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LOW-DIMENSIONAL ELECTRONS AT SILICON SURFACES J. N. Crain 1 , J. L. McChesney 1 , Fan Zheng 1 , M. C. Gallagher 2 , P. C. Snijders 3 , M. Bissen 4 , C. Gundelach 4 , S. C. Erwin 5 , and F. J. Himpsel 1 1 Dept. of Physics, UW-Madison, 1150 University Ave., Madison, Wisconsin 53706 2 Dept. of Physics, Lakehead University, Thunder Bay, ON P7B-5E1 Canada 3 Dept. of NanoScience, Delft University of Technology, Lorentzweg, 2628 CJ Delft, The Netherlands 4 Synchrotron Radiation Center, UW-Madison, 3731 Schneider Dr., Stoughton, WI 53589 5 Center for Computational Materials Science, Naval Research Laboratory, Washington, DC 20375 Electrons become increasingly correlated as the dimensionality is reduced from 3D to 2D and 1D. Already in 2D one observes correlations between electrons and vortices in the quantum Hall effect leading to fractional charge and statistics. Predictions for a 1D metal anticipate a complete breakdown of the single electron concept and the separation of spin and charge into two collective excitations, spinons and holons. It has become possible to systematically engineer two- and one-dimensional surface structures of metals on silicon that are metallic [1,2]. Electrons near the Fermi level are decoupled from the substrate because there energy lies in the band gap. The metal atoms, however, are rigidly tied to the silicon lattice in substitutional positions according to x-ray diffraction [3] and first principles band calculations. That makes a Peierls transition to an insulator unfavorable and creates an opportunity for observing exotic states predicted for onedimensional metallic electrons. Examples of two-dimensional metals are the 3x3 and 21x21 reconstructions of Ag and Au on Si(111), which exhibit an intricate pattern of Fermi surfaces induced by the superlattice [2]. Information about the Fourier components of the superlattice potential is obtained from avoided band crossings. One-dimensional atomic chains are created by growing Au and a variety of other metals at vicinal Si(111) surfaces in the 1/5 monolayer coverage regime [1]. This appears to be a rather universal phenomenon, and even the flat Si(111) surface breaks its three-fold symmetry to accommodate chain structures. This wide-open territory of 1D structures is explored in real and reciprocal space by scanning tunneling microscopy (STM) and angleresolved photoemission. The resulting energy bands and Fermi surfaces can be tuned between 2D and 1D by increasing the chain spacing, with the intra-chain / inter-chain coupling ratio varying from 10:1 to >70:1. Unexpected metallic bands are found, such as a pair of nearly degenerate, half-filled bands, a quarter-filled band, and a fractional electron count of 8/3 electrons per 1x1 cell [1]. A possible explanation for the fractional electron count is suggested, where extra Si atoms in a 2D cell “dope” the 1D chain embedded in it. This would be analogous to the doping in HiT c materials, where a 3D cell dopes an embedded 2D plane. References: [1] Losio, et al., Phys. Rev. Lett. 86, 4632 (2001); Altmann et al. Phys. Rev. B 64, 035406 (2001); Crain et al., Phys Rev. Lett., in press (2003). [2] Crain, et al., Phys. Rev. B 66, 205302 (2002). [3] Robinson, et al., Phys. Rev. Lett. 88, 096104 (2002).
THE CANADIAN LIGHT SOURCE: A BRIGHT LIGHT SHINING IN A COLD LANDSCAPE J.N. Cutler Canadian Light Source, University of Saskatchewan, Saskatoon, Saskatchewan, S7N 5C6 The Canadian Light Source (CLS), a 2.9 GeV synchrotron facility, is currently being constructed at the University of Saskatchewan. The immense 84 m x 83 m building is now complete; and major accelerator equipment (e.g. the booster ring) is currently being commissioned. The facility (with at least six beamlines) will be operational by the end of 2003. Fifteen beamlines (with very heavy involvement from the Canadian chemistry community) have now been approved to go forward; and proposals for two other beamlines are being developed. Most of these beamlines and associated endstations, will be extremely useful for research ranging from materials and environmental science to life sciences – using infrared spectroscopy and spectromicroscopy, µ-EXAFS, single crystal diffraction, and soft and hard x-ray XANES and EXAFS. This poster will present the current status of the Canadian Light Source project and some insight into the future of the facility.
Page 2 and 3: Welcome to the 36 th SRC Users’ M
Page 4 and 5: 12:20 - 1:10 Lunch 1:10 -1:45 Poste
Page 6 and 7: Administration Executive Director D
Page 8 and 9: STATUS OF THE SRC BEAMLINES AND INS
Page 10 and 11: ACCELERATOR DEVELOPMENTS Ken Jacobs
Page 12 and 13: HIGH ENERGY RESEARCH POSSIBILITIES
Page 14 and 15: ATOMICALLY UNIFORM THIN FILMS ON SI
Page 16 and 17: calculated binding energies of the
Page 18 and 19: MANY-ELECTRON EFFECTS ON THE XE 5S
Page 20 and 21: PHOTOELECTRON SPECTROMETRY OF ATOMI
Page 22 and 23: PHOTOEMISSION STUDY OF USb AND UTe
Page 24 and 25: CANADIAN SYNCHROTRON RADIATION FACI
Page 26 and 27: SELF-ASSEMBLY OF BLOCK COPOLYMERS O
Page 28 and 29: A B S T R A C T S
Page 30 and 31: Photoemission spectra, a.u. -0.3 -0
Page 32 and 33: THE INITIAL AND FINAL STATE BANDS I
Page 34 and 35: TRANSITION LAYERS AT BURIED FERROMA
Page 38 and 39: SUBCELLULAR DISTRIBUTION OF MOTEXAF
Page 40 and 41: LINEAR POLARIZATION MEASUREMENTS OF
Page 42 and 43: Fig.1: Photoemission spectra of opt
Page 44 and 45: The sample manipulator has a cool d
Page 46 and 47: Cr and Fe but for these U systems t
Page 48 and 49: [4] G. -H. Gweon, J. W. Allen, and
Page 50 and 51: References [1] S. Cho, Y. Kim, A. D
Page 52 and 53: [3] D. L. Mills, Physical Review B
Page 54 and 55: CHARACTERIZATION OF SULPHATE INTERA
Page 56 and 57: in the data acquisition chamber. Th
Page 58 and 59: spatially resolved chemistry of the
Page 60 and 61: THE RELATIONSHIP BETWEEN PHOSPHATE
Page 62 and 63: PHOTOEMISSION STUDIES OF QUANTUM WE
Page 64 and 65: Ag surface state such that it moves
Page 66 and 67: HIGH-RESOLUTION STUDY OF THE LITHIU
Page 68 and 69: RELATIVE PARTIAL CROSS SECTIONS AND
Page 70 and 71: Christian Ast Max-Planck Institute
Page 72 and 73: David L. Huber Physical Sciences La
Page 74 and 75: Tom Miller University of Illinois a
Page 76 and 77: Eric Wiedemann University of Wiscon
Page 78 and 79: Pete Hagen Phone: (608) 877-2154 Em
Page 80: NOTES

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