Structural studies of molecular and metallic overlayers using angle- resolved photoemission extended fine structure
Angle-resolved photoemission extended fine structure (ARPEFS) was used to study molecular and metallic overlayers on metal surfaces through analysis of p2mg(2[times]1)CO/Ni(110) and the p(2[times]2)K/Ni(111) adsorption. For the dense p2mg(2[times]1)CO/Ni(110) surface layer, photoemission intensities from C 1s level were measured in three directions at photoelectron kinetic energies 60-400 eV. Using multiple-scattering spherical-wave (MSSW) modeling, it was found that CO molecules are adsorbed on short-bridge sites, with adjacent CO along the [110] direction displaced alternatively in opposite directions towards the [001] azimuths to form a zigzag chain geometry. The tilt angle is 16[plus minus]2[degree] from the surface normal for the direction linking the C atom and the center of the Ni bridge. The carbon C-Ni interatomic distance was determined to be 1.94[plus minus]0.02[Angstrom]. The first- to second-layer spacing of Ni is 1.27[plus minus]0.04[Angstrom], up from 1.10[Angstrom] for the clean Ni(110) surface, but close to the 1.25[Angstrom] Ni interlayer spacing in the bulk. The C-O bond length and tilt angle were varied within small ranges (1.10--1.20[Angstrom] and 15--23[degrees]) in our MSSW simulations. Best agreement between experiment and simulations was achieved at 1.16[Angstrom] and 19[degrees]. This yields an O-O distance of 2.95[Angstrom] for the two nearest CO molecules, (van der Waals' radius [approximately] 1.5 [Angstrom] for oxygen). Two different partial-wave phase-shifts were used in MSSW, and structural results from both are in very good agreement. For the p(2[times]2)K/Ni(111) overlayer, ARPEFS [chi](k) curves from K 1s level measured along [111] and [771] at 130K showed that the K atoms are preferentially adsorbed on the atop sites, in agreement with a LEED study of the same system.
- Research Organization:
- Lawrence Berkeley Lab., CA (United States)
- Sponsoring Organization:
- DOE; USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 6946944
- Report Number(s):
- LBL-33040; ON: DE93004700
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360104 -- Metals & Alloys-- Physical Properties
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ADSORPTION
ALKALI METALS
BOND LENGTHS
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CHALCOGENIDES
DIMENSIONS
DISTANCE
ELEMENTS
EMISSION
FOURIER TRANSFORMATION
INTEGRAL TRANSFORMATIONS
INTERATOMIC DISTANCES
LAYERS
LENGTH
METALS
NICKEL
OXIDES
OXYGEN COMPOUNDS
PHOTOEMISSION
POTASSIUM
SECONDARY EMISSION
SORPTION
SORPTIVE PROPERTIES
SURFACE PROPERTIES
SURFACES
TRANSFORMATIONS
TRANSITION ELEMENTS