeO2 (GDC thin film heterointerface under applied dc bias. In HX-PES, Ce3d and O1s core levels show a parallel chemical shift as large as 3.2 eV, corresponding to the redox window where ionic conductivity is predominant. The window width is equal to the energy gap between donor and acceptor levels of the GDC electrolyte. The Ce M-edge SX-XAS spectra also show a considerable increase of Ce3+ satellite peak intensity, corresponding to electrochemical reduction by oxide ion migration. In addition to the reversible redox reaction, two distinct phenomena by the electrochemical transport of oxide ions are observed as an irreversible reduction of the entire oxide film by O2 evolution from the GDC film to the gas phase, as well as a vigorous precipitation of oxygen gas at the bottom electrode to lift off the GDC film. These in situ spectroscopic observations describe well the electrochemical polarization behavior of a metal/GDC/metal capacitor-like two-electrode cell at room temperature.

  1. Soft X-ray absorption and photoemission spectroscopy study of semiconductor oxide nanoparticles for dye-sensitized solar cell: ZnSnO3 and Zn2SnO4

    Science.gov (United States)

    Kim, Hyun Woo; Lee, Eunsook; Kim, D. H.; Seong, Seungho; Moon, Soo Yeon; Shin, Yu-Ju; Baik, J.; Shin, H. J.; Kang, J.-S.

    2016-06-01

    The electronic structures of the Zn-stannate nanoparticles of ZnSnO3 and Zn2SnO4, which are the potential nano-structured semiconductor oxides for a dye sensitized solar cell (DSSC), have been investigated by employing photoemission spectroscopy (PES) and soft X-ray absorption spectroscopy (XAS), and compared to those of reference materials. The divalent and tetravalent valence states of Zn2+ and Sn4+ ions are confirmed experimentally. The energy levels of both the valence-band and conduction-band edges are determined experimentally. The top of the valence band in PES is slightly higher in Zn2SnO4 than in ZnSnO3. The onset energies of the O 1s XAS spectra of the Zn-stannates are found to be similar to each other, but higher than that of TiO2. The O 1 s XAS spectrum of ZnSnO3 exhibits the higher unoccupied density of states near the bottom of the conduction band than those of Zn2SnO4, SnO2 and ZnO, reflecting the larger number of holes in the Zn 3 d bands of ZnSnO3. Hence, the easier electron transfer is expected from the LUMO (lowest unoccupied molecular orbital) of a dye molecule to the conduction band of ZnSnO3 nanoparticles on the transparent conductive electrode of a DSSC.

  2. Photoemission, Correlation and Superconductivity:

    Science.gov (United States)

    Abrecht, M.; Ariosa, D.; Cloëtta, D.; Pavuna, D.; Perfetti, L.; Grioni, M.; Margaritondo, G.

    We review some of the problems still affecting photoemission as a probe of high-temperature superconductivity, as well as important recent results concerning their solution. We show, in particular, some of the first important results on thin epitaxial films grown by laser ablation, which break the monopoly of cleaved BCSCO in this type of experiments. Such results, obtained on thin LSCO, may have general implications on the theory of high-temperature superconductivity.

  3. Spectroscopy of the electronic states of the Heusler compounds Co2FeAl and Co2Cr0.6Fe0.4Al and the influence of oxidation

    Science.gov (United States)

    Jourdan, Martin; Große-Schulte, Fabian; Hahn, Michaela; Schönhense, Gerd

    2011-04-01

    The band structures of the Heusler compounds Co2Cr0.6Fe0.4Al and Co2FeAl were investigated in situ by angle-resolved ultraviolet photoemission spectroscopy. The samples were prepared by a sputtering process optimized for tunnelling junction preparation, the photoemission process in the normal direction of the (0 0 1)-oriented thin films was excited by a helium gas discharge lamp (hν = 21.2 eV and hν = 40.8 eV). The spectra of clean samples are compared with calculations of the total and partial bulk density of states and are evaluated within the three-step model of photoemission. Basic agreement with theoretical predictions of the bulk band structure is concluded. At oxygen exposures of the thin films of only 1 Langmuir a chemisorption phase with significant changes in the valence-band spectrum near the Fermi energy is observed. At 10 L oxygen the spectra are indicative of an oxide within the UPS probing depth.

  4. Spectroscopy of the electronic states of the Heusler compounds Co2FeAl and Co2Cr0.6Fe0.4Al and the influence of oxidation

    International Nuclear Information System (INIS)

    The band structures of the Heusler compounds Co2Cr0.6Fe0.4Al and Co2FeAl were investigated in situ by angle-resolved ultraviolet photoemission spectroscopy. The samples were prepared by a sputtering process optimized for tunnelling junction preparation, the photoemission process in the normal direction of the (0 0 1)-oriented thin films was excited by a helium gas discharge lamp (hν = 21.2 eV and hν = 40.8 eV). The spectra of clean samples are compared with calculations of the total and partial bulk density of states and are evaluated within the three-step model of photoemission. Basic agreement with theoretical predictions of the bulk band structure is concluded. At oxygen exposures of the thin films of only 1 Langmuir a chemisorption phase with significant changes in the valence-band spectrum near the Fermi energy is observed. At 10 L oxygen the spectra are indicative of an oxide within the UPS probing depth.

  5. Automated angle-scanning photoemission end-station with molecular beam epitaxy at KEK-PF BL-1C

    CERN Document Server

    Ono, K; Horiba, K; Oh, J H; Nakazono, S; Kihara, T; Nakamura, K; Mano, T; Mizuguchi, M; Oshima, M; Aiura, Y; Kakizaki, A

    2001-01-01

    In order to satisfy demands to study the electronic structure of quantum nanostructures, a VUV beamline and a high-resolution and high-throughput photoemission end-station combined with a molecular beam epitaxy (MBE) system have been constructed at the BL-1C of the Photon Factory. An angle-resolved photoemission spectrometer, having high energy- and angular-resolutions; VG Microtech ARUPS10, was installed. The total energy resolution of 31 meV at the 60 eV of photon energy is achieved. For the automated angle-scanning photoemission, the electron spectrometer mounted on a two-axis goniometer can be rotated in vacuum by the computer-controlled stepping motors. Another distinctive feature of this end-station is a connection to a MBE chamber in ultahigh vacuum (UHV). In this system, MBE-grown samples can be transferred into the photoemission chamber without breaking UHV. Photoemission spectra of MBE-grown GaAs(0 0 1) surfaces were measured with high-resolution and bulk and surface components are clearly resolved.

  6. Pulsed laser deposition for in-situ photoemission studies on YBa2Cu3O7-δ and related oxide films

    Science.gov (United States)

    Schmauder, T.; Frazer, B.; Gatt, R.; Xi, Xiaoxing; Onellion, Marshall; Ariosa, Daniel; Grioni, M.; Margaritondo, Giorgio; Pavuna, Davor

    1998-12-01

    We describe a new pled laser deposition (PLD) system that is linked to an angle-resolved photoemission (ARPES) chamber at the Synchrotron Radiation Center (SRC) in Wisconsin, USA. We also discuss our first results on epitaxially grown YBa2Cu3O7-(delta ) (YBCO) films. The core level photoemission data indicate that a Ba-oxide layer is the dominant surface layer. We were not able to reproducibly detect a sharp fermi edge in the photoemission spectra and thus conclude that the surface layer is non-metallic, probably due to oxygen loss at the surface. The absence of screening of the Y and Ba core levels is a further argument for this conclusion. Further experiments with ozone treated film surfaces are currently under way.

  7. Interface study of transition metal (Fe, Zr) on 4H-SiC(0 0 0 1)Si face: photoemission electron microscopy and soft X-ray fluorescence spectroscopy

    International Nuclear Information System (INIS)

    We have studied interface electronic structure of transition metal film (Fe, Zr)/4H-SiC (substrate) contact systems by using a photoemission electron microscopy (PEEM) and a soft X-ray fluorescence spectroscopy (SXFS). PEEM can show surface micro- and/or nano-structures, whereas SXFS can tell details of chemical bonding states. For specimens of Fe(10 nm)/4H-SiC(0 0 0 1)Si face contact system annealed at 300-900 deg. C, PEEM images have shown dramatic change in surface morphology above 550 deg. C, where the Si L2,3 fluorescence spectra can be explained by considering formation of iron silicides. On the other hand, PEEM images and the Si L2,3 fluorescence spectra for specimens of Zr(film)/4H-SiC(0 0 0 1)Si face contact system annealed at 650-1100 deg. C have indicated that interfaces of specimens are stable up to 1100 deg. C without any reaction

  8. Electronic structure of Li{sub 1+x}[Mn{sub 0.5}Ni{sub 0.5}]{sub 1−x}O{sub 2} studied by photoemission and x-ray absorption spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Yokoyama, Y. [Department of Physics, University of Tokyo, Chiba 277-8561 (Japan); Institute for Solid State Physics, University of Tokyo, Chiba 277-8581 (Japan); Ootsuki, D. [Department of Physics, University of Tokyo, Chiba 277-8561 (Japan); Sugimoto, T. [Department of Complexity Science and Engineering, University of Tokyo, Chiba 277-8561 (Japan); Wadati, H. [Institute for Solid State Physics, University of Tokyo, Chiba 277-8581 (Japan); Okabayashi, J. [Research Center for Spectrochemistry, University of Tokyo, Tokyo 113-0033 (Japan); Yang, Xu; Du, Fei; Chen, Gang [Key Laboratory of Physics and Technology for Advanced Batteries (Ministry of Education), College of Physics, Jilin University, Changchun 130012 (China); Mizokawa, T. [Department of Applied Physics, Waseda University, Tokyo 169-8555 (Japan)

    2015-07-20

    We have studied the electronic structure of Li{sub 1+x}[Mn{sub 0.5}Ni{sub 0.5}]{sub 1−x}O{sub 2} (x = 0.00 and 0.05), one of the promising cathode materials for Li ion battery, by means of x-ray photoemission and absorption spectroscopy. The results show that the valences of Mn and Ni are basically 4+ and 2+, respectively. However, the Mn{sup 3+} component in the x = 0.00 sample gradually increases with the bulk sensitivity of the experiment, indicating that the Jahn-Teller active Mn{sup 3+} ions are introduced in the bulk due to the site exchange between Li and Ni. The Mn{sup 3+} component gets negligibly small in the x = 0.05 sample, which indicates that the excess Li suppresses the site exchange and removes the Jahn-Teller active Mn{sup 3+}.

  9. Filling factor and electronic structure of Dy3N@C-80 filled single-wall carbon nanotubes studied by photoemission spectroscopy

    Czech Academy of Sciences Publication Activity Database

    Shiozawa, H.; Rauf, H.; Pichler, T.; Knupfer, M.; Kalbáč, Martin; Yang, S.; Dunsch, L.; Büchner, B.; Batchelor, D.; Kataura, H.

    2006-01-01

    Roč. 73, č. 20 (2006), 205411/1/-205411/6/. ISSN 1098-0121 Grant ostatní: Alexander von Humboldt Foundation(DE) DFG Pl 440/1/3 Institutional research plan: CEZ:AV0Z40400503 Keywords : high- energy spectroscopy * rare-earth-metals * charge-transfer * states Subject RIV: CG - Electrochemistry Impact factor: 3.107, year: 2006

  10. Surface photo-voltage effect on Cr/GaAs(100) studied by photoemission spectroscopy with the combination of synchrotron radiation and laser

    Science.gov (United States)

    Takahashi, Kazutoshi; Tokudomi, Sinji; Nagata, Yusuke; Azuma, Junpei; Kamada, Masao

    2011-12-01

    The surface photo-voltage (SPV) effect and its temporal profile on a Cr/p-GaAs(100) surface were measured by core-level photoelectron spectroscopy with the combination of synchrotron radiation and laser. It was found that the SPV value at the Cr thickness of 0.05 and 0.1 nm is enhanced in comparison with the clean surface, while that at the Cr thickness larger than 0.2 nm is remarkably suppressed. The dependence on the Cr thickness can be interpreted in terms of the change in the band bending and the escape process, which are associated with the electronic structures induced by the Cr deposition.

  11. Application of hard X-ray photoemission spectroscopy to material science using synchrotron radiation. Lubricant molecule on diamond like carbon (DLC) for hard disk

    International Nuclear Information System (INIS)

    Third generation [3G] high-intensity synchrotron X-ray source combined with a high-energy electron analyzer has enabled us to perform photoelectron spectroscopy with high-resolution at hard X-ray regions. The detection depth of the apparatus installed to SPring-8/BL-47XU is 5-20 nm in the solid sample compared to ∼1 nm in case of conventional XPS. Thus, the method has a much broader range of application in the study of electronic structure of the materials. The present paper introduces the system component of the apparatus of hard X-ray photoelectron spectroscopy (HAXPES), its main features and performance. Furthermore, as an application example, the research results on a thin A20H film, which consists of perfluoropolyether (PFPE) as lubricant molecule developed on DLC (Diamond-like Carbon) substrate, used for hard disk is demonstrated. From the comparison of the various C 1s peaks observed, the author concluded that P-N ring structure in the end group of phosphazene selectively absorbed chemically to DLC. (S. Ohno)

  12. Fullerene photoemission time delay explores molecular cavity in attoseconds

    CERN Document Server

    Magrakvelidze, Maia; Dixit, Gopal; Madjet, Mohamed El-Amine; Chakraborty, Himadri S

    2014-01-01

    Time-resolved photoelectron spectroscopy can probe interference oscillations in C60 valence emissions that produce series of minima whose energy separation depends on the molecular size. We show that the quantum phase associated with these minima exhibits rapid variations due to electron correlations, causing rich structures in the photoemission time delay. These findings provide a way to utilize temporal information to access the fullerene cavity size, that is making the time to "see" the space, and can be generalized to photoemissions from clusters and nanostructures.

  13. Photoemission and magnetic response in the bipolaronic superconductor

    CERN Document Server

    Dent, C

    2001-01-01

    in the cuprates is extended to explain the crossing point in the curves of induced magnetization divided by the square root of field against temperature in the less anisotropic cuprates. This model has already been shown to provide a parameter-free expression for T sub c in a wide range of cuprates. We compare our results with experiment in YBa sub 2 Cu sub 3 O sub 7 sub - subdelta. A theory of angle-resolved photoemission (ARPES) in doped charge-transfer Mott insulators is developed taking into account the realistic band structure, (bi)polaron formation due to the strong electron-phonon interaction, and a random field potential. We derive the coherent part of the ARPES spectra with the oxygen hole spectral function calculated in the non-crossing (ladder) approximation and with the exact spectral function of a one-dimensional hole in a random potential. On the basis of this theory, explanations are proposed for several features of the ARPES spectra taken from the cuprate superconductors. These include the pol...

  14. Plasmon Enhanced Photoemission

    Energy Technology Data Exchange (ETDEWEB)

    Polyakov, Aleksandr [Univ. of California, Berkeley, CA (United States)

    2012-05-08

    Next generation ultrabright light sources will operate at megahertz repetition rates with temporal resolution in the attosecond regime. For an X-Ray Free Electron Laser (FEL) to operate at such repetition rate requires a high quantum efficiency (QE) cathode to produce electron bunches of 300 pC per 1.5 μJ incident laser pulse. Semiconductor photocathodes have sufficient QE in the ultraviolet (UV) and the visible spectrum, however, they produce picosecond electron pulses due to the electron-phonon scattering. On the other hand, metals have two orders of magnitude less QE, but can produce femtosecond pulses, that are required to form the optimum electron distribution for high efficiency FEL operation. In this work, a novel metallic photocathode design is presented, where a set of nano-cavities is introduced on the metal surface to increase its QE to meet the FEL requirements, while maintaining the fast time response. Photoemission can be broken up into three steps: (1) photon absorption, (2) electron transport to the surface, and (3) crossing the metal-vacuum barrier. The first two steps can be improved by making the metal completely absorbing and by localizing the fields closer to the metal surface, thereby reducing the electron travel distance. Both of these effects can be achieved by coupling the incident light to an electron density wave on the metal surface, represented by a quasi-particle, the Surface Plasmon Polariton (SPP). The photoemission then becomes a process where the photon energy is transferred to an SPP and then to an electron. The dispersion relation for the SPP defines the region of energies where such process can occur. For example, for gold, the maximum SPP energy is 2.4 eV, however, the work function is 5.6 eV, therefore, only a fourth order photoemission process is possible. In such process, four photons excite four plasmons that together excite only one electron. The yield of such non-linear process depends strongly on the light intensity. In

  15. Na and Cs intercalation of 2H-TaSe2 studied by photoemission

    International Nuclear Information System (INIS)

    The electronic structure of the layered compound 2H-TaSe2 has been studied using angle-resolved photoemission before and after in situ intercalation with Na and Cs. Core level spectra verified that Na and Cs both intercalate easily at room temperature, with only small amounts remaining on the surface. Valence band spectra revealed changes in the electronic band structure which were much more extensive than predicted by the rigid band model, but which were in reasonable agreement with theoretical bands calculated by the LAPW method. Some discrepancies between the experimental and calculated results are probably due to intercalation induced changes in the stacking of host layers. A general similarity with results from transition metal dichalcogenides with 1T structure indicates that the intercalation properties are not critically dependent on the internal structure of the host layers. (author)

  16. Temperature-dependent photoemission features for overdoped Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+x} cuprates

    Energy Technology Data Exchange (ETDEWEB)

    Rast, S.; Frazer, B.H.; Onellion, M. [Wisconsin Univ., Madison, WI (United States). Dept. of Physics; Schmauder, T.; Abrecht, M.; Touzelet, O.; Berger, H.; Margaritondo, G.; Pavuna, D. [Ecole Polytechnique Federale, Lausanne (Switzerland). Inst. de Physique Appliquee

    2000-07-01

    We report temperature-dependent angle-resolved photoemission spectra for overdoped Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+x} single-crystal samples. The data indicate that there is a special temperature (T{sup +}) where the spectral function changes intensity, and where the energy difference between the peak and dip features changes. The data also demonstrate that immediately above the superconducting transition temperature, the system exhibits a non-Lorentzian lineshape. We discuss implications of the data. (orig.)

  17. Transfer of chirality from adsorbed chiral molecules to the substrates highlighted by circular dichroism in angle-resolved valence photoelectron spectroscopy

    DEFF Research Database (Denmark)

    Contini, G.; Turchini, S.; Sanna, Simone;

    2012-01-01

    state, that the presence of molecular chiral domains induces asymmetry in the interaction with the substrate and locally transfers the chiral character to the underlying metal atoms participating in the adsorption process; combined information related to the asymmetry of the initial electronic state......Studies of self-assembled chiral molecules on achiral metallic surfaces have mostly focused on the determination of the geometry of adsorbates and their electronic structure. The aim of this paper is to provide direct information on the chirality character of the system and on the chirality......, which is expected to be chiral, and the final electronic state, which locally probes the asymmetry of the potential, has been obtained. Identification of chirality in the adsorption footprint sheds new light on the transfer of chirality from a chiral modifier to a symmetric metal surface and represents...

  18. Observation by resonant angle-resolved photoemission of a critical thickness for 2-dimensional electron gas formation in SrTiO$_3$ embedded in GdTiO$_3$

    OpenAIRE

    Nemšák, S.; CONTI, G; Pálsson, G. K.; Conlon, C.; Cho, S.; Rault, J.; Avila, J.; Asensio, M. -C.; Jackson, C; Moetakef, P.; Janotti, A.; Bjaalie, L.; Himmetoglu, B.; Van de Walle, C. G.; Balents, L.

    2015-01-01

    For certain conditions of layer thickness, the interface between GdTiO$_3$ (GTO) and SrTiO$_3$ (STO) in multilayer samples has been found to form a two-dimensional electron gas (2DEG) with very interesting properties including high mobilities and ferromagnetism. We have here studied two trilayer samples of the form [2 nm GTO/1.0 or 1.5 unit cells STO/10 nm GTO] as grown on (001) (LaAlO$_3$)$_{0.3}$(Sr$_2$AlTaO$_6$)$_{0.7}$ (LSAT), with the STO layer thicknesses being at what has been suggeste...

  19. Crystal momentum dependence of the correlation satellite intensity in the 3p → 3d resonant photoemission spectra of Bi2Sr2CaCu2O8 + δ

    Science.gov (United States)

    Goldoni, A.; Corradini, V.; del Pennino, U.; Sangalli, P.; Parmigiani, F.; Avila, J.; Teodorescu, C.

    2000-05-01

    Angle-resolved resonant photoemission measurements at the Cu3p → Cu3d threshold have been performed on the superconducting cuprate Bi2Sr2CaCu2O8 + δ. We have investigated in particular the correlation satellite appearing in the valence band photoemission spectrum to investigate the effect of solid state on the interference effect occurring at resonance. We found that the intensity of the correlation satellite changes with the electron take-off angle in a way that depends on the particular crystallographic direction and on the sample hole doping. These results indicate that the intensity enhancement at the absorption edge is a real resonance albeit the intermediate state in the autoionization process is partly delocalised. This fact does not prevent the occurrence of interference between indirect and direct photoemission.

  20. Crystal momentum dependence of the correlation satellite intensity in the 3p {yields} 3d resonant photoemission spectra of Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}}

    Energy Technology Data Exchange (ETDEWEB)

    Goldoni, A. [INFM, Trieste (Italy); Corradini, V.; Del Pennino, U. [INFM, Modena (Italy); Sangalli, P. [INFM, Pavia (Italy); Parmigiani, F. [INFM, Brescia (Italy); Avila, J. [CSIC, Madrid (Spain). Inst. de Ciencia de Materiales; Laboratoire pour l' Utilisation du Rayonnement Electromagnetique (LURE), Paris-11 Univ., 91 - Orsay (France); Teodorescu, C. [Laboratoire pour l' Utilisation du Rayonnement Electromagnetique (LURE), Paris-11 Univ., 91 - Orsay (France)

    2000-05-01

    Angle-resolved resonant photoemission measurements at the Cu3p {yields} Cu3d threshold have been performed on the superconducting cuprate Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}}. We have investigated in particular the correlation satellite appearing in the valence band photoemission spectrum to investigate the effect of solid state on the interference effect occurring at resonance. We found that the intensity of the correlation satellite changes with the electron take-off angle in a way that depends on the particular crystallographic direction and on the sample hole doping. These results indicate that the intensity enhancement at the absorption edge is a real resonance albeit the intermediate state in the autoionization process is partly delocalised. This fact does not prevent the occurrence of interference between indirect and direct photoemission. (orig.)

  1. Crystal momentum dependence of the correlation satellite intensity in the 3p → 3d resonant photoemission spectra of Bi2Sr2CaCu2O8+δ

    International Nuclear Information System (INIS)

    Angle-resolved resonant photoemission measurements at the Cu3p → Cu3d threshold have been performed on the superconducting cuprate Bi2Sr2CaCu2O8+δ. We have investigated in particular the correlation satellite appearing in the valence band photoemission spectrum to investigate the effect of solid state on the interference effect occurring at resonance. We found that the intensity of the correlation satellite changes with the electron take-off angle in a way that depends on the particular crystallographic direction and on the sample hole doping. These results indicate that the intensity enhancement at the absorption edge is a real resonance albeit the intermediate state in the autoionization process is partly delocalised. This fact does not prevent the occurrence of interference between indirect and direct photoemission. (orig.)

  2. Angle-resolved cathodoluminescence nanoscopy

    NARCIS (Netherlands)

    T. Coenen

    2014-01-01

    The field of microscopy is an important cornerstone of physical and biological sciences. The development of high-resolution microscopy/nanoscopy techniques has enabled a revolution in science and technology, greatly improving our understanding of the microscopic world around us, and forming the basi

  3. Omnidirectional Measurements of Angle-Resolved Heat Capacity for Complete Detection of Superconducting Gap Structure in the Heavy-Fermion Antiferromagnet UPd_{2}Al_{3}.

    Science.gov (United States)

    Shimizu, Yusei; Kittaka, Shunichiro; Sakakibara, Toshiro; Tsutsumi, Yasumasa; Nomoto, Takuya; Ikeda, Hiroaki; Machida, Kazushige; Homma, Yoshiya; Aoki, Dai

    2016-07-15

    Quasiparticle excitations in UPd_{2}Al_{3} were studied by means of heat-capacity (C) measurements under rotating magnetic fields using a high-quality single crystal. The field dependence shows C(H)∝H^{1/2}-like behavior at low temperatures for both two hexagonal crystal axes, i.e., H∥[0001] (c axis) and H∥[112[over ¯]0] (a axis), suggesting the presence of nodal quasiparticle excitations from heavy bands. At low temperatures, the polar-angle (θ) dependence of C exhibits a maximum along H∥[0001] with a twofold symmetric oscillation below 0.5 T, and an unusual shoulder or hump anomaly has been found around 30°-60° from the c axis in C(θ) at intermediate fields (1≲μ_{0}H≲2  T). These behaviors in UPd_{2}Al_{3} purely come from the superconducting nodal quasiparticle excitations, and can be successfully reproduced by theoretical calculations assuming the gap symmetry with a horizontal linear line node. We demonstrate the whole angle-resolved heat-capacity measurements done here as a novel spectroscopic method for nodal gap determination, which can be applied to other exotic superconductors. PMID:27472129

  4. Electronic structure of germanium selenide investigated using ultra-violet photo-electron spectroscopy

    International Nuclear Information System (INIS)

    The valence band electronic structure of GeSe single crystals has been investigated using angle resolved photoemission spectroscopy (ARPES) and x-ray photoelectron spectroscopy. The experimentally observed bands from ARPES, match qualitatively with our LDA-based band structure calculations along the Γ–Z, Γ–Y and Γ–T symmetry directions. The valence band maximum occurs nearly midway along the Γ–Z direction, at a binding energy of −0.5 eV, substantiating the indirect band gap of GeSe. Non-dispersive features associated with surface states and indirect transitions have been observed. The difference in hybridization of Se and Ge 4p orbitals leads to the variation of dispersion along the three symmetry directions. The predominance of the Se 4pz orbitals, evidenced from theoretical calculations, may be the cause for highly dispersive bands along the Γ–T direction. Detailed electronic structure analysis reveals the significance of the cation–anion 4p orbitals hybridization in the valence band dispersion of IV–VI semiconductors. This is the first comprehensive report of the electronic structure of a GeSe single crystal using ARPES in conjugation with theoretical band structure analysis. (paper)

  5. Electronic structure of germanium selenide investigated using ultra-violet photo-electron spectroscopy

    Science.gov (United States)

    Mishra, P.; Lohani, H.; Kundu, A. K.; Patel, R.; Solanki, G. K.; Menon, Krishnakumar S. R.; Sekhar, B. R.

    2015-07-01

    The valence band electronic structure of GeSe single crystals has been investigated using angle resolved photoemission spectroscopy (ARPES) and x-ray photoelectron spectroscopy. The experimentally observed bands from ARPES, match qualitatively with our LDA-based band structure calculations along the Γ-Z, Γ-Y and Γ-T symmetry directions. The valence band maximum occurs nearly midway along the Γ-Z direction, at a binding energy of -0.5 eV, substantiating the indirect band gap of GeSe. Non-dispersive features associated with surface states and indirect transitions have been observed. The difference in hybridization of Se and Ge 4p orbitals leads to the variation of dispersion along the three symmetry directions. The predominance of the Se 4pz orbitals, evidenced from theoretical calculations, may be the cause for highly dispersive bands along the Γ-T direction. Detailed electronic structure analysis reveals the significance of the cation-anion 4p orbitals hybridization in the valence band dispersion of IV-VI semiconductors. This is the first comprehensive report of the electronic structure of a GeSe single crystal using ARPES in conjugation with theoretical band structure analysis.

  6. Photoemission on Co and Cu quantum wires

    International Nuclear Information System (INIS)

    The coverage dependent electronic structure of Cu and Co on vicinal W(110) surfaces has been investigated with angle resolved photoelectron spectroscopy. To prepare the quasi-one-dimensional Cu and Co systems the method of step edge decoration of the vicinal W(110) surfaces has been used. The vicinal surfaces with step edges in (110), (100) and (111) direction has been investigated using LEED. From the characteristic spot splitting a terrace width of 11 atom rows was determined. The band structures of the flat and the vicinal surfaces have indicated that the step edges have no bearing on the bulk band structure at k parallel =0. But the surface band structure shows a different dispersion and different energy positions of surface states. An analysis of the W 4fτ/2 core level spectra has resulted in an additional contribution of the step edges in the spectra of the vicinal surfaces with a surface core level shift between 120 and 150 meV. A Cu and Co coverage dependent investigation of the core levels shows that there is no Co induced surface reconstruction and up to 0.15 monolayer no Cu induced surface reconstruction. In the range of 0.15 and 0.3 monolayer Cu the surface peak shifts to higher binding energies. This is probably a result of a surface reconstruction of the W substrate In the core level spectra with Co coverage the intensity of the surface peak decreases linear with Co coverage and the intensity of a new contribution, the interface structure, increases with Co coverage. With Co respectively Cu coverage the contribution of the step edge shifts to lower respectively higher binding energies. This can be attributed to a charge transfer between the adsorbat and the substrate in different directions. (orig.)

  7. 5f-band width and resonant photoemission of uranium intermetallic compounds

    International Nuclear Information System (INIS)

    New experimental results and theoretical arguments are used in conjunction with previously published data to demonstrate that resonant photoemission (RPS) does not provide a reliable measure of the occupied 5f density of states in uranium intermetallic compounds. We implicate a resonant Auger process in this phenomenon and argue that RPS measurements (in conjunction with x-ray photoemission spectroscopy data) in this context are more useful as a qualitative guide to U 5f--ligand hybridization

  8. Analysis on photoemission spectrum of superconducting FeSe

    International Nuclear Information System (INIS)

    In this paper, we present the result of soft X-ray photoemission spectroscopy and its comparison with the density functional calculation. Although local density approximation seems to be a good starting point for describing the electronic structure of FeSe, the simulated spectrum poorly reproduced the structure around EB=2eV. This result suggests the necessity of theoretical treatment beyond local density approximation.

  9. Automated classification of single airborne particles from two-dimensional angle-resolved optical scattering (TAOS) patterns by non-linear filtering

    Science.gov (United States)

    Crosta, Giovanni Franco; Pan, Yong-Le; Aptowicz, Kevin B.; Casati, Caterina; Pinnick, Ronald G.; Chang, Richard K.; Videen, Gorden W.

    2013-12-01

    Measurement of two-dimensional angle-resolved optical scattering (TAOS) patterns is an attractive technique for detecting and characterizing micron-sized airborne particles. In general, the interpretation of these patterns and the retrieval of the particle refractive index, shape or size alone, are difficult problems. By reformulating the problem in statistical learning terms, a solution is proposed herewith: rather than identifying airborne particles from their scattering patterns, TAOS patterns themselves are classified through a learning machine, where feature extraction interacts with multivariate statistical analysis. Feature extraction relies on spectrum enhancement, which includes the discrete cosine FOURIER transform and non-linear operations. Multivariate statistical analysis includes computation of the principal components and supervised training, based on the maximization of a suitable figure of merit. All algorithms have been combined together to analyze TAOS patterns, organize feature vectors, design classification experiments, carry out supervised training, assign unknown patterns to classes, and fuse information from different training and recognition experiments. The algorithms have been tested on a data set with more than 3000 TAOS patterns. The parameters that control the algorithms at different stages have been allowed to vary within suitable bounds and are optimized to some extent. Classification has been targeted at discriminating aerosolized Bacillus subtilis particles, a simulant of anthrax, from atmospheric aerosol particles and interfering particles, like diesel soot. By assuming that all training and recognition patterns come from the respective reference materials only, the most satisfactory classification result corresponds to 20% false negatives from B. subtilis particles and <11% false positives from all other aerosol particles. The most effective operations have consisted of thresholding TAOS patterns in order to reject defective ones

  10. Probing many body effects using Fourier Transform Scanning Tunneling Spectroscopy: Can spin-orbit splitting in dispersion be observed in q-space?

    Science.gov (United States)

    Farahi, Gelareh; UBC Labortory for Atomic Imaging Research (LAIR)) Team

    Well studied surface systems such as Ag and Cu provide a safe platform to test novel spectroscopy methods that can have extended applications in near future. Our current focus is given to Fourier Transform Scanning Tunneling Spectroscopy (FT-STS) that allows us to study scattering effects (quasiparticle interactions - namely QPI) of CO and Co on Cu(111) surface. Magnetic Co adatoms are expected to generate a spin-orbit split in dispersion in QPI(q) space, the existence of which is confirmed by the k-space angle-resolved photo-emission spectroscopy (ARPES) of Cu(111) surface in the recent years. Hence the previously observed electron-phonon kink and spin-orbit splitting of the dispersion, as well as the scattering properties of CO molecules and Co adatoms, should also be observable in QPI space via FT-STS of Cu(111), and compatible with previous studies on similar systems. We are using a low temperature (4.2 K) commercial Scanning Tunneling Microscope (CREATEC STM) that operates using Nanonis electronic controllers and software which allows us to perform FT-STS as well as topological imaging.

  11. Scanning internal photoemission microscopy for the identification of hot carrier transport mechanisms

    Science.gov (United States)

    Differt, D.; Pfeiffer, W.; Diesing, D.

    2012-09-01

    Linear and nonlinear internal photoemission in a thin-film metal-insulator-metal heterosystem, i.e., a Ta-TaOx-Ag junction, together with surface reflectivity are mapped with a lateral resolution of better than 5 μm. The spatial correlation of the different signals and time-resolved internal photoemission spectroscopy reveal excitation mechanisms and ballistic hot carrier injection. The internal photoemission yield variation with Ag layer thickness is quantitatively explained by above-barrier injection. The hot-spot-like behavior of the two-photon induced internal photoemission observed for short pulse excitation is attributed to local field enhancements because of Ag-film thickness reduction and plasmonic effects at structural defects.

  12. Fermi-surface topology of YBa2Cu3Ox with varied oxygen stoichiometry: A photoemission study

    International Nuclear Information System (INIS)

    High-resolution angle-resolved photoemission measurements are reported for YBa2Cu3Ox when oxygen stoichiometry x was varied between 6.3 and 6.9. Fermi surfaces were measured and their dependence on oxygen stoichiometry was monitored by observing the dispersing behavior of spectral features, scanning the entire first Brillouin zone. For x=6.9, measured Fermi surfaces correspond very well with the plane-related Fermi surfaces calculated from band theory. Relatively small changes in Fermi surfaces were observed when oxygen stoiochiometry was varied in the range 6.5≤x≤6.9, where the material is metallic. However, significant changes in the spectral behavior were observed when the material becomes insulating

  13. Photocathode device that replenishes photoemissive coating

    Energy Technology Data Exchange (ETDEWEB)

    Moody, Nathan A.; Lizon, David C.

    2016-06-14

    A photocathode device may replenish its photoemissive coating to replace coating material that desorbs/evaporates during photoemission. A linear actuator system may regulate the release of a replenishment material vapor, such as an alkali metal, from a chamber inside the photocathode device to a porous cathode substrate. The replenishment material deposits on the inner surface of a porous membrane and effuses through the membrane to the outer surface, where it replenishes the photoemissive coating. The rate of replenishment of the photoemissive coating may be adjusted using the linear actuator system to regulate performance of the photocathode device during photoemission. Alternatively, the linear actuator system may adjust a plasma discharge gap between a cartridge containing replenishment material and a metal grid. A potential is applied between the cartridge and the grid, resulting in ejection of metal ions from the cartridge that similarly replenish the photoemissive coating.

  14. Hot Electron Photoemission from Plasmonic Nanostructures: The Role of Surface Photoemission and Transition Absorption

    DEFF Research Database (Denmark)

    Babicheva, Viktoriia; Zhukovsky, Sergei; Ikhsanov, Renat Sh;

    2015-01-01

    enhancement of photoemission in the surface scenario. We calculate the ratio of photoemission cross-section for a gold nanosphere embedded in different materials such as silicon, zinc oxide, and titanium dioxide. For the calculations, we include both surface and bulk mechanisms of photoemission, using quantum...

  15. Theory on photoemission and inverse photoemission spectra in VO2

    International Nuclear Information System (INIS)

    The photoemission (PES) and inverse photoemission (IPES) spectra in VO2 at temperatures above and below the metal-insulator transition (MIT) are discussed with a two-band Hubbard model. An abrupt change in the valence top character of the theoretical PES spectra at the MIT caused by a switching in the t2g orbital occupation in the ground state is found. In the insulating phase, the structure of the valence top is well described within a single-band Hubbard model, where only the d|| band participates. Since the ratio t/U∼0.2 is small, the structure of the spectrum extends to ∼1.5eV below the Fermi level. On the other hand, in the metallic phase, both the dparallel and π* bands are involved and the spectral weight is concentrated in the vicinity of the Fermi level within a range ∼0.5eV. Such a large spectral weight transfer is consistent with experiments. For the IPES spectra, a structure corresponding to the upper Hubbard band of the single-band Hubbard model is appeared at ∼1.5eV above the Fermi level in the insulating phase. However the structure is absent in the metallic phase

  16. Non linear photoemission from silicon

    Science.gov (United States)

    Bensoussan, M.; Moison, J. M.

    1983-03-01

    Two well-defined photoemission regimes are observed from clean (111) Si surfaces under various laser irradiation conditions and photon energies. At low fluences and at photon energies above half the work function two and three quantum process are the outstanding emission mechanisms. Density of state effects of initial and intermediate states appear as the dominant spectral features. At higher fluences or at low photon energies the prevailing emission is thermoemission characterized by a Maxwellian distribution revailing a temperature quite different from the lattice one during the excitation pulse.

  17. Watching Electrons Transfer from Metals to Insulators using Two Photon Photoemission

    Energy Technology Data Exchange (ETDEWEB)

    Johns, James E.

    2010-05-01

    Ultrafast angle-resolved two photon photoemission was used to study the dynamics and interfacial band structure of ultrathin films adsorbed onto Ag(111). Studies focused on the image potential state (IPS) in each system as a probe for measuring changes in electronic behavior in differing environments. The energetics and dynamics of the IPS at the toluene/Ag(111) interface are strongly dependent upon coverage. For a single monolayer, the first IPS is bound by 0.81 eV below the vacuum level and has a lifetime of 50 femtoseconds (fs). Further adsorption of toluene creates islands of toluene with an exposed wetting layer underneath. The IPS is then split into two peaks, one corresponding to the islands and one corresponding to the monolayer. The wetting layer IPS shows the same dynamics as the monolayer, while the lifetime of the islands increases exponentially with increasing thickness. Furthermore, the island IPS transitions from delocalized to localized within 500 fs, and electrons with larger parallel momenta decay much faster. Attempts were made using a stochastic model to extract the rates of localization and intraband cooling at differing momenta. In sexithiophene (6T) and dihexyl-sexithiophene (DH6T), the IPS was used as a probe to see if the nuclear motion of spectating side chains can interfere with molecular conduction. The energy and band mass of the IPS was measured for 6T and two geometries of DH6T on Ag(111). Electrons injected into the thicker coverages of DH6T grew exponentially heavier until they were completely localized by 230 fs, while those injected into 6T remained nearly free electron like. Based off of lifetime arguments and the density of defects, the most likely cause for the mass enhancement of the IPS in this system is small polaron formation caused by coupling of the electron to vibrations of the alkyl substituents. The energetic relaxation of the molecular adsorbate was also measured to be 20 meV/100 fs for the DH6T, and 0 meV/100 fs for

  18. Recoil and related effects in molecular photoemission

    International Nuclear Information System (INIS)

    Highlights: ► We present a overview of recoil-related effects for general audience of experimentalists working in the field of photoelectron spectroscopy. ► Photoelectron recoil is shown to alter vibrational structure. ► Photoelectron rotational recoil is shown to induce line shifts and broadenings. ► Interference and scattering of the outgoing photoelectron wave(s) are shown to introduce oscillations of branching ratios in molecular photoelectron spectra. -- Abstract: Photoemission from free molecules in the gas phase results in a complex spectral structure of electronic, vibrational and rotational transitions. In this review, the effects that can alter this structure and particularly the branching ratios in photoelectron spectra at the kinetic energies well above the ionization thresholds are considered. Simplified models that have nevertheless been found to describe the observations well are presented for photoelectron vibrational and rotational recoil, rotational Doppler broadening, photoelectron scattering and Cohen–Fano type interference phenomena. Experimental examples are shown together with the models. Some future developments and applications of the recoil-related phenomena are briefly considered.

  19. Recoil and related effects in molecular photoemission

    Energy Technology Data Exchange (ETDEWEB)

    Kukk, E., E-mail: edwin.kukk@utu.fi [Dept. of Physics and Astronomy, University of Turku, FIN-20014 Turku (Finland); Ueda, K. [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577 (Japan); Miron, C. [Synchrotron SOLEIL, L' Orme des Merisiers, Saint-Aubin, BP 48, FR-91192 Gif-sur-Yvette Cedex (France)

    2012-09-15

    Highlights: Black-Right-Pointing-Pointer We present a overview of recoil-related effects for general audience of experimentalists working in the field of photoelectron spectroscopy. Black-Right-Pointing-Pointer Photoelectron recoil is shown to alter vibrational structure. Black-Right-Pointing-Pointer Photoelectron rotational recoil is shown to induce line shifts and broadenings. Black-Right-Pointing-Pointer Interference and scattering of the outgoing photoelectron wave(s) are shown to introduce oscillations of branching ratios in molecular photoelectron spectra. -- Abstract: Photoemission from free molecules in the gas phase results in a complex spectral structure of electronic, vibrational and rotational transitions. In this review, the effects that can alter this structure and particularly the branching ratios in photoelectron spectra at the kinetic energies well above the ionization thresholds are considered. Simplified models that have nevertheless been found to describe the observations well are presented for photoelectron vibrational and rotational recoil, rotational Doppler broadening, photoelectron scattering and Cohen-Fano type interference phenomena. Experimental examples are shown together with the models. Some future developments and applications of the recoil-related phenomena are briefly considered.

  20. Understanding photoemission spectra in uranium based heavy fermion systems

    International Nuclear Information System (INIS)

    In 4f compounds, there is a two-peaked structure associated with 4f photoemission spectroscopy, while most 5f compounds yield a single broad triangular-shaped 5f intensity. Evidence is presented from measurements on ternary alloys that show that at least part of the extra-5f intensity is due to the hitherto missing main peak (or d-screened f-hole peak) just as in the 4f systems. The remaining intensity is consistent with a band structure DOS. (The compounds used were URh3B/sub x/, UPd/sub x/Rh/sub 3-x/, ThBe13, UIr3, and UBe13.)

  1. Soft X-ray Absorption and Photoemission Studies of Ferromagnetic Mn-Implanted 3$C$-SiC

    OpenAIRE

    Song, Gyong Sok; Kataoka, Takashi; Kobayashi, Masaki; Hwang, Jong Il; Takizawa, Masaru; Fujimori, Atsushi; Ohkochi, Takuo; Takeda, Yukiharu; Okane, Tetsuo; Saitoh, Yuji; Yamagami, Hiroshi; Takano, Fumiyoshi; Akinaga, Hiro

    2008-01-01

    We have performed x-ray photoemission spectroscopy (XPS), x-ray absorption spectroscopy (XAS), and resonant photoemission spectroscopy (RPES) measurements of Mn-implanted 3$C$-SiC (3$C$-SiC:Mn) and carbon-incorporated Mn$_{5}$Si$_{2}$ (Mn$_{5}$Si$_{2}$:C). The Mn 2$p$ core-level XPS and XAS spectra of 3$C$-SiC:Mn and Mn$_{5}$Si$_{2}$:C were similar to each other and showed "intermediate" behaviors between the localized and itinerant Mn 3$d$ states. The intensity at the Fermi level was found t...

  2. Xclaim: A graphical interface for the calculation of core-hole spectroscopies

    International Nuclear Information System (INIS)

    Highlights: • The program Xclaim (X-ray core level atomic multiplets) calculates core-hole spectra. • Crystal field under an arbitrary point symmetry and hybridization with ligands. • X-ray absorption spectroscopy (XAS), X-ray photoemission spectroscopy (XPS), photoemission spectroscopy (PES) and inverse photoemission (IPES). - Abstract: Xclaim (X-ray core level atomic multiplets) is a graphical interface for the calculation of core-hole spectroscopy and ground state properties within a charge-transfer multiplet model taking into account a many-body Hamiltonian with Coulomb, spin–orbit, crystal-field, and hybridization interactions. Using Coulomb and spin–orbit parameters calculated in the Hartree–Fock limit and ligand field parameters (crystal-field, hybridization and charge-transfer energy) the program calculates X-ray absorption spectroscopy (XAS), X-ray photoemission spectroscopy (XPS), photoemission spectroscopy (PES) and inverse photoemission (IPES). The program runs on Linux, Windows and MacOS platforms

  3. Photoemission study of the IBr graphite intercalation compound using the synchrotron radiation light source

    OpenAIRE

    Negishi, Saiko; Negishi, H.; Nakatake, Masashi; Yamazaki, K; Sato, Hitoshi; Shimada, Kenya; Namatame, Hirofumi; Taniguchi, Masaki; Kobayashi, K.; Sugihara, K; Oshima, H

    2006-01-01

    We measured the photoemission spectra of the IBr graphite intercalation compounds (IBr-GIC) with stage-2 and stage-4 structures at 16 K with incident photon energies hν=40-200 eV. The peak positions of the I 4d and Br 3d core-levels are unchanged for the stage-2 and stage-4 IBr-GICs. Partial density-of-states of the I 5p and Br 4p states in the valence bands have been evaluated by resonant photoemission spectroscopy. These spectra indicate a significant hybridization between the host and the ...

  4. Coherent and incoherent processes in resonant photoemission

    Energy Technology Data Exchange (ETDEWEB)

    Magnuson, M.; Karis, O.; Weinelt, M. [Uppsala Univ. (Sweden)] [and others

    1997-04-01

    In this contribution the authors present the distinction between coherent and incoherent processes in resonant photoemission. As a first step they determine whether an autoionization process is photoemission-like or Auger-like. The discussion is based on measurements for a weakly bonded adsorption system, Ar/Pt(111). This type of system is well adapted to investigate these effects since it yields distinctly shifted spectral features depending on the nature of the process. After this, the question of resonance photoemission in metallic systems is addressed. This is done in connection with measurements at the 2p edges for Ni metal. Ni has been one of the prototype systems for resonant photoemission. The resonances have been discussed in connection with the strong correlation and d-band localization effects in this system. Based on the results some general comments about the appearance of resonant effects in metallic systems are made.

  5. Nondipole Photoemission from Chiral Enantiomers of Camphor

    Science.gov (United States)

    Bowen, K. P.; Stolte, W. C.; Young, J. A.; Demchenko, I. N.; Guillemin, R.; Hemmers, O.; Piancastelli, M. N.; Lindle, D. W.

    2010-03-01

    K-shell photoemission from the carbonyl carbon in the chiral molecule camphor has been studied in the region just above the core-shell ionization threshold. Differences between angular distributions of emitted photoelectrons from the two enantiomers are attributed to the influence of chirality combined with nondipole effects in the photoemission process, despite the fact the measurements were taken using linearly polarized x-rays. The results suggest the possibility of a new form of linear dichroism.

  6. Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Hellman, Hal

    1968-01-01

    This booklet discusses spectroscopy, the study of absorption of radiation by matter, including X-ray, gamma-ray, microwave, mass spectroscopy, as well as others. Spectroscopy has produced more fundamental information to the study of the detailed structure of matter than any other tools.

  7. X-ray photoemission study of MgB2

    International Nuclear Information System (INIS)

    A c-axis oriented thin film and a high-density sintered pellet of MgB2 have been studied by x-ray photoemission spectroscopy, and compared to measurements from MgO and MgF2 single crystals. The as-grown surface has a layer which is Mg-rich and oxidized, which is effectively removed by a nonaqueous etchant. The subsurface region of the pellet is Mg deficient. This nonideal near-surface region may explain varied scanning tunneling spectroscopy results. The MgB2 core level and Auger signals are similar to measurements from metallic Mg and transition-metal diborides, and the measured valence band is consistent with the calculated density of states

  8. Spectroscopy

    CERN Document Server

    Walker, S

    1976-01-01

    The three volumes of Spectroscopy constitute the one comprehensive text available on the principles, practice and applications of spectroscopy. By giving full accounts of those spectroscopic techniques only recently introduced into student courses - such as Mössbauer spectroscopy and photoelectron spectroscopy - in addition to those techniques long recognised as being essential in chemistry teaching - sucha as e.s.r. and infrared spectroscopy - the book caters for the complete requirements of undergraduate students and at the same time provides a sound introduction to special topics for graduate students.

  9. Measurement of the background in Auger-photoemission coincidence spectra (APECS) associated with inelastic or multi-electron valence band photoemission processes

    OpenAIRE

    Satyal, S.; Joglekar, P. V.; Shastry, K.; Kalaskar, S.; Dong, Q.; Hulbert, S. L.; Bartynksi, R. A.; Weiss, A. H.

    2014-01-01

    Auger Photoelectron Coincidence Spectroscopy (APECS), in which the Auger spectra is measured in coincidence with the core level photoelectron, is capable of pulling difficult to observe low energy Auger peaks out of a large background due mostly to inelastically scattered valence band (VB) photoelectrons. However the APECS method alone cannot eliminate the background due to valence band photoemission processes in which the initial photon energy is shared by two or more electrons and one of th...

  10. High Pressure Scanning Tunneling Microscopy and High PressureX-ray Photoemission Spectroscopy Studies of Adsorbate Structure,Composition and Mobility during Catalytic Reactions on A Model SingleCrystal

    Energy Technology Data Exchange (ETDEWEB)

    Montano, M.O.

    2006-05-12

    Our research focuses on taking advantage of the ability of scanning tunneling microscopy (STM) to operate at high-temperatures and high-pressures while still providing real-time atomic resolution images. We also utilize high-pressure x-ray photoelectron spectroscopy (HPXPS) to monitor systems under identical conditions thus giving us chemical information to compare and contrast with the structural and dynamic data provided by STM.

  11. Resonance and threshold effects in photoemission up to 3500 eV

    Energy Technology Data Exchange (ETDEWEB)

    Shirley, D.A.; Kobrin, P.H.; Lindle, D.W.; Truesdale, C.M.; Southworth, S.H.; Becker, U.; Kerkhoff, H.G.

    1982-08-01

    Beam lines at the Stanford Synchrotron Radiation Laboratory (SSRL) now provide photon beams throughout the entire energy range 5 to 5000 eV, with a pulse structure very well-suited to time-of-flight (TOF) photoelectron spectroscopy. We have used this facility, together with a TOF spectrometer, to measure photoemission cross sections sigma(epsilon) and asymmetry parameters ..beta..(epsilon) for several interesting systems. A summary of early results is given. Metal vapors (Ba, Cd, Mn, Hg) were studied using a high-temperature oven. Resonant photoemission was observed in several cases. Both sigma(epsilon) and ..beta..(epsilon) showed resonant behavior at 21.1 eV for several lines in Cd. The 4d, 5s, and 5p sigma(epsilon) line profiles differed dramatically, illustrating the detailed information about continuum states that is available from photoemission. Correlation satellites in photoemission from rare gases have been observed over a very wide energy range, including those seen in the K-shells of He, Ne and Ar and in the L-shell of Ne. The structure and preliminary intensity variations of these satellites will be discussed. Molecular shape resonances in C(1s), N(1s), and O(1s) photoemission were observed for the first time, in the molecules CO, CO/sub 2/, OCS, CF/sub 4/, N/sub 2/ and NO. Both the ..pi.. and sigma resonances were observed in KVV Auger emission, and the sigma resonances were studied by photoemission. The asymmetry parameters were measured in all cases. The results are in fair agreement with theory, but show systematic deviations and trends. 31 references.

  12. Spectroscopy

    DEFF Research Database (Denmark)

    Berg, Rolf W.

    This introductory booklet covers the basics of molecular spectroscopy, infrared and Raman methods, instrumental considerations, symmetry analysis of molecules, group theory and selection rules, as well as assignments of fundamental vibrational modes in molecules.......This introductory booklet covers the basics of molecular spectroscopy, infrared and Raman methods, instrumental considerations, symmetry analysis of molecules, group theory and selection rules, as well as assignments of fundamental vibrational modes in molecules....

  13. Nitrogen termination of single crystal (100) diamond surface by radio frequency N2 plasma process: An in-situ x-ray photoemission spectroscopy and secondary electron emission studies

    International Nuclear Information System (INIS)

    In this letter, we report the electronic and chemical properties of nitrogen terminated (N-terminated) single crystal (100) diamond surface, which is a promising candidate for shallow NV− centers. N-termination is realized by an indirect RF nitrogen plasma process without inducing a large density of surface defects. Thermal stability and electronic property of N-terminated diamond surface are systematically investigated under well-controlled conditions by in-situ x-ray photoelectron spectroscopy and secondary electron emission. An increase in the low energy cut-off of the secondary electron energy distribution curve (EDC), with respect to a bare diamond surface, indicates a positive electron affinity of the N-terminated diamond. Exposure to atomic hydrogen results in reorganization of N-terminated diamond to H-terminated diamond, which exhibited a negative electron affinity surface. The change in intensity and spectral features of the secondary electron EDC of the N-terminated diamond is discussed

  14. Status of research on high Tc superconductor using SR

    International Nuclear Information System (INIS)

    Structural and physical experiments carried out by means of synchrotron radiation have been playing an important, and sometimes decisive, role in the research on the mechanism of superconductivity. And high energy spectroscopic studies, including photoemission spectroscopy using synchrotron radiation, are currently expected to provide a major clue to the clarification of the mechanism of high Tc superconductivity. Photoemission spectroscopy provides information on occupied electronic states while soft X-ray absorption spectroscopy studies the unoccupied electronic states. Variable energy of synchrotron radiation is used for resonant photoemission spectroscopy, which provides information on the contribution from each electron orbit. Angle-resolved photoemission spectroscopy serves to study the band structure of high Tc superconducting materials. Some problems to be solved concerning the electronic state in high Tc superconductors are described, and some observations made by resonant and angle-resolved photoemission spectroscopy and soft X-ray absorption spectroscopy are presented and briefly discussed. (N.K.)

  15. Study of the electronic properties of Zn{sub 0.8–4x}Ho{sub x}O{sub y} (0.05 ≤ x ≤ 0.09) by X-ray absorption and photoemission spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Ekicibil, A. [Physic Department, University of Cukurova, 01330 Adana (Turkey); Ozkendir, O.M. [Tarsus Technology Faculty, Mersin University, 33400 Tarsus (Turkey); Farha, A.H. [Department of Electrical and Computer Engineering, Old Dominion University, Norfolk, VA 23529 (United States); Department of Physics, Faculty of Science, Ain Shams University, Cairo 11566 (Egypt); Ufuktepe, Y., E-mail: ufuk@cu.edu.tr [Physic Department, University of Cukurova, 01330 Adana (Turkey)

    2015-07-15

    Highlights: • The electronic structure of Ho doped ZnO was investigated by XANES and XPS. • The electronic structure was directly influenced by the Ho concentration in the ZnO. • The crystal structure showed little/no correlation to the substitution of Ho. • The substitution of Ho causes a weaker antiferromagnetic interaction. • The blue shift in band gap is observed and discussed. - Abstract: The electronic structure of Zn{sub 0.8–4x}Ho{sub x}O{sub y} (0.05 ≤ x ≤ 0.09) was investigated using X-ray absorption near edge structure (XANES) and X-ray photoelectron spectroscopy (XPS). Samples were prepared by the solid state reaction method. Using X-ray absorption spectroscopy, the investigation of M{sub 4,5} absorption edge of Ho revealed that the electronic structure was directly influenced by the Ho concentration in the Zn{sub 0.8–4x}Ho{sub x}O{sub y} sample whereas the crystal structure properties showed little/no correlation to the substitution of Ho. The electronic structure differs substantially from those of the reference ZnO. The O K-edge spectra suggest that the combination of the Ho with ZnO enhances the effective charge of the O ions. A systematic study on the composition from lower to higher value of Ho dopant showed the blue shift in band gaps and is discussed in the view of the electronic structure of the Zn{sub 0.8–4x}Ho{sub x}O{sub y} samples. The inverse susceptibility (1/χ) against temperature curves is plotted to identify the magnetic contribution. Those curves indicate that the substitution of Ho into the ZnO compound causes a weaker antiferromagnetic (AFM) interaction.

  16. Study of the electronic properties of Zn0.8–4xHoxOy (0.05 ≤ x ≤ 0.09) by X-ray absorption and photoemission spectroscopy

    International Nuclear Information System (INIS)

    Highlights: • The electronic structure of Ho doped ZnO was investigated by XANES and XPS. • The electronic structure was directly influenced by the Ho concentration in the ZnO. • The crystal structure showed little/no correlation to the substitution of Ho. • The substitution of Ho causes a weaker antiferromagnetic interaction. • The blue shift in band gap is observed and discussed. - Abstract: The electronic structure of Zn0.8–4xHoxOy (0.05 ≤ x ≤ 0.09) was investigated using X-ray absorption near edge structure (XANES) and X-ray photoelectron spectroscopy (XPS). Samples were prepared by the solid state reaction method. Using X-ray absorption spectroscopy, the investigation of M4,5 absorption edge of Ho revealed that the electronic structure was directly influenced by the Ho concentration in the Zn0.8–4xHoxOy sample whereas the crystal structure properties showed little/no correlation to the substitution of Ho. The electronic structure differs substantially from those of the reference ZnO. The O K-edge spectra suggest that the combination of the Ho with ZnO enhances the effective charge of the O ions. A systematic study on the composition from lower to higher value of Ho dopant showed the blue shift in band gaps and is discussed in the view of the electronic structure of the Zn0.8–4xHoxOy samples. The inverse susceptibility (1/χ) against temperature curves is plotted to identify the magnetic contribution. Those curves indicate that the substitution of Ho into the ZnO compound causes a weaker antiferromagnetic (AFM) interaction

  17. Photoemission from optoelectronic materials and their nanostructures

    CERN Document Server

    Ghatak, Kamakhya Prasad; Bhattacharya, Sitangshu

    2009-01-01

    This monograph investigates photoemission from optoelectronic materials and their nanostructures. It contains open-ended research problems which form an integral part of the text and are useful for graduate courses as well as aspiring Ph.D.'s and researchers..

  18. Inverse photoemission in strongly correlated electron systems

    NARCIS (Netherlands)

    Eder, R; Ohta, Y.

    1996-01-01

    Based on exact results for small clusters of t-J models, we point out the existence of several distinct channels in the inverse photoemission (IPSE) spectrum. Holelike quasiparticles can either be annihilated completely or leave behind a variable number of spin excitations, which formed the dressing

  19. Synchrotron photoemission study of (Zn,Co)O films with uniform Co distribution

    Energy Technology Data Exchange (ETDEWEB)

    Guziewicz, E., E-mail: guzel@ifpan.edu.pl [Institute of Physics, Polish Academy of Sciences, 02-668 Warsaw (Poland); Lukasiewicz, M.I.; Wachnicki, L.; Kopalko, K. [Institute of Physics, Polish Academy of Sciences, 02-668 Warsaw (Poland); Kovacs, A.; Dunin-Borkowski, R.E. [Center for Electron Nanoscopy, Technical University of Denmark, Lyngby 2800 (Denmark); Witkowski, B.S.; Kowalski, B.J. [Institute of Physics, Polish Academy of Sciences, 02-668 Warsaw (Poland); Sadowski, J. [Institute of Physics, Polish Academy of Sciences, 02-668 Warsaw (Poland); MAX-Lab, Lund University, Box 118, SE-22100 Lund (Sweden); Sawicki, M.; Jakiela, R. [Institute of Physics, Polish Academy of Sciences, 02-668 Warsaw (Poland); Godlewski, M. [Institute of Physics, Polish Academy of Sciences, 02-668 Warsaw (Poland); Department of Mathematics and Natural Sciences, College of Science, Cardinal Wyszynski University, 01-815 Warsaw (Poland)

    2011-10-15

    We present results of a resonant photoemission study of (Zn,Co)O films with Co content between 2% and 7%. The films were grown by Atomic Layer Deposition (ALD) at low temperature of 160 deg. C, and show fully paramagnetic behavior. The Co ions are uniformly distributed in the ZnO matrix and are free of foreign phases and metal accumulations as indicated by TEM data. The electronic structure of (Zn,Co)O films was studied by Resonant Photoemission Spectroscopy across the Co3p-Co3d photoionization threshold. We have observed that the resonant enhancement of the photoemission intensity from the Co3d shell is not the same for samples with different cobalt content. We suggest that the Co3d contribution to the valence band depends on both Co and H content. - Highlights: > (Zn,Co)O films with uniform Co distribution were studied by Resonant Photoemission. > Resonant PES enhancement from the Co3d shell is not the same for samples with different Co contents. > Observed Co3d distributions depend on both cobalt and hydrogen content.

  20. A medium-energy photoemission and ab-initio investigation of cubic yttria-stabilised zirconia

    International Nuclear Information System (INIS)

    Experimental and theoretical investigations into the electronic properties and structure of cubic yttria-stabilized zirconia are presented. Medium-energy x-ray photoemission spectroscopy measurements have been carried out for material with a concentration of 8-9 mol. % yttria. Resonant photoemission spectra are obtained for a range of photon energies that traverse the L2 absorption edge for both zirconium and yttrium. Through correlation with results from density-functional theory (DFT) calculations, based on structural models proposed in the literature, we assign photoemission peaks appearing in the spectra to core lines and Auger transitions. An analysis of the core level features enables the identification of shifts in the core level energies due to different local chemical environments of the constituent atoms. In general, each core line feature can be decomposed into three contributions, with associated energy shifts. Their identification with results of DFT calculations carried out for proposed atomic structures, lends support to these structural models. The experimental results indicate a multi-atom resonant photoemission effect between nearest-neighbour oxygen and yttrium atoms. Near-edge x-ray absorption fine structure spectra for zirconium and yttrium are also presented, which correlate well with calculated Zr- and Y-4d electron partial density-of-states and with Auger electron peak area versus photon energy curve

  1. A medium-energy photoemission and ab-initio investigation of cubic yttria-stabilised zirconia

    Energy Technology Data Exchange (ETDEWEB)

    Cousland, G. P. [School of Physics, The University of Sydney, New South Wales 2006 (Australia); Australian Nuclear Science and Technology Organisation, Lucas Heights, New South Wales 2234 (Australia); Cui, X. Y. [School of Physics, The University of Sydney, New South Wales 2006 (Australia); Australian Centre for Microscopy and Microanalysis, The University of Sydney, New South Wales 2006 (Australia); Smith, A. E. [School of Physics, Monash University, Clayton, Victoria 3800 (Australia); Stampfl, C. M. [School of Physics, The University of Sydney, New South Wales 2006 (Australia); School of Materials Science and Engineering, Yonsei University, Seoul 120-749 (Korea, Republic of); Wong, L.; Tayebjee, M.; Yu, D.; Triani, G.; Evans, P. J. [Australian Nuclear Science and Technology Organisation, Lucas Heights, New South Wales 2234 (Australia); Ruppender, H.-J. [OmniVac GmbH, Espensteigstrasse 16, 67661 Kaiserslautern (Germany); Jang, L.-Y. [National Synchrotron Radiation Research Center, Hsinchu Science Park, Hsinchu 30076, Taiwan (China); Stampfl, A. P. J. [Australian Nuclear Science and Technology Organisation, Lucas Heights, New South Wales 2234 (Australia); School of Chemistry, The University of Sydney, New South Wales 2006 (Australia)

    2014-04-14

    Experimental and theoretical investigations into the electronic properties and structure of cubic yttria-stabilized zirconia are presented. Medium-energy x-ray photoemission spectroscopy measurements have been carried out for material with a concentration of 8-9 mol. % yttria. Resonant photoemission spectra are obtained for a range of photon energies that traverse the L2 absorption edge for both zirconium and yttrium. Through correlation with results from density-functional theory (DFT) calculations, based on structural models proposed in the literature, we assign photoemission peaks appearing in the spectra to core lines and Auger transitions. An analysis of the core level features enables the identification of shifts in the core level energies due to different local chemical environments of the constituent atoms. In general, each core line feature can be decomposed into three contributions, with associated energy shifts. Their identification with results of DFT calculations carried out for proposed atomic structures, lends support to these structural models. The experimental results indicate a multi-atom resonant photoemission effect between nearest-neighbour oxygen and yttrium atoms. Near-edge x-ray absorption fine structure spectra for zirconium and yttrium are also presented, which correlate well with calculated Zr- and Y-4d electron partial density-of-states and with Auger electron peak area versus photon energy curve.

  2. The d-band of disordered Cu3Au as determined by constant initial state photoemission spectroscopy: a search for the origins of the disorder/order phase transition

    International Nuclear Information System (INIS)

    Full text: Binary alloys must either order or phase separate as the temperature is lowered. Substitutionally disordered Cu3Au is known to order below a transition temperature of Tc=390 deg C. The driving force (of ordering) is believed to be the lowering of free energy as a result of changes to the electronic and compositional structure. Details of the role that particular electronic levels play and the amount of coupling between the electronic and phonon structures, is as yet not fully understood. Gyorffy and Stocks have indeed suggested that instabilities in the electronic structure of the Fermi surface of Cu-Pd alloys may be the driving force for the disorder/order phase transition. It is expected, however, that the Fermi surfaces of ordered and disordered Cu3Au to be nearly similar. Our work on the Fermi surface of disordered Cu3Au supports this view. Large differences, however, are observed in the d-band region between the ordered and disordered phases and it has been suggested that these states may exhibit a type of electronic instability upon approaching Tc. We present our initial study of the d-band region of disordered Cu3Au using a constant initial state spectroscopy technique which we previously developed to map the Fermi surface of Cu. Our technique allows the accurate k-space mapping of very flat bands such as d-levels. The k-space shape of the d-bands are compared to calculation and a discussion is given as to their likely role in the phase transition

  3. Occupied and unoccupied band structure of Ag(100) determined by photoemission from Ag quantum wells and bulk samples

    International Nuclear Information System (INIS)

    Angle-resolved photoemission spectra taken from atomically uniform films of Ag on Fe(100) show layer-resolved quantum-well peaks. The measured peak positions as a function of film thickness permit a unique determination of the initial band dispersion via the Bohr-Sommerfeld quantization rule. This information, combined with normal-emission data taken from a single crystal Ag(100), leads to a unique determination of the final band dispersion. In this study, we employ a two-band model with four adjustable parameters for a simultaneous fit to these experimental results. The initial and final band dispersions deduced from the fit are accurate to better than 0.03 eV at any wave vector k within the range of measurement. The analytic formula for the band dispersions and the parameters for the best fit are given for future reference. The Fermi wave vector along [100], normalized to the Brillouin-zone size, is determined to be kF/kΓX=0.828±0.001, which is more accurate than the de Haas-van Alphen result. The corresponding Fermi velocity is νF=1.06 in units of the free-electron value. The combined reflection phase for the electron wave at the two boundaries is also deduced and compared with a semiempirical formula. This comparison allows us to deduce the edges of the hybridization gap in the Fe substrate. (c) 2000 The American Physical Society

  4. Raising Photoemission Efficiency with Surface Acoustic Waves

    Energy Technology Data Exchange (ETDEWEB)

    A. Afanasev, F. Hassani, C.E. Korman, V.G. Dudnikov, R.P. Johnson, M. Poelker, K.E.L. Surles-Law

    2012-07-01

    We are developing a novel technique that may help increase the efficiency and reduce costs of photoelectron sources used at electron accelerators. The technique is based on the use of Surface Acoustic Waves (SAW) in piezoelectric materials, such as GaAs, that are commonly used as photocathodes. Piezoelectric fields produced by the traveling SAW spatially separate electrons and holes, reducing their probability of recombination, thereby enhancing the photoemission quantum efficiency of the photocathode. Additional advantages could be increased polarization provided by the enhanced mobility of charge carriers that can be controlled by the SAW and the ionization of optically-generated excitons resulting in the creation of additional electron-hole pairs. It is expected that these novel features will reduce the cost of accelerator operation. A theoretical model for photoemission in the presence of SAW has been developed, and experimental tests of the technique are underway.

  5. Resonant photoemission and magnetic x-ray circular dichroism in the M shell of ultrathin films of Fe

    International Nuclear Information System (INIS)

    Using magnetic ultra thin films (2--4 ml) of Fe on Cu(001) and bulk-like Fe, the Fe3p and Fe3s core states have been investigated with resonant photoemission and core-level photoemission, including, magnetic x-ray circular dichroism (MXCD) experiments. The resonant photoemission experiment has been done in fine steps over a wide photon energy range (hν = 695 eV - 715 eV), to probe the parentage of various spectral structures. The onset of secondary channels at the L3(hν = 707 eV) and L2(hν = 72O eV) edges will be analyzed in light of results from bulk Ni. The MXCD photoelectron spectroscopy of the Fe3p exhibits a 0.2 eV shift with circular polarization variation. The previously observed split peak structure in the Fe3s will be discussed with regard to the new resonant photoemission results. The resonant photoemission results will also be put into the context of our MXCD absorption results for monolayer and multilayers of Fe

  6. A photoemission study of cluster growth and morphology on inert substrates

    International Nuclear Information System (INIS)

    Thin metal overlayer growth on solid xenon was characterized by means of synchrotron radiation photoemission spectroscopy. We employed a simple experimental arrangement in which a closed-cycle refrigerator and in situ evaporated metal films were used as substrate for Xe condensation. A ''sandwich'' geometry, in which the overlayer metal was used as substrate for Xe condensation, simplified the isolation of metal and Xe emission features. The evolution of the Xe and metal photoemission intensity and the line shape of core and valence states, as a function of metal coverage, were used to estimate average particle size and nucleation site density. The coverage dependence of the Sm 4f binding energy, as well as a number of newly identified spectral fingerprints of particle coalescence, support the measured film morphology and particle size

  7. Electronic Structures of Purple Bronze KMo6O17 Studied by X-Ray Photoemission Spectra

    Science.gov (United States)

    Qin, Xiaokui; Wei, Junyin; Shi, Jing; Tian, Mingliang; Chen, Hong; Tian, Decheng

    X-ray photoemission spectroscopy study has been performed for the purple bronze KMo6O17. The structures of conduction band and valence band are analogous to the results of ultraviolet photoemission spectra and are also consistent with the model of Travaglini et al., but the gap between conduction and valence band is insignificant. The shape of asymmetric and broadening line of O-1s is due to unresolved contributions from the many inequivalent oxygen sites in this crystal structure. Mo 3d core-level spectrum reveals that there are two kinds of valence states of Molybdenum (Mo+5 and Mo+6). The calculated average valence state is about +5.6, which is consistent with the expectation value from the composition of this material. The tail of Mo-3d spectrum toward higher binding energy is the consequence of the excitation of electron-hole pairs with singularity index of 0.21.

  8. Highly resolved spatial and temporal photoemission analysis of integrated circuits

    International Nuclear Information System (INIS)

    We develop an optical system for highly resolved photoemission analysis of integrated circuits. Photons emitted by switching transistors allow the operation of an integrated circuit to be observed by recording the individual photoemission acts. The ongoing feature size reduction makes the space–time-resolved detection of these extremely weak photoemissions challenging. We combine different optical and photonic solutions to achieve both a high spatial and temporal resolution in a compact analysis system. Imaging and detection modules capture photons through the substrate during normal chip operation and perform highly resolved optical analysis. We demonstrate the system capability by photoemission records of a real-world IC device. (paper)

  9. Photoemission Spectroscopy and Orbital Imaging from Koopmans-Compliant Functionals

    OpenAIRE

    Nguyen, Ngoc Linh; Borghi, Giovanni; Ferretti, Andrea; Dabo, Ismaila; Marzari, Nicola

    2014-01-01

    The determination of spectral properties from first principles can provide powerful connections between microscopic theoretical predictions and experimental data, but requires complex electronic-structure formulations that fall outside the domain of applicability of common approaches, such as density-functional theory. We show here that Koopmans-compliant functionals, constructed to enforce piecewise linearity in energy functionals with respect to fractional occupations - i.e. with respect to...

  10. Electronic structure and photoemission in plutonium chalcogenides

    Czech Academy of Sciences Publication Activity Database

    Shick, Alexander; Havela, L.; Gouder, T.

    Warrendale, PA : Materials Research Society, 2008 - (Shuh, D.; Chung, B.; Albrecht-Schmitt, T.; Gouder, T.; Thompson, J.), s. 53-58 ISBN 978-1-60511-074-5. - (Materials Research Society Symposium Proceedings. NN. 1104). [Actinides 2008-Basic Science, Applications, and Technology. San Francisco (US), 24.03.2008-28.03.2008] R&D Projects: GA MŠk OC 144; GA ČR GA202/07/0644 Institutional research plan: CEZ:AV0Z10100520 Keywords : electronic sructure * photoemission * magnetism * strong electron correlations Subject RIV: BM - Solid Matter Physics ; Magnetism

  11. Photoemission from glass dust grains: First measurements

    Science.gov (United States)

    Nouzak, Libor; Pechal, Radim; Pavlu, Jiri; Safrankova, Jana; Nemecek, Zdenek

    2014-05-01

    Dust grains are present in the interstellar space and also on surfaces of space objects like the Moon. The grains are charged by photoemission caused by solar UV radiation and by charged particles from the ambient plasma (solar wind, planetary magnetospheres). A balance of different charging processes on both sunlit and night sides of the Moon causes interesting phenomena as dust horizon glow, dust fountains, and dust levitation. To contribute to a better understanding of these processes, we present laboratory investigations that use a single SiO2 grain of micron size (an archetype of the lunar dust) caught in the electrodynamic trap. We irradiate it by HeI (21.2 eV) photons and electrons and discuss a contribution of these two processes to the grain charge. The grain specific charge is evaluated by an analysis of its motion and position in the trap. We compare equilibrium charge-to-mass ratios given by the electron emissions induced by electrons and by the UV photons from the HeI lamp. First measurements indicate that the resulting charge is about twice larger for photoemission than that caused by an electron impact.

  12. Direct surface magnetometry with photoemission magnetic x-ray dichroism

    Energy Technology Data Exchange (ETDEWEB)

    Tobin, J.G.; Goodman, K.W. [Lawrence Berkeley National Lab., CA (United States); Schumann, F.O. [Pennsylvania State Univ., University Park, PA (United States)] [and others

    1997-04-01

    Element specific surface magnetometry remains a central goal of synchrotron radiation based studies of nanomagnetic structures. One appealing possibility is the combination of x-ray absorption dichroism measurements and the theoretical framework provided by the {open_quotes}sum rules.{close_quotes} Unfortunately, sum rule analysis are hampered by several limitations including delocalization of the final state, multi-electronic phenomena and the presence of surface dipoles. An alternative experiment, Magnetic X-Ray Dichroism in Photoelectron Spectroscopy, holds out promise based upon its elemental specificity, surface sensitivity and high resolution. Computational simulations by Tamura et al. demonstrated the relationship between exchange and spin orbit splittings and experimental data of linear and circular dichroisms. Now the authors have developed an analytical framework which allows for the direct extraction of core level exchange splittings from circular and linear dichroic photoemission data. By extending a model initially proposed by Venus, it is possible to show a linear relation between normalized dichroism peaks in the experimental data and the underlying exchange splitting. Since it is reasonable to expect that exchange splittings and magnetic moments track together, this measurement thus becomes a powerful new tool for direct surface magnetometry, without recourse to time consuming and difficult spectral simulations. The theoretical derivation will be supported by high resolution linear and circular dichroism data collected at the Spectromicroscopy Facility of the Advanced Light Source.

  13. Photoemission Fingerprints for Structural Identification of Titanium Dioxide Surfaces.

    Science.gov (United States)

    Borghetti, Patrizia; Meriggio, Elisa; Rousse, Gwenaëlle; Cabailh, Gregory; Lazzari, Rémi; Jupille, Jacques

    2016-08-18

    The wealth of properties of titanium dioxide relies on its various polymorphs and on their mixtures coupled with a sensitivity to crystallographic orientations. It is therefore pivotal to set out methods that allow surface structural identification. We demonstrate herein the ability of photoemission spectroscopy to provide Ti LMV (V = valence) Auger templates to quantitatively analyze TiO2 polymorphs. The Ti LMV decay reflects Ti 4sp-O 2p hybridizations that are intrinsic properties of TiO2 phases and orientations. Ti LMV templates collected on rutile (110), anatase (101), and (100) single crystals allow for the quantitative analysis of mixed nanosized powders, which bridges the gap between surfaces of reference and complex materials. As a test bed, the anatase/rutile P25 is studied both as received and during the anatase-to-rutile transformation upon annealing. The agreement with X-ray diffraction measurements proves the reliability of the Auger analysis and highlights its ability to detect surface orientations. PMID:27453254

  14. Photoemission study of tris(8-hydroxyquinoline) aluminum/aluminum oxide/tris(8-hydroxyquinoline) aluminum interface

    International Nuclear Information System (INIS)

    The evolution of the interface electronic structure of a sandwich structure involving aluminum oxide and tris(8-hydroxyquinoline) aluminum (Alq), i.e. (Alq/AlOx/Alq), has been investigated with photoemission spectroscopy. Strong chemical reactions have been observed due to aluminum deposition onto the Alq substrate. The subsequent oxygen exposure releases some of the Alq molecules from the interaction with aluminum. Finally, the deposition of the top Alq layer leads to an asymmetry in the electronic energy level alignment with respect to the AlOx interlayer

  15. X-ray photoemission study of the infinite-layer cuprate superconductor Sr(0.9) La (0.1) CuO(2)

    Science.gov (United States)

    Vasquez, R. P.; Jung, C. U.; Kim, J. Y.; Kim, M. S.; Lee, S. Y.; Lee, S. I.

    2001-01-01

    The electron-doped infinite-layer superconductor Sr(0.9)La(0.1) CuO(2) is studied with x-ray photoemission spectroscopy (XPS). A nonaqueous chemical etchant is shown to effectively remove contaminants and to yield surfaces from which signals intrinsic to the superconductor dominate.

  16. High-energy photoemission studies of oxide interfaces

    Science.gov (United States)

    Claessen, Ralph

    2015-03-01

    The interfaces of complex oxide heterostructures can host novel quantum phases not existing in the bulk of the constituents, with the high-mobility 2D electron system (2DES) in LaAlO3/SrTiO3 (LAO/STO) representing a prominent example. Despite extensive research the origin of the 2DES and its unusual properties - including the supposed coexistence of superconductivity and ferromagnetism - are still a matter of intense debate. Photoelectron spectroscopy, recently extended into the soft (SX-ARPES) and hard (HAXPES) X-ray regime, is a powerful method to provide detailed insight into the electronic structure of these heterostructures and, in particular, of the buried interface. This includes the identification of the orbital character of the 2DES as well as the determination of vital band structure information, such as band alignment, band bending, and even k-resolved band dispersions and Fermi surface topology. Moreover, resonant photoemission at the Ti L-edge reveals the existence of two different species of Ti 3d states, localized and itinerant, which can be distinguished and identified by their different resonance behavior. The role of oxygen vacancies is studied by controlled in-situ oxidation, which allows us to vary the composition from fully stoichiometric to strongly O-deficient. By comparison to free STO surfaces we can thus demonstrate that the metallicity of the heteointerfaces is intrinsic, i . e . it persists even in the absence of O defects. I will discuss our photoemission results on LAO/STO heterostructures in both (100) and (111) orientation as well as on the related system γ-Al2O3/STO(100), which also hosts a 2DES with an even higher mobility. Work in collaboration with J. Mannhart (MPI-FKF, Stuttgart), N. Pryds (TU Denmark), G. Rijnders (U Twente), S. Suga (U Osaka), M. Giorgoi (BESSY, HZB), W. Drube (DESY Photon Science), V.N. Strocov (Swiss Light Source), J. Denlinger (Advanced Light Source, LBNL), and T.-L. Lee (Diamond Light Source). Support by

  17. Photoemission studies of f-electron systems: Many-body effects: Final report, March 1, 1985--March 31, 1988

    International Nuclear Information System (INIS)

    Both initial and final state effects contribute to many-body features in photoemission on solids. The former reflect the ground state properties of the system, while the latter are due to the reaction of the solid state environment to the creation of a photoelectron hole. In f-electron systems both effects are expected to contribute to the photoemission spectra and one objective of this project was to separate final state effects from ground state properties. Final state effects provide valuable information about the interaction of f electrons with conduction electrons. The degree of f-electron localization and the strength of f-conduction electron hybridization for Ce- and U-based systems can be extracted from these measurements. The energy dependence of the photoemission cross section, which shows pronounced maxima in rare earth and uranium systems, also proved to be sensitive to the exact electronic state of the Ce ion. Core level photoemission spectroscopy was used as a species-specific probe to determine the electronic state of the f-shell ions and their ligands in scientific interesting systems. Application to high temperature superconducting compounds helped to determine the electronic properties necessary for superconductivity

  18. Resonant photoemission from SmS(100)

    International Nuclear Information System (INIS)

    A strong, sharp resonance enhancement of 4f photoemission has been observed on SmS(100) surfaces for photon energies in the region of the 4d-4f transitions at about 126 eV. The discrete final state reached via the excitation hν + 4d104f6 → 4d94f7 autoionizes primarily via a super Coster-Kronig transition of the type 4d94f7 → 4d104f5 + unbound electron. Other decay channels, e.g. Sm 5p emission, as well as a surface induce binding energy shift in the Sm3+ final state are identified and discussed. (author)

  19. Short pulse photoemission from a dispenser cathode

    Science.gov (United States)

    Bergeret, H.; Boussoukaya, M.; Chehab, R.; Leblond, B.; Le Duff, J.

    1991-03-01

    Pulsed photoemission in the picosecond regime has been obtained from a standard thermionic dispenser cathode (WBaCa) at temperatures below the measurable thermoemission threshold. A picosecond Nd : YAG mode locked laser has been used at both green and UV light. Micropulse charges up to 0.5 nC have been measured on a wideband coaxial pickup located behind the anode. They correspond to an electron saturation limit from an approximately 20 mm 2 illuminated cathode area with a surface field of 3 MV/m. The effective cathode efficiency at small laser energies, defined as the number of electrons impinging on the coaxial pickup divided by the number of photons impinging on the cathode, is about 2 × 10 -5.

  20. Time-resolved photoemission using attosecond streaking

    CERN Document Server

    Nagele, Stefan; Wais, Michael; Wachter, Georg; Burgdörfer, Joachim

    2014-01-01

    We theoretically study time-resolved photoemission in atoms as probed by attosecond streaking. We review recent advances in the study of the photoelectric effect in the time domain and show that the experimentally accessible time shifts can be decomposed into distinct contributions that stem from the field-free photoionization process itself and from probe-field induced corrections. We perform accurate quantum-mechanical as well as classical simulations of attosecond streaking for effective one-electron systems and determine all relevant contributions to the time delay with attosecond precision. In particular, we investigate the properties and limitations of attosecond streaking for the transition from short-ranged potentials (photodetachment) to long-ranged Coulomb potentials (photoionization). As an example for a more complex system, we study time-resolved photoionization for endohedral fullerenes $A$@$\\text{C}_{60}$ and discuss how streaking time shifts are modified due to the interaction of the $\\text{C}_...

  1. Efficient photoemission from robust ferroelectric ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Boscolo, I. [Milan Univ., Milan (Italy); Istituto Nazionale di Fisica Nucleare, Milan, (Italy); Castellano, M.; Catani, L.; Ferrario, M.; Tazzioli, F. [Istituto Nazionale di Fisica Nucleare, Frascati, RM (Italy); Giannessi, L. [ENEA, Frascati, Rome (Italy). Centro Ricerche Elettronica

    1999-07-01

    Experimental results on photoemission by ferroelectric ceramic disks, with a possible interpretation, are presented. Two types of lead zirconate titanate lanthanum doped, PLZT, ceramics have been used for tests. 25 ps light pulses of 532 and 355 nm were used for excitation. The intensity ranged within the interval 0.1-3 GW/cm{sup 2}. The upper limit of the intensity was established by the damage threshold tested by the onset of ion emission. At low value of the intensity the yield was comparable at the two wavelengths. At the highest intensity of green light the emitted charge was 1 nC per 10 mm{sup 2}, but it was limited by the space charge effect. In fact, the applied field was only 20 kV/cm, allowed both by the mechanical design of the apparatus and the poor vacuum, 10{sup -4} mbar. No surface processing was required. The measurement of the electron pulse length under way.

  2. Time delays in correlated photoemission processes

    Science.gov (United States)

    Pazourek, R.; Nagele, S.; Burgdörfer, J.

    2015-09-01

    We theoretically study time-resolved two-photon double ionization (TPDI) of helium as probed by attosecond streaking. We review recent advances in the understanding of the photoelectric effect in the time domain and discuss the differences between one- and two-photon ionization, as well as one- and two-electron emission. We perform exact ab-initio simulations for attosecond streaking experiments in the sequential TPDI regime and compare the results to the two-electron Eisenbud-Wigner-Smith delay for the process. Our calculations directly show that the timing of the emission process sensitively depends on the energy sharing between the two outgoing electrons. In particular, we identify Fano-like interferences in the relative time delay of the two emitted electrons when the sequential ionization channel occurs via intermediate excited ionic (shake-up) states. Furthermore, we find that the photoemission time delays are only weakly dependent on the relative emission angle of the ejected electrons.

  3. Short pulse photoemission from a dispenser cathode

    International Nuclear Information System (INIS)

    Pulsed photoemission in picosecond regime has been obtained from a standard thermionic dispenser cathode (W - Ba - Ca) at temperatures below measurable thermoemission threshold. A picosecond Nd: YAG mode locked laser has been used at both green and U.V. light. Micro-pulse charges up to 0.5 nC have been measured on a wideband coaxial pick up located behind the anode. They correspond to an electron saturation limit from an approximately 20 mm2 illuminated cathode area with a surface field of 3 MV/m. The effective cathode efficiency at small laser energies, defined as the number of electron impinging the coaxial pick up divided by the number of photons impinging the cathode, is about 2.10-5

  4. High- Tc superconductivity: new issues from photoemission data

    Science.gov (United States)

    Margaritondo, G.; Grioni, M.; Vobornik, I.; Pavuna, D.

    2001-11-01

    Recent high-resolution photoemission results on high- Tc superconductors and other low-dimensional systems solve some critical issues but also open new fundamental questions. A recent breakthrough enabled us to clarify the interplay of conflicting periodicities in photoemission data, thus legitimizing the photoemission analysis of crystals with super-periodicities. On the other hand, results on the role of doping and of intentional disorder in Bi 2Sr 2CaCu 2O 8+ x single crystals raise questions about the origin of the pseudogap.

  5. Polarization Effects in Attosecond Photoelectron Spectroscopy

    DEFF Research Database (Denmark)

    Baggesen, Jan Conrad; Madsen, Lars Bojer

    2010-01-01

    following the field instead. We show that polarization effects may lead to an apparent temporal shift that needs to be properly accounted for in the analysis. The effect may be isolated and studied by angle-resolved photoelectron spectroscopy from oriented polar molecules. We also show that polarization......We study the influence of polarization effects in streaking by combined atto- and femtosecond pulses. The polarization-induced terms alter the streaking spectrum. The conventional streaking spectrum, which maps to the vector potential of the femtosecond pulse, is modified by a contribution...

  6. Colloquium: Graphene spectroscopy

    OpenAIRE

    Basov, D. N.; Fogler, M. M.; A. Lanzara; Wang, Feng; Zhang, Yuanbo

    2014-01-01

    Spectroscopic studies of electronic phenomena in graphene are reviewed. A variety of methods and techniques are surveyed, from quasiparticle spectroscopies (tunneling, photoemission) to methods probing density and current response (infrared optics, Raman) to scanning probe nanoscopy and ultrafast pump-probe experiments. Vast complimentary information derived from these investigations is shown to highlight unusual properties of Dirac quasiparticles and many-body interaction effects in the phys...

  7. Photoemission and inverse photoemission study of the electronic structure of C60 fullerenes encapsulated in single-walled carbon nanotubes

    OpenAIRE

    Shiozawa, Hidetsugu; Ishii, Hiroyoshi; Kihara, Hideo; Sasaki, Naoya; Nakamura, Satoshi; Yoshida, Tetsuo; Takayama, Yasuhiro; Miyahara, Tsuneaki; Suzuki, Shinzo; Achiba, Yohji; Kodama, Takeshi; Higashiguchi, Mitsuharu; Chi, Xiaoyu; Nakatake, Masashi; Shimada, Kenya

    2006-01-01

    We have measured the valence-band photoemission and inverse photoemission spectra of single-walled carbon nanotubes (SWNTs) with mean radii of 0.7 and 0.64 nm encapsulating C60 fullerenes (peas), so-called "peapods." The photoemission spectrum of the C60 peas in the SWNTs is obtained by subtracting the spectrum of empty SWNTs from the spectrum of the peapod. The structures in the C60 pea spectra correspond well to those in the spectrum of a C60 face-centered-cubic solid. No structure is obser...

  8. Photoemission measurements for low energy x-ray detector applications

    International Nuclear Information System (INIS)

    Photoemission has been studied for nearly 100 years as both a means of investigating quantum physics, and as a practical technique for transducing optical/x-ray photons into electrical currents. Numerous x-ray detection schemes, such as streak cameras and x-ray sensitive diodes, exploit this process because of its simplicity, adaptability, and speed. Recent emphasis on diagnostics for low temperature, high density, and short-lived, plasmas for inertial confinement fusion has stimulated interest in x-ray photoemission in the sub-kilovolt regime. In this paper, a review of x-ray photoemission measurements in the 50 eV to 10 keV x-ray region is given and the experimental techniques are reviewed. A semiempirical model of x-ray photoemission is discussed and compared to experimental measurements. Finally, examples of absolutely calibrated instruments are shown

  9. In-adlayers on non-polar and polar InN surfaces: Ion scattering and photoemission studies

    International Nuclear Information System (INIS)

    The surface structure of In-polarity c-plane InN has been investigated by low energy ion scattering spectroscopy. Comparison of ion scattering spectra recorded along the [1 0 0 0] azimuth with model calculations indicates that the clean In-polarity c-plane InN surface is terminated by In-adlayers with a laterally contracted topmost In layer. This is consistent with previous X-ray photoemission and electron diffraction results. Additionally, the surface properties of a-plane InN have been investigated using core-level and valence band X-ray photoemission spectroscopy (XPS). From the ratio of the In and N core-level XPS signal intensities, the clean a-plane InN surface has also been found to be terminated by In-adlayers. Photoemission measurements of the valence band maximum to surface Fermi level separation for a-plane InN indicate the existence of an electron accumulation layer at the surface. This observation of electron accumulation at non-polar InN surfaces in the presence of In-adlayers is in agreement with the predictions of previous first-principles calculations

  10. Dynamical Processes in Open Quantum Systems from a TDDFT Perspective: Resonances and Electron Photoemission.

    Science.gov (United States)

    Larsen, Ask Hjorth; De Giovannini, Umberto; Rubio, Angel

    2016-01-01

    We present a review of different computational methods to describe time-dependent phenomena in open quantum systems and their extension to a density-functional framework. We focus the discussion on electron emission processes in atoms and molecules addressing excited-state lifetimes and dissipative processes. Initially we analyze the concept of an electronic resonance, a central concept in spectroscopy associated with a metastable state from which an electron eventually escapes (electronic lifetime). Resonances play a fundamental role in many time-dependent molecular phenomena but can be rationalized from a time-independent context in terms of scattering states. We introduce the method of complex scaling, which is used to capture resonant states as localized states in the spirit of usual bound-state methods, and work on its extension to static and time-dependent density-functional theory. In a time-dependent setting, complex scaling can be used to describe excitations in the continuum as well as wave packet dynamics leading to electron emission. This process can also be treated by using open boundary conditions which allow time-dependent simulations of emission processes without artificial reflections at the boundaries (i.e., borders of the simulation box). We compare in detail different schemes to implement open boundaries, namely transparent boundaries using Green functions, and absorbing boundaries in the form of complex absorbing potentials and mask functions. The last two are regularly used together with time-dependent density-functional theory to describe the electron emission dynamics of atoms and molecules. Finally, we discuss approaches to the calculation of energy and angle-resolved time-dependent pump-probe photoelectron spectroscopy of molecular systems. PMID:25860253

  11. Molecular photoemission studies using synchrotron radiation

    Energy Technology Data Exchange (ETDEWEB)

    Truesdale, C.M.

    1983-04-01

    The angular distributions of photoelectrons and Auger electrons were measured by electron spectroscopy using synchrotron radiation. The experimental results are compared with theoretical calculations to interpret the electronic behavior of photoionization for molecular systems.

  12. Molecular photoemission studies using synchrotron radiation

    International Nuclear Information System (INIS)

    The angular distributions of photoelectrons and Auger electrons were measured by electron spectroscopy using synchrotron radiation. The experimental results are compared with theoretical calculations to interpret the electronic behavior of photoionization for molecular systems

  13. Spectroscopic imaging, diffraction, and holography with x-ray photoemission

    International Nuclear Information System (INIS)

    X-ray probes are capable of determining the spatial structure of an atom in a specific chemical state, over length scales from about a micron all the way down to atomic resolution. Examples of these probes include photoemission microscopy, energy-dependent photoemission diffraction, photoelectron holography, and X-ray absorption microspectroscopy. Although the method of image formation, chemical-state sensitivity, and length scales can be very different, these X-ray techniques share a common goal of combining a capability for structure determination with chemical-state specificity. This workshop will address recent advances in holographic, diffraction, and direct imaging techniques using X-ray photoemission on both theoretical and experimental fronts. A particular emphasis will be on novel structure determinations with atomic resolution using photoelectrons

  14. Time of flight-photoemission electron microscope for ultrahigh spatiotemporal probing of nanoplasmonic optical fields

    International Nuclear Information System (INIS)

    Nanoplasmonic excitations as generated by few-cycle laser pulses on metal nanostructures undergo ultrafast dynamics with timescales as short as a few hundred attoseconds (1 as = 10-18 s). So far, the spatiotemporal dynamics of optical fields localized on the nanoscale (nanoplasmonic field) have been hidden from direct access in the real space and time domain. An approach which combines photoelectron emission microscopy and attosecond streaking spectroscopy and which provides direct and non-invasive access to the nanoplasmonic field with nanometer-scale spatial resolution and temporal resolution of the order of 100 as has been proposed (Stockman et al 2007 Nat. Photon. 1 539). To implement this approach, a time of flight-photoemission electron microscope (TOF-PEEM) with ∼25 nm spatial and ∼50 meV energy resolution, which has the potential to detect a nanoplasmonic field with nanometer spatial and attosecond temporal resolution, has been developed and characterized using a 400 nm/60 ps pulsed diode laser. The first experimental results obtained using this newly developed TOF-PEEM in a two-photon photoemission mode with a polycrystalline Cu sample and an Ag microstructure film show that the yield and the kinetic energy of the emitted photoelectrons are strongly affected by the nanolocalized plasmonic field.

  15. Electronic band structure and photoemission: A review and projection

    International Nuclear Information System (INIS)

    A brief review of electronic-structure calculations in solids, as a means of interpreting photoemission spectra, is presented. The calculations are, in general, of three types: ordinary one-electron-like band structures, which apply to bulk solids and are the basis of all other calculations; surface modified calculations, which take into account, self-consistently if at all possible, the presence of a vacuum-solid interface and of the electronic modifications caused thereby; and many-body calculations, which go beyond average-field approximations and consider dynamic rearrangement effects caused by electron-electron correlations during the photoemission process. 44 refs

  16. Einstein's Photoemission from Quantum Confined Superlattices.

    Science.gov (United States)

    Debbarma, S; Ghatak, K P

    2016-01-01

    This paper is dedicated to the 83th Birthday of Late Professor B. R. Nag, D.Sc., formerly Head of the Departments of Radio Physics and Electronics and Electronic Science of the University of Calcutta, a firm believer of the concept of theoretical minimum of Landau and an internationally well known semiconductor physicist, to whom the second author remains ever grateful as a student and research worker from 1974-2004. In this paper, an attempt is made to study, the Einstein's photoemission (EP) from III-V, II-VI, IV-VI, HgTe/CdTe and strained layer quantum well heavily doped superlattices (QWHDSLs) with graded interfaces in the presence of quantizing magnetic field on the basis of newly formulated electron dispersion relations within the frame work of k · p formalism. The EP from III-V, II-VI, IV-VI, HgTe/CdTe and strained layer quantum wells of heavily doped effective mass superlattices respectively has been presented under magnetic quantization. Besides the said emissions, from the quantum dots of the aforementioned heavily doped SLs have further investigated for the purpose of comparison and complete investigation in the context of EP from quantum confined superlattices. Using appropriate SLs, it appears that the EP increases with increasing surface electron concentration and decreasing film thickness in spiky manners, which are the characteristic features of such quantized hetero structures. Under magnetic quantization, the EP oscillates with inverse quantizing magnetic field due to Shuvnikov-de Haas effect. The EP increases with increasing photo energy in a step-like manner and the numerical values of EP with all the physical variables are totally band structure dependent for all the cases. The most striking features are that the presence of poles in the dispersion relation of the materials in the absence of band tails create the complex energy spectra in the corresponding HD constituent materials of such quantum confined superlattices and effective electron

  17. Surface and bulk 4f-photoemission spectra of CeIn3 and CeSn3

    International Nuclear Information System (INIS)

    Resonant photoemission spectroscopy was performed on CeIn3 and CeSn3 at the 4d-4f and 3d-4f core thresholds. Using the different surface sensitivity between the two photon energies, surface and bulk 4f-photoemission spectra were derived for both compounds. With the noncrossing approximation of the Anderson impurity model, the 4d-4f resonant spectra together with the surface and bulk spectra were self-consistently analyzed to obtain the microscopic parameters such as the 4f-electron energy and the hybridization strength with conduction electrons. The result shows a substantial difference in these parameters between the surface and the bulk, indicating that it is important to take into account the surface effect in analyzing photoemission spectra of Ce compounds. It is also found that the 4f surface core-level shift is different between CeIn3 and CeSn3. copyright 1997 The American Physical Society

  18. Strongly anisotropic spin-orbit splitting in a two-dimensional electron gas

    DEFF Research Database (Denmark)

    Michiardi, Matteo; Bianchi, Marco; Dendzik, Maciej; Miwa, Jill; Hoesch, Moritz; Kim, Timur K.; Matzen, Peter; Mi, Jianli; Bremholm, Martin; Iversen, Bo Brummerstedt; Hofmann, Philip

    2015-01-01

    Near-surface two-dimensional electron gases on the topological insulator Bi$_2$Te$_2$Se are induced by electron doping and studied by angle-resolved photoemission spectroscopy. A pronounced spin-orbit splitting is observed for these states. The $k$-dependent splitting is strongly anisotropic to a...

  19. Controllable magnetic doping of the surface state of a topological insulator

    DEFF Research Database (Denmark)

    Schlenk, T.; Bianchi, M.; Koleini, Mohammad; Eich, A.; Pietzsch, O.; O. Wehling, T.; Frauenheim, T.; Balatsky, A.; -L. Mi, J.; Iversen, Bo Brummerstedt; Wiebe, J.; A. Khajetoorians, A.; Hofmann, Philip; Wiesendanger, R.

    2013-01-01

    thermally-activated diffusion. Angle-resolved photoemission spectroscopy in combination with ab-initio calculations suggest that the doping behavior changes from electron donation for the Fe adatom to neutral or electron acceptance for Fe incorporated into substitutional Bi sites. According to first...

  20. Time-resolved Fermi surface mapping of the charge density wave material DyTe3

    Directory of Open Access Journals (Sweden)

    Wolf M.

    2013-03-01

    Full Text Available The femtosecond dynamics of the Fermi surface of DyTe3 and its band structure are investigated by time- and angle-resolved photoemission spectroscopy. We directly monitor the ultrafast collapse of the charge density wave gap within 200 fs.

  1. Electronic structure of elemental curium studied by photoemission

    Czech Academy of Sciences Publication Activity Database

    Gouder, T.; van der Laan, G.; Shick, Alexander; Haire, R.G.; Caciuffo, R.

    2011-01-01

    Roč. 83, č. 12 (2011), "125111-1"-"125111-6". ISSN 1098-0121 R&D Projects: GA ČR(CZ) GAP204/10/0330 Institutional research plan: CEZ:AV0Z10100520 Keywords : photoemission * actinides Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.691, year: 2011

  2. Relativistic calculations of angular dependent photoemission time delay

    CERN Document Server

    Kheifets, A S; Deshmukh, P C; Dolmatov, V K; Manson, S T

    2016-01-01

    Angular dependence of photoemission time delay for the valence $np_{3/2}$ and $np_{1/2}$ subshells of Ar, Kr and Xe is studied in the dipole relativistic random phase approximation. Strong angular anisotropy of the time delay is reproduced near respective Cooper minima while the spin-orbit splitting affects the time delay near threshold.

  3. Practical Photoemission Characterization Of Molecular Films And Related Interfaces

    International Nuclear Information System (INIS)

    Even though the term ‘organic electronics’ evokes rather organic devices, a significant part of its scope deals with physical properties of ‘active elements’ such as organic films and interfaces. Examination of the film growth and the evolution of the interface formation are particularly needful for the understanding a mechanism controlling their final properties. Performing such experiments in an ultra-high vacuum allows both to ‘stretch’ the time scale for pseudo real-time observations and to control properties of the probed systems on the atomic level. Photoemission technique probes directly electronic and chemical structure and it has thereby established among major tools employed in the field.This review primarily focuses to electronic properties of oligomeric molecular films and their interfaces examined by photoemission. Yet, it does not aspire after a complete overview on the topic; it rather aims to otherwise standard issues encountered at the photoemission characterization and analysis of the organic materials, though requiring to consider particularities of molecular films in terms of the growth, electronic properties, and their characterization and analysis. In particular, the fundamental electronic parameters of molecular films such as the work function, the ionization energy, and the interfacial energy level alignment, and their interplay, will be pursued with considering often neglected influence of the molecular orientation. Further, the implication on the band bending in molecular films based on photoemission characterization, and a model on the driving mechanism for the interfacial energy level alignment will be addressed. (author)

  4. Angle Integrated Photoemission Study of SmO0.85F0.15FeAs

    Institute of Scientific and Technical Information of China (English)

    OU Hong-Wei; WU Tao; CHEN Xian-Hui; CHEN Yan; FENG Dong-Lai; ZHAO Jia-Feng; ZHANG Yan; SHEN Da-Wei; ZHOU Bo; YANG Le-Xian; HE Cheng; CHEN Fei; XU Min

    2008-01-01

    The electronic structure of the new superconductor SmO1-xFxFeAs (x = 0.15) is studied by angle-integrated photoemission spectroscopy. Our data show a sharp feature very close to the Fermi energy, and a relative fiat distribution of the density of states between 0.SeV and 3eV binding energy, which agrees well with the band structure calculations considering an antiferromagnetic ground state. No noticeable gap opening is observed at 12 K below the superconducting transition temperature, indicating the existence of large ungapped regions in the Brillouin zone.

  5. Heavy Fermion Behavior of Pr 4f Electrons in Filled Skutterudites Studied by Bulk-Sensitive Photoemission

    International Nuclear Information System (INIS)

    Pr 4 f electronic structures in Pr-based filled skutterudites PrT4X12 (T = Fe and Ru; X = P and Sb) have been studied by the high-resolution bulk-sensitive Pr 3d → 4f resonance photoemission spectroscopy. A very strong Pr 4f spectral intensity is observed just below the Fermi level in the heavy-Fermion PrFe4P12. This is the first observation of the Kondo resonance due to the quadrupolar Kondo effect, the origin of which is attributed to the strong hybridization between the Pr 4f and the conduction electrons. (author)

  6. Stoner vs. spin-mixing behavior in the bulk magnetism of Gd: A spin-resolved photoemission study

    Indian Academy of Sciences (India)

    K Maiti; M C Malagoli; A Dallmeyer; C Carbone

    2002-05-01

    The temperature dependence of the rare-earth 2-bulk band has been regarded as an exemplary case which realizes the simple Stoner behavior. We examined the evolution of Gd2 bulk bands with temperature in the range 0.5 ≤ /C ≤ 1 with spin-resolved, photoemission spectroscopy. The direct observation of the spin-dependent spectral line shapes reveals a complex temperature dependence and manifests a clear inadequacy of the Stoner model to the description of the magnetism in rare earths.

  7. X-ray photoemission study of CoFeB/MgO thin film bi-layers

    OpenAIRE

    Read, J. C.; Mather, P. G.; Buhrman, R.A.

    2007-01-01

    We present results from an X-ray photoemission spectroscopy (XPS) study of CoFeB/MgO bi-layers where we observe process-dependent formation of B, Fe, and Co oxides at the CoFeB/MgO interface due to oxidation of CoFeB during MgO deposition. Vacuum annealing reduces the Co and Fe oxides but further incorporates B into the MgO forming a composite MgBxOy layer. Inserting an Mg layer between CoFeB and MgO introduces an oxygen sink, providing increased control over B content in the barrier.

  8. Nanoelectron spectroscopy for chemical analysis: a novel energy filter for imaging x-ray photoemission spectroscopy

    International Nuclear Information System (INIS)

    A novel instrument for imaging ESCA is described. It is based on a tandem arrangement of two hemispherical energy analysers used as an imaging energy filter. The main spherical aberration (α2-term) of the analyser is corrected by the antisymmetry of the tandem configuration. The kinetic energy range usable for imaging extends up to 1.6 keV; this is compatible with Mg and Al Kα laboratory x-ray sources. First experiments on the chemical surface composition of a Cu0.98Bi0.02 polycrystal, a GaAs/AlGaAs heterostructure and Ag crystallites on Si(111) have been performed using synchrotron radiation. The results reveal an energy resolution of 190 meV and a lateral resolution (edge resolution) of 120 nm. Besides elimination of the analyser's spherical aberration, the tandem arrangement largely retains the time structure of the electron signal, unlike a single hemispherical analyser

  9. Adsorption energy and geometry of adsorbed organic molecules on Au(111) probed by surface-state photoemission

    Energy Technology Data Exchange (ETDEWEB)

    Ziroff, Johannes; Forster, Frank [Universitaet Wuerzburg, Experimentelle Physik II, D-97074 Wuerzburg (Germany); Reinert, Friedrich [Universitaet Wuerzburg, Experimentelle Physik II, D-97074 Wuerzburg (Germany); Forschungszentrum Karlsruhe, Gemeinschaftslabor fuer Nanoanalytik, D-76021 Karlsruhe (Germany)

    2009-07-01

    The modification of the Au(111) surface states by an adsorbed monolayer of large {pi}-conjugated molecules (PTCDA, NTCDA, CuPc) was investigated by high-resolution angle-resolved photoelectron spectroscopy. We determined binding energy, band mass, and Rashba-splitting and discuss the results in the context of rare-gas adsorption on noble metals. This comparison allows the determination of the bonding strength of the adsorbates, found to be physisorptive with derived binding energies per molecule of 2.0 eV for PTCDA and 1.5 eV for NTCDA. We will also present a superstructure model for the NTCDA/Au(111) system, deduced from low energy electron diffraction images in combination with band-backfolding of the Tamm and Shockley states. The coverage dependent evolution of the surface states was also investigated for the three molecules, giving evidence for a dilute-phase growth of the CuPc molecule on the Au(111) surface.

  10. Generalized Franck-Condon principle for resonant photoemission

    Science.gov (United States)

    Sałek, Paweł; Gel'mukhanov, Faris; Ågren, Hans; Björneholm, Olle; Svensson, Svante

    1999-10-01

    A generalized Franck-Condon (GFC) principle for resonant x-ray Raman scattering and for resonant photoemission in particular is derived and numerically investigated. The GFC amplitudes differ from ordinary FC amplitudes by the presence of photon and photoelectron phase factors which describe the coupling-or interference-of the x-ray photons or Auger electrons with the nuclear motion. With the GFC amplitudes, a Kramers-Heisenberg relation is obtained for vibronic transitions that corrects the so-called lifetime-vibrational interference formula. For resonant photoemission in the soft-x-ray region involving typical bound potential surfaces, the generalization gives a contribution to the FC factors that can amount to 20%. For core excitation above the dissociation threshold, the GFC principle relates to Doppler effects on the ejected photoelectron both for the so-called ``molecular'' and ``atomic'' bands. The role of the GFC principle in direct photoionization is briefly discussed.

  11. Thermal and Field Enhanced Photoemission Comparison of Theory to Experiment

    CERN Document Server

    Lynn-Jensen, Kevin

    2004-01-01

    Photocathodes are a critical component of high-gain FEL’s and the analysis of their emission is complex. Relating their performance under laboratory conditions to conditions of an rf photoinjector is difficult. Useful models must account for cathode surface conditions and material properties, as well as drive laser parameters. We have developed a time-dependent model accounting for the effects of laser heating and thermal propagation on photoemission. It accounts for surface conditions (coating, field enhancement, reflectivity), laser parameters (duration, intensity, wavelength), and material characteristics (reflectivity, laser penetration depth, scattering rates) to predict current distribution and quantum efficiency. The applicatIon will focus on photoemission from metals and, in particular, dispenser photocathodes: the later introduces complications such as coverage non-uniformity and field enhancement. The performance of experimentally characterized photocathodes will be extrapolated to 0.1 - 1 nC bunch...

  12. Reversible switching in self-assembled monolayers of azobenzene thiolates on Au (111) probed by threshold photoemission

    International Nuclear Information System (INIS)

    Highlights: ► Photoelectron spectroscopy of liquid phase prepared SAMs of azobenzene derivative. ► Photo-induced reversible switching in densely packed SAM is monitored. ► Maximum density of switched molecules in SAM is derived from photoemission data. ► Switching reaction only enabled at defects sites within the molecular layer. - Abstract: The reversible photo- and thermally activated isomerization of the molecular switch 3-(4-(4-Hexyl-phenylazo)-phenoxy)-propane-1-thiol (ABT, short for AzoBenzeneThiol) deposited by self-assembly from solution on Au (111) was studied using laser-based photoelectron spectroscopy. Differences in the molecular dipole moment characteristic for the trans and the cis isomer of ABT were monitored via changes in the sample work function, accessible by detection of the threshold energy for photoemission. A quantitative analysis of our data shows that the fraction of molecules within the densely packed monolayer that undergoes a switching process is of the order of 1%. This result indicates the relevance of substrate and film defects required to overcome the steric or electronic hindrance of the isomerization reaction in a densely packed monolayer.

  13. THE ORGANIC LED SURFACE: A SYNCHROTRON RADIATION PHOTOEMISSION STUDY

    OpenAIRE

    TUN-WEN PI; T. C. YU

    2007-01-01

    Tris(8-hydroxyquinolato) aluminum (Alq3), a prototypical molecule for organic light-emitting devices, has been studied via synchrotron radiation photoemission to investigate (1) the surface electronic structure of the molecules at room temperature and at elevated temperatures, (2) adsorption onto the inorganic Si(001)-2×1 surface, and (3) doping with the alkaline metal Mg. For case (1), three chemical environments of carbon are resolved. Moreover, the shake-up satellite structures are detecte...

  14. Quantification of plasmon excitations in core-level photoemission

    International Nuclear Information System (INIS)

    Calculation of photoelectron spectra (PES) based on our previous dielectric response model [A. C. Simonsen et al. Phys. Rev. B 56, 1612 (1997)] for electronic excitations in PES are compared with recently reported experimental data. It is found that the dielectric description of electron energy losses in photoemission reproduces quantitatively the angular dependence of the surface and bulk electron losses observed experimentally for the Al2s photoemission spectra of Al(111), excited with MgKα radiation. The model also allows to calculate the separate intrinsic and extrinsic effects in photoemission. Thus, the extrinsic losses account for more than 95% of the total surface excitations. Regarding the bulk excitations, both extrinsic and intrinsic contributions vary significantly with emission angle. The intrinsic contribution represents ∼35% of the intensity at the bulk plasmon position at normal emission while only 18% at 80 deg. glancing emission. The calculations presented here can easily be used to interpret PES spectra of other materials in terms of intrinsic and extrinsic effects, if their dielectric properties are known

  15. Soft X-ray photoemission study of Co2(Cr1−xFex)Ga Heusler compounds

    International Nuclear Information System (INIS)

    We have performed soft X-ray photoemission spectroscopy (SXPES) and X-ray absorption spectroscopy (XAS) of the Co-based Heusler compounds Co2(Cr1−xFex)Ga (x = 0.0, 0.4, and 1.0) in order to study their electronic structures. Band-structure calculation was carried out and compared with the experimental results. SXPES spectra show hν-dependence, revealing the contributions of the Co, Cr, and Fe 3d electronic states in the valence band. The band width observed by the SXPES seems to be narrower than that predicted by the band-structure calculation. XAS spectra depend strongly on the value of x in Co2(Cr1−xFex)Ga. The electron correlation effects are found to be stronger as x changes from 0.0 to 1.0. (author)

  16. Quasiparticle and Optical Spectroscopy of Organic Semiconductors Pentacene and PTCDA from First Principles

    OpenAIRE

    Sharifzadeh, Sahar; Biller, Ariel; Kronik, Leeor; Neaton, Jeffrey B.

    2011-01-01

    The broad use of organic semiconductors for optoelectronic applications relies on quantitative understanding and control of their spectroscopic properties. Of paramount importance are the transport gap - the difference between ionization potential and electron affinity - and the exciton binding energy - inferred from the difference between the transport and optical absorption gaps. Transport gaps are commonly established via photoemission and inverse photoemission spectroscopy (PES/IPES). How...

  17. Investigating crystalline-polarity-dependent electronic structures of GaN by hard x-ray photoemission and ab-initio calculations

    Science.gov (United States)

    Ohsawa, Takeo; Ueda, Shigenori; Suzuki, Motohiro; Tateyama, Yoshitaka; Williams, Jesse R.; Ohashi, Naoki

    2015-10-01

    Crystalline-polarity-dependent electronic structures of gallium nitride (GaN) were studied by photoemission spectroscopy (PES) using soft and hard x-rays with different linear polarizations. A peak located near the valence band (VB) maximum was enhanced for a (0001) surface compared with that for a ( 000 1 ¯ ) surface regardless of photon energy. Comparison of the VB density of states obtained by ab-initio calculations with the observed VB-PES spectra indicates that the crystalline-polarity dependence is associated with the Ga 4p and N 2p states. The most plausible origin of the crystalline-polarity-dependent VB feature is based on the photoemission phenomena of electrons in the pz-orbitals due to spontaneous electric polarization along the c-axis of GaN.

  18. Two-photon photoemission from ex-situ prepared butanethiol SAMs on Au (111)

    International Nuclear Information System (INIS)

    Graphical abstract: The occupied and unoccupied electronic structure of butanethiolate SAMs deposited from liquid phase has been studied by two-photon photoelectron spectroscopy. Next to an adsorbate resonance we identify an interface state as well as indications for the formation of image potential states. Highlights: → 2PPE study of liquid phase prepared alkanethiolate SAMs. → 2PPE fingerprint of sulfur gold bond identified. → Indication for the formation of image potential states at ex-situ prepared SAMs. - Abstract: Self-assembled monolayers (SAMs) of butanethiol on a Au (111) single crystalline surface in the px√(3) lying-down phase prepared by deposition from solution were studied with two-photon photoemission (2PPE) spectroscopy. The spectra reveal clear signatures of two unoccupied resonance states at energies E - EF = 3.7 eV and 3.9 eV. The low-energy state is assigned to the characteristic σ*-resonance associated with the Au-S bond of the thiolate. The energy of the other resonance state agrees well with an interface state reported before for different alkanethiol SAMs on Au (111) in a standing-up phase. Furthermore the 2PPE data provide indications that the high quality of the ex-situ prepared SAMs support the formation of image potential states.

  19. Femtosecond-laser photoemission and photodesorption from magnesia supported gold clusters

    Energy Technology Data Exchange (ETDEWEB)

    Vaida, Mihai E.; Gleitsmann, Tobias; Tchitnga, Robert; Bernhardt, Thorsten M. [Institute of Surface Chemistry and Catalysis, University of Ulm (Germany)

    2010-05-15

    Nanosize gold clusters were grown by thermal evaporation on ultrathin magnesia films on Mo(100) and investigated by femtosecond (fs)-laser photoemission spectroscopy. The surface work function in this system was found to increase with increasing nominal gold coverage. Methyl bromide (CH{sub 3}Br) molecules adsorb molecularly on the magnesia surface as well as on the gold clusters. At sub-monolayer coverage the CH{sub 3}Br molecules were, however, considerably stronger bound to the gold particles than to the magnesia surface as revealed by temperature programmed desorption spectroscopy. To investigate the photoreaction dynamics of the adsorbate molecules fs-laser pump-probe mass spectrometry was applied. In this new approach the methyl fragment appearance was monitored after photoexcitation of the adsorbed CH{sub 3}Br with fs time resolution. The transient methyl data revealed that the CH{sub 3}Br dissociation and subsequent methyl desorption proceeded in less than one picosecond. Most interestingly, a part of the transient signal could be unambiguously assigned to the dynamics of methyl desorption from the gold clusters. The appearance of this signal at about 270 fs after photoexcitation illustrates the massive distortion of the CH{sub 3}Br electronic level structure due to the strong interaction with the gold clusters compared to the bare magnesia surface. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  20. A high performance angle-resolving electron spectrometer

    CERN Document Server

    Rossnagel, K; Skibowski, M; Harm, S

    2001-01-01

    We report on our new versatile photoelectron spectrometer Angular Spectrometer for Photoelectrons with High Energy REsolution (ASPHERE) which is part of beamline W3.2 (photon energies from 5 to 40 eV) but also compatible with beamline BW3 (40-1500 eV) at the Hamburger Synchrotronstrahlungslabor (HASYLAB). ASPHERE is a 180 deg. spherical analyzer (r sub 0 =100 mm) with a four-element input lens and is mounted on a two-axes goniometer with computer-controlled stepper motors which enables sequential angle-scanned measurements. The input lens is equipped with an iris aperture so that the angular resolution can be continuously adjusted from 0.2 deg. to 5 deg. sign . The fringe field of the condenser has been corrected for by tilting the angle of the input lens against the base plane of the hemispheres resulting in an overall energy resolution of 10 meV. To improve the speed of data acquisition three standard channeltron detectors are installed in the image plane of the analyzer which will be replaced by a multidet...

  1. Angle-resolved heat capacity of heavy fermion superconductors.

    Science.gov (United States)

    Sakakibara, Toshiro; Kittaka, Shunichiro; Machida, Kazushige

    2016-09-01

    Owing to a strong Coulomb repulsion, heavy electron superconductors mostly have anisotropic gap functions which have nodes for certain directions in the momentum space. Since the nodal structure is closely related to the pairing mechanism, its experimental determination is of primary importance. This article discusses the experimental methods of the gap determination by bulk heat capacity measurements in a rotating magnetic field. The basic idea is based on the fact that the quasiparticle density of states in the vortex state of nodal superconductors is field and direction dependent. We present our recent experimental results of the field-orientation dependence of the heat capacity in heavy fermion superconductors CeTIn5 (T  =  Co, Ir), UPt3, CeCu2Si2, and UBe13 and discuss their gap structures. PMID:27482621

  2. Operating experience with a GaAs photoemission electron source

    Energy Technology Data Exchange (ETDEWEB)

    Tang, F.C.; Lubell, M.S.; Rubin, K.; Vasilakis, A.; Eminyan, M.; Slevin, J.

    1986-12-01

    We report on the development of several operating procedures that promise to make GaAs photoemission electron sources easier to construct, more reliable to operate, and more amenable to use in dynamic vacuum systems. We describe in particular a method for ''ohmically'' heating a <100> crystal of GaAs under vacuum to approximately 600 /sup 0/C. We also discuss our observations of the role of oxygen in the activation of the crystal surface, the use of continuous cesiation, and of the performance of the crystal under varying vacuum conditions.

  3. Operating experience with a GaAs photoemission electron source

    International Nuclear Information System (INIS)

    We report on the development of several operating procedures that promise to make GaAs photoemission electron sources easier to construct, more reliable to operate, and more amenable to use in dynamic vacuum systems. We describe in particular a method for ''ohmically'' heating a crystal of GaAs under vacuum to approximately 600 0C. We also discuss our observations of the role of oxygen in the activation of the crystal surface, the use of continuous cesiation, and of the performance of the crystal under varying vacuum conditions

  4. Measurements of relative photoemission time delays in noble gas atoms

    International Nuclear Information System (INIS)

    We determine relative photoemission time delays between valence electrons in different noble gas atoms (Ar, Ne and He) in an energy range between 31 and 37 eV. The atoms are ionized by an attosecond pulse train synchronized with an infrared laser field and the delays are measured using an interferometric technique. We compare our results with calculations using the random phase approximation with exchange and multi-configurational Hartree–Fock. We also investigate the influence of the different ionization angular channels. (paper)

  5. Polarized resonance photoemission for Nd2CuO4

    International Nuclear Information System (INIS)

    We present calculations of resonance photoemission spectra for Nd2CuO4. The calculations use a model Hamiltonian for which all parameters for the valence electrons are obtained from ab initio calculations or atomic data. Most features of the calculated sp agree well with experiment where comparison is possible. A substantial dependence on the polarization of the light is predicted for the occurrence of resonance behavior, and for the off-resonance intensity of the local singlet and one of the satellites

  6. Theory of photoemission from the Ni 2p core level

    International Nuclear Information System (INIS)

    Photoemission spectra are calculated for the Ni 2p core level within a small-cluster many-body scheme. The interplay between Coulomb, exchange, and spin-orbit interactions is discussed, as well as the role of extra-atomic screening. The spin-dependent transfer of spectral weight, both within and across the levels, is considered. Effects due to circular, linear, and unpolarized excitation are also examined. Local final-state configurations are reported, and a physical interpretation of the various spectral features is given. copyright 1997 The American Physical Society

  7. Photoemission study of TiO2/VO2 interfaces

    OpenAIRE

    Maekawa, K; Takizawa, M.; Wadati, H.; Yoshida, T.; Fujimori, A.; Kumigashira, H.; Oshima, M.; Muraoka, Y.; Nagao, Y.; Hiroi, Z.

    2006-01-01

    We have measured photoemission spectra of two kinds of TiO$_2$-capped VO$_2$ thin films, namely, that with rutile-type TiO$_2$ (r-TiO$_2$/VO$_2$) and that with amorphous TiO$_2$ (a-TiO$_2$/VO$_2$) capping layers. Below the Metal-insulator transition temperature of the VO$_2$ thin films, $\\sim 300$ K, metallic states were not observed for the interfaces with TiO$_2$, in contrast with the interfaces between the band insulator SrTiO$_3$ and the Mott insulator LaTiO$_3$ in spite of the fact that ...

  8. Photoemission Electronic States and Correlation Energies of Magnetite Based Compounds

    International Nuclear Information System (INIS)

    The photoemission spectra (XPS/UPS) for iron oxides, stoichiometric magnetite and for selected Ti and Zn doped magnetite single crystals are presented. From the Fe-3s split lines the exchange energies for FeO, Fe2O3 and magnetite based samples were estimated. It was shown that Ti and Zn ions are of 4+ and 2+ valency, respectively. The correlation energies were estimated from the Fe2p3/2 core-level spectra and from the L3- M4,5, M4,5 Auger lines. The type of insulating gap in these compounds was discussed. (author)

  9. Aberration Corrected Photoemission Electron Microscopy with Photonics Applications

    Science.gov (United States)

    Fitzgerald, Joseph P. S.

    Photoemission electron microscopy (PEEM) uses photoelectrons excited from material surfaces by incident photons to probe the interaction of light with surfaces with nanometer-scale resolution. The point resolution of PEEM images is strongly limited by spherical and chromatic aberration. Image aberrations primarily originate from the acceleration of photoelectrons and imaging with the objective lens and vary strongly in magnitude with specimen emission characteristics. Spherical and chromatic aberration can be corrected with an electrostatic mirror, and here I develop a triode mirror with hyperbolic geometry that has two adjacent, field-adjustable regions. I present analytic and numerical models of the mirror and show that the optical properties agree to within a few percent. When this mirror is coupled with an electron lens, it can provide a large dynamic range of correction and the coefficients of spherical and chromatic aberration can be varied independently. I report on efforts to realize a triode mirror corrector, including design, characterization, and alignment in our microscope at Portland State University (PSU). PEEM may be used to investigate optically active nanostructures, and we show that photoelectron emission yields can be identified with diffraction, surface plasmons, and dielectric waveguiding. Furthermore, we find that photoelectron micrographs of nanostructured metal and dielectric structures correlate with electromagnetic field calculations. We conclude that photoemission is highly spatially sensitive to the electromagnetic field intensity, allowing the direct visualization of the interaction of light with material surfaces at nanometer scales and over a wide range of incident light frequencies.

  10. Revisiting Photoemission and Inverse Photoemission Spectra of Nickel Oxide from First Principles: Implications for Solar Energy Conversion

    Energy Technology Data Exchange (ETDEWEB)

    Alidoust, Nima; Toroker, Maytal; Carter, Emily A.

    2014-07-17

    We use two different ab initio quantum mechanics methods, complete active space self-consistent field theory applied to electrostatically embedded clusters and periodic many-body G₀W₀ calculations, to reanalyze the states formed in nickel(II) oxide upon electron addition and ionization. In agreement with interpretations of earlier measurements, we find that the valence and conduction band edges consist of oxygen and nickel states, respectively. However, contrary to conventional wisdom, we find that the oxygen states of the valence band edge are localized whereas the nickel states at the conduction band edge are delocalized. We argue that these characteristics may lead to low electron-hole recombination and relatively efficient electron transport, which, coupled with band gap engineering, could produce higher solar energy conversion efficiency compared to that of other transition-metal oxides. Both methods find a photoemission/inverse-photoemission gap of 3.6-3.9 eV, in good agreement with the experimental range, lending credence to our analysis of the electronic structure of NiO.

  11. Electronic structure and excited state dynamics in optically excited PTCDA films investigated with two-photon photoemission

    Science.gov (United States)

    Marks, M.; Sachs, S.; Schwalb, C. H.; Schöll, A.; Höfer, U.

    2013-09-01

    We present an investigation of the electronic structure and excited state dynamics of optically excited 3,4,9,10-perylene-tetracarboxylic acid dianhydride (PTCDA) thin films adsorbed on Ag(111) using two-photon photoemission spectroscopy (2PPE). 2PPE allows us to study both occupied and unoccupied electronic states, and we are able to identify signals from the highest occupied and the two lowest unoccupied electronic states of the PTCDA thin film in the 2PPE spectra. The energies for occupied states are identical to values from ultraviolet photoelectron spectroscopy. Compared to results from inverse photoelectron spectroscopy (IPES), the 2PPE signals from the two lowest unoccupied electronic states, LUMO and LUMO+1, are found at 0.8 eV and 1.0 eV lower energies, respectively. We attribute this deviation to the different final states probed in 2PPE and IPES and the attractive interaction of the photoexcited electron and the remaining hole. Furthermore, we present a time-resolved investigation of the excited state dynamics of the PTCDA film in the femtosecond time regime. We observe a significantly shorter inelastic excited state lifetime compared to findings from time-resolved photoluminescence spectroscopy of PTCDA single crystals which could originate from excitation quenching by the metal substrate.

  12. Ultrathin Pb film growth on Cu(111) studied by photoemission

    Institute of Scientific and Technical Information of China (English)

    M.C.Xu; H.J.Qian; F.Q.Liu; K.Ibrahim; W.Y.Lai; S.C.Wu

    2001-01-01

    The valence bands and the Pb 5d,Cu 3p core levels of Pb films evaporated on Cu(111) were measured by synchrotron radiation photoemission and characterized by low-energy electron diffraction(LEED) and Auger electron spectroscopy(AES).The variation of the surafce state at the center of the surface Brillouin zone (SBZ) of Cu(111) with Pb coverage shows that the submonolayer Pb grows on Cu(111) at room temperature(RT) as two-dimensional(2D) islands.With the Pb coverage increasing,the Pb 5d5/2 core level shifts to higher binding energy monotonically.While the Cu 3p3/2 core level is shifted toward higher binding energy by about 120 meV due to the deposition of 1.0ML Pb.At low Ph coverage,subsequent annealing at 200℃ gives rise to Pb-Cu surface alloy formation in the first layer of Cu(111).The Pb 5d core level is shifted toward Fermi level by 20-30 meV due to the surface alloying.An assumption about electron charge transfer from Cu to Pb was adopted to interpret the observed cored level shifts.2001 Published by Elsevier Science Ltd.

  13. Halide-Substituted Electronic Properties of Organometal Halide Perovskite Films: Direct and Inverse Photoemission Studies.

    Science.gov (United States)

    Li, Chi; Wei, Jian; Sato, Mikio; Koike, Harunobu; Xie, Zhong-Zhi; Li, Yan-Qing; Kanai, Kaname; Kera, Satoshi; Ueno, Nobuo; Tang, Jian-Xin

    2016-05-11

    Solution-processed perovskite solar cells are attracting increasing interest due to their potential in next-generation hybrid photovoltaic devices. Despite the morphological control over the perovskite films, quantitative information on electronic structures and interface energetics is of paramount importance to the optimal photovoltaic performance. Here, direct and inverse photoemission spectroscopies are used to determine the electronic structures and chemical compositions of various methylammonium lead halide perovskite films (MAPbX3, X = Cl, Br, and I), revealing the strong influence of halide substitution on the electronic properties of perovskite films. Precise control over halide compositions in MAPbX3 films causes the manipulation of the electronic properties, with a qualitatively blue shift along the I → Br → Cl series and showing the increase in ionization potentials from 5.96 to 7.04 eV and the change of transport band gaps in the range from 1.70 to 3.09 eV. The resulting light absorption of MAPbX3 films can cover the entire visible region from 420 to 800 nm. The results presented here provide a quantitative guide for the analysis of perovskite-based solar cell performance and the selection of optimal carrier-extraction materials for photogenerated electrons and holes. PMID:27101940

  14. A photoemission study of the interaction of Ga with CeO2(1 1 1) thin films

    International Nuclear Information System (INIS)

    The interaction of gallium with CeO2(1 1 1) layers was studied using standard and resonant photoelectron spectroscopy, by means of both a laboratory X-ray source and tunable synchrotron light. Firstly a 1.5-nm thick CeO2 film was grown on a Cu(1 1 1) substrate. Secondly Ga was deposited in six steps up to a thickness of 0.35 nm, at room temperature. The interaction of gallium with the oxide layer induced partial CeO2 reduction, and gallium oxidation. The photoemission data suggest that a mixed Ga-Ce-O oxide was established similarly to the Sn-Ce-O case for Sn deposited on cerium oxide layers. As a consequence, gallium-induced weakening of Ce-O bonds provides a higher number of active sites on the surface that play a major role in its catalytic behaviour

  15. Electronic states of titanyl phthalocyanine films on alkanethiolate self-assembled monolayers probed by two-photon photoemission

    Energy Technology Data Exchange (ETDEWEB)

    Ogura, Munehisa [Department of Chemistry, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522 (Japan); Shibuta, Masahiro; Eguchi, Toyoaki [Department of Chemistry, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522 (Japan); JST-ERATO, Nakajima Designer Nanocluster Assembly Project, 3-2-1 Sakado, Takatsu-ku, Kawasaki 213-0012 (Japan); Nakajima, Atsushi, E-mail: nakajima@chem.keio.ac.jp [Department of Chemistry, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522 (Japan); JST-ERATO, Nakajima Designer Nanocluster Assembly Project, 3-2-1 Sakado, Takatsu-ku, Kawasaki 213-0012 (Japan)

    2014-08-15

    We studied both occupied and unoccupied states of titanyl phthalocyanine (TiOPc) films formed on an octanethiolate self-assembled monolayer (SAM) on an Au(1 1 1) surface fabricated in a wet chemical process using two-photon photoemission (2PPE) spectroscopy. A 1.90-nm-thick layer of TiOPc formed an unoccupied state at 2.9 eV above the Fermi level. This state was resonantly enhanced at 4.3–4.4 eV photon energy, suggesting that electrons were excited from the highest occupied molecular orbital of TiOPc. The 2PPE measurements of photon energy dependence and light polarization selectivity revealed that the unoccupied state originates from a charge transfer exciton not observed in organic thin films deposited on bare metallic substrates. The formation of a charge transfer exciton implies that the SAM strongly insulates the molecular monolayer.

  16. Photoemission study of the formation of intimate In-InGaAs(100) contacts at room and cryogenic temperatures

    Science.gov (United States)

    Cammack, D. S.; McGregor, S. M.; McChesney, J. J.; Dharmadasa, I. M.; Clark, S. A.; Dunstan, P. R.; Burgess, S. R.; Wilks, S. P.; Elliott, M.

    1997-06-01

    Previous current-voltage studies of In contacts deposited on atomically clean (intimate) In53Ga47As(100) have indicated the potential to "select" barrier heights in this materials system by cryogenic processing. Soft x-ray photoemission spectroscopy was used to determine the electronic and chemical nature of these interfaces, as a function of formation temperature. Metallization at room temperature results in a predominantly three-dimensional mode of growth, accompanied by the outdiffusion of As. Low temperature metallization appears to reduce clustering and inhibit As outdiffusion. It is proposed that the distribution of surface states and the fermi level pinning position are altered by the changes that occur in the geometry and bonding of the interface at low temperature.

  17. Photoemission study of the uranium ternary compounds U3T3X4 (T = Ni, Cu; X = Sn, Sb)

    International Nuclear Information System (INIS)

    Valence-band structures of U3Ni3Sn4, U3Ni3Sb4, U3Cu3Sn4 and U3Cu3Sb4 ranging from a semiconductor to a heavy fermion system, are studied using photemission spectroscopy with synchrotron radiation. We found that the Ni 3d band in U3Ni3Sn4 is not fully filled up, the Cu 3d states in the ferromagnet U3Cu3Sb4 are strongly hybridized with the Sb 5p states, but the 3d states localized in the heavy-fermion compound U3Cu3Sn4. However, the U 5f emission spectra obtained by the resonant photoemission technique are nearly identical for all compounds and have an asymmetric peak of 1.6 eV in width. (author)

  18. Weight of zero-loss electrons and sum rules in extrinsic processes that can influence photoemission spectra

    Science.gov (United States)

    Schulte, K.; James, M. A.; Steeneken, P. G.; Sawatzky, G. A.; Suryanarayanan, R.; Dhalenne, G.; Revcolevschi, A.

    2001-04-01

    It was argued in a recent paper by Joynt [Science 284, 777 (1999)] that in the case of poorly conducting solids a photoemission spectrum close to the Fermi energy may be strongly influenced by extrinsic loss processes similar to those occurring in high-resolution electron-energy-loss spectroscopy, thereby obscuring information concerning the density of states or one-electron Green's function sought for. In this paper we present a number of arguments, both theoretical and experimental, that demonstrate that energy-loss processes occurring once the electron is outside the solid, contribute only weakly to the spectrum, and can in most cases be either neglected or treated as a weak structureless background.

  19. Weight of zero-loss electrons and sum rules in extrinsic processes that can influence photoemission spectra

    International Nuclear Information System (INIS)

    It was argued in a recent paper by Joynt [Science 284, 777 (1999)] that in the case of poorly conducting solids a photoemission spectrum close to the Fermi energy may be strongly influenced by extrinsic loss processes similar to those occurring in high-resolution electron-energy-loss spectroscopy, thereby obscuring information concerning the density of states or one-electron Green's function sought for. In this paper we present a number of arguments, both theoretical and experimental, that demonstrate that energy-loss processes occurring once the electron is outside the solid, contribute only weakly to the spectrum, and can in most cases be either neglected or treated as a weak structureless background

  20. Characterization of induced nanoplasmonic fields in time-resolved photoemission from gold nanospheres: a classical trajectory approach

    Science.gov (United States)

    Saydanzad, Erfan; Thumm, Uwe

    2016-05-01

    Attosecond time-resolved (XUV-pump, IR-probe) spectroscopy has been shown to be a powerful method for investigating the electron dynamics in atoms, and this technique is now being transferred to the investigation of electronic excitations, electron propagation, and collective electronic (plasmonic) effects in solids. Based on classical trajectory calculations, we simulated (i) the final photoelectron velocity distribution in order to provide observable velocity-map images for gold nanospheres of 10 and 100 nm diameter and (ii) streaked photoemission spectra. By analyzing our numerical results, we illustrate how spatio-temporal information about the sub-IR-cycle plasmonic and electronic dynamics is encoded in velocity-map images and streaked photoelectron spectra. Supported by the NE/KS NSF-EPSCOR program.

  1. Electron spectroscopy on high-temperature superconductors and related compounds

    International Nuclear Information System (INIS)

    In the last two classes of materials have been discovered which distinguish themselves due to a transition into the superconducting state at relatively high temperatures. These are the cuprate superconductors and the alkali metal doped fullerenes. In this work the electronic structure of representatives of these materials, undoped and Ca-doped YBa2Cu4O8 and A3C60 (A=K, Rb), has been investigated using electron energy-loss spectroscopy and photoemission spectroscopy. (orig.)

  2. High temperature thermal stability of the HfO2/Ge (100) interface as a function of surface preparation studied by synchrotron radiation core level photoemission

    International Nuclear Information System (INIS)

    High resolution soft x-ray photoemission spectroscopy (SXPS) have been used to study the high temperature thermal stability of ultra-thin atomic layer deposited (ALD) HfO2 layers (∼1 nm) on sulphur passivated and hydrofluoric acid (HF) treated germanium surfaces. The interfacial oxides which are detected for both surface preparations following HfO2 deposition can be effectively removed by annealing upto 700 °C without any evidence of chemical interaction at the HfO2/Ge interface. The estimated valence and conduction band offsets for the HfO2/Ge abrupt interface indicated that effective barriers exist to inhibit carrier injection.

  3. Electronic structure of MoSe2, MoS2, and WSe2. I. Band-structure calculations and photoelectron spectroscopy

    OpenAIRE

    Coehoorn, R.; Haas, C.; Dijkstra, J.; Flipse, C.J.F.; de Groot, R. A.; Wold, A.

    1987-01-01

    The band structures of the semiconducting layered compounds MoSe2, MoS2, and WSe2 have been calculated self-consistently with the augmented-spherical-wave method. Angle-resolved photoelectron spectroscopy of MoSe2 using He I, He II, and Ne I radiation, and photon-energy-dependent normal-emission photoelectron spectroscopy using synchrotron radiation, show that the calculational results give a good description of the valence-band structure. At about 1 eV below the top of the valence band a dis...

  4. Microlens Array Laser Transverse Shaping Technique for Photoemission Electron Source

    CERN Document Server

    Halavanau, A; Qiang, G; Gai, W; Power, J; Piot, P; Wisniewski, E; Edstrom, D; Ruan, J; Santucci, J

    2016-01-01

    A common issue encountered in photoemission electron sources used in electron accelerators is distortion of the laser spot due to non ideal conditions at all stages of the amplification. Such a laser spot at the cathode may produce asymmetric charged beams that will result in degradation of the beam quality due to space charge at early stages of acceleration and fail to optimally utilize the cathode surface. In this note we study the possibility of using microlens arrays to dramatically improve the transverse uniformity of the drive laser pulse on UV photocathodes at both Fermilab Accelerator Science \\& Technology (FAST) facility and Argonne Wakefield Accelerator (AWA). In particular, we discuss the experimental characterization of the homogeneity and periodic patterned formation at the photocathode. Finally, we compare the experimental results with the paraxial analysis, ray tracing and wavefront propagation software.

  5. Photoemission from Coated Surfaces A Comparison of Theory to Experiment

    CERN Document Server

    Jensen, K

    2005-01-01

    Photocathodes for FELs and accelerators will benefit from rugged and self-rejuvenating photocathodes with high QE at the longest possible wavelength. The needs of a high power FEL are not met at present by existing photocathode-drive laser combinations: requirements generally necessitate barrier-lowering coatings which are degraded by operation. We seek to develop a controlled porosity dispenser cathode, and shall report on our coordinated experimental and theoretical studies. Our models account for field, thermal, and surface effects of cesium monolayers on photoemission, and compare well with concurrent experiments examining the QE, patchiness, and evolution of the coatings. Field enhancement, thermal variation of specific heat and electron relaxation rates and their relation to high laser intensity and/or short pulse-to-pulse separation, variations in work function effects due to coating non-uniformity, and the dependence on the wavelength of the incident light are included. The status of methods by which ...

  6. Electric field stimulation setup for photoemission electron microscopes

    International Nuclear Information System (INIS)

    Manipulating magnetisation by the application of an electric field in magnetoelectric multiferroics represents a timely issue due to the potential applications in low power electronics and the novel physics involved. Thanks to its element sensitivity and high spatial resolution, X-ray photoemission electron microscopy is a uniquely suited technique for the investigation of magnetoelectric coupling in multiferroic materials. In this work, we present a setup that allows for the application of in situ electric and magnetic fields while the sample is analysed in the microscope. As an example of the performances of the setup, we present measurements on Ni/Pb(Mg0.66Nb0.33)O3-PbTiO3 and La0.7Sr0.3MnO3/PMN-PT artificial multiferroic nanostructures

  7. Electric field stimulation setup for photoemission electron microscopes

    Energy Technology Data Exchange (ETDEWEB)

    Buzzi, M.; Vaz, C. A. F.; Raabe, J.; Nolting, F., E-mail: frithjof.nolting@psi.ch [Paul Scherrer Institut, 5232 Villigen PSI (Switzerland)

    2015-08-15

    Manipulating magnetisation by the application of an electric field in magnetoelectric multiferroics represents a timely issue due to the potential applications in low power electronics and the novel physics involved. Thanks to its element sensitivity and high spatial resolution, X-ray photoemission electron microscopy is a uniquely suited technique for the investigation of magnetoelectric coupling in multiferroic materials. In this work, we present a setup that allows for the application of in situ electric and magnetic fields while the sample is analysed in the microscope. As an example of the performances of the setup, we present measurements on Ni/Pb(Mg{sub 0.66}Nb{sub 0.33})O{sub 3}-PbTiO{sub 3} and La{sub 0.7}Sr{sub 0.3}MnO{sub 3}/PMN-PT artificial multiferroic nanostructures.

  8. Electric field stimulation setup for photoemission electron microscopes

    Science.gov (United States)

    Buzzi, M.; Vaz, C. A. F.; Raabe, J.; Nolting, F.

    2015-08-01

    Manipulating magnetisation by the application of an electric field in magnetoelectric multiferroics represents a timely issue due to the potential applications in low power electronics and the novel physics involved. Thanks to its element sensitivity and high spatial resolution, X-ray photoemission electron microscopy is a uniquely suited technique for the investigation of magnetoelectric coupling in multiferroic materials. In this work, we present a setup that allows for the application of in situ electric and magnetic fields while the sample is analysed in the microscope. As an example of the performances of the setup, we present measurements on Ni/Pb(Mg0.66Nb0.33)O3-PbTiO3 and La0.7Sr0.3MnO3/PMN-PT artificial multiferroic nanostructures.

  9. Measurement and analysis of thermal photoemission from a dispenser cathode

    Science.gov (United States)

    Jensen, Kevin L.; Feldman, Donald W.; Virgo, Matt; O'Shea, Patrick G.

    2003-08-01

    Photocathodes for free electron lasers (FELs) are required to produce nano-Coulomb pulses in picosecond time scales with demonstrable reliability, lifetime, and efficiency. Dispenser cathodes, traditionally a rugged and long-lived thermionic source, are under investigation to determine their utility as a photocathode and have shown promise. The present study describes theoretical models under development to analyze experimental data from dispenser cathodes and to create predictive time-dependent models to predict their performance as an FEL source. Here, a steady-state model of a dispenser cathode with partial coverage of a low work function coating and surface nonuniformity is developed. Quantitative agreement is found for experimental data, especially with regard to temperature, field, laser intensity, and quantum efficiency versus laser wavelength dependence. In particular, for long wavelength incident lasers of sufficient intensity, the majority of the absorbed energy heats the electron gas and background lattice, and photoemission from the heated electron distribution constitutes the emitted current.

  10. Ultrafast Multiphoton Pump-probe Photoemission Excitation Pathways in Rutile TiO2(110)

    Energy Technology Data Exchange (ETDEWEB)

    Argondizzo, Adam; Cui, Xuefeng; Wang, Cong; Sun, Huijuan; Shang, Honghui; Zhao, Jin; Petek, Hrvoje

    2015-04-27

    We investigate the spectroscopy and photoinduced electron dynamics within the conduction band of reduced rutile TiO2(110) surface by multiphoton photoemission (mPP) spectroscopy with wavelength tunable ultrafast (!20 fs) laser pulse excitation. Tuning the mPP photon excitation energy between 2.9 and 4.6 eV reveals a nearly degenerate pair of new unoccupied states located at 2.73 ± 0.05 and 2.85 ± 0.05 eV above the Fermi level, which can be analyzed through the polarization and sample azimuthal orientation dependence of the mPP spectra. Based on the calculated electronic structure and optical transition moments, as well as related spectroscopic evidence, we assign these resonances to transitions between Ti 3d bands of nominally t2g and eg symmetry, which are split by crystal field. The initial states for the optical transition are the reduced Ti3+ states of t2g symmetry populated by formation oxygen vacancy defects, which exist within the band gap of TiO2. Furthermore,we studied the electron dynamics within the conduction band of TiO2 by three-dimensional time-resolved pump-probe interferometric mPP measurements. The spectroscopic and time-resolved studies reveal competition between 2PP and 3PP processes where the t2g-eg transitions in the 2PP process saturate, and are overtaken by the 3PP process initiated by the band-gap excitation from the valence band of TiO2.

  11. Photoelectron spectroscopy bulk and surface electronic structures

    CERN Document Server

    Suga, Shigemasa

    2014-01-01

    Photoelectron spectroscopy is now becoming more and more required to investigate electronic structures of various solid materials in the bulk, on surfaces as well as at buried interfaces. The energy resolution was much improved in the last decade down to 1 meV in the low photon energy region. Now this technique is available from a few eV up to 10 keV by use of lasers, electron cyclotron resonance lamps in addition to synchrotron radiation and X-ray tubes. High resolution angle resolved photoelectron spectroscopy (ARPES) is now widely applied to band mapping of materials. It attracts a wide attention from both fundamental science and material engineering. Studies of the dynamics of excited states are feasible by time of flight spectroscopy with fully utilizing the pulse structures of synchrotron radiation as well as lasers including the free electron lasers (FEL). Spin resolved studies also made dramatic progress by using higher efficiency spin detectors and two dimensional spin detectors. Polarization depend...

  12. Photoemission study of Ca-intercalated graphite superconductor CaC6

    International Nuclear Information System (INIS)

    In this work, we have performed resonant photoemission studies of Ca-intercalated graphite superconductor CaC6. Using photon energy of the Ca 2p-3d threshold, the photoemission intensity of the peak at Fermi energy (EF) is resonantly enhanced. This result provides spectroscopic evidence for the existence of Ca 3d states at EF, and strongly supports that Ca 3d state plays a crucial role for the superconductivity of this material with relatively high Tc.

  13. Final-state interference effects in valence band photoemission of (C59N)2

    OpenAIRE

    Hunt, Michael R.C.; Pichler, Thomas; Šiller, Lidija; Brühwiler, Paul A.; Golden, Mark S.; Tagmatarchis, Nikos; Prassides, Kosmas; Rudolf, Petra

    2002-01-01

    Oscillatory behavior of photoemission intensity with incident photon energy has been observed for several fullerenes and fullerene derivatives. However, until now it has been unclear if these effects arise from interference associated with the spatial distribution of the initial state within the molecule or are due to scattering of the outgoing photoelectron. In order to resolve this issue we performed synchrotron radiation excited valence band photoemission measurements on multilayer (C59N)2...

  14. Fully relativistic surface green function and its application to surface spectroscopies

    International Nuclear Information System (INIS)

    A fully relativistic layer-KKR formalism was developed and implemented for calculating the single-particle Green function in atomic layers parallel to crystalline surfaces magnetic and non magnetic materials: The method was applied to the calculation surface spectroscopies, such as low energy electron diffraction (LEED), angle-resolve ultraviolet photo emission spectroscopy (UPS), and photoelectron scattering. Numeric tests were performed for non magnetic actinide surfaces and magnetic Fe surface Theoretical angle-resolved UPS spectra are presented for uranium monolayers on Pt(111) and for f.c.c. u(lll) surfaces. We find that u island formation can take place if a peak in the UPS spectra appears just before the Fermi energy immediately as u is deposited on P and we suggest an experimental procedure for testing this prediction. An intensity map photo excited electrons from the 2p3/2 core states of Fe(110) surface is also show Sizable magnetic anisotropy is found due to the interference between exchange and spin-orbit interaction, which is suitable for studying a possible surface-induced magnetism actinide adlayers

  15. Core-resonant double photoemission from palladium films

    Science.gov (United States)

    Kostanovskiy, I.; Schumann, F. O.; Aliaev, Y.; Wei, Z.; Kirschner, J.

    2016-01-01

    We studied the core-resonant double photoemission process from palladium films with linearly polarized synchrotron radiation. We excited either the 3d or 4p core level and focused on the Auger transitions which leave two holes in the valence band. We find that the two-dimensional energy distributions are markedly different for the 3d and 4p decay. The 3d decay can be understood by a sequential emission of the two electrons while the 4p decay proceeds in a single step. Despite the large differences in the two-dimensional energy spectra we find the shape of the energy sum spectra rather similar. For the description of the 4p decay we propose a model which uses available single electron spectra, but suggest an alternative interpretation of these data. With this we are able to explain the range over which the available energy is shared. Key assumptions of the model are verified by our experiments on the 3d decay.

  16. Photoemission electron microscopy using extreme ultraviolet attosecond pulse trains

    International Nuclear Information System (INIS)

    We report the first experiments carried out on a new imaging setup, which combines the high spatial resolution of a photoemission electron microscope (PEEM) with the temporal resolution of extreme ultraviolet (XUV) attosecond pulse trains. The very short pulses were provided by high-harmonic generation and used to illuminate lithographic structures and Au nanoparticles, which, in turn, were imaged with a PEEM resolving features below 300 nm. We argue that the spatial resolution is limited by the lack of electron energy filtering in this particular demonstration experiment. Problems with extensive space charge effects, which can occur due to the low probe pulse repetition rate and extremely short duration, are solved by reducing peak intensity while maintaining a sufficient average intensity to allow imaging. Finally, a powerful femtosecond infrared (IR) beam was combined with the XUV beam in a pump-probe setup where delays could be varied from subfemtoseconds to picoseconds. The IR pump beam could induce multiphoton electron emission in resonant features on the surface. The interaction between the electrons emitted by the pump and probe pulses could be observed.

  17. Investigation of slider surfaces after wear using photoemission electron microscopy

    International Nuclear Information System (INIS)

    The tribo-chemical interactions between the slider and the hard disk surface strongly influence the performance properties of a disk drive. To study these interactions, uncoated and carbon coated sliders were subjected to various wear tests using different disks. After the wear, the test slider surfaces were studied by photoemission electron microscopy (PEEM) using tunable x rays produced by a synchrotron. Using PEEM, one can identify the elemental and chemical state of the surfaces with a high spatial resolution. It was found that wear reduces the thickness of the carbon coating in some local areas of the slider surface. In particular, the coating was removed on elevated areas and in scratches. Scratches were found on the rails of the carbon coated and uncoated sliders after wear that showed the accumulation of a degraded (oxidized) lubricant which was transferred to the slider from the disk. It was also possible to analyze the chemical composition of the debris found on the slider surface. In the present case, the debris had the same chemical composition as the carbon coating of the slider. copyright 1999 American Vacuum Society

  18. Einstein's photoemission emission from heavily-doped quantized structures

    CERN Document Server

    Ghatak, Kamakhya Prasad

    2015-01-01

    This monograph solely investigates the Einstein's Photoemission(EP) from Heavily Doped(HD) Quantized Structures on the basis of newly formulated electron dispersion laws. The materials considered are quantized structures of HD non-linear optical, III-V, II-VI, Ge, Te, Platinum Antimonide, stressed materials, GaP, Gallium Antimonide, II-V, Bismuth Telluride together with various types of HD superlattices and their Quantized counterparts respectively. The EP in HD opto-electronic materials and their nanostructures is studied in the presence of strong light waves and intense electric fields  that control the studies of such quantum effect devices. The suggestions for the experimental determinations of different important physical quantities in HD 2D and 3D materials  and the importance of measurement of band gap in HD optoelectronic materials under intense built-in electric field in nano devices and strong external photo excitation (for measuring   physical properties in the presence of intense light waves w...

  19. Photoemission experiments of a large area scandate dispenser cathode

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Huang, E-mail: bamboobbu@hotmail.co [Institute of Fluid Physics, CAEP, P.O. Box 919-106, Mianyang 621900 (China); Liu Xingguang; Chen Yi; Chen Debiao; Jiang Xiaoguo; Yang Anmin; Xia Liansheng; Zhang Kaizhi; Shi Jinshui; Zhang Linwen [Institute of Fluid Physics, CAEP, P.O. Box 919-106, Mianyang 621900 (China)

    2010-09-21

    A 100-mm-diameter scandate dispenser cathode was tested as a photocathode with a 10 ns Nd:YAG laser (266 nm) on an injector test stand for linear induction accelerators. This thermionic dispenser cathode worked at temperatures ranging from room temperature to 930 {sup o}C (below or near the thermionic emission threshold) while the vacuum was better than 4x10{sup -7} Torr. The laser pulse was synchronized with a 120 ns diode voltage pulse stably and they were in single pulse mode. Emission currents were measured by a Faraday cup. The maximum peak current collected at the anode was about 100 A. The maximum quantum efficiency measured at low laser power was 2.4x10{sup -4}. Poisoning effect due to residual gas was obvious and uninterrupted heating was needed to keep cathode's emission capability. The cathode was exposed to air one time between experiments and recovered after being reconditioned. Photoemission uniformity of the cathode was also explored by changing the laser spot's position.

  20. Photoemission electron microscopy using extreme ultraviolet attosecond pulse trains

    Energy Technology Data Exchange (ETDEWEB)

    Mikkelsen, A.; Schwenke, J.; Fordell, T.; Luo, G.; Kluender, K.; Hilner, E.; Anttu, N.; Lundgren, E.; Mauritsson, J.; Andersen, J. N.; Xu, H. Q.; L' Huillier, A. [Department of Physics, Lund University, Box 118, 22100 Lund (Sweden); Zakharov, A. A. [MAX-lab, Lund University, Box 118, 22100 Lund (Sweden)

    2009-12-15

    We report the first experiments carried out on a new imaging setup, which combines the high spatial resolution of a photoemission electron microscope (PEEM) with the temporal resolution of extreme ultraviolet (XUV) attosecond pulse trains. The very short pulses were provided by high-harmonic generation and used to illuminate lithographic structures and Au nanoparticles, which, in turn, were imaged with a PEEM resolving features below 300 nm. We argue that the spatial resolution is limited by the lack of electron energy filtering in this particular demonstration experiment. Problems with extensive space charge effects, which can occur due to the low probe pulse repetition rate and extremely short duration, are solved by reducing peak intensity while maintaining a sufficient average intensity to allow imaging. Finally, a powerful femtosecond infrared (IR) beam was combined with the XUV beam in a pump-probe setup where delays could be varied from subfemtoseconds to picoseconds. The IR pump beam could induce multiphoton electron emission in resonant features on the surface. The interaction between the electrons emitted by the pump and probe pulses could be observed.