Extending the range of low energy electron diffraction (LEED) surface structure determination: Co-adsorbed molecules, incommensurate overlayers and alloy surface order studied by new video and electron counting LEED techniques
LEED multiple scattering theory is briefly summarized, and aspects of electron scattering with particular significance to experimental measurements such as electron beam coherence, instrument response and phonon scattering are analyzed. Diffuse LEED experiments are discussed. New techniques that enhance the power of LEED are described, including a real-time video image digitizer applied to LEED intensity measurements, along with computer programs to generate I-V curves. The first electron counting LEED detector using a ''wedge and strip'' position sensitive anode and digital electronics is described. This instrument uses picoampere incident beam currents, and its sensitivity is limited only by statistics and counting times. Structural results on new classes of surface systems are presented. The structure of the c(4 x 2) phase of carbon monoxide adsorbed on Pt(111) has been determined, showing that carbon monoxide molecules adsorb in both top and bridge sites, 1.85 +- 0.10 A and 1.55 +- 0.10 A above the metal surface, respectively. The structure of an incommensurate graphite overlayer on Pt(111) is analyzed. The graphite layer is 3.70 +- 0.05 A above the metal surface, with intercalated carbon atoms located 1.25 +- 0.10 A above hollow sites supporting it. The (2..sqrt..3 x 4)-rectangular phase of benzene and carbon monoxide coadsorbed on Pt(111) is analyzed. Benzene molecules adsorb in bridge sites parallel to and 2.10 +- 0.10 A above the surface. The carbon ring is expanded, with an average C-C bond length of 1.72 +- 0.15 A. The carbon monoxide molecules also adsorb in bridge sites. The structure of the (..sqrt..3 x ..sqrt..3) reconstruction on the (111) face of the ..cap alpha..-CuAl alloy has been determined.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 6062638
- Report Number(s):
- LBL-22593; ON: DE88001401
- Resource Relation:
- Other Information: Thesis (Ph.D.). Portions of this document are illegible in microfiche products
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GENERAL PHYSICS
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ELECTRON DIFFRACTION
DATA ACQUISITION SYSTEMS
MULTIPLE SCATTERING
SURFACES
ADSORPTION
CHEMICAL COMPOSITION
TOPOLOGY
A CODES
ALUMINIUM ALLOYS
ATOMIC BEAM DIFFRACTION
BENZENE
CARBON MONOXIDE
CHEMISORPTION
COMPUTER CALCULATIONS
COPPER ALLOYS
DOMAIN STRUCTURE
ELECTRON BEAMS
ELECTRON DETECTION
ELECTRON GUNS
EXPERIMENTAL DATA
FORTRAN
GRAPHITE
ION BEAMS
PLATINUM
RHODIUM
SEMICONDUCTOR MATERIALS
SURFACE PROPERTIES
THEORETICAL DATA
ALLOYS
AROMATICS
BEAMS
CARBON
CARBON COMPOUNDS
CARBON OXIDES
CHALCOGENIDES
CHARGED PARTICLE DETECTION
CHEMICAL REACTIONS
COHERENT SCATTERING
COMPUTER CODES
DATA
DETECTION
DIFFRACTION
ELEMENTAL MINERALS
ELEMENTS
HYDROCARBONS
INFORMATION
LEPTON BEAMS
MATERIALS
MATHEMATICS
METALS
MINERALS
NONMETALS
NUMERICAL DATA
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PARTICLE BEAMS
PLATINUM METALS
PROGRAMMING LANGUAGES
RADIATION DETECTION
SCATTERING
SEPARATION PROCESSES
SORPTION
TRANSITION ELEMENTS
640301* - Atomic
Molecular & Chemical Physics- Beams & their Reactions
656003 - Condensed Matter Physics- Interactions between Beams & Condensed Matter- (1987-)