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PHOTOEMISSION STUDIES OF QUANTUM WELL SYSTEMS WITH VICINAL INTERFACES D. Ricci, T. Miller, and T.-C. Chiang Department of Physics, University of Illinois at Urbana-Champaign, 1110 West Green Street, Urbana, Illinois 61801-3080 Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, 104 South Goodwin Avenue, Urbana, Illinois 61801-2902 The electronic structures of thin metallic films on semiconductor surfaces have been shown to be profoundly influenced by the films’ interfaces with the substrate and with the vacuum. As seen using synchrotron-based angle-resolved photoemission spectroscopy, wellordered systems grown on low-index faces may exhibit discrete electronic spectra characteristic of quantum wells [1]. In turn, the quantized electronic structure has been observed to impact various physical properties of the film [2]. Vicinal surfaces possess periodic arrangements of steps which influence the growth and development of adsorbate structures [3], and thus may produce systems with electronic properties that differ from those formed with substrates oriented along a high symmetry axis [4]. Currently, we are probing the surface and quantum well states arising in Ag/vicinal Si(111) and Ag/vicinal Si(001) systems, with an eye towards developing an understanding of their electronic and physical properties. In this regard, comparison to the existing results from the simpler on-axis systems should prove useful. This work is supported by the U.S. Department of Energy, Division of Materials Sciences (grant DEFG02-91ER45439). We acknowledge the Petroleum Research Fund, administered by the American Chemical Society, and the U.S. National Science Foundation (grant DMR-02- 03003), for partial support of the synchrotron beamline operation and the central facilities of the Frederick Seitz Materials Research Laboratory. The Synchrotron Radiation Center of the University of Wisconsin-Madison is supported by the U.S. National Science Foundation (grant DMR-00-84402.). References: [1] M. Upton, T. Miller, and T.-C. Chiang, Phys. Rev. B (in press); J. J. Paggel, T. Miller, and T.-C. Chiang, Science 283, 1709 (1999); T.-C. Chiang, Surf. Sci. Rep. 39, 181 (2000), and references therein. [2] J. J. Paggel, C. M. Wei, M. Y. Chou, D.-A. Luh, T. Miller, and T.-C. Chiang, Phys. Rev. B66 233403 (2002); D.-A. Luh, T. Miller, J. J. Paggel, and T.-C. Chiang, Phys. Rev. Lett. 88, 256802 (2002); D.-A. Luh, T. Miller, J. J. Paggel, M. Y. Chou, and T.-C. Chiang, Science, 292 1131 (2001). [3] E. Hoque, A. Petkova, M. Henzler, Surf. Sci. 515, 312 (2002) [4] A.P. Shapiro, T. Miller, and T.-C. Chiang, Phys. Rev. B, 38, 1779 (1988)
GROWTH OF THIN FILMS ON RECONSTRUCTED SURFACES: AG ON AU/SI(111)- 3 3 S. –J. Tang, T. Miller, and T.-C. Chiang Department of Physics, University of Illinois at Urbana-Champaign, 1110 West Green Street, Urbana, Illinois 61801-3080 Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, 104 South Goodwin Avenue, Urbana, Illinois 61801-2902 Both for fundamental studies and for potential applications, it is oftentimes desireable to be able to grow uniform films in a layer-by-layer fashion on a substrate of different material. The interface with the substrate is an important factor controlling the nature of film growth. Generally, epitaxial growth of thin films is facilitated by a lattice-matched starting substrate, as there is a tendency for the substrate to serve as a template for further crystalline growth of the film. In typical cases there exists lattice mismatch which must be accommodated by strain or by the development of crystal imperfections in the substrate, film, or at the interface; consequently it may be more difficult to achieve layer-by-layer growth in these systems. Similar problems may be caused by reconstructions of the substrate surface, which may be quite complex. In these cases, it may happen that the presence of a third species at the interface can facilitate a desired growth pattern. Ag films grown on the Si (111) surface provide examples of these issues. The equilibrium (111) Si surface has the well-known, but complicated, (7x7) reconstruction. Ag and Si both have fcc as their basic lattice but have large lattice mismatch with each other ( Si: a= 5.43 Å, Ag: a= 4.09 Å). Depending on growth conditions, Ag on this surface can form flat or three-dimensional islands, or strained epitaxial layers. In the current work, we use Au to produce a commensurate Au/Si(111)- 3 3 reconstructed surface as a seed layer before depositing Ag films. This has the effect of simplifying the surface reconstruction as well as modifying its chemical properties [1]. Subsequent growth of Ag films of various coverages was carried out at -165C, and the films were annealed to RT. The electronic structure of the Ag thin film was probed by angle resolved photoemission using the high-resolution low energy synchrotron beam provided by U1-NIM beamline at SRC. Figure 1 shows a series of energy distribution curves at normal emission from Ag films on Au/Si - 3 3 at coverages ranging from 6 to 22 monolayers (ML). Each spectrum shows a series of discrete peaks representing the states of the quantum well formed by the thin metallic film. As is evident, the quantum well states peaks become narrower and shift to lower binding energies as the Ag film coverage increases. This coverage dependent behavior of the quantum well states can be simply explained through the phase accumulation model. The appearance of the intense and sharp Ag surface state near Fermi level is significant as it not only reflects good crystallinity of the film but also the important role of the intermediate 3 3 seed layer in reducing the strain in the Ag film. This is because in films grown without the seed layer, the strain due to the Ag/Si lattice mismatch is known to significantly shift the initial state energy of
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Welcome to the 36 th SRC Users’ M
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12:20 - 1:10 Lunch 1:10 -1:45 Poste
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Administration Executive Director D
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STATUS OF THE SRC BEAMLINES AND INS
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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 36 and 37: LOW-DIMENSIONAL ELECTRONS AT SILICO
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
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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 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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