Browsing by Author "Riley, JD"

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    Comparison between calculated and measured photoelectron diffraction patterns for Cu (001)
    (Australian Institute of Physics, 2008-01-30) Cousland, GP; Smith, AE; Riley, JD; Homolya, S; Stampfl, APJ; King-Lacroix, J
    We compare the results of X-ray photoelectron diffraction experiments with simulations obtained using the EDAC multiple scattering computer simulation package. Comparisons are presented for Cu (111) at photon energies of ~ 600eV. With an intention to study Cu3Mn, our initial work considers experimental and simulated data for Cu (001) at photon energies from 100 to 380eV.
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    The electronic structure of S-layer proteins from Lactobacillus brevis
    (IEEE, 2008-07-28) Graham, SM; Asquith, NL; Wilde, KL; Short, KT; Holden, PJ; Stampfl, APJ; Holmes, AJ; Ruys, AJ; Stojanov, P; Riley, JD; Fang, LJ; Yang, YW; Hwu, YK
    The valence electronic structure of the S-layer of Lactobacillus brevis is determined using synchrotron-based photoelectron spectroscopy and soft X-ray absorption spectroscopy. Spectra are compared to experimental work on amino-acids and S-layers of Bacillus sphaericus. While it is indeed possible to identify energy levels with those of natural amino-acids, distinct energy shifts are indeed observed which cannot be reconciled using such simple comparisons. Furthermore a strong nitrogen signal observed in both the occupied and unoccupied energy levels suggests that the Lactobacillus brevis protein is amine-terminated. A discussion of the surface of this protein is given. © 2008 IEEE
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    The fermi surface of Cu3Mn {100} and spinglass magnetism
    (Australian Institute of Physics, 2009-02-05) Stampfl, APJ; Loh, NA; Hsieh, KY; Yu, DH; Brigden, P; Stojanov, P; Riley, JD; Stamps, RL; Yuh, JY; Pi, TW; Chang, J; Hwu, YK
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    Low energy photoelectron diffraction analysis at high angular resolution of Cu and Mn/Cu surfaces
    (American Institute of Physics, 2009-11-01) Cousland, GP; Smith, AE; Riley, JD; Stampfl, APJ
    X-ray photoelectron diffraction simulations using a real-space approach are Shown to accurately produce the extraordinarily detailed photoelectron diffraction pattern from Cu{111} at an electron kinetic energy of 523.5 eV. These same simulations show that most sensitivity is obtained when using low energy electrons at high angular resolution Structural differences are observed to be greatest around a kinetic energy of similar to 100 eV and many of the features observed in the photoelectron diffraction patterns may be directly related to phenomena observed in low energy electron diffraction patterns from the same Surface. For Cu{100}. simulations of buckled surfaces with a Mn overlayer predict that low energy photoelectron diffraction can easily discriminate chemical and structural differences. Even the effects of the relaxed Surface of Cu{100} is indeed observable along azimuthal scans around a kinetic energy of 100 eV Our results show that low energy photoelectron diffraction is extremely sensitive to changes in Surface Structure If high resolution patterns are acquired. © 2009, American Institute of Physics.
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    Towards ARPES at the Australian Synchrotron: 4th generation toroidal angle resolving electron energy spectrometer
    (Australian Institute of Physics, 2017-02-02) Tadich, A; Huwald, E; Riley, JD
    Angle Resolved Photoelectron Spectroscopy (ARPES) is the “complete” photoemission experiment. It simultaneously measures a photoelectron’s kinetic energy, emission angle and sometimes spin, relative to the crystallographic axes, constructing a direct image of the electronic bandstructure. This makes ARPES the most powerful contemporary technique for determining the electronic structure of novel materials. ARPES has been instrumental in the discovery and understanding of new electronic phases of matter. For example, important aspects of the electronic structure of high-Tc superconductors, such as the pseudogap were discovered using ARPES, as was the experimental discovery of three dimensional topological insulators Bi1-xSbx and Bi2(Se,Te)3. Over the years, a dramatic improvement in the energy and momentum resolution possible with ARPES has occurred as a result of advances in photoelectron analysers and 2D detectors, allowing a range of new physics to be probed. Despite the popularity of ARPES overseas, within Australia it has until now remained as a niche technique due to a small (albeit dedicated) user community. However, the continually growing local interest in studying novel materials with exotic electronic properties has led to the demand for our own synchrotron – based ARPES instrument. Here, an overview of a forthcoming ARPES instrument, an advanced 4th generation “toroidal” electron spectrometer, at the Australian Synchrotron will be given. Constructed at La Trobe University, the instrument will arrive at the soft x-ray beamline in early 2017, and will be located in an offline staging area between its times on the beamline. An advanced helium discharge lamp will allow for offline work to be carried out. In contrast to the previous 3rd generation instrument installed at BESSY2, the 4th generation Toroidal Analyser is equipped with a liquid helium cryostat and radiation shielding to allow for ARPES measurements to be conducted with the sample at cryogenic temperatures. An overview of the system’s principles of operation, and sample preparation environment will be given.