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Simple valence force field-bond energy bond order (SVFF-BEBO) model for chemisorption of oxygen on Si(111)
A277 Surface Science 108 (1981) 587-604 North-Holland Publishing Company
587
SIMPLE VALENCE FORCE FIELD-BOND (SVFF-BEBO)
ENERGY BOND ORDER
MODEL FOR CHEMISORPTION
OF OXYGEN ON Si( 111)
AS. BHANDIA and J.A. SCHWARZ Department of Chemical Engineering Syracuse, New York 13210, USA
and Materials Science, Syracuse University,
Received
for publication
20 October
1980; accepted
16 March
1981
When information is available for the configuration of an adsorbate during various stages of chemisorption on an absorbent, in principle, the energetics of the adsorption process can be calculated. Oxygen adsorption on silicon (111) has been studied extensively and various configurations of the silicon-oxygen molecular complex have been proposed. A Simple Valence Force Field-Bond Energy Bond Order (SVFFBEBO) semi-empirical model has been used to determine the energetics of the initial stages of the oxidation of the ideal silicon (111) surface. The SVFF-BEBO method allows consideration of the lattice strain energy that is involved in the localized surface bonding during the formation of the surface complex. Using the best available data we show that direct oxidation of silicon to produce a SiOz-like surface configuration is energetically feasible, but unlikely. A large activation barrier separates this possible final chemisorbed oxide state from an easily formed peroxide-bridge structure. The results of this calculation are compared with, and are in agreement with, the most recent experimental data.
Surface Science 108 (1981) 605-616 North-Holland Publishing Company
THE CHEMISORPTION LEED *
605
OF OXYGEN ON Cu(ll0)
STUDIED BY EELS AND
J.F. WENDELKEN Solid State Division, Oak Ridge National Laboratory, Received
10 January
198 1; accepted
for publication
Oak Ridge, Tennessee 37830,
USA
20 March 198 1
The chemisorption of oxygen on Cu(ll0) has been studied with electron energy loss vibrational spectroscopy and low energy electron diffraction. Depending on crystal temperatures during oxygen exposure and subsequent heat treatments, (1 X I), c(6 X 2), and (2 X 1) LEED patterns are obtained. However, in all cases and independent of exposure, a single vibrational energy was observed at 49 meV for ’ 6O and at 46 meV for r80. This invariance of energy sug gests a shielded site location in or beneath the surface in support of the result of a recent ion scattering study. The (2 X 1) structure is shown to form in islands at less than saturation coverage on the basis of observed vibrational intensities.
587
SIMPLE VALENCE FORCE FIELD-BOND (SVFF-BEBO)
ENERGY BOND ORDER
MODEL FOR CHEMISORPTION
OF OXYGEN ON Si( 111)
AS. BHANDIA and J.A. SCHWARZ Department of Chemical Engineering Syracuse, New York 13210, USA
and Materials Science, Syracuse University,
Received
for publication
20 October
1980; accepted
16 March
1981
When information is available for the configuration of an adsorbate during various stages of chemisorption on an absorbent, in principle, the energetics of the adsorption process can be calculated. Oxygen adsorption on silicon (111) has been studied extensively and various configurations of the silicon-oxygen molecular complex have been proposed. A Simple Valence Force Field-Bond Energy Bond Order (SVFFBEBO) semi-empirical model has been used to determine the energetics of the initial stages of the oxidation of the ideal silicon (111) surface. The SVFF-BEBO method allows consideration of the lattice strain energy that is involved in the localized surface bonding during the formation of the surface complex. Using the best available data we show that direct oxidation of silicon to produce a SiOz-like surface configuration is energetically feasible, but unlikely. A large activation barrier separates this possible final chemisorbed oxide state from an easily formed peroxide-bridge structure. The results of this calculation are compared with, and are in agreement with, the most recent experimental data.
Surface Science 108 (1981) 605-616 North-Holland Publishing Company
THE CHEMISORPTION LEED *
605
OF OXYGEN ON Cu(ll0)
STUDIED BY EELS AND
J.F. WENDELKEN Solid State Division, Oak Ridge National Laboratory, Received
10 January
198 1; accepted
for publication
Oak Ridge, Tennessee 37830,
USA
20 March 198 1
The chemisorption of oxygen on Cu(ll0) has been studied with electron energy loss vibrational spectroscopy and low energy electron diffraction. Depending on crystal temperatures during oxygen exposure and subsequent heat treatments, (1 X I), c(6 X 2), and (2 X 1) LEED patterns are obtained. However, in all cases and independent of exposure, a single vibrational energy was observed at 49 meV for ’ 6O and at 46 meV for r80. This invariance of energy sug gests a shielded site location in or beneath the surface in support of the result of a recent ion scattering study. The (2 X 1) structure is shown to form in islands at less than saturation coverage on the basis of observed vibrational intensities.