The Structure of Mixed H(2)O-OH Monolayer Films on Ru (0001)
Scanning tunneling microscopy (STM) and x-ray absorption spectroscopy (XAS) have been used to study the structures produced by water on Ru(0001) at temperatures above 140 K. It was found that while undissociated water layers are metastable below 140 K, heating above this temperature produces drastic transformations, whereby a fraction of the water molecules partially dissociate and form mixed H{sub 2}O-OH structures. X-ray photoelectron spectroscopy and XAS revealed the presence of hydroxyl groups with their O-H bond essentially parallel to the surface. STM images show that the mixed H{sub 2}O-OH structures consist of long narrow stripes aligned with the three crystallographic directions perpendicular to the close-packed atomic rows of the Ru(0001) substrate. The internal structure of the stripes is a honeycomb network of H-bonded water and hydroxyl species. We found that the metastable low temperature molecular phase can also be converted to a mixed H{sub 2}O-OH phase through excitation by the tunneling electrons when their energy is 0.5 eV or higher above the Fermi level. Structural models based on the STM images were used for density functional theory optimizations of the stripe geometry. The optimized geometry was then utilized to calculate STM images for comparison with the experiment.
- Research Organization:
- Stanford Linear Accelerator Center (SLAC)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC02-76SF00515
- OSTI ID:
- 953585
- Report Number(s):
- SLAC-REPRINT-2009-298
- Journal Information:
- J. Chem. Phys. 129:154109,2008, Journal Name: J. Chem. Phys. 129:154109,2008 Journal Issue: 15 Vol. 129; ISSN JCPSA6; ISSN 0021-9606
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ABSORPTION SPECTROSCOPY
DENSITY
ELECTRONS
ENERGY
EXCITATION
FERMI LEVEL
FILMS
FUNCTIONALS
GEOMETRY
HEATING
IMAGES
LAYERS
MOLECULES
Other
CHEM
PHYS
RUTHENIUM
SCANNING TUNNELING MICROSCOPY
STRUCTURAL MODELS
TEMPERATURE RANGE 0065-0273 K
TRANSFORMATIONS
WATER
X-RAY PHOTOELECTRON SPECTROSCOPY